[Federal Register Volume 63, Number 68 (Thursday, April 9, 1998)]
[Proposed Rules]
[Pages 17492-17627]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-8756]
[[Page 17491]]
_______________________________________________________________________
Part II
Department of Labor
_______________________________________________________________________
Mine Safety and Health Administration
_______________________________________________________________________
30 CFR Parts 72 and 75
Diesel Particulate Matter Exposure of Underground Coal Miners; Proposed
Rule
Federal Register / Vol. 63, No. 68 / Thursday, April 9, 1998 /
Proposed Rules
[[Page 17492]]
DEPARTMENT OF LABOR
Mine Safety and Health Administration
30 CFR Parts 72 and 75
RIN 1219-AA74
Diesel Particulate Matter Exposure of Underground Coal Miners
AGENCY: Mine Safety and Health Administration (MSHA), Labor.
ACTION: Proposed rule.
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SUMMARY: This proposed rule would establish new health standards for
underground coal mines that use equipment powered by diesel engines.
This proposal is designed to reduce the risks to underground coal
miners of serious health hazards that are associated with exposure to
high concentrations of diesel particulate matter (dpm). DPM is a very
small particle in diesel exhaust. Underground miners are exposed to far
higher concentrations of this fine particulate than any other group of
workers. The best available evidence indicates that such high exposures
put these miners at excess risk of a variety of adverse health effects,
including lung cancer.
The proposed rule for underground coal mines would require that
mine operators install and maintain high-efficiency filtration systems
on certain types of diesel-powered equipment. Underground coal mine
operators would also be required to train miners about the hazards of
dpm exposure.
By separate notice, MSHA will soon propose a rule to reduce dpm
exposures in underground metal and nonmetal mines.
DATES: Comments must be received on or before August 7, 1998. Submit
written comments on the information collection requirements by August
7, 1998.
ADDRESSES: Comments on the proposed rule may be transmitted by
electronic mail, fax, or mail, or dropped off in person at any MSHA
office. Comments by electronic mail must be clearly identified as such
and sent to this e-mail address: comments@msha.gov. Comments by fax
must be clearly identified as such and sent to: MSHA, Office of
Standards, Regulations, and Variances, 703-235-5551. Send mail comments
to: MSHA, Office of Standards, Regulations, and Variances, Room 631,
4015 Wilson Boulevard, Arlington, VA 22203-1984, or any MSHA district
or field office. The Agency will have copies of the proposal available
for review by the mining community at each district and field office
location, at the National Mine Safety and Health Academy, and at each
technical support center. The document will also be available for loan
to interested members of the public on an as needed basis. MSHA will
also accept written comments from the mining community at the field and
district offices, at the National Mine Safety and Health Academy, and
at technical support centers. These comments will become a part of the
official rulemaking record. Interested persons are encouraged to
supplement written comments with computer files or disks; please
contact the Agency with any questions about format.
Written comments on the information collection requirements may be
submitted directly to the Office of Information and Regulatory Affairs,
New Executive Office Building, 725 17th Street, NW., Rm. 10235,
Washington, D.C. 20503, Attn: Desk Officer for MSHA.
FOR FURTHER INFORMATION CONTACT: Patricia W. Silvey, Director; Office
of Standards, Regulations, and Variances; MSHA; 703-235-1910.
SUPPLEMENTARY INFORMATION:
I. Questions and Answers About This Proposed Rule
(A) General Information of Interest to the Entire Mining Community
(1) What Actions Are Being Proposed?
MSHA has determined that action is essential to reduce the exposure
of miners to a harmful substance emitted from diesel engines--and that
regulations are needed for this purpose in underground mines. This
notice proposes requirements for underground coal mines; by separate
notice, MSHA will soon propose a rule for underground metal and
nonmetal mines.
The harmful substance is known as diesel particulate matter (dpm).
As shown in Figure I-1, average concentrations of dpm observed in
dieselized underground mines are up to 200 times as high as average
environmental exposures in the most heavily polluted urban areas and up
to 10 times as high as median exposures estimated for the most heavily
exposed workers in other occupational groups. The best available
evidence indicates that exposure to such high concentrations of dpm
puts miners at significantly increased risk of incurring serious health
problems, including lung cancer.
The goal of the proposed rule is to reduce underground miner
exposures to attain the highest degree of safety and health protection
that is feasible.
BILLING CODE 4510-43-P
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[GRAPHIC] [TIFF OMITTED] TP09AP98.000
BILLING CODE 4510-43-C
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In underground coal mines, MSHA's proposal would require the
installation of high-efficiency filters on diesel-powered equipment to
trap diesel particles before they enter the mine atmosphere. Following
18 months of education and technical assistance by MSHA after the rule
is issued, filters would first have to be installed on permissible
diesel-powered equipment. By the end of the following year (i.e., 30
months after the rule is issued), such filters would also have to be
installed on any heavy-duty outby equipment. No specific concentration
limit would be established in this sector; the proposed rule would
require that filters be installed and properly maintained. Miner
awareness training on the hazards of dpm would also be required.
MSHA is not at this time proposing a rule applicable to surface
mines. As illustrated in Figure I-1, in certain situations the
concentrations of dpm at surface mines may exceed those to which rail,
trucking and dock workers are exposed. Problem areas identified in this
sector include production areas where miners work in the open air in
close proximity to loader-haulers and trucks powered by older, out-of-
tune diesel engines, or other confined spaces where diesel engines are
running. The Agency believes, however, that these problems are
currently limited and readily controlled through education and
technical assistance. Using tailpipe exhaust extenders, or directing
the exhaust across the engine fan, can dilute the high concentrations
of dpm that might otherwise occur in areas immediately adjacent to
mining equipment. Surface mine operators using or planning to switch to
environmentally conditioned cabs to reduce noise exposure to equipment
operators might also be able to incorporate filtration features that
would protect these miners from high dpm concentrations as well.
Completing already planned purchases of new trucks containing cleaner
engines may also help reduce the isolated instances of high dpm
concentrations at such mines.
The Agency would like to emphasize, however, that surface miners
are entitled to the same level of protection as other miners, and that
the Agency's risk assessment indicates that even short-term exposures
to concentrations of dpm like those observed may result in serious
health problems. Accordingly, in addition to providing education and
technical assistance to surface mines, the Agency will also continue to
evaluate the hazards of diesel particulate exposure at surface mines
and will take any necessary action, including regulatory action if
warranted, to help the mining community minimize any hazards.
(2) How Is This Notice of Proposed Rulemaking Organized?
The proposed rule for underground coal mines can be found at the
end of this Notice. The remainder of this preamble to the proposed rule
(Supplementary Information) describes the Agency's rationale for what
is being proposed.
Part I consists of twelve ``Questions and Answers.'' The Agency
hopes they will provide most of the information you will need to
formulate your comments. The first ten of these (Section A) cover
general topics. The last two (Section B) contain additional detail
about the proposed rule for the underground coal sector, and a
discussion of two alternatives on which the Agency would particularly
like additional comment.
Part II provides some background information on nine topics that
are relevant to this rulemaking. In order, the topics covered are: (1)
the role of diesel-powered equipment in mining; (2) the composition of
diesel exhaust and diesel particulate; (3) measurement of diesel
particulate; (4) reducing soot at the source--EPA regulation of diesel
engine design; (5) limiting the public's exposure to soot--EPA ambient
air quality standards; (6) controlling diesel particulate emissions in
mining--a toolbox; (7) existing mining standards that limit miner
exposure to occupational diesel particulate emissions; (8) how other
jurisdictions are restricting occupational exposure to diesel soot; and
(9) MSHA's initiative to limit miner exposure to diesel particulate--
the history of this rulemaking and related actions. Appended to the end
of this document is a copy of an MSHA publication, ``Practical Ways to
Reduce Exposure to Diesel Exhaust in Mining--A Toolbox,'' which
includes additional information on methods for controlling dpm, and a
glossary of terms.
Part III is the Agency's risk assessment. The first section
presents the Agency's data on current dpm exposure levels in each
sector of the mining industry. The second section reviews the
scientific evidence on the risks associated with exposure to dpm. The
third section evaluates this evidence in light of the Mine Act's
statutory criteria.
Part IV is a detailed section-by-section explanation and discussion
of the elements of the proposed rule.
Part V is an analysis of whether the proposed rule meets the
Agency's statutory obligation to attain the highest degree of safety or
health protection for miners, with feasibility a consideration. This
part begins with a review of the law and a profile of the coal
industry's economic position. This next part explores the extent to
which the proposed rule is expected to impact existing concentration
levels, reviews significant alternatives that might provide more
protection than the rule being proposed but which have not been adopted
by the Agency due to feasibility concerns, and then discusses the
feasibility of the rule being proposed. Part V draws upon a computer
simulation of how the proposed rule in underground coal mines is
expected to impact dpm concentrations; accordingly, an Appendix to this
discussion provides information about the simulation methodology. The
simulation method, which can be performed using a standard spreadsheet
program, can be used to model conditions and control impacts in any
underground mine; copies of this model are available to the mining
community from MSHA.
Part VI reviews several impact analyses which the Agency is
required to provide in connection with a proposed rulemaking. This
information summarizes a more complete discussion that can be found in
the Agency's Preliminary Regulatory Economic Analysis (PREA). Copies of
this document are available from the Agency and will be posted on the
MSHA Web site (http://www.msha.gov).
Part VII is a complete list of publications referenced by the
Agency in the preamble.
(3) What Evidence Does MSHA Have That Current Underground
Concentrations of DPM Need To Be Controlled?
The best available evidence MSHA has at this time is that miners
subjected to an occupational lifetime of dpm exposure at concentrations
we presently find in underground mines face a significant risk of
material impairment to their health.
It has been recognized for some time that miners working in close
contact with diesel emissions can suffer acute reactions--e.g., eye,
nose and throat irritations--but questions have persisted as to what
component of the emissions was causing these problems, whether exposure
increased the risk of other adverse health effects, and the level of
exposure creating health consequences.
In recent years, there has been growing evidence that it is the
very small respirable particles in diesel exhaust (dpm) that trigger a
variety of
[[Page 17495]]
adverse health outcomes. These particles are generally less than one-
millionth of a meter in diameter (submicron), and so can readily
penetrate into the deepest recesses of the lung. They consist of a core
of the element carbon, with up to 1,800 different organic compounds
adsorbed onto the core, and some sulfates as well. (A diagram of dpm
can be found in part II of this preamble--see Figure II-3). The
physiological mechanism by which dpm triggers particular health
outcomes is not yet known. One or more of the organic substances
adsorbed onto the surface of the core of the particles may be
responsible for some health effects, since these include many known or
suspected mutagens and carcinogens. But some or all of the health
effects might also be triggered by the physical properties of these
tiny particles, since some of the health effects are observed with high
exposures to any ``fine particulate,'' whether the particle comes from
diesel exhaust or another source.
There is clear evidence that exposure to high concentrations of dpm
can result in a variety of serious health effects. These health effects
include: (i) sensory irritations and respiratory symptoms serious
enough to distract or disable miners; (ii) death from cardiovascular,
cardiopulmonary, or respiratory causes; and (iii) lung cancer.
By way of example of the non-cancer effects, there is evidence that
workers exposed to diesel exhaust during a single shift suffer material
impairment of lung capacity. A control group of unexposed workers
showed no such impairment, and workers exposed to filtered diesel
exhaust (i.e., exhaust from which much of the dpm has been removed)
experienced, on average, only about half as much impairment. Moreover,
there are a number of studies quantifying significant adverse health
effects--as measured by lost work days, hospitalization and increased
mortality rates--suffered by the general public when exposed to
concentrations of fine particulate matter like dpm far lower than
concentrations to which some miners are exposed. The evidence from
these fine particulate studies was the basis for recent rulemaking by
the Environmental Protection Agency to further restrict the exposure of
the general public to fine particulates, and the evidence was given
very widespread and close scrutiny before that action was made final.
Of particular interest to the mining community is that these fine
particulate studies indicate that those who have pre-existing pulmonary
problems are particularly at risk. Many individual miners in fact have
such pulmonary problems, and the mining population as a whole is known
to have such conditions at a higher rate than the general public.
Although no epidemiological study is flawless, numerous
epidemiological studies have shown that long term exposure to diesel
exhaust in a variety of occupational circumstances is associated with
an increased risk of lung cancer. With only rare exceptions, involving
relatively few workers and/or observation periods too short to reliably
detect excess cancer risk, the human studies have consistently shown a
greater risk of lung cancer among workers exposed to dpm than among
comparable unexposed workers. When results from the human studies are
combined, the risk is estimated to be 30-40 percent greater among
exposed workers, if all other factors (such as smoking habits) are held
constant. The consistency of the human study results, supported by
experimental data establishing the plausibility of a causal connection,
provides strong evidence that chronic dpm exposure at high levels
significantly increases the risk of lung cancer in humans.
Moreover, all of the human occupational studies indicating an
increased frequency of lung cancer among workers exposed to dpm
involved average exposure levels estimated to be far below the levels
observed in underground mines. As noted in Part III, MSHA views
extrapolations from animal experiments as subordinate to results
obtained from human studies. However, it is noteworthy that dpm
exposure levels recorded in some underground mines have been within the
exposure range that produced tumors in rats.
Based on the scientific data available in 1988, the National
Institute for Occupational Safety and Health (NIOSH) identified dpm as
a probable or potential human carcinogen and recommended that it be
controlled. Other organizations have made similar recommendations.
MSHA carefully evaluated all the evidence available in light of the
requirements of the Mine Act. Based on this evaluation, MSHA has
reached several conclusions:
(1) The best available evidence is that the health effects
associated with exposure to dpm can materially impair miner health or
functional capacity.
(2) At levels of exposure currently observed in underground mining,
many miners are presently at significant risk of incurring these
material impairments over a working lifetime.
(3) The reduction in dpm exposures that is expected to result from
implementation of the proposed rule for underground coal mines would
substantially reduce the significant risks currently faced by
underground coal miners exposed to dpm.
MSHA had its risk assessment independently peer reviewed. The risk
assessment presented here incorporates revisions made in accordance
with the reviewers recommendations. The reviewers stated that:
* * * principles for identifying evidence and characterizing risk
are thoughtfully set out. The scope of the document is carefully
described, addressing potential concerns about the scope of
coverage. Reference citations are adequate and up to date. The
document is written in a balanced fashion, addressing uncertainties
and asking for additional information and comments as appropriate.
(Samet and Burke, Nov. 1997).
The proposed rule would reduce the concentration of one type of
fine particulate in underground coal mines--that from diesel
emissions--but would not explicitly control miner exposure to other
fine airborne particulates present underground. In light of the
evidence presented in the Agency's risk assessment on the risks that
fine particulates in general may pose to the mining population, MSHA
would welcome comments as to whether the Agency should also consider
restricting the exposure of underground coal miners to all fine
particulates, regardless of the source.
(4) Aren't NIOSH and the NCI Working on a Study That Will Provide
Critical Information? Why Proceed Before the Evidence Is Complete?
NIOSH and the National Cancer Institute (NCI) are collaborating on
a cancer mortality study that will provide additional information about
the relationship between dpm exposure levels and disease outcomes, and
about which components of dpm may be responsible for the observed
health effects. The study is projected to take about seven years. The
protocol for the study was recently finalized.
The information the study is expected to generate will be a
valuable addition to the scientific evidence on this topic. But given
its conclusions about currently available evidence, MSHA believes the
Agency needs to take action now to protect miners' health. Moreover, as
noted by the Supreme Court in an important case on risk involving the
Occupational Safety and Health Administration, the need to evaluate
risk does not mean an agency is placed into a ``mathematical
straightjacket.'' Industrial Union Department, AFL-CIO v. American
Petroleum Institute, 448 U.S. 607, 100 S.Ct. 2844 (1980). The Court
noted that
[[Page 17496]]
when regulating on the edge of scientific knowledge, absolute
scientific certainty may not be possible, and ``so long as they are
supported by a body of reputable scientific thought, the Agency is free
to use conservative assumptions in interpreting the data * * * risking
error on the side of overprotection rather than underprotection.'' (Id.
at 656). This advice has special significance for the mining community,
because a singular historical factor behind the enactment of the
current Mine Act was the slowness in coming to grips with the harmful
effects of other respirable dust (coal dust).
It is worth noting that while the cohort selected for the NIOSH/NCI
study consists of underground miners (specifically, underground metal
and nonmetal miners), this choice is in no way linked to MSHA's
regulatory framework or to miners in particular. This cohort was
selected for the study because it provides the best population for
scientists to study. For example, one part of the study would compare
the health experiences of miners who have worked underground in mines
with long histories of diesel use with the health experiences of
similar miners who work in surface areas where exposure is
significantly lower. Since the general health of these two groups is
very similar, this will help researchers to quantify the impacts of
diesel exposure. No other population is as easy to study for this
purpose. But as with any such epidemiological study, the insights
gained are not limited to the specific population used in the study.
Rather, the study will provide information about the relationship
between exposure and health effects that will be useful in assessing
the risks to any group of workers in a dieselized industry.
(5) What are the Impacts of the Proposed Rule?
Costs. Tables I-1 and I-2 provide cost information. Some
explanation is necessary.
Costs consist of two components: ``initial'' costs (e.g., capital
costs for equipment, or the one-time costs of developing a procedure),
which are then amortized over a period of years in accordance with a
standardized formula to provide an ``annualized'' cost; and ``annual''
costs that occur every year (e.g., maintenance or training costs).
Adding together the ``annualized'' initial costs and the ``annual''
costs provides the per year costs for the rule.
It should be noted that in amortizing the initial costs, a net
present value factor was applied to certain costs: those associated
with provisions where mine operators do not have to make capital
expenditures until some period of time after the effective date.
Detailed information on this point is contained in the Agency's
Preliminary Regulatory Economic Analysis (PREA), as are the Agency's
cost assumptions.
The costs per year to the underground coal industry are about $10
million. Diesel equipment manufacturers would have a yearly cost
increase of about $14,000.
The Agency spent considerable time developing its cost assumptions,
which are discussed in detail in the Agency's PREA, and would encourage
the mining community to provide detailed comments in this regard so as
to ensure these cost estimates are as accurate as possible.
Table I-1.--Compliance Costs for Underground Coal Mines
[Dollars + 1,000]
Large mines (20) Small mines (<20) total="" mines="" -----------------------------------------------------------------------------------------------------------="" detail="" total="" total="" total="" [col.="" b+c]="" annualized="" annual="" [col.="" e+f]="" annualized="" annual="" [col.="" h+i]="" annualized="" annual="" (a)="" (b)="" (c)="" (d)="" (e)="" (f)="" (g)="" (h)="" (i)="" --------------------------------------------------------------------------------------------------------------------------------------------------------="" 75.1915.....................................="" $9="" $9="" $0="" $1="" $1="" $0="" $10="" $10="" $0="" 72.500(a)...................................="" 4,910="" 457="" 4,453="" 95="" 22="" 73="" 5,005="" 479="" 4,526="" 72.500(b)...................................="" 4,768="" 1,335="" 3,433="" 22="" 12="" 10="" 4,790="" 1,347="" 3,443="" 72.510......................................="" 185="" 0="" 185="" 1="" 0="" 1="" 186="" 0="" 186="" 75.371qq="" and="" 75.370.........................="" 1="" 1="" 0="" 1="" 1="" 0="" 2="" 2="" 0="" -----------------------------------------------------------------------------------------------------------="" total...................................="" 9,873="" 1,802="" 8,071="" 120="" 36="" 84="" 9,993="" 1,838="" 8,155="" --------------------------------------------------------------------------------------------------------------------------------------------------------="" table="" i-2.--compliance="" costs="" for="" manufacturers="" [dollars="" x="" 1,000]="" ------------------------------------------------------------------------="" manufacturers="" -------------------------------="" detail="" total="" [col.="" annualized="" annual="" b+c]="" ------------------------------------------------------------------------="" (a)="" (b)="" (c)="" part="" 36.................................="" $14="" $14="" $0="" -------------------------------="" total...............................="" $14="" $14="" $0="" ------------------------------------------------------------------------="" as="" required="" by="" the="" regulatory="" flexibility="" act,="" msha="" has="" performed="" a="" review="" of="" the="" effects="" of="" the="" proposed="" rule="" on="" ``small="" entities''.="" the="" results--including="" information="" about="" the="" average="" cost="" for="" mines="" in="" each="" sector="" with="" less="" than="" 500="" employees="" and="" mines="" in="" each="" sector="" with="" less="" than="" 20="" miners--are="" summarized="" in="" response="" to="" question="" 7.="" paperwork="" tables="" i-3="" and="" i-4="" show="" additional="" paperwork="" burden="" hours="" which="" the="" proposed="" rule="" would="" require.="" only="" those="" existing="" or="" proposed="" regulatory="" requirements="" which="" would,="" as="" a="" result="" of="" this="" rulemaking,="" result="" in="" new="" burden="" hours,="" are="" noted.="" the="" costs="" for="" these="" paperwork="" burdens,="" a="" subset="" of="" the="" overall="" costs="" of="" the="" proposed="" rule,="" are="" specifically="" noted="" in="" part="" vii="" of="" the="" agency's="" prea.="" each="" of="" these="" tables="" shows="" separately="" the="" burden="" hours="" on="" smaller="" mines--those="" with="" less="" than="" 20="" miners.="" table="" i-3="" shows="" additional="" paperwork="" burden="" hours="" for="" underground="" coal="" operators.="" table="" i-3.--underground="" coal="" mine="" burden="" hours="" ------------------------------------------------------------------------="" detail="" large="" small="" total="" ------------------------------------------------------------------------="" 75.370.......................................="" 93="" 9="" 102="" 75.371.......................................="" 158="" 8="" 166="" 75.1915......................................="" 12="" 1="" 13="" 72.510.......................................="" 347="" 5="" 352="" --------------------------="" total....................................="" 610="" 23="" 633="" ------------------------------------------------------------------------="" table="" i-4="" shows="" the="" additional="" burden="" hours="" for="" diesel="" equipment="" manufacturers.="" all="" of="" the="" manufacturer="" burden="" hours="" will="" occur="" once="" and="" not="" recur="" annually.="" [[page="" 17497]]="" table="" i-4.--diesel="" equipment="" manufacturers="" burden="" hours="" ------------------------------------------------------------------------="" detail="" total="" ------------------------------------------------------------------------="" part="" 36........................................................="" 520="" --------="" total......................................................="" 520="" ------------------------------------------------------------------------="" benefits="" the="" proposed="" rule="" would="" reduce="" the="" exposure="" of="" underground="" miners="" to="" dpm,="" thereby="" reducing="" the="" risk="" of="" adverse="" health="" effects="" and="" their="" concomitant="" effects.="" the="" risks="" being="" addressed="" by="" this="" rulemaking="" arise="" because="" some="" miners="" are="" exposed="" to="" high="" concentrations="" of="" the="" very="" small="" particles="" produced="" by="" engines="" that="" burn="" diesel="" fuel.="" as="" discussed="" in="" part="" ii="" of="" the="" preamble,="" diesel="" powered="" engines="" are="" used="" increasingly="" in="" underground="" mining="" operations="" because="" they="" permit="" the="" use="" of="" mobile="" equipment="" and="" provide="" a="" full="" range="" of="" power="" for="" both="" heavy-duty="" and="" light-duty="" operations="" (i.e.,="" for="" production="" equipment="" and="" support="" equipment,="" respectively),="" while="" avoiding="" the="" explosive="" hazards="" associated="" with="" gasoline.="" but="" underground="" mines="" are="" confined="" spaces="" which,="" despite="" ventilation="" requirements,="" tend="" to="" accumulate="" significant="" concentrations="" of="" particles="" and="" gases--both="" those="" produced="" by="" the="" mine="" itself="" (e.g.,="" methane="" gas="" and="" coal="" dust="" liberated="" by="" mining="" operations)="" and="" those="" produced="" by="" equipment="" used="" in="" the="" mine.="" as="" discussed="" in="" msha's="" risk="" assessment="" (part="" iii="" of="" this="" preamble),="" the="" concentrations="" of="" diesel="" particulates="" to="" which="" some="" underground="" miners="" are="" currently="" exposed="" are="" significantly="" higher="" than="" the="" concentrations="" reported="" for="" other="" occupations="" involving="" the="" use="" of="" dieselized="" equipment;="" and="" at="" such="" concentrations,="" exposure="" to="" dpm="" by="" underground="" miners="" over="" a="" working="" lifetime="" is="" associated="" with="" an="" excess="" risk="" of="" a="" variety="" of="" adverse="" health="" effects.="" the="" nature="" of="" the="" adverse="" health="" effects="" associated="" with="" such="" exposures="" suggests="" the="" nature="" of="" the="" savings="" to="" be="" derived="" from="" controlling="" exposure.="" acute="" reactions="" can="" result="" in="" lost="" production="" time="" for="" the="" operator="" and="" lost="" pay="" (and="" perhaps="" medical="" expenses)="" for="" the="" worker.="" hospital="" care="" for="" acute="" breathing="" crises="" or="" cancer="" treatment="" can="" be="" expensive,="" result="" in="" lost="" income="" for="" the="" worker,="" lost="" income="" for="" family="" members="" who="" need="" to="" provide="" care="" and="" lost="" productivity="" for="" their="" employers,="" and="" may="" well="" involve="" government="" payments="" (e.g.,="" social="" security="" disability="" and="" medicare).="" serious="" illness="" and="" death="" lead="" to="" long="" term="" income="" losses="" for="" the="" families="" involved,="" with="" the="" potential="" for="" costs="" from="" both="" employers="" (e.g.,="" workers'="" compensation="" payouts,="" pension="" payouts)="" and="" society="" as="" a="" whole="" (e.g.,="" government="" assisted="" aid="" programs).="" the="" information="" available="" to="" the="" agency="" suggests="" that="" as="" exposure="" is="" reduced,="" so="" are="" the="" adverse="" health="" consequences.="" for="" example,="" data="" collected="" on="" the="" effects="" of="" environmental="" exposure="" to="" fine="" particulates="" suggest="" that="" reducing="" occupational="" dpm="" exposures="" by="" as="" little="" as="" 75="">g/m\3\ (roughly corresponding to a reduction of 25 g/
m\3\ in 24-hour ambient atmospheric concentration) could lead to
significant reductions in the risk of various acute responses,
including mortality. And chronic occupational exposure has been linked
to an estimated 30 to 40 percent increase in the risk of lung cancer.
All the quantitative risk models reviewed by NIOSH suggest excess risks
of lung cancer of more than one per thousand for miners who have long-
term occupational exposures to dpm concentrations in excess of 1000
g/m\3\, and the epidemiologically-based risk estimates suggest
higher risks.
Despite these quantitative indications, quantification of the
benefits is difficult. Although increased risk of lung cancer has been
shown to be associated with dpm exposure among exposed workers, a
conclusive dose-response relationship upon which to base quantification
of benefits has not been demonstrated. The Agency nevertheless intends,
to the extent it can, to develop an appropriate analysis quantifying
benefits in connection with the final rule.
The Agency does not have much experience in quantifying benefits in
the case of a proposed health standard (other than its recent proposal
on controlling mining noise, where years of compliance data and hearing
loss studies provide a much more complete quantitative picture than
with dpm). MSHA therefore welcomes suggestions for the appropriate
approach to use to quantify the benefits likely to be derived from this
rulemaking. Please identify scientific studies, models, and/or
assumptions suitable for estimating risk at different exposure levels,
and data on numbers of miners exposed to different levels of dpm.
(6) Did MSHA Actively Consider Alternatives to What Is Being Proposed?
Yes. Once MSHA determined that the evidence of risk required a
regulatory action, the Agency considered a number of alternative
approaches, the most significant of which are reviewed in part V of the
preamble.
The consideration of options proceeded in accordance with the
requirements of section 101(a)(6)(A) of the Federal Mine Safety and
Health Act of 1977 (the ``Mine Act''). In promulgating standards
addressing toxic materials or harmful physical agents, the Secretary
must promulgate standards which most adequately assure, on the basis of
the best available evidence, that no miner will suffer material
impairment of health over his/her working lifetime. In addition, the
Mine Act requires that the Secretary, when promulgating mandatory
standards pertaining to toxic materials or harmful physical agents,
consider other factors, such as the latest scientific data in the
field, the feasibility of the standard and experience gained under the
Mine Act and other health and safety laws. Thus, the Mine Act requires
that the Secretary, in promulgating a standard, attain the highest
degree of health and safety protection for the miner, based on the
``best available evidence,'' with feasibility a consideration.
As a result, MSHA seriously considered a number of alternatives
that would, if adopted as part of the proposed rule, have provided
increased protection--and would also have significantly increased
costs. For example, in underground coal mining, the Agency considered
requiring filtration of all light-duty diesel-powered equipment as well
as heavier equipment. The Agency concluded, however, that such an
approach may not be feasible for the underground coal sector at this
time, although it is asking for comment as to whether there are some
types of light-duty equipment whose dpm emissions should, and could
feasibly, be controlled.
MSHA also considered alternatives that would have led to a
significantly lower-cost proposal, e.g., increasing the time for mine
operators to come into compliance. However, based on the current
record, MSHA has tentatively concluded that such approaches would not
be as protective as those being proposed, and that the approach
proposed is both economically and technologically feasible. As a
result, the Agency has not proposed to adopt these alternatives.
MSHA also explored whether to permit the use of administrative
controls (e.g., rotation of personnel) and personal protective
equipment (e.g., respirators) to reduce the diesel particulate exposure
of miners. It is generally accepted industrial hygiene practice,
however, to eliminate or minimize hazards at the source before
resorting to personal protective
[[Page 17498]]
equipment. Moreover, such a practice is generally not considered
acceptable in the case of carcinogens since it merely places more
workers at risk.
Other alternatives the Agency considered include: establishing a
concentration limit for dpm in this sector; requiring filters on some
light-duty equipment; and looking at the filter and the engine as a
package that has to meet a particular emission standard, instead of
requiring that all engines be equipped with a high-efficiency filter.
The Agency also spent a considerable amount of time studying whether it
could simply propose a concentration limit for dpm in underground coal
mines. Such an approach would provide underground coal mine operators
with flexibility to elect any combination of engineering controls they
wish as long as the concentration of dpm in the mine remains below a
set level. At this point in the rulemaking process, however, the Agency
is not confident that there is a measurement method for dpm that will
provide accurate, consistent and verifiable results at lower
concentration levels in underground coal mines. As discussed in detail
in part II of this preamble, the problem arises because coal dust
contains organic compounds that might be mistaken for dpm in the
methods otherwise validated for use at lower dpm concentrations. The
Agency is continuing to explore questions about the measurement of dpm
in underground coal mines in consultation with NIOSH, and welcomes
comment on this issue. However, at this point in the rulemaking
process, the Agency believes that the best approach for the underground
coal sector would be one which does not require measurement of ambient
dpm levels to ascertain compliance or noncompliance.
MSHA recognizes that a specification standard does not allow for
the use of future alternative technologies that might provide the same
or enhanced protection at the same or lower cost. MSHA welcomes comment
as to whether and how the proposed rule can be modified to enhance its
flexibility in this regard.
MSHA did consider two alternative specification standards which
would provide somewhat more flexibility for coal mine operators.
Alternative 1 would treat the filter and engine as a package that has
to meet a particular emission standard. Instead of requiring that all
engines be equipped with a high-efficiency filter, this approach would
provide some credit for the use of lower-polluting engines. Alternative
2 would also provide credit for mine ventilation beyond that required.
The Agency believes, however, that these alternatives may be less
protective of miners than the alternative proposed, although it is
seeking comment on them. More information on these two alternatives can
be found in this part in response to Question 12.
(7) What Will the Impact Be on the Smallest Underground Coal Mines?
What Consideration Did MSHA Give to Alternatives for the Smallest
Mines?
The Regulatory Flexibility Act requires MSHA and other regulatory
agencies to conduct a review of the effects of proposed rules on small
entities. That review is summarized here; a copy of the full review is
included in part VI of this preamble, and in the Agency's PREA. The
Agency encourages the mining community to provide comments on this
analysis.
The Small Business Administration generally considers a small
mining entity to be one with less than 500 employees. MSHA has
traditionally defined a small mine to be one with less than 20 miners,
and has focused special attention on the problems experienced by such
mines in implementing safety and health rules, e.g., the Small Mine
Summit, held in 1996. Accordingly, MSHA has separately analyzed the
impact of the proposed rule on mines with 500 employees or less, and
those with less than 20 miners.
Table I-5 summarizes MSHA's estimates of the average costs of the
proposed rule to a small underground coal entity or small underground
coal mine.
Table I-5.--Average Cost per Small Underground Coal Mine
------------------------------------------------------------------------
UG Coal UG Coal
Size <500><20 ------------------------------------------------------------------------="" cost="" per="" mine.....................................="" $58,000="" $8,000="" ------------------------------------------------------------------------="" pursuant="" to="" the="" regulatory="" flexibility="" act,="" msha="" must="" determine="" whether="" the="" costs="" of="" the="" proposed="" rule="" constitute="" a="" ``significant="" impact="" on="" a="" substantial="" number="" of="" small="" entities.''="" pursuant="" to="" the="" regulatory="" flexibility="" act,="" if="" an="" agency="" determines="" that="" a="" proposed="" rule="" does="" not="" have="" such="" an="" impact,="" it="" must="" publish="" a="" ``certification''="" to="" that="" effect.="" in="" such="" a="" case,="" no="" additional="" analysis="" is="" required="" (5="" u.s.c.="" 605).="" in="" evaluating="" whether="" certification="" is="" appropriate,="" msha="" utilized="" a="" ``screening="" test,''="" comparing="" the="" costs="" of="" the="" proposal="" to="" the="" revenues="" of="" the="" sector="" involved="" (only="" the="" revenues="" for="" underground="" coal="" mines="" are="" used="" in="" this="" calculation).="" for="" underground="" coal="" mines,="" the="" costs="" of="" the="" proposed="" rule="" appear="" to="" be="" significantly="" less="" than="" one="" percent="" of="" revenues--even="" for="" mines="" with="" less="" than="" 20="" miners.="" as="" a="" result,="" msha="" is="" certifying="" that="" the="" proposed="" rule="" for="" underground="" coal="" mines="" does="" not="" have="" a="" ``significant="" impact="" on="" a="" substantial="" number="" of="" small="" entities,''="" and="" has="" performed="" no="" further="" analyses.="" in="" promulgating="" standards,="" msha="" does="" not="" reduce="" protection="" for="" miners="" employed="" at="" small="" mines.="" but="" msha="" does="" consider="" the="" impact="" of="" its="" standards="" on="" even="" the="" smallest="" mines="" when="" it="" evaluates="" the="" feasibility="" of="" various="" alternatives.="" for="" example,="" a="" major="" reason="" why="" msha="" concluded="" it="" needed="" to="" stagger="" the="" effective="" dates="" of="" some="" of="" the="" requirements="" in="" the="" proposed="" rule="" is="" to="" ensure="" that="" it="" would="" be="" feasible="" for="" the="" smallest="" mines="" to="" have="" adequate="" time="" to="" come="" into="" compliance.="" consistent="" with="" recent="" amendments="" to="" the="" regulatory="" flexibility="" act="" under="" sbrefa="" (the="" small="" business="" regulatory="" enforcement="" fairness="" act),="" msha="" has="" already="" started="" considering="" actions="" it="" can="" take="" to="" minimize="" the="" anticipated="" compliance="" burdens="" of="" this="" proposed="" rule="" on="" smaller="" mines.="" for="" example,="" no="" equipment="" filtration="" would="" be="" required="" for="" 18="" months,="" and="" during="" that="" time,="" the="" agency="" plans="" to="" provide="" extensive="" compliance="" assistance="" to="" the="" mining="" community.="" msha="" intends="" to="" focus="" its="" efforts="" on="" smaller="" operators="" in="" particular="" to="" provide="" training="" to="" them="" and="" technical="" assistance="" on="" available="" controls.="" the="" agency="" will="" also="" issue="" a="" compliance="" guide,="" and="" continue="" its="" current="" efforts="" to="" disseminate="" educational="" materials="" and="" software.="" comment="" is="" invited="" on="" whether="" compliance="" workshops="" or="" other="" such="" approaches="" would="" be="" valuable.="" (8)="" why="" would="" the="" proposed="" rule="" require="" special="" training="" for="" underground="" miners="" exposed="" to="" diesel="" exhaust?="" and="" why="" does="" the="" proposed="" rule="" not="" address="" medical="" surveillance="" and="" medical="" removal="" protection="" for="" affected="" miners?="" training.="" diesel="" particulate="" exposure="" has="" been="" linked="" to="" a="" number="" of="" serious="" health="" hazards,="" and="" the="" agency's="" risk="" assessment="" indicates="" that="" the="" risks="" should="" be="" reduced="" as="" much="" as="" feasible.="" it="" has="" been="" the="" experience="" of="" the="" mining="" community="" that="" miners="" must="" be="" active="" and="" committed="" partners="" along="" with="" government="" and="" industry="" in="" successfully="" reducing="" these="" risks.="" therefore,="" training="" miners="" as="" to="" workplace="" risks="" is="" a="" key="" component="" of="" mine="" safety="" and="" health="" programs.="" this="" rulemaking="" continues="" this="" approach.="" specifically,="" pursuant="" to="" proposed="" sec.="" 72.510,="" any="" underground="" coal="" miner="" ``who="" can="" reasonably="" be="" expected="" to="" be="" [[page="" 17499]]="" exposed="" to="" diesel="" emissions''="" would="" have="" to="" receive="" instruction="" in:="" (a)="" the="" health="" risks="" associated="" with="" dpm="" exposure;="" (b)="" in="" the="" methods="" used="" in="" the="" mine="" to="" control="" diesel="" particulate="" concentrations;="" (c)="" in="" identification="" of="" the="" personnel="" responsible="" for="" maintaining="" those="" controls;="" and="" (d)="" in="" actions="" miners="" must="" take="" to="" ensure="" the="" controls="" operate="" as="" intended.="" the="" training="" is="" to="" be="" provided="" annually="" in="" all="" mines="" using="" diesel-powered="" equipment,="" and="" is="" to="" be="" provided="" without="" charge="" to="" the="" miner.="" msha="" does="" not="" expect="" this="" training="" to="" be="" a="" significant="" new="" burden="" for="" mine="" operators.="" the="" training="" required="" can="" be="" provided="" at="" minimal="" cost="" and="" with="" minimal="" disruption.="" the="" proposal="" would="" not="" require="" any="" special="" qualifications="" for="" instructors,="" nor="" would="" it="" specify="" the="" minimum="" hours="" of="" instruction.="" the="" purpose="" of="" the="" proposed="" requirement="" is="" miner="" awareness,="" and="" msha="" believes="" this="" can="" be="" accomplished="" by="" operators="" in="" a="" variety="" of="" ways.="" in="" mines="" that="" have="" regular="" safety="" meetings="" before="" the="" shift="" begins,="" devoting="" one="" of="" those="" meetings="" to="" the="" topic="" of="" diesel="" particulate="" would="" probably="" be="" a="" very="" easy="" way="" to="" convey="" the="" necessary="" information.="" mines="" not="" having="" such="" a="" regular="" meeting="" can="" schedule="" a="" ``toolbox''="" talk="" for="" this="" purpose.="" msha="" will="" be="" developing="" an="" outline="" of="" educational="" material="" that="" can="" be="" used="" in="" these="" settings.="" simply="" providing="" miners="" with="" a="" copy="" of="" msha's="" toolbox,="" and="" reviewing="" how="" to="" use="" it,="" can="" cover="" several="" of="" the="" training="" requirements.="" operators="" may="" choose="" to="" include="" required="" dpm="" training="" under="" part="" 48="" training="" as="" an="" additional="" topic.="" part="" 48="" training="" plans,="" however,="" must="" be="" approved.="" there="" is="" no="" existing="" requirement="" that="" part="" 48="" training="" include="" a="" discussion="" of="" the="" hazards="" and="" control="" of="" diesel="" emissions.="" while="" mine="" operators="" are="" free="" to="" cover="" additional="" topics="" during="" the="" part="" 48="" training="" sessions,="" the="" topics="" that="" must="" be="" covered="" during="" the="" required="" time="" frame="" may="" make="" it="" impracticable="" to="" cover="" other="" matters="" within="" the="" prescribed="" time="" limits.="" where="" the="" time="" is="" available="" in="" mines="" using="" diesel-powered="" equipment,="" operators="" should="" be="" free="" to="" include="" the="" dpm="" instruction="" in="" their="" proposed="" part="" 48="" training="" plans.="" the="" agency="" does="" not="" believe="" special="" language="" in="" the="" proposed="" rule="" is="" needed="" to="" permit="" this="" action="" under="" part="" 48,="" but="" welcomes="" comment="" in="" this="" regard.="" the="" proposal="" would="" not="" require="" the="" mine="" operator="" to="" separately="" certify="" the="" completion="" of="" the="" diesel="" particulate="" training,="" but="" some="" evidence="" that="" the="" training="" took="" place="" would="" have="" to="" be="" produced="" upon="" request.="" a="" serial="" log="" with="" the="" employee's="" signature="" is="" a="" perfectly="" acceptable="" practice="" in="" this="" regard.="" medical="" surveillance="" another="" important="" source="" of="" information="" that="" miners="" and="" operators="" can="" use="" to="" protect="" health="" can="" come="" from="" medical="" surveillance="" programs.="" such="" programs="" provide="" for="" medical="" evaluations="" or="" tests="" of="" miners="" exposed="" to="" particularly="" hazardous="" substances,="" at="" the="" operator's="" expense,="" so="" that="" a="" miner="" exhibiting="" symptoms="" or="" adverse="" test="" results="" can="" receive="" timely="" medical="" attention,="" ensure="" that="" personal="" exposure="" is="" reduced="" as="" appropriate="" and="" controls="" are="" reevaluated.="" sometimes,="" to="" ensure="" that="" this="" source="" of="" information="" is="" effective,="" medical="" removal="" (transfer)="" protection="" must="" also="" be="" required.="" medical="" transfer="" may="" address="" protection="" of="" a="" miner's="" employment,="" a="" miner's="" pay="" retention,="" a="" miner's="" compensation,="" and="" a="" miner's="" right="" to="" opt="" for="" medical="" removal.="" as="" a="" general="" rule,="" medical="" surveillance="" programs="" have="" been="" considered="" appropriate="" when="" the="" exposures="" are="" to="" potential="" carcinogens.="" msha="" has="" in="" fact="" been="" considering="" a="" generic="" requirement="" for="" medical="" surveillance="" as="" part="" of="" its="" air="" quality="" standards="" rulemaking.="" and="" msha="" recently="" proposed="" a="" medical="" surveillance="" program="" for="" hearing,="" as="" part="" of="" the="" agency's="" proposed="" rule="" on="" noise="" exposure.="" (61="" fr="" 66348).="" msha="" is="" not="" proposing="" such="" a="" program="" for="" dpm="" at="" this="" time="" because="" it="" is="" still="" gathering="" information="" on="" this="" issue.="" the="" agency,="" however,="" welcomes="" comments="" regarding="" this="" issue="" and="" also,="" on="" medical="" removal.="" specifically,="" the="" agency="" would="" welcome="" comment="" on="" the="" following="" questions:="" (a)="" what="" kinds="" of="" examinations="" or="" tests="" would="" be="" appropriate="" to="" detect="" whether="" miners="" are="" suffering="" ill="" effects="" as="" a="" result="" of="" dpm="" exposure;="" (b)="" the="" qualifications="" of="" those="" who="" would="" have="" to="" perform="" such="" examinations="" or="" tests="" and="" their="" availability;="" (c)="" whether="" such="" examinations="" or="" tests="" need="" to="" be="" provided="" and="" how="" frequently="" once="" the="" provisions="" of="" the="" rule="" are="" in="" effect;="" and="" (d)="" whether="" medical="" removal="" protections="" should="" be="" a="" component="" of="" a="" medical="" surveillance="" program.="" (9)="" what="" are="" the="" major="" issues="" on="" which="" msha="" wants="" comments?="" msha="" wants="" the="" benefit="" of="" your="" experience="" and="" expertise:="" whether="" as="" a="" miner="" or="" mine="" operator="" in="" any="" mining="" sector;="" a="" manufacturer="" of="" diesel-powered="" engines,="" equipment,="" or="" emission="" control="" devices;="" or="" as="" a="" scientist,="" doctor,="" engineer,="" or="" safety="" and="" health="" professional.="" msha="" intends="" to="" review="" and="" consider="" all="" comments="" submitted="" to="" the="" agency.="" the="" following="" list="" reflects="" some="" topics="" on="" which="" the="" agency="" would="" particularly="" like="" information;="" requests="" for="" information="" on="" other="" topics="" can="" be="" found="" throughout="" the="" preamble.="" (a)="" assessment="" of="" risk/benefits="" of="" the="" rule.="" part="" iii="" of="" this="" preamble="" reviews="" information="" that="" the="" agency="" has="" been="" able="" to="" obtain="" to="" date="" on="" the="" risks="" of="" dpm="" exposure="" to="" miners.="" the="" agency="" welcomes="" your="" comments="" on="" the="" significance="" of="" the="" material="" already="" in="" the="" record,="" and="" any="" information="" that="" can="" supplement="" the="" record.="" for="" example,="" additional="" information="" on="" existing="" and="" projected="" exposures="" to="" dpm="" and="" to="" other="" fine="" particulates="" in="" various="" mining="" environments="" would="" be="" useful="" in="" getting="" a="" more="" complete="" picture="" of="" the="" situation="" in="" various="" parts="" of="" the="" mining="" industry.="" additional="" information="" on="" the="" health="" risks="" associated="" with="" exposure="" to="" dpm--especially="" observations="" by="" trained="" observers="" or="" studies="" of="" acute="" or="" chronic="" effects="" of="" exposure="" to="" known="" levels="" of="" dpm="" or="" fine="" particles="" in="" general,="" information="" about="" pre-="" existing="" health="" conditions="" in="" individual="" miners="" or="" miners="" as="" a="" group="" that="" might="" affect="" their="" reactions="" to="" exposures="" to="" dpm="" or="" other="" fine="" particles,="" and="" information="" about="" how="" dpm="" affects="" human="" health--would="" help="" provide="" a="" more="" complete="" picture="" of="" the="" relationship="" between="" current="" exposures="" and="" the="" risk="" of="" health="" outcomes.="" information="" on="" the="" costs="" to="" miners,="" their="" families="" and="" their="" employers="" of="" the="" various="" health="" problems="" linked="" to="" dpm="" exposure,="" and="" the="" prevalence="" thereof,="" would="" help="" provide="" a="" more="" complete="" picture="" of="" the="" benefits="" to="" be="" expected="" from="" reducing="" exposure.="" and="" as="" discussed="" in="" response="" to="" question="" and="" answer="" 5,="" the="" agency="" would="" welcome="" advice="" about="" the="" assumptions="" and="" approach="" to="" use="" in="" quantifying="" the="" benefits="" to="" be="" derived="" from="" this="" rule.="" (b)="" proposed="" rule.="" part="" iv="" of="" this="" preamble="" reviews="" each="" provision="" of="" the="" proposed="" rule,="" part="" v="" discusses="" the="" economic="" and="" technological="" feasibility="" of="" the="" proposed="" rule,="" and="" part="" vi="" reviews="" the="" projected="" impacts="" of="" the="" proposed="" rule.="" the="" agency="" would="" welcome="" comments="" on="" each="" of="" these="" topics.="" the="" agency="" would="" like="" your="" thoughts="" on="" the="" specific="" alternative="" approaches="" discussed="" in="" part="" v.="" the="" options="" discussed="" include:="" establishing="" a="" concentration="" limit="" for="" dpm="" in="" this="" sector;="" requiring="" filters="" on="" some="" light-duty="" equipment;="" and="" looking="" at="" the="" filter="" [[page="" 17500]]="" and="" the="" engine="" as="" a="" package="" that="" has="" to="" meet="" a="" particular="" emission="" standard,="" instead="" of="" requiring="" that="" all="" engines="" be="" equipped="" with="" a="" high-efficiency="" filter.="" the="" agency="" would="" also="" like="" your="" thoughts="" on="" more="" specific="" changes="" to="" the="" proposed="" rule="" that="" should="" be="" considered.="" the="" agency="" is="" also="" interested="" in="" obtaining="" as="" many="" examples="" as="" possible="" as="" to="" the="" specific="" situation="" in="" individual="" mines:="" the="" composition="" of="" the="" diesel="" fleet,="" what="" controls="" cannot="" be="" utilized="" due="" to="" special="" conditions,="" and="" any="" studies="" of="" alternative="" controls="" using="" the="" computer="" spreadsheet="" described="" in="" the="" appendix="" to="" part="" v="" of="" this="" preamble.="" (see="" adequacy="" of="" protection="" and="" the="" feasibility="" of="" the="" proposed="" rule).="" information="" about="" the="" availability="" and="" costs="" of="" various="" control="" technologies="" that="" are="" being="" developed="" (e.g.,="" high-efficiency="" ceramic="" filters),="" experience="" with="" the="" use="" of="" available="" controls,="" and="" information="" that="" will="" help="" the="" agency="" evaluate="" alternative="" approaches="" for="" underground="" coal="" mines="" would="" be="" most="" welcome.="" and="" the="" agency="" would="" appreciate="" information="" about="" any="" unusual="" situations="" that="" might="" warrant="" the="" application="" of="" special="" provisions.="" (c)="" compliance="" guidance.="" the="" agency="" welcomes="" comments="" on="" any="" topics="" on="" which="" initial="" guidance="" ought="" to="" be="" provided="" as="" well="" as="" any="" alternative="" practices="" which="" msha="" should="" accept="" for="" compliance="" before="" various="" provisions="" of="" the="" rule="" go="" into="" effect.="" (d)="" minimizing="" adverse="" impact="" of="" the="" proposed="" rule.="" the="" agency="" has="" set="" forth="" its="" assumptions="" about="" impacts="" (e.g.,="" costs,="" paperwork,="" and="" impact="" on="" smaller="" mines="" in="" particular)="" in="" some="" detail="" in="" this="" preamble="" and="" in="" the="" prea,="" and="" would="" welcome="" comments="" on="" the="" methodology.="" information="" on="" current="" operator="" equipment="" replacement="" planning="" cycles,="" tax,="" state="" requirements,="" or="" other="" information="" that="" might="" be="" relevant="" to="" purchasing="" new="" engines="" or="" control="" technology="" would="" likewise="" be="" helpful.="" (10)="" when="" will="" the="" rule="" become="" effective?="" will="" msha="" provide="" adequate="" guidance="" before="" implementing="" the="" rule?="" some="" requirements="" of="" the="" proposed="" rule="" would="" go="" into="" effect="" 60="" days="" after="" the="" date="" of="" promulgation:="" specifically,="" the="" requirement="" to="" provide="" basic="" hazard="" training="" to="" miners="" who="" are="" exposed="" underground="" to="" dpm.="" the="" next="" set="" of="" requirements="" would="" go="" into="" effect="" 18="" months="" after="" the="" date="" the="" rule="" is="" promulgated.="" underground="" coal="" mines="" would="" have="" to="" properly="" filter="" permissible="" diesel-powered="" equipment.="" a="" year="" later="" (30="" months="" after="" the="" date="" of="" promulgation),="" underground="" coal="" mines="" would="" have="" to="" properly="" filter="" heavy-duty="" nonpermissible="" equipment.="" msha="" intends="" to="" provide="" considerable="" technical="" assistance="" and="" guidance="" to="" the="" mining="" community="" before="" the="" various="" requirements="" go="" into="" effect,="" and="" be="" sure="" msha="" personnel="" are="" fully="" trained="" in="" the="" requirements="" of="" the="" rule.="" a="" number="" of="" actions="" have="" already="" been="" taken="" toward="" this="" end.="" the="" agency="" held="" workshops="" on="" this="" topic="" in="" 1995="" which="" provided="" the="" mining="" community="" an="" opportunity="" to="" share="" advice="" on="" how="" to="" control="" dpm="" concentrations.="" the="" agency="" has="" published="" a="" ``toolbox''="" of="" methods="" available="" to="" mining="" operators="" to="" achieve="" reductions="" in="" dpm="" concentration="" (a="" copy="" is="" attached="" as="" an="" appendix="" at="" the="" end="" of="" this="" document).="" the="" ``toolbox''="" provides="" information="" on="" filter="" technology="" as="" well="" as="" on="" other="" actions="" mine="" operators="" can="" take="" to="" address="" dpm="" concentrations="" in="" their="" mines.="" the="" agency="" is="" committed="" to="" issuing="" a="" compliance="" guide="" for="" mine="" operators="" providing="" additional="" advice="" on="" implementing="" the="" rule.="" msha="" would="" welcome="" suggestions="" on="" matters="" that="" should="" be="" discussed="" in="" such="" a="" guide.="" msha="" would="" also="" welcome="" comments="" on="" other="" actions="" it="" could="" take="" to="" facilitate="" implementation,="" and="" in="" particular="" whether="" a="" series="" of="" additional="" workshops="" would="" be="" useful.="" (b)="" additional="" information="" about="" the="" proposed="" rule="" for="" underground="" coal="" mines="" (11)="" more="" specifically,="" what="" changes="" does="" the="" proposal="" make="" to="" the="" current="" rules="" on="" the="" use="" of="" diesel-powered="" equipment="" in="" underground="" coal="" mines?="" the="" proposal="" builds="" on="" the="" changes="" to="" part="" 75="" recently="" adopted="" in="" msha's="" final="" rule="" ``approval,="" exhaust="" gas="" monitoring,="" and="" safety="" requirements="" for="" the="" use="" of="" diesel-powered="" equipment="" in="" underground="" coal="" mines.''="" (61="" fr="" 55412).="" as="" a="" result="" of="" these="" changes,="" grounded="" in="" safety="" considerations,="" underground="" coal="" mines="" must="" already="" comply="" with="" certain="" rules="" that="" have="" the="" added="" benefit="" of="" reducing="" harmful="" dpm="" emissions="" from="" diesel-powered="" equipment.="" these="" include="" a="" requirement="" that="" only="" low-sulfur="" diesel="" fuel="" be="" used="" underground,="" restrictions="" on="" the="" idling="" of="" diesel-powered="" equipment,="" ensuring="" that="" maintenance="" of="" diesel-powered="" equipment="" is="" performed="" only="" by="" qualified="" personnel,="" weekly="" tailpipe="" tests="" to="" ensure="" the="" engines="" are="" operating="" in="" approved="" condition,="" and="" the="" requirement="" that="" the="" entire="" diesel="" fleet="" have="" approved="" engines="" before="" the="" year="" 2000.="" the="" proposed="" rule="" would="" require="" that="" all="" permissible="" and="" heavy-duty="" nonpermissible="" diesel-powered="" equipment="" be="" equipped="" with="" a="" filtration="" system="" that="" is="" capable="" of="" removing,="" on="" average,="" at="" least="" 95%="" by="" mass="" of="" the="" particulate="" emissions="" coming="" out="" of="" that="" equipment.="" these="" filtration="" systems="" must="" be="" properly="" maintained="" in="" accordance="" with="" manufacturer="" specifications="" (e.g.,="" changing="" paper="" filters="" at="" the="" proper="" interval).="" the="" permissible="" equipment="" must="" be="" so="" equipped="" within="" 18="" months="" after="" the="" rule="" becomes="" final,="" and="" the="" heavy-duty="" nonpermissible="" equipment="" a="" year="" later.="" the="" mine's="" ventilation="" and="" dust="" control="" plan="" must="" contain="" a="" list="" of="" the="" diesel-powered="" equipment="" used="" in="" the="" mine="" and="" the="" filtration="" system="" installed="" on="" each.="" and="" finally,="" to="" ensure="" they="" can="" better="" contribute="" to="" dpm="" reduction="" efforts,="" underground="" coal="" miners="" who="" can="" reasonably="" be="" expected="" to="" be="" exposed="" to="" diesel="" emissions="" must="" be="" annually="" trained="" about="" the="" hazards="" associated="" with="" that="" exposure="" and="" in="" the="" controls="" being="" used="" by="" the="" operator="" to="" reduce="" dpm="" concentrations.="" the="" proposed="" rule="" would="" not="" require="" the="" filtration="" of="" light-duty="" outby="" diesel="" equipment.="" it="" would="" not="" establish="" a="" concentration="" limit="" for="" dpm="" in="" underground="" coal="" mines.="" and="" it="" would="" not="" require="" monitoring="" of="" dpm="" concentrations="" by="" either="" operators="" or="" msha="" in="" this="" sector.="" enforcement="" of="" the="" proposed="" requirements="" would="" be="" through="" observation="" by="" msha="" inspectors="" who="" are="" at="" the="" mine="" on="" a="" regular="" basis.="" msha's="" decision="" to="" propose="" this="" approach="" for="" underground="" coal="" mines="" was="" driven="" by="" two="" interrelated="" considerations.="" first,="" the="" agency="" is="" not="" confident="" that="" there="" is="" a="" measurement="" method="" for="" dpm="" that="" will="" provide="" accurate,="" consistent="" and="" verifiable="" results="" at="" lower="" concentration="" levels="" in="" underground="" coal="" mines.="" the="" available="" measurement="" methods="" for="" determining="" dpm="" concentrations="" in="" underground="" coal="" mines="" were="" carefully="" evaluated="" by="" the="" agency,="" including="" field="" testing,="" before="" the="" agency="" reached="" this="" conclusion.="" the="" problems="" are="" discussed="" in="" detail="" in="" part="" ii="" of="" this="" preamble.="" basically,="" coal="" dust="" contains="" compounds="" that="" could="" be="" mistaken="" for="" dpm="" in="" the="" methods="" that="" do="" not="" exclude="" organic="" materials.="" a="" size="" selective="" impactor="" minimizes="" this="" problem="" by="" screening="" out="" most="" of="" the="" coal="" dust="" before="" it="" can="" reach="" the="" filter="" medium,="" but="" doesn't="" eliminate="" it.="" measuring="" only="" the="" elemental="" carbon="" in="" a="" sample="" does="" provide="" a="" way="" to="" distinguish="" dpm="" from="" coal="" dust,="" but="" there="" remain="" questions="" about="" whether="" a="" [[page="" 17501]]="" measured="" amount="" of="" elemental="" carbon="" can="" be="" equated="" to="" a="" prescribed="" amount="" of="" whole="" diesel="" particulate="" under="" the="" variable="" engine="" conditions="" found="" in="" actual="" mining="" environments.="" the="" agency="" is="" continuing="" to="" explore="" questions="" about="" the="" measurement="" of="" dpm="" in="" underground="" coal="" mines="" in="" consultation="" with="" niosh,="" and="" welcomes="" comment="" on="" this="" issue.="" if="" at="" some="" future="" time="" it="" can="" be="" established="" that="" a="" particular="" measurable="" component="" of="" dpm="" is="" responsible="" for="" the="" adverse="" health="" effects="" observed="" (e.g.,="" the="" elemental="" carbon="" cores),="" the="" agency="" would="" evaluate="" the="" question="" of="" measurement="" in="" that="" light.="" second,="" filtration="" systems="" for="" the="" diesel="" equipment="" used="" in="" this="" sector="" are="" readily="" available,="" and="" if="" properly="" maintained="" can="" provide="" generally="" consistent,="" highly="" effective="" elimination="" of="" dpm="" from="" underground="" mine="" atmospheres.="" msha's="" analysis="" of="" dpm="" emissions="" in="" underground="" coal="" mines="" indicates="" that="" it="" is="" currently="" the="" permissible="" equipment="" used="" for="" face="" haulage="" that="" contributes="" most="" to="" high="" dpm="" levels,="" but="" heavy-duty="" outby="" equipment="" can="" also="" generate="" significant="" dpm="" emissions.="" on="" the="" permissible="" equipment,="" paper="" type="" filtration="" systems="" can="" be="" installed="" directly="" on="" the="" tailpipes;="" accordingly,="" the="" rule="" would="" require="" these="" filters="" to="" be="" installed="" within="" 18="" months.="" in="" the="" case="" of="" outby="" equipment,="" scrubbers="" and="" cooling="" system="" upgrades="" will="" need="" to="" be="" added="" to="" cool="" the="" exhaust="" before="" the="" paper="" type="" filters="" can="" be="" installed,="" or="" a="" dry="" technology="" system="" would="" need="" to="" be="" utilized.="" the="" agency="" is="" seeking="" information="" as="" to="" whether="" ceramic="" filters="" might="" achieve="" the="" required="" efficiency="" once="" a="" market="" develops;="" but="" at="" this="" time,="" the="" proposal="" would="" provide="" an="" additional="" year="" for="" the="" nonpermissible="" equipment="" to="" be="" converted="" and="" fitted="" with="" high="" efficiency="" filtration="" systems.="" the="" proposed="" rule="" specifies="" a="" laboratory="" method="" that="" equipment="" manufacturers="" can="" use="" to="" determine="" whether="" a="" particular="" filtration="" system="" meets="" the="" requirement="" that="" the="" system="" be="" at="" least="" 95%="" effective="" in="" removing="" dpm.="" (12)="" why="" not="" consider="" a="" more="" flexible="" approach="" under="" which="" the="" filter,="" the="" engine,="" and="" the="" available="" ventilation="" is="" viewed="" as="" a="" single="" system="" that="" has="" to="" meet="" a="" defined="" emission="" limit?="" msha="" has="" considered="" some="" approaches="" along="" this="" line.="" the="" agency="" welcomes="" comment="" on="" such="" ideas="" so="" it="" can="" better="" evaluate="" whether="" they="" provide="" more="" protection="" to="" underground="" coal="" miners.="" alternative="" 1="" would="" in="" essence="" provide="" some="" credit="" in="" filter="" selection="" to="" those="" operators="" who="" use="" less="" polluting="" engines.="" under="" this="" approach,="" the="" engine="" and="" aftertreatment="" filter="" would="" be="" bench="" tested="" as="" a="" unit;="" and="" if="" the="" emissions="" from="" the="" unit="" are="" below="" a="" certain="" level="" per="" defined="" volume="" of="" air="" (e.g.,="">DPM g/
m3), the package would be acceptable without regard to the
efficiency of just the filter component. Alternative 2 would also
provide credit in filter selection for extra ventilation used in an
underground coal mine. If the bench test of the combined engine and
filter package was conducted at the name plate ventilation, a mine's
use of more than that level of ventilation would be factored into the
calculation of what package would be acceptable.
One practical effect of these alternatives would be to permit some
operators to save the costs of installing heat exchangers or other
exhaust-cooling devices on nonpermissible heavy-duty equipment. Such
devices are necessary in order for this equipment to be fitted with
paper filters--and as noted in response to the previous question, at
the moment these are the only filters on the market capable of
providing 95% and more filtration capability.
The appropriateness of Alternative 1 is not clear. With the proper
equipment to cool the exhaust, a 95% paper filter can be installed on
any piece of heavy-duty equipment in coal mines--and of course directly
on any permissible piece of equipment. And, as indicated herein, the
Agency is tentatively concluding that such an approach is economically
feasible as well. Installing a 95% efficient filter on an engine lowers
the dpm concentration in the mine more than would installing a less
efficient filter. Hence for engines whose emissions can, with a 95%
filter, be reduced below 120DPM g/m3 or
whatever other dpm limit is set under such an approach, the alternative
approach may result in less miner protection.
Moreover, it is not clear to MSHA that 95% filtration of the
engines used on the majority of permissible machines in underground
coal mines can meet an emissions limit of 120DPM g/
m3 using MSHA's name plate ventilation. These engines are of
older design and produce higher concentrations of diesel particulate.
Thus adopting a rule with such an emissions limit would in effect
require these engines to be replaced with cleaner engines. Of course,
it follows that such a rule would be more costly than the one proposed,
because it would require the 95% filters plus the replacement of these
engines.
The second alternative appears to be less protective in all cases.
To provide mines who need extra ventilation for other reasons (e.g., to
keep methane in check) with a credit for this fact in determining the
required filter efficiency would not reduce dpm concentrations as much
as simply requiring a 95% filter.
The Agency welcomes comments on these approaches and information
that will help it assess them in light of the requirements of the Mine
Act.
II. Background Information
This part provides the context for this rulemaking. The nine topics
covered are:
(1) The role of diesel-powered equipment in mining;
(2) Diesel exhaust and diesel particulate;
(3) Methods available to measure DPM;
(4) Reducing soot at the source--engine standards;
(5) Limiting the public's exposure to soot -- ambient air quality
standards;
(6) Controlling diesel particulate emissions in mining--a toolbox;
(7) Existing mining standards that limit miner exposure to
occupational diesel particulate emissions;
(8) How other jurisdictions are restricting occupational exposure
to diesel soot; and
(9) MSHA's initiative to limit miner exposure to diesel
particulates--the history of this rulemaking and related actions.
In addition, an Appendix at the end of this document reprints a
recent MSHA publication, ``Practical Ways to Reduce Exposure to Diesel
Exhaust in Mining--A Toolbox'', which contains considerable information
of interest in this rulemaking.
These topics will be of interest to the entire mining community,
even though this rulemaking is specifically confined to the underground
coal sector.
(1) The Role of Diesel-Powered Equipment in Mining. Diesel engines
now power a full range of mining equipment on the surface and
underground, in both coal and in metal/nonmetal mining. Many in the
mining industry believe that diesel-powered equipment has a number of
productivity and safety advantages over electrically-powered equipment.
Nevertheless, concern about miner safety and health has slowed the
spread of this technology, and in certain states resulted in a complete
ban on its use in underground coal mines. As the industry has moved to
realize the advantages this equipment may provide, the Agency has
endeavored to address
[[Page 17502]]
the miner safety and health issues presented.
Historical Patterns of Use
The diesel engine was developed in 1892 by the German engineer
Rudolph Diesel. It was originally intended to burn coal dust with high
thermodynamic efficiency. Later, the diesel engine was modified to burn
middle distillate petroleum (diesel fuel). In diesel engines, liquid
fuel droplets are injected into a prechamber or directly into the
cylinder of the engine. Due to compression of air in the cylinder the
temperature rises high enough in the cylinder to ignite the fuel.
The first diesel engines were not suited for many tasks because
they were too large and heavy (weighing 450 lbs. per horsepower). It
was not until the 1920's that the diesel engine became an efficient
lightweight power unit. Since diesel engines were built ruggedly and
had few operational failures, they were used in the military, railway,
farm, construction, trucking, and busing industries. The U.S. mining
industry was slow, however, to begin using these engines. Thus, when in
1935 the former U.S. Bureau of Mines published a comprehensive overview
on metal mine ventilation (McElroy, 1935), it did not even mention
ventilation requirements for diesel-powered equipment. By contrast, the
European mining community began using these engines in significant
numbers, and various reports on the subject were published during the
1930's. According to a 1936 summary of these reports (Rice, 1936), the
diesel engine had been introduced into German mines by 1927. By 1936,
diesel engines were used extensively in coal mines in Germany, France,
Belgium and Great Britain. Diesel engines were also used in potash,
iron and other mines in Europe. Their primary use was in locomotives
for hauling material.
It was not until 1939 that the first diesel engine was used in the
United States mining industry, when a diesel haulage truck was used in
a limestone mine in Pennsylvania, and not until 1946 was a diesel
engine used in coal mines. Today, however, diesel engines are used to
power a wide variety of equipment in all sectors of U.S. mining, such
as: air compressor; ambulance; crane truck; ditch digger; foam machine;
forklift; generator; grader; haul truck; load-haul-dump machine;
longwall retriever; locomotive; lube unit; mine sealant machine;
personnel car; hydraulic pump machine; rock dusting machine; roof/floor
drill; shuttle car; tractor; utility truck; water spray unit and
welder.
Estimates of Current Use
Estimates of the current inventory of diesel engines in the mining
industry are displayed in Table II-1. Not all of these engines are in
actual use. Some may be retained rather than junked, and others are
spares. MSHA has been careful to take this into account in developing
cost estimates for this proposed rule; its assumptions in this regard
are detailed in the Agency's PREA.
Table II-1.--Diesel Equipment in Three Mining Sectors
------------------------------------------------------------------------
No.
Mine type No. Mines w/ No.
Mines Diesel Engines
----------------------------------------------\2\-----------------------
Underground Coal......................... 971 \3\ 173 \4\ 2,950
\1\ Small............................ 426 15 50
Large................................ 545 158 2,900
Underground M/NM......................... 261 \5\ 203 \6\ 4,100
\1\ Small............................ 130 82 625
Large................................ 131 121 3,475
Surface Coal............................. 1,673 \7\ 1,67
3 \8\ 22,00
0
\1\ Small............................ 1,175 1,175 7,000
Large................................ 498 498 15,000
Surface M/NM............................. 10,474 \9\ 10,4
74 \10\ 97,0
00
------------------------------------------------------------------------
Notes on Table II-1:
\1\ A mine with less than 20 miners. MSHA traditionally regards mines
with less than 20 miners as ``small'' mines, and those with 20 or more
miners as ``large'' mines based on differences in operation. However,
in examining the impact of the proposed regulations on the mining
community, MSHA, consistent with the Small Business Administration
definition for small mines, which refers to employers with 500
employees or less, has analyzed impact for this size. This is
discussed in the Agency's preliminary regulatory economic analysis for
this proposed rule.
\2\ Preliminary 1996 MSHA data.
\3\ Data from MSHA approval and certification center, Oct.95.
\4\ Actual inventory, rounded to nearest 50.
\5\ Estimates are based on a January 1998 count, by MSHA inspectors, of
underground mines that use diesel powered equipment.
\6\ The estimates are based on a January 1998 count, by MSHA inspectors,
of diesel powered equipment normally in use.
\7\ Based on assumption that all surface coal mines had some diesel
powered equipment.
\8\ Based on MSHA survey of 25% of surface coal mines.
\9\ MSHA assumes all surface M/NM mines use some diesel engines.
\10\ Derived by applying ratios (engines per mine) from MSHA survey of
surface coal mines to M/NM mines.
As noted in Table II-1, nearly all underground metal and nonmetal
mines, and all surface mines, use diesel-powered equipment. This is not
true in underground coal mines--in no small measure because, as
discussed later in this part, several key underground coal states have
for many years banned the use of diesel-powered equipment in such
mines.
Neither the diesel engines nor the diesel-powered equipment are
identical from sector to sector. This relates to the equipment needs in
each sector. This is important information because the type of engine,
and the type of equipment in which it is installed, can have important
consequences for particulate production and control.
As the horsepower size of the engine increases, the mass of dpm
emissions produced per hour increases. (A smaller engine may produce
the same or higher levels of particulate emissions per volume of
exhaust as a large engine, due to the airflow, but the mass of
particulate matter increases with the engine size.) Accordingly, as
engine size increases, control of emissions may require additional
efforts.
Diesel engines in underground metal and nonmetal mines, and in
surface coal mines, range up to 750 HP or greater; by contrast, in
underground coal mines, the average engine size is less than 150 HP.
The reason for this disparity is the nature of the equipment powered by
diesel engines. In underground metal and nonmetal mines, and surface
mines, diesel engines are widely used in all types of equipment--both
the equipment used under the heavy stresses of production and the
equipment used for support. By contrast, the great majority of the
diesel usage in underground coal mines is in support equipment. For
example, in underground metal and nonmetal mines, of the approximate
4,100 pieces of diesel equipment normally in use, about 1,800 units are
for loading and hauling. By contrast, of the approximate 3,000 pieces
of diesel equipment in underground coal, MSHA estimates that less than
50 pieces are for coal haulage. The largest diesel engines are used in
surface operations; in underground metal and nonmetal mines, the size
of the engine can be limited by the size of the shaft opening.
The type of equipment in the sectors also varies in another way
that can affect particulate control directly, as well as constrain
engine size. In underground coal, equipment that is used in face
(production) areas of the coal mine must be MSHA-approved part 36
permissible equipment. These locations are the areas where methane gas
is likely to accumulate in higher concentrations. This includes the in-
by section starting at the tailpiece (coal dump point) and all returns.
Part 36 permissible equipment for coal requires the use of flame
arresters on the intake and exhaust systems and surface temperature
control to below 302 deg.F. As
[[Page 17503]]
discussed in more detail elsewhere in this notice, the cooler exhaust
from these permissible pieces of equipment permits the direct
installation of particulate filtration devices such as paper type
filters that cannot be used directly on engines with hot exhaust. In
addition, the permissibility requirements have had the effect of
limiting engine size. This is because prior to MSHA's issuance of a
diesel equipment rule in 1996, surface temperature control was done by
water jacketing. This limited the horsepower range of the permissible
engines because manufacturers have not expended resources to develop
systems that could meet the 302 deg.F surface temperature limitation
using a water jacketed turbocharger.
In the future, larger engines may be used on permissible equipment,
because the new diesel rule allows the use of new technologies in lieu
of water jacketing. This new technology, plus the introduction of air-
charged aftercoolers on diesel engines, may lead to the application of
larger size diesel engines for underground coal production units.
Moreover, if manufacturers choose to develop this type of technology
for underground coal production units, the number of diesel production
machines may increase.
There are also a few underground metal and nonmetal mines that are
gassy, and these require the use of part 36 permissible equipment.
Permissible equipment in metal and nonmetal mines must be able to
control surface temperatures to 400 deg. F. MSHA estimates that there
are currently less than 15 metal and nonmetal mines classified as gassy
and which, therefore, must use part 36 permissible equipment if diesels
are utilized in areas where permissible equipment is required. These
gassy metal and nonmetal mines have been using the same permissible
engines and power packages as those approved for underground coal
mines. (MSHA has not certified a diesel engine exclusively for a part
36 permissible machine for the metal and nonmetal sector since 1985 and
has certified only one permissible power package; however, that engine
model has been retired and is no longer available as a new purchase to
the industry). As a result, these mines are in a similar situation as
underground coal mines: engine size (and thus dpm production of each
engine) is more limited, and the exhaust is cool enough to add the
paper type of filtration device directly to the equipment.
In nongassy underground metal and nonmetal mines, and in all
surface mines, mine operators can use conventional construction
equipment in their production sections without the need for
modifications to the machines. Two examples are haulage vehicles and
dump trucks. Some construction vehicles may be redesigned and
articulated for sharper turns in underground mines; however, the
engines are still the industrial type construction engines. As a
result, these mines can and do use engines with larger horsepower. At
the same time, since the exhaust is not cooled, paper-type filters
cannot be added directly to this equipment without first adding a water
scrubber, heat exchanger or other cooling device. The same is true for
the equipment used in outby areas of coal mines, where the methane
levels do not require the use of permissible equipment.
Future Demand and Emissions
MSHA expects there will be more diesel-powered equipment added to
the Nation's mines. While other types of power sources for mining
equipment are available, many in the mining industry believe that
diesel power provides both safety and economic advantages over
alternative power sources available today. Not many studies have been
done recently on these contentions, and the studies which have been
reviewed by MSHA do not clearly support this hypothesis; but as long as
this view remains prevalent, continued growth is likely.
There are additional factors that could increase growth. As noted
above, permissible equipment can now be designed in such a way to
permit the use of larger engines, and in turn more use of diesel-
powered production equipment in underground coal and other gassy mines.
Moreover, state laws banning the use of diesel engines in the
underground coal sector are under attack. As noted in section 8 of this
part, until recently, three major underground coal states,
Pennsylvania, West Virginia, and Ohio, have prohibited the use of
diesel engines in underground coal mines. In late 1996, Pennsylvania
passed legislation (PA Senate Bill No. 1643) permitting such use under
conditions defined in the statute. West Virginia passed legislation
lifting its ban as of May, 1997 (WV House Bill 2890), subject to
regulations to be developed by a joint labor-industry commission. This
makes the need to address safety and health concerns about the use of
such engines very pressing.
In the long term, the mining industry's diesel fleet will become
cleaner, even if the size of the fleet expands. This is because the old
engines will eventually be replaced by new engines that will emit fewer
particulates than they do at present. As discussed in section 4 of this
part, EPA regulations limiting the emissions of particulates and
various gasses from new diesel engines are already being implemented
for some of the smaller engines used in mining. Under a defined
schedule, these new standards will soon apply to other new engines,
including the larger engines used in mining. Moreover, over time, the
emission standards which new engines will have to pass will become more
and more stringent. Under international accords, imported engines are
also likely to be cleaner: European countries have already established
more stringent emission requirements (Needham, 1993; Sauerteig, 1995).
But MSHA believes that turnover of the mining fleet to these new,
cleaner engines will take a very long time because the mining industry
tends to purchase for mining use older equipment that is being
discarded by other industries. In the meantime, the particulate burden
on miners as a group is expected to remain at current levels or even
grow.
(2) Diesel Exhaust and Diesel Particulate. The emissions from
diesel engines are actually a complex mixture of compounds, containing
gaseous and particulate fractions. The specific composition of the
diesel exhaust in a mine will vary with the type of engines being used
and how they are used. Factors such as type of fuel, load cycle, engine
maintenance, tuning, and exhaust treatment will affect the composition
of both the gaseous and particulate fractions of the exhaust. This
complexity is compounded by the multitude of environmental settings in
which diesel-powered equipment is operated. Elevation, for example, is
a factor. Nevertheless, there are a few basic facts about diesel
emissions that are of general applicability.
The gaseous constituents of diesel exhaust include oxides of
carbon, nitrogen and sulfur, alkanes and alkenes (e.g., butadiene),
aldehydes (e.g., formaldehyde), monocyclic aromatics (e.g., benzene,
toluene), and polycyclic aromatic hydrocarbons (e.g., phenanthrene,
fluoranthene). The oxides of nitrogen (NOX) are worth
particular mention because in the atmosphere they can precipitate into
particulate matter. Thus, controlling the emissions of NOX
is one way that engine manufacturers can control particulate production
indirectly. (See section 4 of this part).
The particulate fraction of diesel exhaust--what is known as soot--
is made up of very small individual particles. Each particle consists
of an insoluble, elemental carbon core and an
[[Page 17504]]
adsorbed, surface coating of relatively soluble organic carbon
(hydrocarbon) compounds. There can be up to 1,800 different organic
compounds adsorbed onto the elemental carbon core. A portion of this
hydrocarbon material is the result of incomplete combustion of fuel;
however, the majority is derived from the engine lube oil. In addition,
the diesel particles contain a fraction of non-organic adsorbed
materials.
Diesel particles released to the atmosphere can be in the form of
individual particles or chain aggregates (Vuk, Jones, and Johnson,
1976). In underground coal mines, more than 90% of these particles and
chain aggregates are submicrometer in size--i.e., less than 1
micrometer (1 micron) in diameter. In underground metal and nonmetal
mines, a greater portion of the aggregates may be larger than 1 micron
in size because of the equipment used. Dust generated by mining and
crushing of material--e.g., silica dust, coal dust, rock dust--is
generally not submicrometer in size.
Figure II-1 shows a typical size distribution of the particles
found in the environment of a mine that uses equipment powered by
diesel engines (Cantrell and Rubow, 1992). The vertical axis represents
relative concentration, and the horizontal axis the particle diameter.
As can be seen, the distribution is bimodal, with dpm generally being
well less than 1 m in size and dust generated by the mining process
being well greater than 1 m. Because of their small size, even when
diesel particles are present in large quantities, the environment might
not be perceived as ``dusty''. Rather, the perception might be
primarily of a vaporous, dirty and smelly ``soot'' or ``smoke''.
[GRAPHIC] [TIFF OMITTED] TP09AP98.001
The particulate nature of diesel soot has special significance for
the mining community, which has a history of significant health and
safety problems associated with dusts in the mining atmosphere. As a
result of this long experience, the mining community is familiar with
the standard techniques to control particulate concentrations. It knows
how to use ventilation systems, for example, to reduce dust levels in
underground mines. It knows how to water down particulates capable of
being impacted by that approach, and to divert particulates away from
where miners are actively working. Moreover, the mining community has
long experience in the sampling and measurement of particulates--and in
all the problems associated therewith. Miners and mine operators are
very familiar with sampling devices that are worn by miners during
normal work activities or placed in specific locations to collect dust.
They understand the significance of sample integrity, the validity of
laboratory analysis, and the concept of statistical error in individual
samples. They know that weather and mine conditions can affect
particulate production, as can changes in mine operations in an area of
the mine. MSHA and the former Bureau of Mines have conducted
considerable research into these topics. While the mining community has
often argued over these points, and continues to do so, the
sophistication of the arguments reflects the thorough familiarity of
the mining community with particulate sampling and analysis techniques.
(3) Methods Available to Measure DPM. There are a number of methods
which can measure dpm concentrations with reasonable accuracy when it
is at high concentrations and when the purpose is exposure assessment.
Measurements for the purpose of compliance determinations must be more
accurate, especially if they are to measure compliance with a dpm
concentration as low as 200 g/m3 or lower. It is
with these considerations in mind that MSHA has carefully analyzed
[[Page 17505]]
the available methods for measuring dpm.
Comments. In its advanced notice of proposed rulemaking (ANPRM) in
1992, MSHA sought information on whether there are methodologies
available for assessing occupational exposures to diesel particulate.
Some commenters argued that at that time there was no validated
sampling method for diesel exhaust and there had been no valid
analytical method developed to determine the concentration of diesel
exhaust. According to the American Mining Congress, (AMC 1992),
sampling methods commonly in use were prototypic in nature, were
primarily being utilized by government agencies and were subject to
interference. Commenters also stated that sampling instrumentation was
not commercially available and that the analytical procedures could
only be conducted in a limited number of laboratories. Several industry
commenters submitted results of studies to support their position on
problems with measuring diesel particulate in underground mines. A
problem with sampler performance was noted in a study using prototype
dichotomous sampling devices. Another commenter indicated that the
prototype sampler developed by the former Bureau of Mines (discussed
later in this section) for collecting the submicrometer respirable dust
was difficult to assemble but easy to use, and that no problems were
encountered. Problems associated with gravimetric analysis were also
noted in assessing a short term exposure limit (STEL). Another
commenter (Morton, 1992) indicated the cost of the sampling was
prohibitive.
Another issue addressed by commenters to the 1992 ANPRM was ``Are
existing sampling and exposure monitoring methods sufficiently
sensitive, accurate and reliable?'' If not, what methods would be more
suitable? Some commenters indicated their views that sampling methods
had not been validated at that time for compliance sampling. They
asserted that, depending on the level of measurement, both the size
selective and elemental carbon techniques have some utility. The
measurement devices give a precise measurement; however, because of
interferants, corrections may need to be made to obtain an accurate
measurement. Commenters also expressed the view that all of the
sampling devices are sophisticated and require some expertise to
assemble and analyze the results, and that MSHA should rely on outside
agencies to evaluate and validate the sampling methods. An on-board
sampler being developed by Michigan Technological University was the
only other emission measurement technology discussed in the comments.
However, this device is still in the development stage. Another
commenter indicated that the standard should be based on the hazard and
that the standard would force the development of measurement
technology.
Submicrometer Sampling
The former Bureau of Mines (BOM) submitted information on the
development of a prototype dichotomous impactor sampling device that
separates and collects the submicrometer respirable particulate from
the respirable dust sampled (See Figure II-2).
[GRAPHIC] [TIFF OMITTED] TP09AP98.002
The sampling device was designed to help measure dpm in coal mine
environments, where, as noted in the last section of this part, nearly
all the dpm is submicrometer (less than 1 micron) in size. In its
submission to MSHA, the former BOM noted it had redesigned a prototype
and had verified the sampler's performance through laboratory and field
tests.
As used by the former BOM in its research, the submicrometer
respirable particulate was collected on a pre-weighed filter. Post-
weighing of the filter provides a measure of the submicrometer
respirable particulate. The relative insensitivity of the gravimetric
method only allows for a lower limit of detection of approximately 200
g/m3. Because submicrometer respirable particulate
can contain particulate material other than diesel particulate,
measurements can be subject to interference from other submicrometer
particulate material.
[[Page 17506]]
NIOSH Method 5040
In response to the ANPRM, NIOSH submitted information relative to
the development of a sampling and analytical method to assess the
diesel particulate concentration in an environment by measuring the
amount of total carbon.
As discussed earlier in this part, diesel particulate consists of a
core of elemental carbon (EC), adsorbed organic carbon (OC) compounds,
sulfates, vapor phase hydrocarbons and traces of other compounds. The
method developed by NIOSH provides for the collection of a sample on a
quartz fiber filter. The filter is mounted in an open face filter
holder that allows for the sample to be uniformly deposited on the
filter surface. After sampling, a section of the filter is analyzed
using a thermal-optical technique (Birch and Cary, 1996). This
technique allows the EC and OC species to be separately identified and
quantified. Adding the EC and OC species together provides a measure of
the total carbon concentration in the environment. This is indicated
diagrammatically in Figure II-3.
Studies have shown that the sum of the carbon (C) components (EC +
OC) associated with dpm accounts for 80-85% of the total dpm
concentration when low sulfur fuel is used (Birch and Cary, 1996).
Since the TC:DPM relationship is consistent, it provides a method for
determining the amount of dpm.
The method can detect as little as 1 g/m3 of
TC.
[GRAPHIC] [TIFF OMITTED] TP09AP98.003
Moreover, NIOSH has investigated the method and found it to meet
NIOSH's accuracy criterion (NIOSH, 1995); i.e., that measurements come
within 25 percent of the true TC concentration at least 95 percent of
the time.
NIOSH Method 5040 is directly applicable for the determination of
diesel particulate levels in underground metal and nonmetal mines. The
only potential sources of carbon in such mines would be organic carbon
from oil mist and cigarette smoke. Oil mist may occur when diesel
equipment malfunctions or is in need of maintenance. MSHA, currently,
has no data as to the frequency of occurrence or the magnitude of the
potential interference from oil mist. However, during studies conducted
by MSHA to evaluate different methods used to measure diesel
particulate concentrations in underground mines, MSHA has not
encountered situations where oil mist was found to be an interferant.
Moreover, the Agency assumes that full operator implementation of
maintenance standards to minimize dpm emissions (which are part of
MSHA's proposed rule) will minimize any remaining potential for such
interference. MSHA welcomes comments or data relative to oil mist
interference. Cigarette smoke is under the control of operators, during
sampling times in particular, and hence should not be a consideration.
While samples in underground metal and nonmetal mines could be
taken with a submicrometer impactor, this could lead to underestimating
the total amount of dpm present. This is because the fraction of dpm
particles greater than 1 micron in size in the environment of noncoal
mines can be as great as 20% (Vuk, Jones, and Johnson, 1976).
When sampling diesel particulate in coal mines, the NIOSH method
recommends that a specialized impactor with a submicrometer cut point,
such as the one developed by the former BOM, be used. Use of the
submicron impactor minimizes the collection of coal particles, which
have an organic carbon content. However, if 10% of coal particles are
submicron, this means that up to 200 micrograms of submicrometer coal
dust could be collected in face areas under current coal dust
standards. Accordingly, for samples collected in underground coal
mines, an adjustment may have to be made for interference from
submicrometer coal dust; however, outby areas where little coal mine
dust is present may not need such an adjustment.
NIOSH further recommends that in using its method in coal mines,
the sample only be analyzed for the EC component. Measuring only the EC
component ensures that only diesel particulate material is being
measured in such cases. However, there are no established relationships
between the concentration of EC and total dpm under various operating
conditions. (The organic carbon component of dpm can vary with engine
type and duty cycle; hence, the amount of whole dpm present for a
measured amount of EC may vary). The Agency welcomes data and
suggestions that would help it ascertain if and how measurements of
[[Page 17507]]
submicrometer elemental carbon could realistically be used to measure
dpm concentrations in underground coal mines.
Although NIOSH Method 5040 requires no specialized equipment for
collecting a dpm sample, the sample would most probably require
analysis by a commercial laboratory. MSHA recognizes that the number of
laboratories currently capable of analyzing samples using the thermal-
optical method is limited. However, there are numerous laboratories
available that have the ability to perform a TC analysis without
identifying the different species of carbon in the sample. Total carbon
determinations using these laboratories would provide the mine with
good information relative to the levels of dpm to which miners are
potentially exposed. MSHA believes that once there is a need (e.g., as
a result of the requirements of the proposed rule), more commercial
laboratories will develop the capability to analyze dpm samples using
the thermo-optical analytical method. Currently, the cost to analyze a
submicrometer particulate sample for its TC content ranges from $30 to
$50. This cost is consistent with costs associated with similar
analysis of minerals such as quartz.
RCD Method
Another method, referred to as the Respirable Combustible Dust
Method (RCD), has been developed in Canada for measuring dpm
concentrations in noncoal mines. Respirable dust is collected with a
respirable dust sampler consisting of a 10 millimeter nylon cyclone and
a filter capsule containing a preweighed, preconditioned silver
membrane filter. Samples are collected at a flow rate of 1.7 liter per
minute. The respirable sample collected includes both combustible and
noncombustible particulate matter.
Samples collected in accordance with the RCD method require
analysis by a commercial laboratory. Total respirable dust is
determined gravimetrically by weighing the filter after the sample is
collected. After the sample has been subjected to a controlled
combustion process at 400 deg.C for two hours, the remainder of the
sample is weighed, and the amount of the particulate burned off
determined by subtraction. This is the RCD. The combustible particulate
matter consists of the soluble organic fraction, the EC core of the
dpm, and any other combustible material collected. Thus, only a portion
of the RCD is attributable to dpm. Oil mist and other combustible
matter collected on the filter are interferants that can affect the
accuracy of dpm concentration determination using this method. Because
the mass of RCD is determined by weighing, the relative insensitivity
of this method is similar to that obtained with the size selective
gravimetric method (approximately 200 g/m3).
One commenter (Inco Limited) indicated experience with this method
for identifying diesel particulate in their mining operations and
suggested that this technique may be appropriate for determining eight
hour exposures. Although this method was commonly used by the commenter
for assessing dpm levels, concerns for the efficiency of the cyclones
used to sample the respirable fraction of the particulate along with
interference from oil mist were expressed.
Canada is now experimenting with the use of a submicron impactor
with the RCD method.
Sampler Availability
The components for conducting sampling according to the
submicrometer and the RCD methods are commercially available, as are
those for NIOSH Method 5040, without a submicrometer particulate
separator (impactor).
A reusable impactor can be manufactured by machine shops following
the design specifications developed by the former U.S. Bureau of Mines
(BOM IC 9324, 1992). The use of the size-selective samplers requires
some training and laboratory time to prepare the impaction plate and
assemble the unit. The cost to manufacture the size-selective units is
approximately $35.
In addition, MSHA has requested NIOSH to develop and provide a
commercially available disposable submicrometer particulate separator
that would be used with existing personal respirable dust sampling
equipment. The commercially available separator will be manufactured
according to design criteria specified by NIOSH. It is anticipated that
other sampling instrument manufacturers will develop commercial units
once there is an established need for such a sampling device.
Use of Alternative Surrogates to Assess DPM Concentrations
A number of commenters on the ANPRM indicated that a number of
surrogates were available to monitor diesel particulate. Of the
surrogates suggested, the most desirable to use would be carbon dioxide
because of its ease of measurement. In 1992 the former Bureau of Mines
(BOM IC 9324, 1992) reported on research being conducted to investigate
the use of CO2 as a surrogate to assess mine air quality
where diesel equipment is utilized. However, because the relationship
between CO2 and other exhaust components depends on the
number, type and duty cycle of the engines in operation, no acceptable
measurement method based on the use of CO2 has been
developed.
(4) Reducing Soot at the Source--Engine Standards. One way to limit
diesel particulate emissions is to redesign diesel engines so they
produce fewer pollutants. Engine manufacturers around the world are
being pressed to do this pursuant to environmental regulations. These
cleaner engine requirements are sometimes referred to as tailpipe
standards because compliance is measured by checking for pollutants as
the exhaust emerges from the engine's tailpipe--before any
aftertreatment devices. This section reviews developments in this area,
and explains the relationship between the environmental standards on
new engines and MSHA engine ``approval'' requirements.
The Clean Air Act and Mobile Sources
The Clean Air Act authorized the Federal Environmental Protection
Agency (EPA) to establish nationwide standards for new mobile vehicles,
including those powered by diesel engines. These standards are
designed, over time, to reduce the volume of certain harmful
atmospheric pollutants emanating from mobile sources: particulate
matter, nitrogen oxides (which as previously noted, can result in the
generation of particulates in the atmosphere), hydrocarbons and carbon
monoxide.
California has its own standards. New engines destined for use in
California must meet standards under the law of that State. The
standards are issued and administered by the California Air Resources
Board (CARB). In recent years, EPA and CARB have worked together with
industry in establishing their respective standards, so most of them
are identical.
Regulatory responsibility for implementation of the Clean Air Act
is vested in the Office of Mobile Sources (OMS), part of the Office of
Air and Radiation of the EPA. Some of the discussion which follows was
derived from materials which can be accessed from the OMS home page on
the World Wide Web at (http://www.epa.gov/docs/omswww/omshome.htm).
Information about the CARB standards may be found at the home page of
that agency at (http://www.arbis.arb.ca.gov/homepage.htm).
Engines are generally divided into three broad categories for
purposes of
[[Page 17508]]
environmental emissions standards, in accordance with the primary use
for which the type of engine is designed: (1) cars and light duty
trucks (i.e., to power passenger transport); (2) heavy duty trucks
(i.e., to power over-the-road hauling); and (3) nonroad vehicles (i.e.,
to power small equipment, construction equipment, locomotives and other
non-highway uses). Engines used in mining equipment are not regulated
as a separate category in this regard, but engines in all three
categories are engaged in mining work, from generator sets to pickup
trucks to huge earth movers and haulers.
New vs. Used
The environmental tailpipe requirements are applicable only to new
engines. In the mining industry, used engines are often purchased; and,
of course, the existing fleet consists of engines that are not new.
Thus, although these tailpipe requirements will bring about gradual
reduction in the overall contribution of diesel pollution to the
atmosphere, the beneficial effects on mining atmospheres may require a
longer timeframe, absent actions to accelerate the turnover of mining
fleets to the cleaner engines.
In underground coal mining, MSHA has already taken actions which
will have such an effect on the fleet. The diesel equipment rule issued
in late 1996 requires that by November 25, 1999, all diesel equipment
used in underground coal mines use an approved engine and maintain that
engine in approved condition. (30 CFR 75.1907.) MSHA expects this will
result in the replacement of about 47 percent of the diesel engines now
in the underground coal mine inventory with engines that emit fewer
pollutants. The timeframe permitted for the turnover was based upon
MSHA's estimates of the useful life in an underground mining
environment of the ``outby'' equipment involved.
Technology-Forcing Schedule
As noted above, the exact environmental tailpipe requirements which
a new diesel engine must meet varies with the date of manufacture. The
Clean Air Act, which was most recently amended in 1990, establishes a
schedule for the reduction of particular pollutants from mobile
sources. EPA and CARB, working closely with the diesel engine industry,
have endeavored to turn this into a regulatory schedule that forces
technology while taking into account certain technological realities
(e.g., actions taken to reduce particulate emissions may increase NOx
emissions, and vice versa). Existing EPA regulations for on-highway
engines (both for light duty vehicles and heavy duty trucks) and non-
road engines schedule the tailpipe standards that must be met for the
rest of this century. Agreements between EPA, CARB and the engine
industry are now leading to proposed rules for engine standards to be
met during the early part of the next century. These standards will be
stricter and will lower the levels of diesel emissions.
Light-Duty Engines
The current regulations on light duty vehicle engines (cars and
passenger trucks) were set in 1991. (56 FR 25724). EPA is currently
considering proposing new standards for this category. Pursuant to a
specific requirement in the Clean Air Act Amendments of 1990, EPA is to
study and report to Congress on whether further reductions in this
category should be pursued. A public workshop was held in the Spring of
1997. EPA plans provide for a draft report to be available for public
comment by Spring of 1998, and a final report completed by July 1998,
although a notice of citizen suit has been filed to speed the process.
Up-to-date information about the progress of this initiative can be
found at the home page for the study (http://www.epa.gov/omswww/
tr2home.htm).
On-Highway Heavy Duty Truck Engines
The first phase of the on-highway standards for heavy duty diesel
engines was applicable to engines manufactured in 1985. (40 CFR 86.085-
11.) For the first time, separate standards for NOX and
hydrocarbons were established. The nitrogen oxides and hydrocarbons are
precursors of ground level ozone, a major component of smog. A number
of hydrocarbons are also toxic, while nitrogen oxides contribute to the
formation of acid rain and can, as previously noted, precipitate into
particulate matter. In 1988, a specific standard limiting particulate
matter emitted from the heavy duty on-highway diesel engines went into
effect. (40 CFR 86.088-11). The Clean Air Act Amendments and the
regulations provided for phasing in even tighter controls on
NOX and particulate matter through 1998. Reductions in
NOX took place in 1990 and 1991 and are to occur again in
1998, and reductions in PM took place in 1991 and 1994. Certain types
of trucks in particularly polluted urban areas must reach even tighter
requirements.
On October 21, 1997, EPA issued a new rule for on-highway engines
that will take effect for engine model years starting in 2004. (62 FR
54693.) The rule establishes a combined requirement for NOX
and HC. The combined standard is set at 2.5gm/bhp-hr, which includes a
cap of 0.5gm/bhp-hr for HC. Prior to the rule, the EPA, CARB, and the
engine manufacturers signed a Statement of Principles (SOP) that agreed
on harmonization of the emission standards and the feasible levels that
could be achieved. The rule allows manufacturers a choice of two
combinations of NOX and HC, with a net expected reduction in
NOX emissions of 50%. The rule does not require further
reductions in tailpipe emissions of PM.
Non-road Engines
Of particular interest to the mining community is the EPA's
regulatory work on the standards that will be applicable to non-road
engines, for these include the engines used in the heaviest mining
equipment.
The 1990 Clean Air Act Amendments specifically directed EPA to
study the contribution of nonroad engines to air pollution, and
regulate them if warranted. In 1991, EPA released a study that
documented higher than expected emission levels across a broad spectrum
of nonroad engines and equipment (EPA Fact Sheet, EPA420-F-96-009,
1996). In response, EPA initiated several regulatory programs. One of
these set emission standards for land-based nonroad engines greater
than 50 horsepower (other than for rail use). Limits are established
for tailpipe emissions of hydrocarbons, carbon monoxide,
NOX, and dpm. The limits are phased in from 1996 to 2000:
starting in 1996 with nonroad engines from 175 to 750 hp, then smaller
engines, and by 2000 the larger nonroad engines. Moreover, in February
1997, restrictions on nonroad engines for locomotives were proposed.
(62 FR 6366.)
In September 1996, EPA announced another Statement of Principles
(SOP) with the engine industry and CARB on new rounds of restrictions
for non-road engines to begin to take place in this century. This led
in September 1997 to a proposed rule setting standards for almost all
types of engines in this category manufactured after 1999-2006 (the
actual year depends on the category). (62 FR 50151.) The applicable
standards for an engine category would be gradually tightened through
three tiers. They would set a cap on the combined NOX and HC
(similar to the on-highway), set CO standards, and lower standards on
PM. The implementation of the final tier of the proposed reductions is
subject to a technology review in 2001 to ensure
[[Page 17509]]
that the appropriateness of the levels to be set is feasible.
Will the Diesel Engine Industry Meet Mining Industry Requirements?
Concern has been expressed from time to time that the diesel
industry might not be able to meet the ever tightening standards on
tailpipe emissions, and might, therefore, stop producing certain
engines needed by the mining community or other industries (Gushee,
1995). To date, however, such concerns have not been realized. The fact
that the most recent regulations have been developed through a
consensus process with the engine industry, and that the non-road plan
includes a scheduled technology review to ensure the proposed emission
standards can really be achieved, suggests that although the EPA
standards are technology forcing, diesel engines will continue to be
available to meet the needs of the mining community for the foreseeable
future. In addition, the nonroad engine agreement with the industry
calls for development of a separate research agreement involving
stakeholders in the exploration of technologies that can achieve very
low emission levels of NOX and PM ``while preserving
performance, reliability, durability, safety, efficiency, and
compatibility with nonroad equipment'' (EPA420-F-96-015, September
1996). Also, Vice President Gore has recently noted that the
Administration is committed to emissions research that would clean up
both the diesels currently on the road, as well as enabling these
engines an opportunity to compete as a new generation of vehicles is
developed that are far more efficient than today's vehicles (White
House Press Release, July 23, 1997). It is always possible, of course,
that some new technological problems could emerge that could impact
diesel engine availability--e.g., confirmation that some of the newer
engines produce high levels of ``nanoparticles'' particulates and that
such emissions pose some sort of a health problem. Research of
nanoparticles and their health effects is currently a topic of
investigation (Bagley et al., 1996).
A related question has been whether the costs of the ``high-tech''
diesel engines will make them unaffordable in practice to the mining
community. MSHA believes the new engines will be affordable. The fact
that the engine industry has agreed to the new standards, and has some
assurance of what the applicable standards will be for the foreseeable
future, should help keep costs in check.
In theory, underground mines can control costs by purchasing
certain types of new engines that do not have to meet the new EPA
standards. The rules on heavy duty on-highway truck engines were not
applied to engines intended to be used in underground coal mines (59 FR
31336), and the new proposed rules on nonroad vehicles would likewise
not be mandatory for engines intended for any underground mining use.
In practice, however, it is not likely that engine manufacturers will
produce special engines once they switch over their production lines to
meet the new EPA standards, because there are few types and sizes of
engines in production for which the mining community is the major
market. Moreover, the larger engines (above 750 hp) are specifically
covered by the EPA nonroad rules (Engine Manufacturers Assn. vs. EPA,
88 F.3d 1075, 319 U.S. App.D.C. 12 (1996)).
MSHA Approved Engines
Acting under its own authority to protect miner safety and health,
MSHA requires that diesel engines used in certain types of mining
operations be ``approved'' as meeting certain tailpipe standards.
In some ways, the standards are akin to those of EPA and CARB. For
example, MSHA, CARB and EPA generally use the same tests to check
emissions. MSHA uses a steady state, 8-mode test cycle, the same as EPA
and CARB use to test engines designed for use in off-road equipment;
however, EPA uses a different, transient test for on-highway engines.
But to be approved by MSHA, an engine does not have to be as clean
as the newer diesel engines, every generation of which must meet ever
tighter EPA and CARB tailpipe standards. Approval of an engine by MSHA
merely ensures that the tailpipe emissions from that engine meet
certain basic standards of cleanliness--cleaner than the engines which
many mines continue to use.
The MSHA approval rules were revised in 1996 (as part of the 1996
rule on the use of diesel equipment in underground coal mines) to
provide the mining community with additional information about the
cleanliness of the emissions emerging from the tailpipe of various
engines. Specifically, the agency now requires that a particulate index
(PI) be reported as part of MSHA's engine approval. This index permits
operators to evaluate the contribution of a proposed new addition to
the fleet to the mine's particulate concentrations.
There is no requirement that approved engines meet a particular PI;
rather, the requirement is for information purposes only. In its 1996
rulemaking, MSHA explicitly deferred until this rulemaking the question
of whether to require engines used in mining environments to meet a
particular PI. (61 FR 55420-21, 55437). The Agency has decided not to
take that approach, for the reasons discussed in part V of this
preamble.
(5) Limiting the Public's Exposure to Soot--Ambient Air Quality
Standards. Pursuant to the Clean Air Act, EPA is responsible for
setting air pollution standards to protect the public from toxic air
contaminants. These include standards to limit exposure to particulate
matter. The pressures to comply with these limits have an impact upon
the mining industry, which contributes various types of particulate
matter into the environment during mining operations, and a special
impact on the coal mining industry whose product is used extensively in
emission-generating power facilities. But those standards hold interest
for the mining community in other ways as well, for underlying some of
them is a large body of evidence on the harmful effects of airborne
particulate matter on human health. Increasingly, that evidence has
pointed toward the risks of the smallest particulates--including the
particles generated by diesel engines.
This section provides an overview of EPA rulemaking on particulate
matter. For more detailed information, commenters are referred to ``The
Plain English Guide to the Clean Air Act,'' EPA 400-K-93-001, 1993, to
the ``Review of the National Ambient Air Quality Standards for
Particulate Matter: Policy Assessment of Scientific and Technical
Information'', EPA-452/R-96-013, 1996; and, on the latest rule, to EPA
Fact Sheets, July 17, 1997. These and other documents are available
from EPA's Web site.
Background
Air quality standards involve a two-step process: standard setting
by EPA, and implementation by each State.
Under the law, EPA is specifically responsible for reviewing the
scientific literature concerning air pollutants, and establishing and
revising National Ambient Air Quality Standards (NAAQS) to minimize the
risks to health and the environment associated with such pollutants. It
is supposed to do a review every five years. Feasibility of compliance
by pollution sources is not supposed to be a factor in establishing
NAAQS. Rather, EPA is required to set the level that provides ``an
adequate margin of safety'' in protecting the health of the public.
[[Page 17510]]
Implementation of each national standard is the responsibility of
the states. Each must develop a state implementation plan that ensures
air quality in the state consistent with the ambient air quality
standard. Thus, each state has a great deal of flexibility in targeting
particular modes of emission (e.g., mobile or stationary, specific
industry or all, public sources of emissions vs. private-sector
sources), and in what requirements to impose on polluters. However, EPA
must approve the state plans pursuant to criteria it establishes, and
then take pollution measurements to determine whether all counties
within the state are meeting each ambient air quality standard. An area
not meeting an NAAQS is known as a ``nonattainment area''.
TSP
Particulate matter originates from all types of stationary, mobile
and natural sources, and can also be created from the transformation of
a variety of gaseous emissions from such sources. In the context of a
global atmosphere, all these particles are mixed together, and both
people and the environment are exposed to a ``particulate soup'' the
chemical and physical properties of which vary greatly with time,
region, meteorology, and source category.
The first ambient air quality standards dealing with particulate
matter did not distinguish among these particles. Rather, the EPA
established a single NAAQS for ``total suspended particulates'', known
as ``TSP.'' Under this approach, the states could come into compliance
with the ambient air requirement by controlling any type or size of
TSP. As long as the total TSP was under the NAAQS which was established
based on the science available in the 1970s--the state met the
requirement.
PM10
When the EPA completed a new review of the scientific evidence in
the mid-eighties, its conclusions led it to revise the particulate
NAAQS to focus more narrowly on those particulates less than 10 microns
in diameter, or PM10. The standard issued in 1987 contained
two components: an annual average limit of 150 g/
m3, and a 24-hour limit of 50 g/m3. This
new standard required the states to reevaluate their situations and, if
they had areas that exceeded the new PM10 limit, to refocus
their compliance plans on reducing those particulates smaller than 10
microns in size. Sources of PM10 include power plants, iron
and steel production, chemical and wood products manufacturing, wind-
blown and roadway fugitive dust, secondary aerosols and many natural
sources.
Some state implementation plans required surface mines to take
actions to help the state meet the PM10 standard. In
particular, some surface mines in Western states were required to
control the coarser particles--e.g., by spraying water on roadways to
limit dust. The mining industry has objected to such controls, arguing
that the coarser particles do not adversely impact health, and has
sought to have them excluded from the EPA ambient air standards (Shea,
1995; comments of Newmont Gold Company, March 11, 1997, EPA docket
number A-95-54, IV-D-2346).
PM2.5
The next scientific review was completed in 1996, following suit by
the American Lung Association and others. A proposed rule was published
in November of 1996, and, after public hearings and review by the
Office of the President, a final rule was promulgated on July 18, 1997.
(62 FR 38651).
The new rule further modifies the standard for particulate matter.
Under the new rule, the existing national ambient air quality standard
for PM10 remains basically the same--an annual average limit
of 150 g/m\3\ (with some adjustment as to how this is measured
for compliance purposes), and a 24-hour ceiling of 50 g/m\3\.
In addition, however, a new NAAQS has now been established for ``fine
particulate matter'' that is less than 2.5 microns in size. The
PM2.5 annual limit is set at 15 g/m\3\, with a 24-
hour ceiling of 65 g/m\3\.
The basis for the PM2.5 NAAQS is a new body of
scientific data suggesting that particles in this size range are the
ones responsible for the most serious health effects associated with
particulate matter. The evidence was thoroughly reviewed by a number of
scientific panels through an extended process. (A chart of the
scientific review process is available on EPA's web site -- http://
ttnwww.rtpnc.epa.gov/naaqspro/pmnaaqs.gif). The proposed rule resulted
in considerable press attention, and hearings by Congress, in which
this scientific evidence was further discussed. Following a careful
review, President Clinton announced his concurrence with the rulemaking
in light of the scientific evidence of risk. However, the
implementation schedule for the rule is long enough so that the next
review of the science is scheduled to be completed before the states
are required to meet the new NAAQS for PM2.5--hence,
adjustment of the standard is still possible before implementation.
Implications for the Mining Community
As noted earlier in this part, diesel particulate matter is mostly
less than 1.0 micron in size. It is, therefore, a fine particulate. The
body of evidence of human health risk from environmental exposure to
fine particulates must, therefore, be considered in assessing the risk
of harm to miners of occupational exposure to one type of fine
particulate--diesel particulate. MSHA has accordingly done so in its
risk assessment (see part III of this preamble).
(6) Controlling Diesel Particulate Emissions in Mining--a Toolbox.
Efforts to control diesel particulate emissions have been under review
for some time within the mining community, and accordingly, there is
considerable practical information available about controls--both in
general terms, and with respect to specific mining situations.
Workshops
In 1995, MSHA sponsored three workshops ``to bring together in a
forum format the U.S. organizations who have a stake in limiting the
exposure of miners to diesel particulate (including) mine operators,
labor unions, trade organizations, engine manufacturers, fuel
producers, exhaust aftertreatment manufacturers, and academia.''
(McAteer, 1995). The sessions provided an overview of the literature
and of diesel particulate exposures in the mining industry, state-of-
the-art technologies available for reducing diesel particulate levels,
presentations on engineering technologies toward that end, and
identification of possible strategies whereby miners' exposure to
diesel particulate matter can be limited both practically and
effectively. One workshop was held in Beckley, West Virginia on
September 12 and 13, and the other two were held on October 6, and
October 12 and 13, 1995, in Mt Vernon, Illinois and Salt Lake City,
Utah, respectively. A transcript was made. During a speech early the
next year, the Deputy Assistant Secretary for MSHA characterized what
took place at these workshops:
The biggest debate at the workshops was whether or not diesel
exhaust causes lung cancer and whether MSHA should move to regulate
exposures. Despite this debate, what emerged at the workshops was a
general recognition and agreement that a health problem seems to
exist with the current high levels of diesel exhaust exposure in the
mines. One could observe that while all the debate about the studies
and the level of risk was going on, something else interesting was
happening at the workshops: One by one miners, mining companies, and
[[Page 17511]]
manufacturers began describing efforts already underway to reduce
exposures. Many are actively trying to solve what they clearly
recognize is a problem. Some mine operators had switched to low
sulfur fuel that reduces particulate levels. Some had increased mine
ventilation. One company had tried a soy-based fuel and found it
lowered particulate levels. Several were instituting better
maintenance techniques for equipment. Another had hired extra diesel
mechanics. Several companies had purchased electronically
controlled, cleaner, engines. Another was testing a prototype of a
new filter system. Yet another was using disposable diesel exhaust
filters. These were not all flawless attempts, nor were they all
inexpensive. But one presenter after another described examples of
serious efforts currently underway to reduce diesel emissions.
(Hricko, 1996).
Toolbox
In March of 1997, MSHA issued, in draft form, a publication
entitled ``Practical Ways to Control Exposure to Diesel Exhaust in
Mining--a Toolbox''. The draft publication was disseminated by MSHA to
all underground mines known to use diesel equipment and posted on
MSHA's Web site. Following comment, the toolbox was finalized in the
Fall of 1997 and disseminated. For the convenience of the mining
community, a copy is reprinted as an Appendix at the end of this
document.
The material on controls is organized as a ``toolbox'' so that mine
operators have the option of choosing the control technology that is
most applicable to their mining operation for reducing exposures to
dpm. The Toolbox provides information about nine types of controls that
can reduce dpm emissions or exposures: Low emission engines; fuels;
aftertreatment devices; ventilation; enclosed cabs; engine maintenance;
work practices and training; fleet management; and respiratory
protective equipment.
The Estimator
MSHA has developed a model that can help mine operators evaluate
the effect of alternative controls on dpm concentrations. The model is
in the form of a template that can be used on standard computer
spreadsheet programs; as information about a new combination of
controls is entered, the results are promptly displayed. A complete
description of this model, referred to as ``the Estimator,'' and
several examples, are presented in part V of this preamble. MSHA
intends to make this model widely available to the mining community,
and hopes to receive comments in connection with this rulemaking based
on the results of estimates conducted with this model.
History of Diesel Aftertreatment Devices in Mining
For many years, the majority of the experience has been with the
use of oxidation catalytic converters (OCCs), but in more recent years
both ceramic and paper filtration systems have also been used more
widely.
OCCs began to be used in underground mines in the 1960's to control
carbon monoxide, hydrocarbons and odor (Haney, Saseen, Waytulonis,
1997). That use has been widespread. It has been estimated that more
than 10,000 OCCs have been put into the mining industry over the years
(McKinnon, dpm Workshop, Beckley, WV, 1995).
When such catalysts are used in conjunction with low sulfur fuel,
there is a reduction of up to 90 percent of carbon monoxide,
hydrocarbons and aldehyde emissions, and nitric oxide can be
transformed to nitrogen dioxide. Moreover, there is also an
approximately 20 percent reduction in diesel particulate mass. The
diesel particulate reduction comes from the elimination of the soluble
organic compounds that, when condensed through the cooling phase in the
exhaust, will attach to the elemental carbon cores of diesel
particulate. Unfortunately, this effect is lost if the fuel contains
more than 0.05 percent sulfur. In such cases, sulfates can be produced
which ``poison'' the catalyst, severely reducing its life. With the use
of low sulfur fuel, some engine manufacturers have certified diesel
engines with catalytic converter systems to meet EPA requirements for
lower particulate levels (see section 4 of this part).
The particulate trapping capabilities of some OCCs are even higher.
In 1995, the EPA implemented standards requiring older buses in urban
areas to reduce the dpm emissions from rebuilt bus engines. (40 CFR
85.1403). Aftertreatment manufacturers developed catalytic converter
systems capable of reducing dpm by 25%. Such systems are available for
larger diesel engines common in the underground metal and nonmetal
sector.
Other types of aftertreatment devices capable of more significant
reductions in particulate levels began to be developed for commercial
applications following EPA rules in 1985 limiting diesel particulate
emissions from heavy duty diesel engines. The wall flow type ceramic
honeycomb diesel particulate filter system was initially the most
promising approach (SAE, SP-735, 1988). However, due to the extensive
work performed by the engine manufacturers on new technological designs
of the diesel engine's combustion system, and the use of low sulfur
fuel, particulate traps turned out to be unnecessary to comply with the
EPA standards of the time.
While this work was underway, efforts were also being made to
transfer this aftertreatment technology to the mining industry. The
former Bureau of Mines investigated the use of catalyzed diesel
particulate filters in underground mines in the United States (BOM, RI-
9478, 1993). The investigation demonstrated that filters could work,
but that there were problems associated with their use on individual
unit installations, and the Bureau made recommendations for
installation of ceramic filters on mining vehicles. But as noted by one
commenter at one of the MSHA workshops in 1995, ``while ceramic filters
give good results early in their life cycle, they have a relatively
short life, are very expensive and unreliable.'' (Ellington, dpm
Workshop, Salt Lake City, UT, 1995).
Canadian mines also began to experiment with ceramic traps in the
1980's with similar results (BOM, IC 9324, 1992). Work in Canada today
continues under the auspices of the Diesel Emission Evaluation Program
(DEEP), established by the Canadian Centre for Mineral and Energy
Technology in 1996 (DEEP Plenary Proceedings, November 1996). The goals
of DEEP are to: (1) Evaluate aerosol sampling and analytical methods
for dpm; and (2) evaluate the in-mine performance and costs of various
diesel exhaust control strategies.
Work with ceramic filters in the last few years has led to the
development of the ceramic fiber wound filter cartridge (SAE, SP-1073,
1995). The ceramic fiber has been reported by the manufacturer to have
dpm reduction efficiencies up to 80 percent. This system has been used
on vehicles to comply with German requirements that all diesel engines
used in confined areas be filtered. Other manufacturers have made the
wall flow type ceramic honeycomb dpm filter system commercially
available to meet the German standard. In the case of some engines, a
choice of the two types is available; but depending upon horsepower,
this may not always be the case.
In the early 1990's, MSHA worked with the former Bureau of Mines
and a filter manufacturer to successfully develop and test a pleated
paper filter for wet water scrubber systems of permissible diesel
powered equipment. The dpm reduction from these filters has been
determined in the field by the former BOM to be up to 95% (BOM, IC
[[Page 17512]]
9324). The same type of filter has been used in recently developed dry
systems for permissible machines, with reported laboratory reductions
in dpm of 98% (Paas, dpm Workshop, Beckley WV, 1995).
ANPRM Comments
The ANPRM requested information about several kinds of work
practices that might be useful in reducing dpm concentrations. These
comments were provided well before the workshops mentioned above, and
before MSHA issued its diesel equipment standard for underground coal
mines, and are thus somewhat dated. But, solely to illustrate the range
of comments received, the following sections review the comments
concerning certain work practices--fuel type, fuel additives, and
maintenance practices.
Type of Diesel Fuel Required
It has been well established that the quality of diesel fuel
influences emissions. Sulfur content, cetane number, aromatic content,
density, viscosity, and volatility are interrelated fuel properties
which can influence emissions. Sulfur content can have a significant
effect on diesel emissions.
Use of low sulfur diesel fuel reduces the sulfate fraction of dpm
matter emissions, reduces objectionable odors associated with diesel
exhaust and allows oxidation catalysts to perform properly. The use of
low sulfur fuel also reduces engine wear and maintenance costs. Fuel
sulfur content is a particularly important parameter when the fuel is
used in low emission diesel engines. Low sulfur diesel fuel is
available nationwide due to EPA regulations. (40 CFR parts 80 and 86.)
In MSHA's ANPRM, information was requested on what reduction in
concentration of diesel particulate can be achieved through the use of
low sulfur fuel. Information was also solicited as to whether the use
of low sulfur fuel reduces the hazard associated with diesel emissions.
Responses from commenters stated that there would be a positive
reduction in particulate with the use of low sulfur fuel. One commenter
stated that the brake specific exhaust emissions (grams/brake
horsepower-hour) of particulate would decrease by about 0.06 g/bhp-hr
for a fuel sulfur reduction of 0.25 weight percent sulfur. The
particulate reduction effect is proportional to the change in sulfur
content. Another commenter stated that a typical No. 2 diesel fuel
containing 0.25 percent weight sulfur will include 1 to 1.6 grams of
sulfate particulate per gallon of fuel consumed. A fuel containing 0.05
percent weight sulfur will reduce sulfate particulate to 0.2-0.3 grams
per gallon of fuel consumed, an 80 percent reduction.
In responding to the question on whether reducing the sulfur
content of the fuel will reduce the health hazard associated with
diesel emissions, several commenters stated that they knew of no
evidence that sulfur reduction reduces the hazard of the particulate.
MSHA also is not aware of any data supporting the proposition that
reducing the sulfur content of the fuel will reduce the health hazard
associated with diesel emissions. However, in the preamble to the final
rule for the EPA requirement for the use of low sulfur fuel, EPA stated
that there were a number of benefits which could be attributed to
lowering the sulfur content of diesel fuel. The first area was in
exhaust aftertreatment technology. Reductions in fuel sulfur content
will result in small reductions in sulfur compounds being emitted. This
will cause the whole particulate concentration from the engine to be
reduced. However, the number of carbon particles is not reduced,
therefore, the total carbon concentration would be the same.
The major benefit of using low sulfur fuel is that the reduction of
sulfur allows for the use of some aftertreatment devices such as
catalytic converters, and catalyzed particulate traps which were
prohibited with fuels of high sulfur content (greater than 0.05 percent
sulfur). The high sulfur content led to sulfate particulate that when
passed through the catalytic converter or catalyzed traps was changed
to sulfuric acid when the sulfates came in contact with water vapor.
Using low sulfur fuel permits these devices to be used.
The second area of benefits that the EPA noted was that of reduced
engine wear with the use of low sulfur fuel. Reducing engine wear will
help maintain engines in their near manufactured condition that would
help limit increases in particulate matter due to lack of maintenance
or age of the engine.
Other questions posed in the ANPRM requested information concerning
the differences in No. 1 and No. 2 diesel fuel regarding particulate
formation; the current sulfur content of diesel fuel used in mines; and
when would 0.05 percent sulfur fuel be available to the mining
industry.
In response to those questions, commenters stated that a difference
in No. 1 and No. 2 fuel regarding particulate formation would be that
No. 1 fuel typically has less sulfur than No. 2 fuel and would
therefore be expected to produce less particulate. Also, the No. 1 fuel
has a lower density, boiling range and aromatic content and a higher
cetane number. All of these fuel property differences tend to cause
lower particulate emissions.
Commenters also stated that the sulfur content of fuels
commercially available for diesel-powered equipment can vary from
nearly zero to 1 percent. The national average sulfur content for
commercial No. 2 diesel fuel is approximately 0.25 percent. One
commenter stated that sulfur content varied from region to region and
the National Institute of Petroleum and Energy Research survey could be
used to get the answers for specific regions.
Commenters noted that low sulfur fuel, less than 0.05 percent
sulfur, would be available for on-highway use as mandated by the EPA by
October 1993. Also, California requires the statewide availability of
0.05 percent sulfur fuel for all diesel engine applications by the same
date. Although the EPA mandate ensures that low sulfur fuel will be
available throughout the nation, commenters indicated the availability
for off-road and mining application was uncertain at that time.
The ANPRM also requested information on the differences in the per
gallon costs among No. 1, No. 2 and 0.05 percent sulfur fuel; how much
fuel is used annually in the mining industry; and what would be the
economic impact on mining of using 0.05 percent sulfur fuel. In
response, commenters stated that No. 1 fuel typically costs the user 10
to 20 percent more than does No. 2 fuel. They also stated that the
price of 0.05 percent sulfur fuel will eventually be set by the
competitive market conditions. No information was submitted for
accurately estimating fuel usage costs to the industry. The economic
impact on the mining industry of using 0.05 percent fuel will vary
greatly from mine to mine. Factors influencing that cost are a mine's
dependence on diesel powered equipment, the location of the mine and
existing regulation. Mines relying heavily on diesel equipment will be
most impacted.
Another commenter stated that the price for 0.05 percent fuel is
forecast to average about 2 cents per gallon higher than the price for
typical current No. 2 fuel. Kerosene and No. 1 distillate are forecast
as 2 to 4 cents per gallon above 0.05 percent fuel and 4 to 6 cents
above current No. 2 fuel. A recent census of mining and manufacturing
dated 1987 showed mining industry energy consumption from all sources
to total 1968.4 trillion BTU per year. Coal mining alone used 9.96
million barrels
[[Page 17513]]
annually of distillate, at a cost of 258.1 million dollars. Included in
these quantities was diesel fuel for surface equipment and vehicles at
or around the mine site. The commenter also stated that applying a cost
increase of 2 cents per gallon to the total industry distillate
consumption would increase annual fuel costs by $24.3 million. For coal
mining only, the cost increase would be $8.4 million annually.
While MSHA does not have an opinion on the accuracy of the
information received in this regard, it is in any event dated. Since
the time that the ANPRM was open, the availability of low sulfur fuel
has become more common. Comments received at MSHA's Diesel Workshops
indicate that low sulfur fuel is readily available and that all that is
needed to obtain it is to specify the desired fuel quality on the
purchase order. The differences in the fuel properties of No. 1 and No.
2 fuel are consistent with specifications provided by ASTM and other
literature information concerning fuel properties.
Fuel Additives
Information relative to fuel additives was requested in MSHA's
ANPRM. The ANPRM requested information on the availability of fuel
additives that can reduce dpm or additives being developed; what diesel
emissions reduction can be expected through the use of these fuel
additives; the cost of additives and advantages to their use; and will
these fuel additives introduce other health hazards. One commenter
stated that cetane improvers and detergent additives can reduce dpm
from 0 to 10 percent. The data, however, does not indicate consistent
benefits as in the case with sulfur reduction. Oxygenate additives can
give larger benefits, as with methanol, but then the oxygenate is not
so much an additive as a fuel blend. Another commenter stated the cost
depended on the price and concentration of the additive. This commenter
estimated the cost to be between three and seven cents per gallon of
fuel.
Another commenter stated that some additives are used for reducing
injector tip fouling, other alternative additives also are offered
specifically for the purpose of reducing smoke or dpm such as
organometallic compounds, i.e., copper, barium, calcium, iron or
platinum; oxygenate supplements containing alcohols or peroxides; and
other proprietary hydrocarbons. The commenter did not quantify the
expected reductions in dpm.
The former Bureau of Mines commented on an investigation of barium-
based, manganese based, and ferrocene fuel additives. Details of the
investigation are found in the literature (BOM, IC 9238, 1990). In
general, fuel additives are not widely used by the mining industry to
reduce dpm or to reduce regeneration temperatures in ceramic
particulate filters. Research has shown aerosol reductions of about 30
percent without significant adverse impacts although new pollutants
derived from the fuel additive remain a question.
One commenter stated that a cetane improver and detergent additives
should not exceed 1 cent per gallon at the treat rates likely to be
used. The use of oxygenates depends on which one and how much but would
be perhaps an order of magnitude higher than the use of a cetane
improver. One commenter also added that any fuel economy advantages
would be very small.
In response to the creation of a health hazard when using
additives, one commenter stated that excessive exposure to cetane
improver (alkyl nitrates), which is hazardous to humans, requires
special handling because of poor thermal stability. Detergent additives
are similar to those used in gasoline and probably have similar safety
and health issues. Except at low load operation, additives are not
likely to result in any significant quantity in the exhaust. Another
commenter stated that the effect on human health of new chemical
exhaust species that may result from the use of some of these additives
has not been determined. Engine manufacturers also are concerned about
the use of such products because their effectiveness has not always
been adequately demonstrated and, in many cases, the effect on engine
durability has not been well-documented for different designs and
operating conditions.
MSHA agrees with the commenters that fuel additives can affect
engine performance and exhaust emissions. MSHA's experience with
additives has shown that they can enhance fuel quality by increasing
the cetane number, depressing the cloud point, or in the case of a
barium based additive, affect the combustion process resulting in a
reduction of particulate output. MSHA's experience also has shown that
in most cases the effects of an additive on engine performance or
emissions cannot be adequately determined without extensive research.
The additives listed on EPA's list of ``registered additives'' meet the
requirements of EPA's standards in 40 CFR part 79.
MSHA is concerned about the use of untested fuel additives. A large
number of additives are currently being marketed to reduce emissions.
These additives include cetane improvers that increase the cetane
number of the fuel, which may reduce emissions and improve starting;
detergents that are used primarily to keep the fuel injectors clean;
dispersants or surfactants that prevent the formation of thicker
compounds that can form deposits on the fuel injectors or plug filters.
While the use of many of these additives will result in reduced
particulate emission, some have been found to introduce harmful agents
into the environment. For this reason, it is a good idea to limit the
use of additives to those that have been registered by the EPA.
Maintenance Practices
The ANPRM requested information concerning what maintenance
procedures are effective in reducing diesel particulate emissions from
existing diesel-powered equipment, and what additional maintenance
procedures would be required in conjunction with anticipated
developments of new diesel particulate reduction technology.
Information was also requested about the amount of time to perform the
maintenance procedures and if any, loss of production time.
Commenters stated that some maintenance procedures have a very
dramatic impact on particulate emissions, while other procedures that
are equally important for other reasons have little or no impact at all
on particulates. Another commenter stated that maintenance procedures
are intended to ensure that the engine operates and will continue to
operate as intended. Such procedures will not reduce diesel particulate
below that of the new, original equipment. A commenter stated that the
diesel engine industry experience has demonstrated that emissions
deterioration over the useful life of an engine is minimal.
Commenters stated that depending on the implied technology, the
need for additional maintenance will be based on complexity of the
control devices. Also, time for maintenance will be dependent on
complexity of the control device. Some production loss will occur due
to increased maintenance procedures.
MSHA agrees with the commenters' view that maintenance does affect
engine emissions, some more dramatically than others. Research has
clearly shown that without engine maintenance, all engine emissions
will increase greatly. For example, the former Bureau of Mines, in
conjunction with Southwest Research, conducted extensive research on
the effects of maintenance on diesel engines which indicated this
result (BOM contract H-0292009, 1979). MSHA agrees that
[[Page 17514]]
emissions increase is minimal over the useful life of the engine only
when proper maintenance is performed daily. However, MSHA believes that
with the awareness of the increased maintenance, production may not be
lost due to the increased time that the machines are able to operate
without unwanted down time due to poor maintenance practices.
MSHA's diesel ``toolbox'' includes an extensive discussion on the
importance of maintenance. It reminds operators and diesel maintenance
personnel of the basic systems on diesel engines that need to be
maintained, and how to avoid various problems. It includes suggestions
from others in the mining community, and information on their success
or difficulties in this regard.
(7) Existing Mining Standards that Limit Miner Exposure to
Occupational Diesel Particulate Emissions. MSHA already has in place
various requirements that help to control miner exposure to diesel
emissions in underground mines--including exposure to diesel
particulate. These include ventilation requirements, engine approval
requirements, and explicit restrictions on the concentration of various
gases in the mine environment.
In addition, in 1996, MSHA promulgated a rule governing the use of
diesel-powered equipment in underground coal mines. (61 FR 55412).
While the primary focus of the rulemaking was to promote the safe use
of diesel engines in the hazardous environment of underground coal
mines, various parts of the rule will help to control exposure to
harmful diesel emissions in those mines. The new rule revised and
updated MSHA's diesel engine approval requirements and the ventilation
requirements for underground coal mines using diesel equipment, and
established requirements concerning diesel fuel sulfur content and the
idling, maintenance and emissions testing of diesel engines in
underground coal mines.
Background
Beginning in the 1940s, mining regulations were promulgated to
promote the safe and healthful use of diesel engines in underground
mines. In 1944, part 31 established procedures for limiting the gaseous
emissions and establishing the recommended dilution air quantity for
mine locomotives that use diesel fuel. In 1949, part 32 established
procedures for testing of mobile diesel-powered equipment for non-coal
mines. In 1961, part 36 was added to provide requirements for the use
of diesel equipment in gassy noncoal mines, in which engines must be
temperature controlled to prevent explosive hazards. These rules
responded to research conducted by the former Bureau of Mines.
Continued research by the former Bureau of Mines in the 1950s and
1960s led to refinements of its ventilation recommendations,
particularly when multiple engines are in use. An airflow of 100 to 250
cfm/bhp was recommended for engines that have a properly adjusted fuel
to air ratio (Holtz, 1960). An additive ventilation requirement was
recommended for operation of multiple diesel units, which could be
relaxed based on the mine operating procedures. This approach was
subsequently refined to become a 100-75-50 percent guideline (MSHA
Policy Memorandum 81-19MM, 1981). Under this guideline, when multiple
pieces of diesel equipment are operated, the required airflow on a
split of air would be the sum of: (a) 100 percent of the nameplate
quantity for the vehicle with the highest nameplate air quantity
requirement; (b) 75 percent of the nameplate air quantity requirement
of the vehicle with the next highest nameplate air quantity
requirement; and (c) 50 percent of the nameplate airflow for each
additional piece of diesel equipment.
Diesel Equipment Rule
On October 6, 1987, MSHA published in the Federal Register (52 FR
37381) a notice establishing a committee to advise the Secretary of
Labor on health and safety standards related to the use of diesel-
powered equipment in underground coal mines. The ``Mine Safety and
Health Advisory Committee on Standards and Regulations for Diesel-
Powered Equipment in Underground Coal Mines'' (the Advisory Committee)
addressed three areas of concern: the approval of diesel-powered
equipment, the safe use of diesel equipment in underground coal mines,
and the protection of miners' health. The Advisory Committee submitted
its recommendations in July 1988.
With respect to the approval of diesel-powered equipment, the
Advisory Committee recommended that all diesel equipment except for a
limited class, be approved for use in underground coal mines. This
approval would involve both safety (e.g., fire suppression systems) and
health factors (e.g., maximum exhaust emissions).
With respect to the safe use of diesel equipment in underground
coal mines, the Advisory Committee recommended that standards be
developed to address the safety aspects of the use of diesel equipment,
including such concerns as equipment maintenance, training of
mechanics, and the storage and transport of diesel fuel.
The Advisory Committee also made recommendations concerning miner
health, discussed later in this section.
As a result of the Advisory Committee's recommendations on approval
and safe use, MSHA developed and, on October 25, 1996, promulgated as a
final rule, standards for the ``Approval, Exhaust Gas Monitoring, and
Safety Requirements for the Use of Diesel-Powered Equipment in
Underground Coal Mines.'' (61 FR 55412).
The October 25, 1996 final rule on diesels focuses on the safe use
of diesels in underground coal mines. Integrated requirements are
established for the safe storage, handling, and transport of diesel
fuel underground, training of mine personnel, minimum ventilating air
quantities for diesel powered equipment, maintenance requirements, fire
suppression, and design features for nonpermissible machines. While the
focus was on safety, certain rules related to emissions are included in
the final rule. For example, the final rule requires maintenance on
diesel powered equipment. Regular maintenance on diesel powered
equipment should keep the diesel engine and vehicle operation at its
original or baseline condition. However, as a check that the
maintenance is being performed, MSHA wrote a standard for checking the
gaseous CO emission levels on permissible and heavy duty outby machines
to determine the need for maintenance. The CO check requires that a
regular repeatable loaded engine condition be run on a weekly basis and
the CO measured. Carbon monoxide is a good indicator of engine
condition. If the CO measurement increases to a higher concentration
than what was normally measured during the past weekly checks, then a
maintenance person would know that either the regular maintenance was
missed or a problem has developed that is more significant than could
be identified by a general daily maintenance program.
Consistent with the Advisory Committee's recommendation, the final
rule, among other things, requires that virtually all diesel-powered
engines used in underground coal mines be approved by MSHA. (30 CFR
part 7 (approval requirements), part 36 (permissible machines defined),
and part 75 (use of such equipment in underground coal mines). The
approval requirements, among other things, are designed to require
clean-burning
[[Page 17515]]
engines in diesel-powered equipment. (61 FR 55417). In promulgating the
final rule, MSHA recognized that clean-burning engines are ``critically
important'' to reducing toxic gasses to levels that can be controlled
through ventilation. (Id.). To achieve the objective of clean-burning
engines, the rule sets performance standards which must be met for
virtually all diesel-powered equipment in underground coal mines (30
CFR part 7).
Consistent with the recommendation of the Advisory Committee, the
technical requirements for approved diesel engines include undiluted
exhaust limits for carbon monoxide and oxides of nitrogen. (61 FR
55419). As recommended by the Advisory Committee, the limits for these
gasses are derived from existing 30 CFR part 36. (61 FR 55419). Also
consistent with the recommendation of the Advisory Committee, the final
rule requires that as part of the approval process, ventilating air
quantities necessary to maintain the gaseous emissions of diesel
engines within existing required ambient limits be set. (61 FR 55420).
As recommended by the Advisory Committee, the ventilating air
quantities are required to appear on the engine's approval plate. (61
FR 55421).
The final rule also implements the Advisory Committee's
recommendation that a particulate index be set for diesel engines. (61
FR 55421). Although, as discussed below, there is not yet a specific
standard limiting miners' exposure to diesel particulate, the
particulate index is nonetheless useful in providing information to the
mining community so that operators can compare the particulate levels
generated by different engines. (61 FR 55421).
Also consistent with the recommendation of the Advisory Committee,
the final rule addresses the monitoring and control of gaseous diesel
exhaust emissions. (30 CFR part 70; 61 FR 55413). In this regard, the
final rule requires that mine operators take samples of carbon monoxide
and nitrogen dioxide. (61 FR 55413, 55430-55431). Samples exceeding an
action level of 50 percent of the threshold limits set forth in 30 CFR
75.322, trigger corrective action by the mine operator. (30 CFR part
70, 61 FR 55413). Also consistent with the Advisory Committee's
recommendation, the final rule requires that diesel-powered equipment
be adequately maintained. (30 CFR 75.1914; 61 FR 55414). Among other
things, as recommended by the Advisory Committee, the rule requires the
weekly examination of diesel-powered equipment, including testing of
undiluted exhaust emissions for certain types of equipment. (30 CFR
75.1914(g)). In addition, consistent with the Advisory Committee's
recommendation, operators are required to establish programs to ensure
that those performing maintenance on diesel equipment are qualified.
(61 FR 55414). As explained in the preamble, maintenance requirements
were included because of MSHA's recognition that inadequate equipment
maintenance can, among other things, result in increased levels of
harmful gaseous and particulate components from diesel exhaust. (61 FR
55413-55414).
Consistent with the Advisory Committee's recommendation, the final
rule also requires that underground coal mine operators use low sulfur
diesel fuel. (30 CFR 75.1901; 61 FR 55413). The use of low sulfur fuel
lowers not only the amount of gaseous emissions, but also the amount of
diesel particulate emissions. (Id.). To further reduce miners' exposure
to diesel exhaust, the final rule prohibits operators from
unnecessarily idling diesel-powered equipment. (30 CFR 75.1916(d)).
Also consistent with the recommendation of the Advisory Committee,
the final rule establishes minimum air quantity requirements in areas
of underground coal mines where diesel-powered equipment is operated.
(30 CFR 75.325). As set forth in the preamble, MSHA believes that
effective mine ventilation is a key component in the control of miners'
exposure to gasses and particulate emissions generated by diesel
equipment. (61 FR 55433). The final rule also requires generally that
mine operators maintain the approval plate quantity minimum airflow in
areas of underground coal mines where diesel-powered equipment is
operated. (30 CFR 75.325 \2\).
---------------------------------------------------------------------------
\2\ On December 23, 1997, the National Mining Association and
Energy West Mining Company filed petitions for review of the final
rule. National Mining Association versus Secretary of Labor, Nos.
96-1489 and 96-1490. These cases were consolidated and held in
abeyance pending discussions between the mining industry and the
Secretary. On March 19, 1998, petitioners filed an Unopposed Joint
Motion for Voluntary Dismissal. This motion is still pending before
the Court.
---------------------------------------------------------------------------
The diesel equipment rule will help the mining community use
diesel-powered equipment more safely in underground coal mines. As
discussed throughout this preamble, the diesel equipment rule has many
features which, though it was not their primary purpose, will
incidently reduce harmful diesel emissions in underground coal mines--
including the particulate component of these emissions. (The
requirements of the diesel equipment rule are highlighted with a
special typeface in MSHA's publication, ``Practical Ways to Control
Exposure to Diesel Exhaust in Mining--a Toolbox'', reprinted as an
Appendix at the end of this document. An example is the requirement in
the diesel equipment rule that all engines used in underground coal
mines be approved engines, and be maintained in approved condition --
thus reducing emissions at the source.
In developing this safety rule, however, MSHA did not explicitly
consider the risks to miners of a working lifetime of dpm exposure at
very high levels, nor the actions that could be taken to specifically
reduce those exposure levels in underground coal mines. Moreover, the
rule does not apply to the remainder of the mining industry, where the
use of diesel machinery is much more intense than in underground coal.
Gas Limits
Various organizations have established or recommended limits for
many of the gasses occurring in diesel exhaust. Some of these are
listed in Table II-2, together with information about the limits
currently enforced by MSHA. MSHA requires mine operators to comply with
gas specific threshold limit values (TLV's) recommended by the American
Conference of Governmental Industrial Hygienists (ACGIH) in 1972 (for
coal mines) and in 1973 (for metal and nonmetal mines).
Table II-2.--Gaseous Exposure Limits (PPM)
----------------------------------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------------------------------
(1)
(1)MSHA limits
-------------------------
Pollutant
(1)Range of limits
(1)recommended Coal a M/NM b
----------------------------------------------------------------------------------------------------------------
HCHO........................................................ c 0.016 d. 0.3 2 2
[[Page 17516]]
CO.......................................................... d 25 50 50 50
CO2......................................................... c 5,000 5,000 5,000 5,000
NO2......................................................... c d e 25 25 25 25
NO2......................................................... f 1 d 3 5 5
SO2......................................................... c d 2 e 5 2 5
----------------------------------------------------------------------------------------------------------------
Table Notes:
a ACGIH, 1972.
b ACGIH, 1973.
c NIOSH recommended exposure limit (REL), based on a 10-hour, time-weighted average.
d ACGIH, 1996.
e OSHA permissible exposure limit (PEL).
f NIOSH recommends only a 1-ppm, 15-minutes, short-term exposure limit (STEL).
In 1989, MSHA proposed changing some of these limits in the context
of a proposed rule on air quality standards. (54 FR 35760). Following
opportunity for comment and hearings, a portion of that proposed rule,
concerning control of drill dust, has been promulgated, but the other
components are still under review. To change a limit at this point in
time requires a regulatory action; the rule does not provide for their
automatic updating.
(8) How Other Jurisdictions are Restricting Occupational Exposure
to Diesel Soot. MSHA's proposed rule is the first effort by the Federal
government to deal with the special risks faced by workers exposed to
diesel exhaust on the job--because, as described in detail in the part
III of this preamble, miner exposures are an order of magnitude above
those of any other group of workers. But others have been looking at
the problem of exposure to diesel soot.
States
As noted in the first section of this part, few underground coal
mines now use diesel engines. Several states have had bans on the use
of such equipment: Pennsylvania, West Virginia, and Ohio.
Recently, Pennsylvania has replaced its ban with a special law that
permits the use of diesel-powered equipment in deep coal mines under
certain circumstances. The Pennsylvania statute goes beyond MSHA's new
regulation on the use of diesel-powered equipment in underground coal
mines. Of particular interest is that it specifically addresses diesel
particulate. The State did not set a limit on the exposure of miners to
dpm, nor did it establish a limit on the concentration of dpm in deep
coal mines. Rather, it approached the issue by imposing controls that
will limit dpm emissions at the source.
First, all diesel engines used in underground deep coal mines in
Pennsylvania must be MSHA-approved engines with an ``exhaust emissions
control and conditioning system'' that meets certain tests. (Article
II-A, Section 203-A, Exhaust Emission Controls). Among these are dpm
emissions from each engine no greater than ``an average concentration
of 0.12 mg/m3 diluted by fifty percent of the MSHA approval
plate ventilation for that diesel engine.'' In addition, any exhaust
emissions control and conditioning system must include a ``Diesel
Particulate Matter (DPM) filter capable of an average of ninety-five
percent or greater reduction of dpm emissions.'' It also requires the
use of an oxidation catalytic converter. Thus, the Pennsylvania statute
requires the use of low-emitting engines, and then the use of
aftertreatment devices that significantly reduce what particulates are
emitted from these engines.
The Pennsylvania law also has a number of other requirements for
the safe use of diesel-powered equipment in the particularly hazardous
environments of underground coal mines. Many of these parallel the
requirements in MSHA's rule. Like MSHA's requirements, they too can
result in reducing miner exposure to diesel particulate--e.g., regular
maintenance of diesel engines by qualified personnel and equipment
operator examinations. The requirements in the Pennsylvania law take
into account the need to maintain the aftertreatment devices required
to control diesel particulate (see, e.g., section 217-A(b)(6)).
West Virginia has also lifted its ban, subject to rules to be
developed by a joint labor-management commission. MSHA understands that
pursuant to the West Virginia law lifting the ban, the Commission has
only a limited time to determine the applicable rules, or the matter is
to be referred to an arbitrator for resolution.
Other Countries
Concerns about air pollution have been a major impetus for most
countries' standards on vehicle emissions, including diesel
particulate. Most industrialized nations recognize the fundamental
principle that their citizens should be protected against recognized
health risks from air pollution and that this requires the control of
particulate such as diesel exhaust. In November of 1995, for example,
the government of the United Kingdom recommended a limit on
PM10, and noted it would be taking further actions to limit
airborne particulate matter (including a special study of dust from
surface minerals workings).
Concerns about international trade have been another impetus.
Diesel engines are sold to an international market to power many types
of industrial and nonindustrial machinery and equipment. The European
Union manufacturers exported more than 50 percent of their products,
mainly to South Korea, Taiwan, China, Australia, New Zealand and the
United States. Germany and the United Kingdom, two major producers,
have pushed for harmonized world standards to level the playing field
among the various countries' engine producers and to simplify the
acceptance of their products by other countries (Financial Times,
1996). This includes products that must be designed to meet pollution
standards. The European Union (EU) is now considering a proposal to set
an EU-wide standard for the control of the emission of pollutants from
non-road mobile machinery (Official Journal of European Communities,
1995). The proposal would largely track that of the U.S. Environmental
Protection Agency's final rule on the Control of Air Pollution
Determination of Significance for Nonroad Sources and Emission
Standards for New Nonroad Compression-Ignition Engines at or above 37
kilowatts (50 HP)p (discussed in section 3 of this part of the
preamble).
A third impetus to action has been the studies of the health
effects of worker exposure to diesel exhaust--many of which have been
epidemiological studies concerning workers in other countries. As noted
in Part III of this preamble, the studies include cohorts of Swedish
dock workers and bus garage workers, Canadian railway workers and
[[Page 17517]]
miners, French workers, London transport workers, and Danish chimney
sweeps.
Below, the agency summarizes some information obtained on exposure
limits of other countries. Due to differences in regulatory schemes
among nations considering the effects of diesel exhaust, countries
which have addressed the issue are more likely to have issued
recommendations rather than a mandatory maximum exposure limit. Some of
these may have issued mandatory design features for diesel equipment to
assist in achieving the recommended exposure level. Measurement systems
also vary.
Germany
German legislation on dangerous substances classifies diesel engine
emissions as carcinogenic. Therefore, diesel engines must be designed
and operated using the latest technology to cut emissions. This always
requires an examination to determine whether the respective operations
and activities may be carried out using other types of less polluting
equipment. If, as a result of the examination, it is decided that the
use of diesel engines is necessary measures must be instituted to
reduce emissions. Such measures can include low-polluting diesel
engines, low sulphur fuels, regular maintenance, and, where technology
permits, the use of particulate traps. To reduce exposure levels
further, diesel engine emissions may be regulated directly at the
source; ventilation systems may be required to be installed.
The use of diesel vehicles in a fully or partly enclosed working
space--such as in an underground mine--may be restricted by the
government, depending on the necessary engine power or load capacity
and on whether the relevant operation could be accomplished using a
non-polluting vehicle, e.g., an electrically powered vehicle. When
determining whether alternate equipment is to be used, the burden to
the operator to use such equipment is also considered.
In April of 1997, the following permissible exposure limits (TRK
\3\) for diesel engine emissions were instituted for workplaces in
mining.
---------------------------------------------------------------------------
\3\ TPK is the technical exposure limit of a hazardous material
that defines the concentration of gas, vapour or airborne
particulates which is the minimum possible with current technology
and which serves as a guide for necessary protective measures and
monitoring in the workplace.
\4\ Colloid dust is defined as that part of total respirable
dust in a workplace that passes the alveolar ducts of the worker.
---------------------------------------------------------------------------
(1) Non-coal underground mining and construction work: TRK = 0.3
mg/m\3\ of colloid dust.\4\
(2) other: TRK = 0.1 mg/m\3\ of colloid dust.
(3) The average concentration of diesel engine emissions within a
period of 15 minutes should never be higher than four times the TRK
value.
The TRK is ascertained by determining the fraction of elemental
carbon in the colloid (fine) dust by coulometric analysis. Determining
the fraction of elemental carbon always involves the determination of
total organic carbon in the course of analysis. If the workplace
analysis shows that the fraction of elemental carbon in total carbon
(elemental carbon plus organic carbon) is lower than 50%, or is subject
to major fluctuations, then the TRK limits total carbon in such
workplaces to 0.15 mg/m\3\.
Irrespective of the TRK levels, the following additional measures
are considered necessary once the concentration reaches 0.1 mg/m\3\
colloid dust:
(1) Informing employees concerned;
(2) Limited working hours for certain staff categories;
(3) Special working hours; and
(4) Medical checkups.
If concentrations continue to fail to meet the TRK level, the
employer must:
(1) Provide appropriate, effective, hygienic breathing apparatus,
and
(2) Ensure that workers are not kept at the workplace for longer
than absolutely necessary and that health regulations are observed.
Workers must use the breathing apparatus if the TRK levels for
diesel engine emissions at the work place are exceeded. Due to the
interference of recognized analysis techniques in coal mining, it is
currently impossible to ascertain exposure levels in the air in coal
mines. As a consequence, the coal mining authorities require the use of
special low-polluting engines in underground mining and impose special
requirements on the supply of fresh air to the workplace.
European Standards
On April 21, 1997, the draft of a European directive that applied
to emissions from non-road mobile machinery was prepared. The directive
proposed technical measures that would result in a reduction in
emissions from internal-combustion engines (gasoline and diesel)
installed in non-road mobile machinery, and type-approval procedures
that would provide uniformity among the member nations for the approval
of these engines.
The directive proposed a two-stage process. Stage 1, proposed to
begin December 31, 1997, was for three different engine categories:
--A: 130 kW <= p=""><= 560="" kw,="" --b:="" 75="" kw=""><= p="">< 130.="" kw,="" --c:="" 37="" kw=""><= p="">< 75="" kw.="" stage="" 2,="" proposed="" to="" begin="" december="" 31,="" 1999,="" consisted="" of="" four="" engine="" categories="" being="" phased-in="" over="" a="" four-year="" period:="" --="" d:="" after="" december="" 31,1999="" for="" engines="" of="" a="" power="" output="" of="" 18="" kw=""><= p="">< 37="" kw,="" --="" e:="" after="" december="" 31,="" 2000="" for="" engines="" of="" a="" power="" output="" of="" 130=""><= p=""><= 560="" kw,="" --f:="" after="" december="" 31,="" 2001="" for="" engines="" of="" a="" power="" output="" of="" 75=""><= p="">< 130="" kw,="" --g:="" after="" december="" 31,="" 2002="" for="" engines="" of="" a="" power="" output="" of="" 37=""><= p=""><=75 kw.="" the="" emissions="" shown="" in="" the="" following="" table="" for="" carbon="" monoxide,="" hydrocarbons,="" oxides="" of="" nitrogen="" and="" particulates="" are="" to="" be="" met="" for="" the="" respective="" engine="" categories="" described="" for="" stage="" i.="" ----------------------------------------------------------------------------------------------------------------="" carbon="" oxides="" of="" monoxide="" hydrocarbon="" nitrogen="" particulates="" net="" power="" (p)="" (kw)="" (p)="" (g/="" s="" (hc)="" (g/="">X) (g/ (PT) (g/
kWH) kWh) kWh) kWh)
----------------------------------------------------------------------------------------------------------------
130P<560........................................ 5.0="" 1.3="" 9.2="" 0.54="">P<130......................................... 5.0="" 1.3="" 9.2="" 0.70="">P<75.......................................... 6.5="" 1.3="" 9.2="" 0.85="" ----------------------------------------------------------------------------------------------------------------="" the="" engine="" emission="" limits="" that="" have="" to="" be="" achieved="" for="" stage="" ii="" are="" shown="" in="" the="" following="" table.="" the="" emissions="" limits="" shown="" are="" engine-out="" limits="" and="" are="" to="" be="" achieved="" before="" any="" aftertreatment="" device="" is="" used.="" [[page="" 17518]]="" ----------------------------------------------------------------------------------------------------------------="" carbon="" oxides="" of="" monoxide="" hydrocarbons="" nitrogen="" particulates="" net="" power="" (p)="" (kw)="" (p)="" (g/="" (hc)="" (g/="">X) (g/ (PT) (g/
kWH) kWh) kWh) kWh)
----------------------------------------------------------------------------------------------------------------
130P<560....................................... 3.5="" 1.0="" 6.0="" 0.2="">P<130........................................ 5.0="" 1.0="" 6.0="" 0.3="">P<75......................................... 5.0="" 1.3="" 7.0="" 0.4="">P<37......................................... 5.5="" 1.5="" 8.0="" 0.8="" ----------------------------------------------------------------------------------------------------------------="" canada="" (related="" developments="" in="" canada)="" the="" mining="" and="" minerals="" research="" laboratories="" (mmrl)="" of="" the="" canada="" centre="" for="" mineral="" and="" energy="" technology="" (canmet),="" an="" arm="" of="" the="" federal="" department="" of="" natural="" resources="" canada="" (nrcan),="" began="" work="" in="" the="" early="" 1970s="" to="" develop="" measurement="" tools="" and="" control="" technologies="" for="" diesel="" particulate="" matter="" (dpm).="" in="" 1978,="" i.w.="" french="" and="" dr.="" anne="" mildon="" produced="" a="" canmet-sponsored="" contract="" study="" entitled:="" ``health="" implications="" of="" exposure="" of="" underground="" mine="" workers="" to="" diesel="" exhaust="" emissions.''="" in="" this="" document,="" an="" air="" quality="" index="" (aqi)="" was="" developed="" involving="" several="" major="" diesel="" contaminants="" (co,="" no,="">2,
SO2 and RCD--respirable combustible dust which is mostly
dpm). These concentrations were divided by their then current
permissible exposure limits, and the sum of the several ratios
indicates the level of pollution in the mine atmosphere. The maximum
value for this Index was fixed at 3.0. This criterion was determined by
the known health hazard associated with small particle inhalation, and
the known chemical composition of dpm, among other matters.
Subsequently, in 1986, the Canadian Ad hoc Diesel Committee was
formed from all segments of the mining industry, including: mine
operators, the labor force, equipment manufacturers, research agencies
including CANMET, and Canadian regulatory bodies. The objective was the
identification of major problems for research and development
attention, the undertaking of the indicated studies, and the
application of the results to reduce the impact of diesel machines on
the health of underground miners.
In 1990-91, CANMET developed an RCD mine sampling protocol on
behalf of the Ad hoc Committee. Then current underground sampling
studies indicated an average ratio of RCD to dpm of 1.5. This factor
accounted for the presence of other airborne combustible liquids
including fuel, lubrication and particularly drilling oils, in addition
to the dpm.
The original 1978 French-Mildon study was updated under a CANMET
contract in 1990. It recommended that the dpm levels be reduced to 0.5
mg/m3 (suggesting a corresponding RCD level of 0.75 mg/
m3).
However, in 1991, the Ad hoc Committee decided to set an interim
recommended RCD level of 1.5 mg/m3 (the equivalent 1.0 mg/
m3). This value matched the then recommended, but not
promulgated, MSHA ``Ventilation Index'' value for dpm of 1.0 mg/
m3. Consequently, all of the North American mining industry
then seemed to be accepting the same maximum levels of dpm.
It should be noted that for coal mine environments or other
environments where a non-diesel carbonaceous aerosol is present, RCD
analysis is not an appropriate measure of dpm levels.
Neither CANMET nor the Ad hoc Committee is a regulatory body. In
Canada, mining is regulated by the individual provinces and
territories. However, the federal laboratories provide: research and
development facilities, advice based on research and development, and
engine/machine certification services, in order to assist the provinces
in their diesel-related mining regulatory functions.
Prior to the 1991 recommendation of the Ad hoc Committee, Quebec
enacted regulations requiring: ventilation, a maximum of 0.25% sulfur
content in diesel fuel; a prohibition on black smoke; exhaust cooling
to a maximum temperature of 85 deg.C; and the setting of maximum
contaminant levels. Since 1997, new regulations add the CSA Standard
for engine certification, a maximum RCD level of 1.5 mg/m3,
and the application of an exhaust treatment system.
Further, after the Ad hoc Committee recommendation was published in
1991 (RCDmax = 1.5 mg/m3), various provinces took the
following actions:
(1) Five provinces--British Columbia, Ontario, Quebec, New
Brunswick, and Nova Scotia, and the Northwest Territories, adopted an
RCD limit of 1.5 mg/m3.
(2) Two others, Manitoba and Newfoundland/Labrador, have been
adopting the ACGIH TLVs.
(3) Two provinces, Alberta and Saskatchewan, and the Yukon
Territory, continue to have no dpm limit.
Most Canadian Inspectorates accept the CSA Standard for diesel
machine/engine certification. This Standard specifies the undiluted
Exhaust Quality Index (EQI) criterion for calculation of the
ventilation in cfm, required for each diesel engine/machine. Fuel
sulfur content, type of aftertreatment device and rated engine load
factor are on-site, variable factors which may alter the ventilation
ultimately required. Diesel fuel may not exceed 0.50% sulfur, and must
have a minimum flash point of 52 deg.C. However, most mines in Canada
now use fuel containing less than 0.05% sulfur by weight.
In addition to limiting the RCD concentration, Qntario, established
rules in 1994 that required diesel equipment to meet the Canadian
Standards Association ``Non-Rail-Bound Diesel-Powered Machines for use
in Non-Gassy Underground Mines'' (CSA M424.2-M90) Standard, excepting
the ventilation assessment clauses. As far as fuel sulfur and
flashpoint are concerned, Ontario is intending to change to: Smax =
0.05% from 0.25%, and maximum fuel flash point = 38 deg.C from
52 deg.C.
New Brunswick, in addition to limiting the RCD concentration,
requires mine operators to submit an ambient air quality monitoring
plan. Diesel engines above 100 horsepower must be certified, and there
is a minimum ventilation requirement of 105 cfm/bhp.
Since 1996, the Ad hoc organization and the industry consortium
called the Diesel Emissions Evaluation Program (DEEP) have been
cooperating in a research and development program designed to reduce
dpm levels in mines.
World Health Organization (WHO)
Environmental Health Criteria 171 on ``Diesel Fuel and Exhaust
Emissions'' is a 1996 monograph published under joint sponsorship of
the United Nations Environment Programme, the International Labour
Organisation, and the World Health Organization. The monograph provides
a comprehensive review of the literature and evaluates the risks for
human health and the
[[Page 17519]]
environment from exposure to diesel fuel and exhaust emissions.
The following tables compiled in the monograph show diesel engine
exhaust limits for various exhaust components and illustrate that there
is international concern about the amount of diesel exhaust being
released into the environment.
Table II-3.--International Limit Values for Components of Diesel Exhaust Light-Duty Vehicles (g/km)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Region Carbon monoxide Nitrogen oxides Hydrocarbons Particulates Comments
--------------------------------------------------------------------------------------------------------------------------------------------------------
Austria..................... 2.1............ 0.62............ 0.25............ 0.124........... 3.5t; since 1991; from 1995, adoption of
European Union standards planned.
Canada...................... 2.1............ 0.62............ 0.25............ 0.12............ Since 1987.
European Union.............. 2.72........... 0.97 (with ................ 0.14............ Since 1992.
hydrocarbons).
1.0............ 0.7............. ................ 0.08............ From 1996.
Finland..................... ............... ................ ................ Since 1993......
Japan....................... 2.1............ 0.7............. 0.62............ None............ Since 1986.
2.1............ 0.5............. 0.4............. 0.2............. Since 1994.
Sweden, Norway.............. 2.1............ 0.62 (city)..... 0.25............ 0.124........... 3.5t; from motor year 1992.
0.76 (highway)
Switzerland................. 2.1............ 0.62 (city)..... 0.25............ 0.124........... 3.5t; since 1988; from 1995, adoption of
0.76 (highway) European Union standard planned.
USA (California)............ 2.1-5.2........ 0.2-0.6......... 0.2-0.3 (except 0.05 (up to Depending on mileage.
methane). 31000 km).
US Environmental Protection 2.1-2.6........ 0.6-0.8......... 0.2............. 0.05-0.12....... Depending on mileage.
Agency.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Table II-4.--International Limit Values for Components of Diesel Exhaust Heavy-Duty Vehicles (g/kWh)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Carbon Nitrogen Hydro
Region monoxide oxides carbons Particulates Comments
--------------------------------------------------------------------------------------------------------------------------------------------------------
Austria............................. 4.9 9.0 1.23 0.4
Canada.............................. 15.5 5.0 1.3 0.25 g/bhp-h.
15.5 5.0 1.3 0.1 g/bhp-h; from 1995-97.
European Union...................... 4.5 8.0 1.1 0.36 Since 1992.
4.0 7.0 1.1 0.15 From 1995-96.
Japan............................... 7.4 5.0 2.9 0.7 Indirect injection engines.
7.4 6.0 2.9 0.7 Direct injection engines.
Sweden.............................. 4.9 9.0 1.23 0.4
USA................................. 15.5 5.0 1.3 0.07 g/bhp-h; bus.
15.5 4.0 1.3 0.1 g/bhp-h; truck.
15.5 5.0 1.3 0.05 g/bhp-h; bus; from 1998.
15.5 4.0 1.3 0.1 g/bhp-h; truck; from 1998.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Adapted from Mercedes-Benz AG (1994b).
With respect to the protection of human health, the monograph
states that the data reviewed supports the conclusion that inhalation
of diesel exhaust is of concern with respect to both neoplastic and
non-neoplastic diseases. The monograph found that diesel exhaust ``is
probably carcinogenic to humans.'' It also states that the particulate
phase appears to have the greatest effect on health, and both the
particle core and the associated organic materials have biological
activity, although the gas-phase components cannot be disregarded. The
monograph recommends the following actions for the protection of human
health:
(1) Diesel exhaust emissions should be controlled as part of the
overall control of atmospheric pollution, particularly in urban
environments.
(2) Emissions should be controlled strictly by regulatory
inspections and prompt remedial actions.
(3) Urgent efforts should be made to reduce emissions, specifically
of particulates, by changing exhaust train techniques, engine design,
and fuel consumption.
(4) In the occupational environment, good work practices should be
encouraged, and adequate ventilation must be provided to prevent
excessive exposure.
The monograph made no recommendations as to what constitutes
excessive exposure.
International Agency for Research on Cancer (IARC)
The carcinogenic risks for human beings were evaluated by a working
group convened by the International Agency for Research on Cancer in
1988 (International Agency for Research on Cancer, 1989b). The
conclusions were:
(1) There is sufficient evidence for the carcinogenicity in
experimental animals of the whole diesel engine exhaust.
(2) There is inadequate evidence for the carcinogenicity in animals
of gas-phase diesel engine exhaust (with particles removed).
(3) There is sufficient evidence for the carcinogenicity in
experimental animals of extracts of diesel engine exhaust particles.
(4) There is limited evidence for the carcinogenicity in humans of
engine exhausts (unspecified as from diesel or gasoline engines).
[[Page 17520]]
Overall IARC Evaluation
Diesel engine exhaust is probably carcinogenic to humans (Group
2A).
(9) MSHA's Initiative to Limit Miner Exposure to Diesel
Particulate--a Brief History of this Rulemaking and Related Actions. As
discussed in part III of this preamble, by the early 1980's, the
evidence indicating that exposure to diesel exhaust might be harmful to
miners, particularly in underground mines, had started to grow. As a
result, formal agency actions were initiated to investigate this
possibility and to determine what, if any, actions might be
appropriate. These actions are summarized here in chronological
sequence, without comment as to the basis of any action or conclusion.
In 1984, in accordance with the Sec. 102(b) of the Mine Act, NIOSH
established a standing Mine Health Research Advisory Committee to
advise it on matters involving or related to mine health research. In
turn, that group established a subgroup to determine if:
* * * there is a scientific basis for developing a
recommendation on the use of diesel equipment in underground mining
operations and defining the limits of current knowledge, and
recommending areas of research for NIOSH, if any, taking into
account other investigators' ongoing and planned research. (49 FR
37174).
In 1985, MSHA established an Interagency Task Group with the
National Institute for Occupational Safety and Health (NIOSH) and the
former Bureau of Mines (BOM) to assess the health and safety
implications of the use of diesel-powered equipment in underground coal
mines. In part, as a result of the recommendation of the Task Group,
MSHA, in April 1986, began drafting proposed regulations on the
approval and use of diesel-powered equipment in underground coal mines.
Also in 1986, the subgroup of the NIOSH advisory committee studying
this issue summarized the evidence available at that time as follows:
It is our opinion that although there are some data suggesting a
small excess risk of adverse health effects associated with exposure
to diesel exhaust, these data are not compelling enough to exclude
diesels from underground mines. In cases where diesel equipment is
used in mines, controls should be employed to minimize exposure to
diesel exhaust. (Interagency Task Group Report, 1986).
As noted previously in section 7 of this part, in discussing MSHA's
diesel equipment rule, on October 6, 1987, pursuant to Section 102(c)
of the Mine Act, 30 U.S.C. Sec. 812(c), MSHA appointed an advisory
committee ``to provide advice on the complex issues concerning the use
of diesel-powered equipment in underground coal mines.'' (52 FR 37381).
MSHA appointed nine members to the Advisory Committee. As required by
Section 101(a)(1), MSHA provided the Advisory Committee with draft
regulations on the approval and use of diesel-powered equipment in
underground coal mines. The draft regulations did not include standards
setting specific limitations on diesel particulate, nor had MSHA at
that time determined that such standards should be promulgated.
In July 1988, the Advisory Committee completed its work with the
issuance of a report entitled ``Report of the Mine Safety and Health
Administration Advisory Committee on Standards and Regulations for
Diesel-Powered Equipment in Underground Coal Mines.'' The Advisory
Committee recommended that MSHA promulgate standards governing the
approval and use of diesel-powered equipment in underground coal mines.
The Advisory Committee recommended that MSHA promulgate standards
limiting underground coal miners' exposure to diesel exhaust.
With respect to diesel particulate, the Advisory Committee
recommended that MSHA ``set in motion a mechanism whereby a diesel
particulate standard can be set.'' (MSHA, 1988). In this regard, the
Advisory Committee determined that because of inadequacies in the data
on the health effects of diesel particulate matter and inadequacies in
the technology for monitoring the amount of diesel particulate matter
at that time, it could not recommend that MSHA promulgate a standard
specifically limiting the level of diesel particulate matter. (Id. 64-
65). Instead, the Advisory Committee recommended that MSHA request
NIOSH and the former BOM to prioritize research in the development of
sampling methods and devices for diesel particulate. The Advisory
Committee also recommended that MSHA request a study on the chronic and
acute effects of diesel emissions (Id.). In addition, the Advisory
Committee recommended that the control of diesel particulate ``be
accomplished through a combination of measures including fuel
requirements, equipment design, and in-mine controls such as the
ventilation system and equipment maintenance in conjunction with
undiluted exhaust measurements.'' The Advisory Committee further
recommended that particulate emissions ``be evaluated in the equipment
approval process and a particulate emission index reported.'' (Id. at
9).
In addition, the Advisory Committee recommended that ``the total
respirable particulate, including diesel particulate, should not exceed
the existing two milligrams per cubic meter respirable dust standard.''
(Id. at 9). Section 202(b)(2) of the Mine Act requires that coal mine
operators maintain the average concentration of respirable dust at
their mines at or below two milligrams per cubic meter which
effectively prohibits diesel particulate matter in excess of two
milligrams per cubic meter, 30 U.S.C. 842(b)(2).
Also in 1988, NIOSH issued a Current Intelligence Bulletin
recommending that whole diesel exhaust be regarded as a potential
carcinogen and controlled to the lowest feasible exposure level (NIOSH,
1988). In its bulletin, NIOSH concluded that although the excess risk
of cancer in diesel exhaust exposed workers has not been quantitatively
estimated, it is logical to assume that reductions in exposure to
diesel exhaust in the workplace would reduce the excess risk. NIOSH
stated that ``[g]iven what we currently know there is an urgent need
for efforts to be made to reduce occupational exposures to DEP [dpm] in
mines.''
Consistent with the Advisory Committee's research recommendations,
MSHA, in September 1988, formally requested NIOSH to perform a risk
assessment for exposure to diesel particulate. (57 FR 500). MSHA also
requested assistance from NIOSH and the former BOM in developing
sampling and analytical methodologies for assessing exposure to diesel
particulate in mining operations. (Id.). In part, as a result of the
Advisory Committee's recommendation, MSHA also participated in studies
on diesel particulate sampling methodologies and determination of
underground occupational exposure to diesel particulate. A list of the
studies requested and reports thereof is set forth in 57 FR 500-501.
On October 4, 1989, MSHA published a Notice of Proposed Rulemaking
on approval requirements, exposure monitoring, and safety requirements
for the use of diesel-powered equipment in underground coal mines. (54
FR 40950). The proposed rule, among other things, addressed, and in
fact followed, the Advisory Committee's recommendation that MSHA
promulgate regulations requiring the approval of diesel engines (54 FR
40951), limiting gaseous pollutants from diesel equipment, (Id.),
establishing ventilation requirements based on approval plate dilution
air quantities (54 FR 40990), requiring equipment maintenance (54 FR
40958), requiring that trained personnel work on diesel-powered
equipment, (54 FR 40995), establishing fuel requirements,
[[Page 17521]]
(Id.), establishing gaseous contaminant monitoring (54 FR 40989), and
requiring that a particulate index indicating the quantity of air
needed to dilute particulate emissions from diesel engines be
established. (54 FR 40953).
On January 6, 1992, MSHA published an Advance Notice of Proposed
Rulemaking (ANPRM) indicating that it was in the early stages of
developing a rule specifically addressing miners' exposure to diesel
particulate. (57 FR 500). In the ANPRM, MSHA, among other things,
sought comment on specific reports on diesel particulate prepared by
NIOSH and the former BOM. (Id.). MSHA also sought comment on reports on
diesel particulate which were prepared by or in conjunction with MSHA.
(57 FR 501). The ANPRM also sought comments on the health effects,
technological and economic feasibility, and provisions which should be
considered for inclusion in a diesel particulate rule. (57 FR 501). The
notice also identified five specific areas where the agency was
particularly interested in comments, and about which it asked a number
of detailed questions: (1) exposure limits, including the basis
therefore; (2) the validity of the NIOSH risk assessment model and the
validity of various types of studies; (3) information about non-cancer
risks, non-lung routes of entry, and the confounding effects of tobacco
smoking; (4) the availability, accuracy and proper use of sampling and
monitoring methods for diesel particulate; and (5) the technological
and economic feasibility of various types of controls, including
ventilation, diesel fuel, engine design, aftertreatment devices, and
maintenance by mechanics with specialized training. The notice also
solicited specific information from the mining community on ``the need
for a medical surveillance or screening program and on the use of
respiratory equipment.'' (57 FR 500). The comment period on the ANPRM
closed on July 10, 1992.
While MSHA was completing a ``comprehensive analysis of the
comments and any other information received'' in response to the ANPRM
(57 FR 501), it took several actions to encourage the mining community
to begin to deal with this problem, and to provide the knowledge and
equipment needed for this task. As described earlier in this part, the
Agency held several workshops in 1995, published a ``toolbox'' of
controls, and developed a spreadsheet template that allows mine
operators to compare the impacts of various controls on dpm
concentrations in individual mines.
On October 25, 1996, MSHA published a final rule addressing
approval, exhaust monitoring, and safety requirements for the use of
diesel-powered equipment in underground coal mines. (61 FR 55412). The
final rule addresses and in large part is consistent with the specific
recommendations made by the Advisory Committee for limiting underground
coal miners' exposure to diesel exhaust. (A further summary of this
rule is contained in section 7 of this part).
On February 26, 1997, the United Mine Workers of America petitioned
the U.S. Court of Appeals for the D.C. Circuit to issue a writ of
mandamus ordering the Secretary of Labor to promulgate a rule on diesel
particulate. In Re: International Union, United Mine Workers of
America, D.C. Cir. Ct. Appeals, No. 97-1109. The matter was scheduled
for oral argument on September 12, 1997. On September 11, 1997, the
Court granted the parties' joint motion to continue oral argument and
hold the proceedings in abeyance. The Court directed the parties to
file status reports or motions to govern future proceedings at 90-day
intervals. Pursuant to that order, on March 10, 1998, the Secretary
filed a status report.
III. Risk Assessment
Table of Contents
Introduction
1. Exposures of U.S. Miners
a. Underground Coal Mines
b. Underground Metal and Nonmetal Mines
c. Surface Mines
d. Comparison of Miner Exposures to Exposures of Other Groups
2. Health Effects Associated with DPM Exposures
a. Relevancy Considerations
i. Relevance of Health Effects Observed in Animals
ii. Relevance of Health Effects that are Reversible
iii. Relevance of Health Effects Associated with Fine
Particulate Matter in Ambient Air
b. Acute Health Effects
i. Symptoms Reported by Exposed Miners
ii. Studies Based on Exposures to Diesel Emissions
iii. Studies Based on Exposures to Particulate Matter in Ambient
Air
c. Chronic Health Effects
i. Studies Based on Exposures to Diesel Emissions
A. Chronic Effects Other than Cancer
B. Cancer
i. Lung Cancer
ii. Bladder Cancer
ii. Studies Based on Exposures to Fine Particulate in Ambient
Air
d. Mechanisms of Toxicity
i. Effects Other than Cancer
ii. Lung Cancer
A. Genotoxicological Evidence
B. Evidence from Animal Studies
3. Characterization of Risk
a. Material Impairments to Miner Health or Functional Capacity
i. Sensory Irritations and Respiratory Symptoms
ii. Excess Risk of Death from Cardiovascular, Cardiopulmonary,
or Respiratory Causes
iii. Lung Cancer
b. Significance of the Risk of Material Impairment to Miners
i. Definition of a Significant Risk
ii. Evidence of Significant Risk at Current Exposure Levels
c. Substantial Reduction of Risk by Proposed Rule
Conclusions
Introduction
MSHA has reviewed the scientific literature to evaluate the
potential health effects of diesel particulate at occupational
exposures encountered in the mining industry. Based on its review of
the currently available information, this part of the preamble assesses
the risks associated with those exposures. Additional material
submitted for the record will be considered by MSHA before final
determinations are made.
Agencies sometimes place risk assessments in the rulemaking record
and provide only a summary in the preamble for a proposed rule. MSHA
has decided that, in this case, it is important to disseminate a
discussion of risk widely throughout the mining community. Therefore,
the full assessment is being included as part of the preamble.
The risk assessment begins with a discussion of dpm exposure levels
observed in the mining industry. This is followed by a review of
information available to MSHA on health effects that have been
associated with diesel particulate exposure. Finally, in the section
entitled ``Characterization of Risk,'' the Agency considers three
questions that must be addressed for rulemaking under the Mine Act, and
relates the available information about risks of dpm exposure at
current levels to the regulatory requirements.
A risk assessment must be technical enough to present the evidence
and describe the main controversies surrounding it. At the same time,
an overly technical presentation could cause stakeholders to lose sight
of the main points. MSHA is guided by the first principle the National
Research Council established for risk characterization: that the
approach be--
[a] decision driven activity, directed toward informing choices
and solving problems * * * Oversimplifying the science or skewing
the results through selectivity can lead to the inappropriate use of
scientific information in risk management decisions,
[[Page 17522]]
but providing full information, if it does not address key concerns
of the intended audience, can undermine that audience's trust in the
risk analysis.
MSHA intends this risk assessment to further the rulemaking
process. The purpose of a proposed rulemaking is to advise the
regulated community of what information the agency is evaluating, how
the agency believes it should evaluate that information, and what
tentative conclusions the agency has drawn. Comments and guidance from
all interested members of the public are encouraged. The risk
assessment presented here is meant to facilitate public comment, thus,
helping to ensure that final rulemaking is based on as complete a
record as possible--on both the evidence itself and the manner in which
it is to be evaluated by the Agency. Those who want additional detail
are welcome to examine the materials cited in this part, copies of
which are included in MSHA's rulemaking record.
While this rulemaking only covers the underground coal sector, this
risk assessment was prepared so as to enable MSHA and to assess the
risks throughout the mining industry. Accordingly, this information
will be of interest to the entire mining community.
MSHA had this risk assessment independently peer reviewed. The risk
assessment presented here incorporates revisions made in accordance
with the reviewers recommendations. The reviewers stated that:
* * * principles for identifying evidence and characterizing
risk are thoughtfully set out. The scope of the document is
carefully described, addressing potential concerns about the scope
of coverage. Reference citations are adequate and up to date. The
document is written in a balanced fashion, addressing uncertainties
and asking for additional information and comments as appropriate.
(Samet and Burke, Nov. 1997).
III.1. Exposures of U.S. Miners
Information about U.S. miner exposures comes from published studies
and from additional mine surveys conducted by MSHA since 1993.\5\
Previously published studies of U.S. miner exposure to dpm are: Watts
(1989, 1992), Cantrell (1992, 1993), Haney (1992), and Tomb and Haney
(1995). MSHA has also conducted surveys subsequent to the period
covered in Tomb and Haney (1995), and the previously unpublished data
from those surveys are included here. Overall, the period covered in
MSHA's surveys, on which this section is based, is late 1988 through
mid 1997.
---------------------------------------------------------------------------
\5\ MSHA has only limited information about miner exposures in
other countries. Based on 223 personal and area samples, average
exposures at 21 Canadian noncoal mines were reported to range from
170 to 1300 g/m\3\ (respirable combustible dust), with
maximum measurements ranging from 1020 to 3100 g/m\3\
(Gangel and Dainty, 1993). Among 622 full shift measurements
collected since 1989 in German underground noncoal mines, 91 (15%)
exceeded 400 g/m\3\ (total carbon) (Dahmann et al., 1996).
As explained in Part II of this preamble, 400 g/m\3\ (total
carbon) corresponds to approximately 500 g/m\3\ dpm.
---------------------------------------------------------------------------
MSHA's field studies involved measuring dpm concentrations at a
total of 48 mines: 25 underground metal and nonmetal (M/NM) mines, 12
underground coal mines, and 11 surface mining operations (both coal and
M/NM). At all surface mines and all underground coal mines, dpm
measurements were made using the size-selective method, based on
gravimetric determination of the amount of submicrometer dust collected
with an impactor. With two exceptions, dpm measurements at underground
M/NM mines were made using the RCD method (with no submicrometer
impactor). Measurements at the two remaining underground M/NM mines
were made using the size-selective method, as in coal and surface
mines. The various methods of measuring dpm are explained in Part II of
this preamble. Weighing errors inherent in the gravimetric analysis
required for both size-selective and RCD methods become statistically
insignificant at the relatively high dpm concentrations observed.
Each underground study typically included personal dpm exposure
measurements for approximately five production workers. Also, area
samples were collected in return airways of underground mines to
determine diesel particulate emission rates. Operational information
such as the amount and type of equipment, airflow rates, fuel, and
maintenance was also recorded. In general, MSHA's studies focused on
face production areas of mines, where the highest concentrations of dpm
could be expected; but, since some miners do not spend their time in
face areas, studies were performed in other areas as well, to get a
more complete picture of miner exposure. Because of potential
interferences from tobacco smoke in underground M/NM mines, samples
were not collected on or near smokers.
Table III-1 summarizes key results from MSHA's studies.
The higher concentrations in underground mines were typically found
in the haulageways and face areas where numerous pieces of equipment
were operating, or where insufficient air was available to ventilate
the operation. In production areas and haulageways of underground mines
where diesel powered equipment is used, the mean dpm concentration
observed was 755 g/m\3\. By contrast, in travelways of
underground mines where diesel powered equipment is used, the mean dpm
concentration (based on 107 samples not included in Table III-1) was
307 g/m\3\. In surface mines, the higher concentrations were
generally associated with truck drivers and front-end loader operators.
The mean dpm concentration observed was less than 200 g/m\3\
at all 11 of the surface mines in which measurements were made. More
information about the dpm concentrations observed in each sector is
presented in the material that follows.
Table III-1.--Full-Diesel Particulate Matter Concentrations Observed in Production Areas and Haulageways of 48
Dieselized U.S. Mines. Intake and Return Area Samples are Excluded.
----------------------------------------------------------------------------------------------------------------
Mean exposure Exposure range
Mine type Number of samples g/m\3\ g/m\3\
----------------------------------------------------------------------------------------------------------------
Surface................................................ 45 88 9-380
Underground Coal....................................... 226 644 0-3,650
Underground Metal and Nonmetal......................... 331 830 10-5,570
----------------------------------------------------------------------------------------------------------------
III.1.a. Underground Coal Mines
Approximately 170 out of the 971 existing underground coal mines
currently utilize diesel powered equipment. Of these 170 mines, fewer
than 20 currently use diesel equipment for face coal haulage. The
remaining mines use diesel equipment for transportation, materials
handling and other support operations. MSHA focused its efforts in
measuring dpm concentrations in coal mines on mines that use diesel
powered equipment for face coal haulage. Twelve mines using diesel-
powered face haulage were
[[Page 17523]]
sampled. Mines with diesel powered face haulage were selected because
the face is an area with a high concentration of vehicles operating at
a heavy duty cycle at the furthest end of the mine's ventilation
system.
Diesel particulate levels in underground mines depend on: (1) the
amount, size, and workload of diesel equipment; (2) the rate of
ventilation; and, (3) the effectiveness of whatever diesel particulate
control technology may be in place. In the dieselized mines studied by
MSHA, the sections used either two or three diesel coal haulage
vehicles. In eastern mines the haulage vehicles were equipped with a
nominal 100 horsepower engine. In western mines the haulage vehicles
were equipped with a nominal 150 horsepower engine. Ventilation rates
ranged from the nameplate requirement, based on the 100-75-50 percent
rule (Holtz, 1960), to ten times the nameplate requirement. In most
cases, the section airflow was approximately twice the name plate
requirement. Control technology involved aftertreatment filters and
fuel. Two types of aftertreatment filters were used. These filters
included a disposable diesel emission filter (DDEF) and a Wire Mesh
Filter (WMF). The DDEF is a commercially available product; the WMF was
developed by and only used at one mine. Both low sulfur and high sulfur
fuels were used.
Figure III-1 displays the range of exposure measurements obtained
by MSHA in the field studies it conducted in underground coal mines. A
study normally consisted of collecting samples on the continuous miner
operator and ramcar operators for two to three shifts, along with area
samples in the haulageways. A total of 142 personal samples and 84 area
samples were collected. No statistically significant difference was
observed in mean dpm concentration between the personal and area
samples.
[GRAPHIC] [TIFF OMITTED] TP09AP98.004
In six mines, measurements were taken both with and without
employment of disposable after treatment filters, so that a total of
eighteen studies, carried out in twelve mines, are displayed. Without
employment of after treatment filters, average observed dpm
concentrations exceeded 500 g/m \3\ in eight of the twelve
mines and exceeded 1000 g/m \3\ in four.\6\
---------------------------------------------------------------------------
\6\ In coal mine E, the average as expressed by the mean
exceeded 1000 g/m \3\, but the median did not.
---------------------------------------------------------------------------
The highest dpm concentrations observed at coal mines were
collected at Mine ``G.'' Eight of these samples were collected during
employment of DDEF's, and eight were collected while filters were not
being employed. Without filters, the mean dpm concentration observed at
Mine ``G'' was 2052 g/m\3\
[[Page 17524]]
(median = 2100 g/m\3\). With disposable filters, the mean
dropped to 1241 g/m\3\ (median = 1235 g/m\3\).
Filters were employed in three of the four studies showing median
dpm concentration at or below 200 g/m\3\. After adjusting for
outby sources of dpm, exposures were found to be reduced by up to 95
percent in mines using the DDEF and by up to 50 percent in the mine
using the WMF. The higher dpm concentrations observed at the mine using
the WMF are attributable partly to the lower section airflow. The only
study without filters showing a median concentration at or below 200
g/m\3\ was conducted in a mine (Mine ``A'') which had section
airflow approximately ten times the nameplate requirement. The section
airflow at the mine using the WMF was approximately the nameplate
requirement.
III.1.b. Underground Metal and Nonmetal Mines. Currently there are
approximately 260 underground M/NM mines in the United States. Nearly
all of these mines utilize diesel powered equipment, and twenty-five of
those doing so were sampled by MSHA for dpm. The M/NM studies typically
included measurements of dpm exposure for dieselized production
equipment operators (such as truck drivers, roof bolters, haulage
vehicles) on two to three shifts. A number of area samples were also
collected. None of the M/NM mines studied were using diesel particulate
afterfilters.
Figure III-2 displays the range of dpm concentrations measured by
MSHA in the twenty-five underground M/NM mines studied. A total of 254
personal samples and 77 area samples were collected. No statistically
significant difference was observed in mean dpm concentration between
the personal and area samples. Personal exposures observed ranged from
less than 100 g/m\3\ to more than 3500 g/m\3\. With
the exception of Mine ``V'', personal exposures were for face workers.
Mine ``V'' did not use dieselized face equipment.
Average observed dpm concentrations exceeded 500 g/m\3\ in
17 of the 25 M/NM mines and exceeded 1000 g/m\3\ in 12.\7\ The
highest dpm concentrations observed at M/NM mines were collected at
Mine ``E''. Based on 16 samples, the mean dpm concentration observed at
Mine ``E'' was 2008 g/m\3\ (median = 1835 g/m\3\).
Twenty-five percent of the dpm measurements at this mine exceeded 2400
g/m\3\. All four of these were based on personal samples.
\7\ At M/NM mines C, I, J, and P, the average as expressed by
the mean exceeded 100 g/m\3\ but the median did not. At N/
NM mines H and S, the median exceeded 1000 g/m\3\ but the
mean did not. At M/NM mine K, the mean exceeded 500 g/m\3\,
but the median did not.
[GRAPHIC] [TIFF OMITTED] TP09AP98.005
As with underground coal mines, dpm levels in underground M/NM
mines are related to the amount and size of equipment, to the
ventilation rate, and to the effectiveness of the diesel particulate
control technology employed. In the dieselized M/NM mines studied by
MSHA, front-end-loaders were used either to load ore
[[Page 17525]]
onto trucks or to haul and load ore onto belts. Additional pieces of
diesel powered support equipment, such as bolters and mantrips, were
also used at the mines. The typical piece of production equipment was
rated at 150 to 350 horsepower. Ventilation rates in the M/NM mines
studied mostly ranged from 100 to 200 cfm per horsepower of equipment.
In only a few of the mines surveyed did ventilation exceed 200 cfm/hp.
For single-level mines, working areas were ventilated in series, i.e.,
the exhaust air from one area became the intake for the next working
area. For multi-level mines, each level typically had a separate fresh
air supply. One or two working areas could be on a level. Control
technology used to reduce diesel particulate emissions in mines
surveyed included oxidation catalytic converters and engine maintenance
programs. Both low sulfur and high sulfur fuel were used; some mines
used aviation grade low sulfur fuel.
III.1.c. Surface Mines. Currently, there are approximately 12,200
surface mining operations in the United States. The total consists of
approximately 1,700 coal mines and 10,500 M/NM mines. Virtually all of
these mines utilize diesel powered equipment.
MSHA conducted diesel particulate studies at eleven surface mining
operations: eight coal mines and three M/NM mines. To help select those
surface facilities likely to have significant dpm concentrations, MSHA
first made a visual examination (based on blackness of the filter) of
surface mine respirable dust samples collected during a November 1994
study of surface coal mines. This preliminary screening of samples
indicated that higher exposures to diesel particulate are typically
associated with front-end-loader operators and haulage-truck operators;
accordingly, sampling focused on these operations. A total of 45
samples were collected.
Figure III-3 displays the range of dpm concentrations measured at
the eleven surface mines. The average dpm concentration observed was
less than 200 g/m\3\ at all mines sampled. The maximum dpm
concentration observed was less than or equal to 200 g/m\3\ in
8 of the 11 mines (73%). The surface mine studies indicate that even
when sampling is performed at the areas of surface mines believed most
likely to have high exposures, dpm concentrations are generally less
than 200 g/m\3\.
[GRAPHIC] [TIFF OMITTED] TP09AP98.006
III.1.d. Comparison of Miner Exposures to Exposures of Other
Groups. Occupational exposure to diesel particulate primarily
originates from industrial operations employing equipment powered with
diesel engines. Diesel engines are used to power ships, locomotives,
heavy duty trucks, heavy machinery, as well as a small number of light-
duty passenger cars and trucks. NIOSH estimates that approximately 1.35
million workers are occupationally exposed to the combustion products
of diesel fuel in approximately 80,000 workplaces in the United States.
Workers who are likely to be exposed to diesel emissions include: mine
workers; bridge and tunnel workers; railroad workers; loading dock
workers; truck drivers; fork-lift drivers; farm workers; and, auto,
truck, and bus maintenance garage workers (NIOSH, 1988). Besides
miners, groups for which occupational exposures have been reported and
health effects have been studied include dock workers, truck drivers,
and railroad workers.
[[Page 17526]]
As estimated by geometric mean, median occupational exposures
reported for dock workers either operating or otherwise exposed to
diesel fork lift trucks have ranged from 23 to 55 g/m\3\, as
measured by submicrometer elemental carbon (NIOSH, 1990; Zaebst et al.,
1991). Watts (1995) states that ``elemental carbon generally accounts
for about 40% to 60% of diesel particulate mass.'' Assuming that, on
average, the submicrometer elemental carbon constituted approximately
50% by mass of the whole diesel particulate, this would correspond to a
range of 46 to 110 g/m\3\ in median dpm concentrations at
various docks.
In a study of dpm exposures in the trucking industry, Zaebst et al.
(1991) reported geometric mean concentrations of submicrometer carbon
ranging from 2 to 7 g/m \3\ for drivers to 5 to 28 g/
m \3\ for mechanics, depending on weather conditions. Again assuming
that, on average, the mass concentration of whole diesel particulate is
about twice that of submicrometer elemental carbon, the corresponding
range of median dpm concentrations would be 4 to 56 g/m \3\.
Exposures of railroad workers to dpm were estimated by Woskie et
al. (1988) and Schenker et al. (1990). As measured by total respirable
particulate matter other than cigarette smoke, Woskie et al. reported
geometric mean concentrations for various occupational categories of
exposed railroad workers ranging from 49 to 191 g/
m3.
Figure III-4 shows the range of median dpm concentrations observed
for mine workers at different mines compared to the range of median
concentrations estimated for dock workers (including forklift drivers
at loading docks), truck drivers and mechanics, railroad workers, and
urban ambient air. The range for ambient air, 1 to 10 g/
m3, was obtained from Cass and Gray (1995). For dock
workers, truck drivers, and railroad workers, the estimated range of
median exposures is respectively 46 to 110 g/m3, 4
to 56 g/m3, and 49 to 191 g/m3.
The range of medians observed at different underground coal mines is 55
to 2100 g/m3, with filters employed at mines
showing the lower concentrations. For underground M/NM mines, the
corresponding range is 68 to 1835 g/m3, and for
surface mines it is 19 to 160 g/m3.
[GRAPHIC] [TIFF OMITTED] TP09AP98.007
As shown in Figure III-4, some miners are exposed to far higher
concentrations of dpm than are any other populations for which data
have been collected. Indeed, median dpm concentrations observed in some
underground mines are up to 200 times as high as average environmental
exposures in the most heavily polluted urban areas, and up to 10 times
as high as median exposures estimated for the most heavily exposed
workers in other occupational groups.
III.2. Health Effects Associated with DPM Exposures.
[[Page 17527]]
This section reviews all the various health effects (of which MSHA
is aware) that may be associated with exposure to diesel particulate.
The review is divided into three main sections: acute effects, such as
diminished pulmonary function and eye irritation; chronic effects, such
as lung cancer; and mechanisms of toxicity. Prior to that review,
however, the relevance of certain types of information will be
considered. This discussion will address the relevance of health
effects observed in animals, health effects that are reversible, and
health effects associated with fine particulate matter in the ambient
air.
III.2.a. Relevancy Considerations.
III.2.a.i. Relevance of Health Effects Observed in Animals. Since
the lungs of different species may react differently to particle
inhalation, it is necessary to treat the results of animal studies with
some caution. Evidence from animal studies can nevertheless be
valuable, and those respondents to MSHA's ANPRM who addressed this
question urged consideration of all animal studies related to the
health effects of diesel exhaust.
Unlike humans, laboratory animals are bred to be homogeneous and
can be randomly selected for either non-exposure or exposure to varying
levels of a potentially toxic agent. This permits setting up
experimental and control groups of animals that do not differ
biologically prior to exposure. The consequences of exposure can then
be determined by comparing responses in the experimental and control
groups. After a prescribed duration of deliberate exposure, laboratory
animals can also be sacrificed, dissected, and examined. This can
contribute to an understanding of mechanisms by which inhaled particles
may exert their effects on health. For this reason, discussion of the
animal evidence is placed in the section entitled ``Mechanisms of
Toxicity'' below.
Animal evidence also can help isolate the cause of adverse health
effects observed among humans exposed to a variety of potentially
hazardous substances. If, for example, the epidemiological data is
unable to distinguish between several possible causes of increased risk
of disease in a certain population, then controlled animal studies may
provide evidence useful in suggesting the most likely explanation--and
provide that information years in advance of definitive evidence from
human observations.
Furthermore, results from animal studies may also serve as a check
on the credibility of observations from epidemiological studies of
human populations. If a particular health effect is observed in animals
under controlled laboratory conditions, this tends to corroborate
observations of similar effects in humans.
Accordingly, MSHA believes that judicious use of evidence from
animal studies is appropriate. The extent to which MSHA relies upon
such evidence to draw specific conclusions will be
[[Page 17528]]
discussed below in connection with those conclusions.
III.2.a.ii. Relevance of Health Effects That Are Reversible. Some
reported health effects associated with dpm are apparently reversible--
i.e., if the worker is moved away from the source for a few days, the
health problem goes away. A good example is eye irritation.
In response to the ANPRM, questions were raised as to whether so-
called ``reversible'' effects can constitute a ``material'' impairment.
For example, one commenter argued that ``it is totally inappropriate
for the agency to set permissible exposure limits based on temporary,
reversible sensory irritation'' because such effects cannot be a
``material'' impairment of health or functional capacity within the
definition of the Mine Act (American Mining Congress, 87-0-21,
Executive Summary, p. 1, and Appendix A).
MSHA does not agree with this categorical view. Although the
legislative history of the Mine Act is silent concerning the meaning of
the term ``material impairment of health or functional capacity,'' and
the issue has not been litigated within the context of the Mine Act,
the statutory language about risk in the Mine Act is similar to that
under the OSH Act. A similar argument was dispositively resolved in
favor of the Occupational Safety and Health Administration (OSHA) by
the 11th Circuit Court of Appeals in AFLCIO v. OSHA, 965 F.2d 962, 974
(1992) (popularly known as the ``PEL's'' decision).
In that case, OSHA proposed new limits on 428 diverse substances.
It grouped these into 18 categories based upon the primary health
effects of those substances: e.g., neuropathic effects, sensory
irritation, and cancer. (54 FR 2402). Challenges to this rule included
the assertion that a ``sensory irritation'' was not a ``material
impairment of health or functional capacity'' which could be regulated
under the OSH Act. Industry petitioners argued that since irritant
effects are transient in nature, they did not constitute a ``material
impairment.'' The Court of Appeals decisively rejected this argument.
The court noted OSHA's position that effects such as stinging,
itching and burning of the eyes, tearing, wheezing, and other types of
sensory irritation can cause severe discomfort and be seriously
disabling in some cases. Moreover, there was evidence that workers
exposed to these sensory irritants could be distracted as a result of
their symptoms, thereby endangering other workers and increasing the
risk of accidents. (Id. at 974). This evidence included information
from NIOSH about the general consequences of sensory irritants on job
performance, as well as testimony by commenters on the proposed rule
supporting the view that such health effects should be regarded as
material health impairments. While acknowledging that ``irritation''
covers a spectrum of effects, some of which can be trivial, OSHA had
concluded that the health effects associated with exposure to these
substances warranted action--to ensure timely medical treatment, reduce
the risks from increased absorption, and avoid a decreased resistance
to infection (Id. at 975). Finding OSHA's evaluation adequate, the
Court of Appeals rejected petitioners' argument and stated the
following:
We interpret this explanation as indicating that OSHA finds that
although minor irritation may not be a material impairment, there is
a level at which such irritation becomes so severe that employee
health and job performance are seriously threatened, even though
those effects may be transitory. We find this explanation adequate.
OSHA is not required to state with scientific certainty or precision
the exact point at which each type of sensory or physical irritation
becomes a material impairment. Moreover, section 6(b)(5) of the Act
charges OSHA with addressing all forms of ``material impairment of
health or functional capacity,'' and not exclusively ``death or
serious physical harm'' or ``grave danger'' from exposure to toxic
substances. See 29 U.S.C. 654(a)(1), 655(c). [Id. at 974.]
III.2.a.iii. Relevance of Health Effects Associated with Fine
Particulate Matter in Ambient Air. There have been many studies in
recent years designed to determine whether the mix of particulate
matter in ambient air is harmful to health. The evidence linking
particulates in air pollution to health problems has long been
compelling enough to warrant direction from the Congress to limit the
concentration of such particulates (see part II, section 5 of this
preamble). In recent years, the evidence of harmful effects due to
airborne particulates has increased, and, moreover, has suggested that
``fine'' particulates (i.e., particles less than 2.5 m in
diameter) are more strongly associated than ``coarse'' particulates
(i.e., respirable particles greater than 2.5 m in diameter)
with the adverse health effects observed (EPA, 1996).
MSHA recognizes that there are two difficulties involved in
utilizing the evidence from such studies in assessing risks to miners
from occupational dpm exposures. First, although dpm is a fine
particulate, ambient air also contains fine particulates other than
dpm. Therefore, health effects associated with exposures to fine
particulate matter in air pollution studies are not associated
specifically with exposures to dpm or any other one kind of fine
particulate matter. Second, observations of adverse health effects in
segments of the general population do not necessarily apply to the
population of miners. Since, due to age and selection factors, the
health of miners differs from that of the public as a whole, it is
possible that fine particles might not affect miners, as a group, to
the same extent as the general population.
Nevertheless, there are compelling reasons to consider this body of
evidence. Since dpm is a type of respirable particle, information about
health effects associated with exposures to respirable particles in
general, and especially to fine particulate matter, is certainly
relevant, even if difficult to apply directly to dpm exposures. Adverse
health effects in the general population have been observed at ambient
atmospheric particulate concentrations well below those studied in
occupational settings. Furthermore, there is extensive literature
showing that occupational dust exposures contribute to Chronic
Obstructive Pulmonary Diseases (COPD), thereby compromising the
pulmonary reserve of some miners, and that miners experience COPD at a
significantly higher rate than the general population (Becklake 1989,
1992; Oxman 1993; NIOSH 1995). This would appear to place affected
miners in a subpopulation specifically identified as susceptible to the
adverse health effects of respirable particle pollution (EPA, 1996).
The Mine Act requires standards that ``* * * most adequately assure on
the basis of the best available evidence that no miner suffer material
impairment of health or functional capacity * * *'' (Section 101(a)(6),
emphasis added).
In sum, MSHA believes it would be a serious omission to ignore the
body of evidence from air pollution studies and the Agency is,
therefore, taking that evidence into account. The Agency would,
however, welcome additional scientific information and analysis on ways
of applying this body of evidence to miners experiencing acute and/or
chronic dpm exposures. MSHA is especially interested in receiving
information on whether the elevated prevalence of COPD among miners
makes them, as a group, highly susceptible to the harmful effects of
fine particulate air pollution, including dpm.
III.2.b. Acute Health Effects
Information relating to the acute health effects of dpm includes
anecdotal reports of symptoms experienced by exposed miners, studies
based on
[[Page 17529]]
exposures to diesel emissions, and studies based on exposures to
particulate matter in the ambient air. These will be discussed in turn.
III.2.b.i. Symptoms Reported by Exposed Miners. Miners working in
mines with diesel equipment have long reported adverse effects after
exposure to diesel exhaust. For example, at the workshops on dpm
conducted in 1995, a miner reported headaches and nausea among several
operators after short periods of exposure (dpm Workshop; Mt. Vernon,
IL, 1995). Another miner reported that the smoke from equipment using
improper fuel or not well maintained is an irritant to nose and throat
and impairs vision. ``We've had people sick time and time again * * *
at times we've had to use oxygen for people to get them to come back
around to where they can feel normal again.'' (dpm Workshop; Beckley,
WV, 1995). Other miners (dpm Workshops; Beckley, WV, 1995; Salt Lake
City, UT, 1995), reported similar symptoms in the various mines where
they worked.
Kahn et al. (1988) conducted a study of the prevalence and
seriousness of such complaints, based on United Mine Workers of America
records and subsequent interviews with the miners involved. The review
involved reports at five underground coal mines in Utah and Colorado
between 1974 and 1985. Of the 13 miners reporting symptoms: 12 reported
mucous membrane irritation, headache and light-headiness; eight
reported nausea; four reported heartburn; three reported vomiting and
weakness, numbness, and tingling in extremities; two reported chest
tightness; and two reported wheezing (although one of these complained
of recurrent wheezing without exposure). All of these incidents were
severe enough to result in lost work time due to the symptoms (which
subsided within 24 to 48 hours).
MSHA welcomes additional information about such effects including
information from medical personnel who have treated miners and
information on work time lost, together with information about the
exposures of miners for whom such effects have been observed. The
Agency would be especially interested in comparisons of effects
observed in workers subjected to filtered exhaust as compared to those
subjected to unfiltered exhaust.
III.2.b.ii. Studies Based on Exposures to Diesel Emissions. Several
scientific studies have been conducted to investigate acute effects of
exposure to diesel emissions.
In a clinical study (Battigelli, 1965), volunteers were exposed to
different levels of diesel exhaust and then the degree of eye
irritation was measured. Exposure for ten minutes to diesel exhaust
produced ``intolerable'' irritation in some subjects while the average
irritation score was midway between ``some'' irritation and a
``conspicuous but tolerable'' irritation level. Cutting the exposure by
50% significantly reduced the irritation.
In a study of underground iron ore miners exposed to diesel
emissions, Jrgensen and Svensson (1970), found no difference in
spirometry measurements taken before and after a work shift. Similarly,
Ames et al. (1982), in a study of coal miners exposed to diesel
emissions, detected no statistically significant relationship between
exposure and pulmonary function. However, the authors noted that the
lack of a positive result might be due to the low concentrations of
diesel emissions involved.
Gamble et al. (1978) did observe decreases in pulmonary function
over a single shift in salt miners exposed to diesel emissions.
Pulmonary function appeared to deteriorate in relation to the
concentration of diesel exhaust, as indicated by NO2; but
this effect was confounded by the presence of NO2 due to the
use of explosives.
Gamble et al. (1987a) assessed response to diesel exposure among
232 bus garage workers by means of a questionnaire and before- and
after-shift spirometry. No significant relationship was detected
between diesel exposure and change in pulmonary function. However,
after adjusting for age and smoking status, a significantly elevated
prevalence of reported symptoms was found in the high-exposure group.
The strongest associations with exposure were found for eye irritation,
labored breathing, chest tightness, and wheeze. The questionnaire was
also used to compare various acute symptoms reported by the garage
workers and a similar population of workers at a lead acid battery
plant who were not exposed to diesel fumes. The prevalence of work-
related eye irritations, headaches, difficult or labored breathing,
nausea, and wheeze was significantly higher in the diesel bus garage
workers, but the prevalence of work-related sneezing was significantly
lower.
Ulfvarson et al. (1987) studied effects over a single shift on 47
stevedores exposed to dpm at particle concentrations ranging from 130
g/m\3\3 to 1000 g/m\3\. A statistically significant
loss of pulmonary function was observed, with recovery after 3 days of
no occupational exposure.
To investigate whether removal of the particles from diesel exhaust
might reduce the ``acute irritative effect on the lungs'' observed in
their earlier study, Ulfvarson and Alexandersson (1990) compared
pulmonary effects in a group of 24 stevedores exposed to unfiltered
diesel exhaust to a group of 18 stevedores exposed to filtered exhaust,
and to a control group of 17 occupationally unexposed workers. Workers
in all three groups were nonsmokers and had normal spirometry values,
adjusted for sex, age, and height, prior to the experimental workshift.
In addition to confirming the earlier observation of significantly
reduced pulmonary function after a single shift of occupational
exposure, the study found that the stevedores in the group exposed only
to filtered exhaust had 50-60% less of a decline in forced vital
capacity (FVC) than did those stevedores who worked with unfiltered
equipment. Similar results were observed for a subgroup of six
stevedores who were exposed to filtered exhaust on one shift and
unfiltered exhaust on another. No loss of pulmonary function was
observed for the unexposed control group. The authors suggested that
these results ``support the idea that the irritative effects of diesel
exhausts to the lungs [sic] is the result of an interaction between
particles and gaseous components and not of the gaseous components
alone.'' They concluded that ``* * * it should be a useful practice to
filter off particles from diesel exhausts in work places even if
potentially irritant gases remain in the emissions.''
Rudell et al., (1996) carried out a series of double-blind
experiments on 12 healthy, non-smoking subjects to investigate whether
a particle trap on the tailpipe of an idling diesel engine would reduce
acute effects of diesel exhaust, compared with exposure to unfiltered
exhaust. Symptoms associated with exposure included headache,
dizziness, nausea, tiredness, tightness of chest, coughing, and
difficulty in breathing, but the most prominent were found to be
irritation of the eyes and nose, and a sensation of unpleasant smell.
Among the various pulmonary function tests performed, exposure was
found to result in significant changes only as measured by increased
airway resistance and specific airway resistance. The ceramic wall flow
particle trap reduced the number of particles by 46 percent, but
resulted in no significant attenuation of symptoms or lung function
effects. The authors concluded that diluted diesel exhaust caused
increased symptoms of the eyes and nose, unpleasant smell, and
bronchoconstriction, but that the 46 percent reduction in median
particle
[[Page 17530]]
number concentration observed was not sufficient to protect against
these effects in the populations studied.
Wade and Newman (1993) documented three cases in which railroad
workers developed persistent asthma following exposure to diesel
emissions while riding immediately behind the lead engines of trains
having no caboose. None of these workers were smokers or had any prior
history of asthma or other respiratory disease. Although this is the
only published report MSHA knows of directly relating exposure to
diesel emissions with the development of asthma, there have been a
number of recent studies indicating that dpm exposure can induce
bronchial inflammation and respiratory immunological allergic responses
in humans. These are reviewed in Peterson and Saxon (1996) and Diaz-
Sanchez (1997).
III.2.b.iii. Studies Based on Exposures to Particulate Matter in
Ambient Air. As early as the 1930's, as a result of an incident in
Belgium's industrial Meuse Valley, it was known that large increases in
particulate air pollution, created by winter weather inversions, could
be associated with large simultaneous increases in mortality and
morbidity. More than 60 persons died from this incident, and several
hundred suffered respiratory problems. The mortality rate during the
episode was more than ten times higher than normal, and it was
estimated that 3,179 sudden deaths would occur if a similar incident
occurred in London. Although no measurements of pollutants in the
ambient air during the episode are available, high PM levels were
obviously present (EPA, 1996).
A significant elevation in particulate matter (along with
SO2 and its oxidation products) was measured during a 1948
incident in Donora, PA. Of the Donora population, 42.7 percent
experienced some adverse health effect, mainly due to irritation of the
respiratory tract. Twelve percent of the population reported difficulty
in breathing, with a steep rise in frequency as age progressed to 55
years (Schrenk, 1949).
Approximately as projected by Firket (1931), an estimated 4,000
deaths occurred in response to a 1952 episode of extreme air pollution
in London. The nature of these deaths is unknown, but there is clear
evidence that bronchial irritation, dyspnea, bronchospasm, and, in some
cases, cyanosis occurred with unusual prevalence (Martin, 1964).
These three episodes ``left little doubt about causality regarding
the induction of serious health effects by very high concentrations of
particle-laden air pollutant mixtures'' and stimulated additional
research to characterize exposure-response relationships (EPA, 1996).
Based on several analyses of the 1952 London data, along with several
additional acute exposure mortality analyses of London data covering
later time periods, the U.S. Environmental Protection Agency (EPA)
concluded that increased risk of mortality is associated with exposure
to particulate and SO2 levels in the range of 500-1000
g/m3. The EPA also concluded that relatively small,
but statistically significant increases in mortality risk exist at
particulate levels below 500 g/m3, with no
indications of any specific threshold level yet indicated at lower
concentrations (EPA, 1986).
Subsequently, between 1986 and 1996, increasingly sophisticated
particulate measurements and statistical techniques have enabled
investigators to address these questions more quantitatively. The
studies on acute effects carried out since 1986 are reviewed in the
1996 EPA Air Quality Criteria for Particulate Matter, which forms the
basis for the discussion below (EPA, 1996).
At least 21 studies have been conducted that evaluate associations
between acute mortality and morbidity effects and various measures of
fine particulate levels in the ambient air. These studies are
identified in Tables III-2 and III-3. Table III-2 lists 11 studies that
measured primarily fine particulate matter using filter-based optical
techniques and, therefore, provide mainly qualitative support for
associating observed effects with fine particles. Table III-3 lists
quantitative results from 10 studies that reported gravimetric
measurements of either the fine particulate fraction or of components,
such as sulfates, that serve as indicators.
A total of 38 studies examining relationships between short-term
particulate levels and increased mortality, including nine with fine
particulate measurements, were published between 1988 and 1996 (EPA,
1996). Most of these found statistically significant positive
associations. Daily or several-day elevations of particulate
concentrations, at average levels as low as 18-58 g/
m3, were associated with increased mortality, with stronger
relationships observed in those with preexisting respiratory and
cardiovascular disease. Overall, these studies suggest that an increase
of 50 g/m3 in the 24-hour average of
PM10 is associated with a 2.5 to 5-percent increase in the
risk of mortality in the general population. Based on Schwartz et al.
(1996), the relative risk of mortality in the general population
increased by 2.6 to 5.5 percent per 25 g/m3 of fine
particulate (PM2.5) (EPA, 1996).
A total of 22 studies were published on associations between short-
term particulate levels and hospital admissions, outpatient visits, and
emergency room visits for respiratory disease, Chronic Obstructive
Pulmonary Disease (COPD), pneumonia, and heart disease (EPA, 1996).
Fifteen of these studies were focussed on the elderly. Of the seven
that dealt with all ages (or in one case, persons less than 65 years
old), all showed positive results. All of the five studies relating
fine particulate measurements to increased hospitalization, listed in
Tables III-2 and III-3, dealt with general age populations and showed
statistically significant associations. The estimated increase in risk
ranges from 3 to 16 percent per 25 g/m3 of fine
particulate. Overall, these studies are indicative of acute morbidity
effects being related to fine particulate matter and support the
mortality findings.
Most of the 14 published quantitative studies on ambient
particulate exposures and acute respiratory symptoms were restricted to
children (EPA, 1996). Although they generally showed positive
associations, and may be of considerable biological relevance, evidence
of toxicity in children is not necessarily applicable to adults. The
few studies on adults have not produced statistically significant
evidence of a relationship.
Fourteen studies since 1982 have investigated associations between
ambient particulate levels and loss of pulmonary function (EPA, 1996).
In general, these studies suggest a short term effect, especially in
symptomatic groups such as asthmatics, but most were carried out on
children only. In a study of adults with mild COPD, Pope and Kanner
(1993) found a 2910 ml decrease in 1-second Forced
Expiratory Volume (FEV1) per 50 g/m3
increase in PM10, which is similar in magnitude to the
change generally observed in the studies on children. In another study
of adults, with PM10 ranging from 4 to 137 g/
m3, Dusseldorp et al. (1995) found 45 and 77 ml/sec
decreases, respectively, for evening and morning Peak Expiratory Flow
Rate (PEFR) per 50 g/m3 increase in PM10
(EPA, 1996). In the only study carried out on adults that specifically
measured fine particulate (PM2.5), Perry et al. (1983) did
not detect any association of exposure with loss of pulmonary function.
This study, however, was conducted on only 24 adults (all asthmatics)
exposed at relatively low concentrations of PM2.5
[[Page 17531]]
and, therefore, had very little power to detect any such association.
III.2.c. Chronic Health Effects
During the 1995 dpm workshops, miners reported observable adverse
health effects among those who have worked a long time in dieselized
mines. For example, a miner (dpm Workshop; Salt Lake City, UT, 1995),
stated that miners who work with diesel ``have spit up black stuff
every night, big black--what they call black (expletive) ***[they] have
the congestion every night*** the 60-year-old man working there 40
years.'' Scientific investigation of the chronic health effects of dpm
exposure includes studies based specifically on exposures to diesel
emissions and studies based more generally on exposures to fine
particulate matter in the ambient air. Only the evidence from human
studies will be addressed in this section. Data from genotoxicology
studies and studies on laboratory animals will be discussed later, in
the section on potential mechanisms of toxicity.
III.2.c.i. Studies Based on Exposures to Diesel Emissions. The
discussion will summarize the epidemiological literature on chronic
effects other than cancer, and then concentrate on the epidemiology of
cancer in workers exposed to dpm.
III.2.c.i.A. Chronic Effects Other than Cancer. There have been a
number of epidemiological studies that investigated relationships
between diesel exposure and the risk of developing persistent
respiratory symptoms, (i.e., chronic cough, chronic phlegm, and
breathlessness), or measurable loss in lung function. Three studies
involved coal miners (Reger et al., 1982; Ames et al., 1984; Jacobson
et al., 1988); four studies involved metal and nonmetal miners
(Jorgenson & Svensson, 1970; Attfield, 1979; Attfield et al., 1982;
Gamble et al., 1983). Three studies involved other groups of workers--
railroad workers (Battigelli et al., 1964), bus garage workers (Gamble
et al., 1987), and stevedores (Purdham et al., 1987).
Reger et al. (1982) examined the prevalence of respiratory symptoms
and the level of pulmonary function among more than 1,600 underground
and surface coal miners, comparing results for workers (matched for
smoking status, age, height, and years worked underground) at diesel
and non-diesel mines. Those working at underground dieselized mines
showed some increased respiratory symptoms and reduced lung function,
but a similar pattern was found in surface miners who presumably would
have experienced less diesel exposure. Miners in the dieselized mines,
however, had worked underground for less than 5 years on average.
In a study of 1,118 coal miners, Ames et al. (1984) did not detect
any pattern of chronic respiratory effects associated with exposure to
diesel emissions. The analysis, however, took no account of baseline
differences in lung function or symptom prevalence, and the authors
noted a low level of exposure to diesel-exhaust contaminants in the
exposed population.
In a cohort of 19,901 coal miners investigated over a 5-year
period, Jacobsen et al. (1988) found increased work absence due to
self-reported chest illness in underground workers exposed to diesel
exhaust, as compared to surface workers, but found no correlation with
their estimated level of exposure.
Jorgenson & Svensson (1970) found higher rates of chronic
productive bronchitis, for both smokers and nonsmokers, among
underground iron ore miners exposed to diesel exhaust as compared to
surface workers at the same mine. No significant difference was found
in spirometry results.
Using questionnaires collected from 4,924 miners at 21 metal and
nonmetal mines, Attfield (1979) evaluated the effects of exposure to
silica dust and diesel exhaust and obtained inconclusive results with
respect to diesel exposure. For both smokers and non-smokers, miners
occupationally exposed to diesel for five or more years showed an
elevated prevalence of persistent cough, persistent phlegm, and
shortness of breath, as compared to miners exposed for less than five
years, but the differences were not statistically significant. Four
quantitative indicators of diesel use failed to show consistent trends
with symptoms and lung function.
Attfield et al. (1982) reported on a medical surveillance study of
630 white male miners at 6 potash mines. No relationships were found
between measures of diesel use or exposure and various health indices,
based on self-reported respiratory symptoms, chest radiographs, and
spirometry.
In a study of salt miners, Gamble et al. (1983) observed some
elevation in cough, phlegm, and dyspnea associated with mines ranked
according to level of diesel exhaust exposure. No association between
respiratory symptoms and estimated cumulative diesel exposure was found
after adjusting for differences among mines. However, since the mines
varied widely with respect to diesel exposure levels, this adjustment
may have masked a relationship.
Battigelli et al. (1964) compared pulmonary function and complaints
of respiratory symptoms in 210 railroad repair shop employees, exposed
to diesel for an average of 10 years, to a control group of 154
unexposed railroad workers. Respiratory symptoms were less prevalent in
the exposed group, and there was no difference in pulmonary function;
but no adjustment was made for differences in smoking habits.
In a study of workers at four diesel bus garages in two cities,
Gamble et al. (1987b) investigated relationships between tenure (as a
surrogate for cumulative exposure) and respiratory symptoms, chest
radiographs, and pulmonary function. The study population was also
compared to an unexposed control group of workers with similar
socioeconomic background.
After indirect adjustment for age, race, and smoking, the exposed
workers showed an increased prevalence of cough, phlegm, and wheezing,
but no association was found with tenure. Age-and height-adjusted
pulmonary function was found to decline with duration of exposure, but
was elevated on average, as compared to the control group.
The number of positive radiographs was too small to support any
conclusions. The authors concluded that the exposed workers may have
experienced some chronic respiratory effects.
Purdham et al. (1987) compared baseline pulmonary function and
respiratory symptoms in 17 exposed stevedores to a control group of 11
port office workers. After adjustment for smoking, there was no
statistically significant difference in self-reported respiratory
symptoms between the two groups. However, after adjustment for smoking,
age, and height, exposed workers showed lower baseline pulmonary
function, consistent with an obstructive ventilatory defect, as
compared to both the control group and the general metropolitan
population.
In a recent review of these studies, Cohen and Higgins (1995)
concluded that they did not provide strong or consistent evidence for
chronic, nonmalignant respiratory effects associated with occupational
exposure to diesel exhaust. These reviewers stated, however, that
``several studies are suggestive of such effects * * * particularly
when viewed in the context of possible biases in study design and
analysis.'' MSHA agrees that the studies are inconclusive but
suggestive of possible effects.
III.2.c.i.B. Cancer. Because diesel exhaust has long been known to
contain traces of carcinogenic compounds (e.g., benzene in the gaseous
fraction and
[[Page 17532]]
benzopyrene and nitropyrene in the dpm fraction), a great deal of
research has been conducted to determine if occupational exposure to
diesel exhaust actually results in an increased risk of cancer.
Evidence that exposure to dpm increases the risk of developing cancer
comes from three kinds of studies: human studies, genotoxicological
studies, and animal studies. MSHA places the most weight on evidence
from the human epidemiological studies and views the genotoxicological
and animal studies as lending support to the epidemiological evidence.
In the epidemiological studies, it is generally impossible to
disassociate exposure to dpm from exposure to the gasses and vapors
that form the remainder of whole diesel exhaust. However, the animal
evidence shows no significant increase in the risk of lung cancer from
exposure to the gaseous fraction alone (Heinrich et al., 1986; Iwai et
al., 1986; Brightwell et al., 1986). Therefore, dpm, rather than the
gaseous fraction of diesel exhaust, is assumed to be the agent
associated with an excess risk of lung cancer.
III.2.c.i.B.i. Lung Cancer. Beginning in 1957, at least 43
epidemiological studies have been published examining relationships
between diesel exhaust exposure and the prevalence of lung cancer. The
most recent published reviews of these studies are by Mauderly (1992),
Cohen and Higgins (1995), Stober and Abel (1996), Morgan et al. (1997),
and Dawson et al. (1998). In addition, in response to the ANPRM,
several commenters provided MSHA with their own reviews. Two
comprehensive statistical ``meta-analyses'' of the epidemiological
literature are also available: Lipsett and Alexeeff (1998) and Bhatia
et al. (1998). These meta-analyses, which analyze and combine results
from the various epidemiological studies, both suggest a statistically
significant increase of 30 to 40 percent in the risk of lung cancer,
attributable to occupational dpm exposure. The studies themselves,
along with MSHA's comments on each study, are summarized in Tables III-
4 (24 cohort studies) and III-5 (19 case-control studies).\8\ Presence
or absence of an adjustment for smoking habits is highlighted, and
adjustments for other potentially confounding factors are indicated
when applicable.
---------------------------------------------------------------------------
\8\ For simplicity, the epidemiological studies considered here
are placed into two broad categories. A cohort study compares the
health of persons having different exposures, diets, etc. A case-
control study starts with two defined groups that differ in terms of
their health and compares their exposure characteristics.
---------------------------------------------------------------------------
Some degree of association between occupational dpm exposure and an
excess risk of lung cancer was observed in 38 of the 43 studies
reviewed by MSHA: 18 of the 19 case-control studies and 20 of the 24
cohort studies. However, the 38 studies reporting a positive
association vary considerably in the strength of evidence they present.
As shown in Tables III-4 and III-5, statistically significant results
were reported in 24 of the 43 studies: 10 of the 18 positive case-
control studies and 14 of the 20 positive cohort studies.\9\ In six of
the 20 cohort studies and nine of the 18 case-control studies showing a
positive association, the association observed was not statistically
significant.
---------------------------------------------------------------------------
\9\ A statistically significant result is a result unlikely to
have arisen by chance in the group, or statistical sample, of
persons being studie. An association arising by chance would have no
predictive value for workers outside the sample. Failure to achieve
statistical significance in an individual study can arise because of
inherent limitations in the study, such as a small number of
subjects in the sample or a short period of observation. Therefore,
the lack of statistical significance in an individual study does not
demonstrate that the results of that study were due merely to
chance--only that the study (viewed in isolation) is inconclusive.
---------------------------------------------------------------------------
Because workers tend to be healthier than non-workers, the
incidence of disease found among workers exposed to a toxic substance
may be lower than the rate prevailing in the general population, but
higher than the rate occurring in an unexposed population of workers.
This phenomenon, called the ``healthy worker effect,'' also applies
when the rate observed among exposed workers is greater than that found
in the general population. In this case, assuming a study is unbiased
with respect to other factors such as smoking, comparison with the
general population will tend to underestimate the excess risk of
disease attributable to the substance being investigated. Several
studies drew comparisons against the general population, including both
workers and nonworkers, with no compensating adjustment for the healthy
worker effect. Therefore, in these studies, the excess risk of lung
cancer attributable to dpm exposure is likely to have been
underestimated, thereby making it more difficult to obtain a
statistically significant result.
Five of the 43 studies listed in Tables III-4 and III-5 are
negative--i.e., a lower rate of lung cancer was found among exposed
workers than in the control population used for comparison. None of
these five results, however, were statistically significant. Four of
the five were cohort studies that drew comparisons against the general
population and did not take the healthy worker effect into account. The
remaining negative study was a case-control study in which vehicle
drivers and locomotive engineers were compared to clerical workers.
Two cohort studies (Waxweiler et al., 1973; Ahlman et al., 1991)
were performed specifically on groups of miners, and one (Boffetta et
al., 1988) addressed miners as a subgroup of a larger population.
Although an elevated prevalence of lung cancer was found among miners
in both the 1973 and 1991 studies, the results were not statistically
significant. The 1988 study found, after adjusting for smoking patterns
and other occupational exposures, an 18-percent increase in the lung
cancer rate among all workers occupationally exposed to diesel exhaust
and a 167-percent increase among miners (relative risk = 2.67). The
latter result is statistically significant.
In addition, four case-control studies, all of which adjusted for
smoking, found elevated rates of lung cancer associated with mining.
The results for miners in three of these studies (Benhamou et al.,
1988; Morabia et al., 1992; Siemiatycki et al., 1988) are given little
weight because of potential confounding by occupational exposures to
other carcinogens. The other study (Lerchen et al., 1987) showed a
marginally significant result for underground non-uranium miners, but
this was based on very few cases and the extent of diesel exposure
among these miners was not reported. Although they do not pertain
specifically to mining environments, other studies showing
statistically significant results (most notably those by Garshick et
al., 1987 and 1988) are based on far more data, contain better diesel
exposure information, and are less susceptible to confounding by
extraneous risk factors.
Since none of the existing human studies is perfect and many
contain major deficiencies, it is not surprising that reported results
differ in magnitude and statistical significance. Shortcomings
identified in both positive and negative studies include: possible
misclassification with respect to exposure; incomplete or questionable
characterization of the exposed population; unknown or uncertain
quantification of diesel exhaust exposure; incomplete, uncertain, or
unavailable history of exposure to tobacco smoke and other carcinogens;
and insufficient sample size, dpm exposure, or latency period (i.e.,
time since exposure) to detect a carcinogenic effect if one exists.
Indeed, in their review of these studies, Stober and Abel (1996)
conclude that ``In this field * * *
[[Page 17533]]
epidemiology faces its limits (Taubes, 1995) * * * Many of these
studies were doomed to failure from the very beginning.''
Such problems, however, are not unique to epidemiological studies
involving diesel exhaust but are common sources of uncertainty in
virtually all epidemiological research involving cancer. Indeed,
deficiencies such as exposure misclassification, small sample size, and
short latency make it difficult to detect a relationship even when one
exists. Therefore, the fact that 38 out of 43 studies showed any excess
risk of lung cancer associated with dpm exposure may itself be a
significant result, even if the evidence in most of those 38 studies is
relatively weak.\10\ The sheer number of studies showing such an
association readily distinguishes this body of evidence from those
criticized by Taubes (1995), where weak evidence is available from only
a single study.
---------------------------------------------------------------------------
\10\ The high proportion of positive studies is statistically
significant according to the 2-tailed sign test, which rejects, at a
high confidence level, the null hypothesis that each study is
equally likely to be positive or negative. Assuming that the studies
are independent, and that there is no systematic bias in one
direction or the other, the probability of 38 or more out of 43
studies being either positive or negative is less than one per
million under the null hypothesis.
---------------------------------------------------------------------------
At the same time, MSHA recognizes that simply tabulating outcomes
can sometimes be misleading, since there are generally a variety of
outcomes that could render a study positive or negative and some
studies use related data sets. Therefore, rather than limiting its
assessment to such a tabulation, MSHA is basing its evaluation with
respect to lung cancer largely on the two comprehensive meta-analyses
(Lipsett and Alexeeff, 1998; Bhatia et al., 1998) described later, in
the ``material impairments'' section of this risk assessment. In
addition to restricting themselves to independent studies meeting
certain minimal requirements, both meta-analyses investigated and
rejected publication bias as an explanation for the generally positive
results reported.
All of the studies showing negative or statistically insignificant
positive associations were either based on relatively short observation
or follow-up periods, lacked good information about dpm exposure,
involved low duration or intensity of dpm exposure, or, because of
inadequate sample size, lacked the statistical power to detect effects
of the magnitude found in the ``positive'' studies. As stated by
Boffetta et al. (1988, p. 404), studies failing to show a statistically
significant association--
* * * often had low power to detect any association, had
insufficient latency periods, or compared incidence or mortality
rates among workers to national rates only, resulting in possible
biases caused by the `healthy worker effect.'
Some respondents to the ANPRM argued that such methodological
weaknesses may explain why not all of the studies showed a
statistically significant association between dpm exposure and an
increased prevalence of lung cancer. According to these commenters, if
an epidemiological study shows a statistically significant result, this
often occurs in spite of methodological weaknesses rather than because
of them. Limitations such as potential exposure misclassification,
inadequate latency, inadequate sample size, and insufficient duration
of exposure all make it more difficult to obtain a statistically
significant result when a real relationship exists.
On the other hand, Stober and Abel (1996) argue, long with Morgan
et al. (1997) and some commenters, that even in those epidemiological
studies showing a statistically significant association, the magnitude
of relative or excess risk observed is too small to demonstrate any
causal link between dpm exposure and cancer. Their reasoning is that in
these studies, errors in the collection or interpretation of smoking
data can create a bias in the results larger than any potential
contribution attributable to diesel particulate. They propose that
studies failing to account for smoking habits should be disqualified
from consideration, and that evidence of an association from the
remaining studies should be discounted because of potential confounding
due to erroneous, incomplete, or otherwise inadequate characterization
of smoking histories.
MSHA concurs with Cohen and Higgins (1995), Lipsett and Alexeeff
(1998), and Bhatia et al. (1998) in not accepting this view. MSHA does
recognize that unknown exposures to tobacco smoke or other human
carcinogens, such as asbestos, can distort the results of some lung
cancer studies. MSHA also agrees that significant differences in the
distribution of confounding factors, such as smoking history, between
study and control groups can lead to misleading results. MSHA also
recognizes, however, that it is not possible to design a human
epidemiological study that perfectly controls for all potentially
confounding factors. Some degree of informed subjective judgement is
always required in evaluating the potential significance of unknown or
uncontrolled factors.
Sixteen of the published epidemiological studies involving lung
cancer did, in fact, control or adjust for exposure to tobacco smoke,
and some of these also controlled or adjusted for exposure to asbestos
and other carcinogenic substances (e.g., Garshick et al., 1987;
Steenland et al., 1990; Boffetta et al., 1988). All but one of these 16
epidemiological studies reported some degree of excess risk associated
with exposure to diesel particulate, with statistically significant
results reported in seven. These results are less likely to be
confounded than results from studies with no adjustment. In addition,
several of the other studies drew comparisons against internal control
groups or control groups likely to have similar smoking habits as the
exposed groups (e.g., Garshick et al., 1988; Gustavsson et al., 1990;
and Hansen, 1993). MSHA places more weight on these studies than on
studies drawing comparisons against dissimilar groups with no controls
or adjustments.
According to Stober and Abel, the potential confounding effects of
smoking are so strong that they could explain even statistically
significant results observed in studies where smoking was explicitly
taken into account. MSHA agrees that variable exposures to non-diesel
lung carcinogens, including relatively small errors in smoking
classification, could bias individual studies. However, the potential
confounding effect of tobacco smoke and other carcinogens can cut in
either direction. Spurious positive associations of dpm exposure with
lung cancer would arise only if the group exposed to dpm had a greater
exposure to these confounders than the unexposed control group used for
comparison. If, on the contrary, the control group happened to be more
exposed to confounders, then this would tend to make the association
between dpm exposure and lung cancer appear negative. Therefore,
although smoking effects could potentially distort the results of any
single study, this effect could reasonably be expected to make only
about half the studies that were explicitly adjusted for smoking come
out positive. Smoking is unlikely to have been responsible for finding
an excess prevalence of lung cancer in 15 out of 16 studies in which a
smoking adjustment was applied. Based on a 2-tailed sign test, this
possibility can be rejected at a confidence level greater than 99.9
percent.
Even in the 27 studies involving lung cancer for which no smoking
adjustment was made, tobacco smoke and other carcinogens are important
confounders only to the extent that the
[[Page 17534]]
populations exposed and unexposed to diesel exhaust differed
systematically with respect to these other exposures. Twenty-three of
these studies, however, reported some degree of excess lung cancer risk
associated with diesel exposure. This result could be attributed to
non-diesel exposures only in the unlikely event that, in nearly all of
these studies, diesel-exposed workers happened to be more highly
exposed to these other carcinogens than the control groups of workers
unexposed to diesel. All five studies not showing any association
(Kaplan, 1959; DeCoufle, 1977; Waller, 1981; Edling, 1987; and Bender,
1989) may have failed to detect such a relationship because of too
small a study group, lack of accurate exposure information, low
duration or intensity of exposure, and/or insufficient latency or
follow-up time.
It is also significant that the two most comprehensive, complete,
and well-controlled studies available (Garshick et al., 1987 and 1988)
both point in the direction of an association between dpm exposure and
an excess risk of lung cancer. These studies took care to address
potential confounding by tobacco smoke and asbestos exposures. In
response to the ANPRM, a consultant to the National Coal Association
who was critical of all other available studies acknowledged that these
two:
* * * have successfully controlled for severally [sic]
potentially important confounding factors * * * Smoking represents
so strong a potential confounding variable that its control must be
nearly perfect if an observed association between cancer and diesel
exhaust is * * * [inferred to be causal]. In this regard, two
observations are relevant. First, both case-control [Garshick et
al., 1987] and cohort [Garshick et al., 1988] study designs revealed
consistent results. Second, an examination of smoking related causes
of death other than lung cancer seemed to account for only a
fraction of the association observed between diesel exposure and
lung cancer. A high degree of success was apparently achieved in
controlling for smoking as a potentially confounding variable.
[Submission 87-0-10, Robert A. Michaels, RAM TRAC Corporation,
prepared for National Coal Association].
Potential biases due to extraneous risk factors are unlikely to
account for a significant part of the excess risk in all studies
showing an association. Excess rates of lung cancer were associated
with dpm exposure in all epidemiologic studies of sufficient size and
scope to detect such an excess. Although it is possible, in any
individual study, that the potentially confounding effects of
differential exposure to tobacco smoke or other carcinogens could
account for the observed elevation in risk otherwise attributable to
diesel exposure, it is unlikely that such effects would give rise to
positive associations in 38 out of 43 studies. As stated by Cohen and
Higgins (1995):
* * * elevations [of lung cancer] do not appear to be fully
explicable by confounding due to cigarette smoking or other sources
of bias. Therefore, at present, exposure to diesel exhaust provides
the most reasonable explanation for these elevations. The
association is most apparent in studies of occupational cohorts, in
which assessment of exposure is better and more detailed analyses
have been performed. The largest relative risks are often seen in
the categories of most probable, most intense, or longest duration
of exposure. In general population studies, in which exposure
prevalence is low and misclassification of exposure poses a
particularly serious potential bias in the direction of observing no
effect of exposure, most studies indicate increased risk, albeit
with considerable imprecision. [Cohen and Higgins (1995), p. 269].
III.2.c.i.B.ii. Bladder Cancer. With respect to cancers other than
lung cancer, MSHA's review of the literature identified only bladder
cancer as a possible candidate for a causal link to dpm. Cohen and
Higgins (1995) identified and reviewed 14 epidemiological case-control
studies containing information related to dpm exposure and bladder
cancer. All but one of these studies found elevated risks of bladder
cancer among workers in jobs frequently associated with dpm exposure.
Findings were statistically significant in at least four of the studies
(statistical significance was not evaluated in three).
These studies point quite consistently toward an excess risk of
bladder cancer among truck or bus drivers, railroad workers, and
vehicle mechanics. However, the four available cohort studies do not
support a conclusion that exposure to dpm is responsible for the excess
risk of bladder cancer associated with these occupations. Furthermore,
most of the case-control studies did not distinguish between exposure
to diesel-powered equipment and exposure to gasoline-powered equipment
for workers having the same occupation. When such a distinction was
drawn, there was no evidence that the prevalence of bladder cancer was
higher for workers exposed to the diesel-powered equipment.
This, along with the lack of corroboration from existing cohort
studies, suggests that the excessive rates of bladder cancer observed
may be a consequence of factors other than dpm exposure that are also
associated with these occupations. For example, truck and bus drivers
are subjected to vibrations while driving and may tend to have
different dietary and sleeping habits than the general population. For
these reasons, MSHA does not find that any convincing evidence
currently exists for a causal relationship between dpm exposure and
bladder cancer.
III.2.c.ii. Studies Based on Exposures to Fine Particulate in
Ambient Air.
Longitudinal studies examine responses at given locations to
changes in conditions over time, whereas cross-sectional studies
compare results from locations with different conditions at a given
point in time. Prior to 1990, cross sectional studies were generally
used to evaluate the relationship between mortality and long-term
exposure to particulate matter, but unaddressed spatial confounders and
other methodological problems inherent in such studies limited their
usefulness (EPA, 1996).
Two recent prospective cohort studies provide better evidence of a
link between excess mortality rates and exposure to fine particulate,
although the uncertainties here are greater than with the short-term
exposure studies conducted in single communities. The two studies are
known as the Six Cities study (Dockery et al., 1993), and the American
Cancer Society (ACS) study (Pope et al., 1995).\11\ The first study
followed about 8,000 adults in six U.S. cities over 14 years; the
second looked at survival data for half a million adults in 151 U.S.
cities for 7 years. After adjusting for potential confounders,
including smoking habits, the studies considered differences in
mortality rates between the most polluted and least polluted cities.
---------------------------------------------------------------------------
\11\ A third such study only looked at TSP, rather than fine
particulate. It did not find a significant association between total
mortality and TSP. It is known as the California Seventh Day
Adventist study (Abbey et al., 1991).
---------------------------------------------------------------------------
Both the Six Cities study and the ACS study found a significant
association between increased concentration of PM2.5 and
total mortality.\12\ The authors of the Six Cities Study concluded that
the results suggest that exposures to fine particulate air pollution
``contributes to excess mortality in certain U.S. cities.'' The ACS
study, which not only controlled for smoking habits and various
occupational exposures, but also, to some extent, for passive exposure
to tobacco smoke, found results qualitatively consistent with those of
the Six Cities Study.\13\ In the
[[Page 17535]]
ACS study, however, the estimated increase in mortality associated with
a given increase in fine particulate exposure was lower, though still
statistically significant. In both studies, the largest increase
observed was for cardiopulmonary mortality. Both studies also showed an
increased risk of lung cancer associated with increased exposure to
fine particulate, but these results were not statistically significant.
---------------------------------------------------------------------------
\12\ The Six Cities study also found such relationships at
elevated levels of PM15/10 and sulfates. The ACS study
was designed to follow up on the fine particle result of the Six
Cities study, but also looked at sulfates.
\13\ The Six Cities study did not find a statistically
significant increase in risk among non-smokers, suggesting that this
group might not be as sensitive to adverse health effects from
exposure to fine particulate; however, the ACS study, with more
statistical power, did find an association even for non-smokers.
---------------------------------------------------------------------------
The few studies on associations between chronic PM2.5
exposure and morbidity in adults show effects that are difficult to
separate from PM10 measures and measures of acid aerosols.
The available studies, however, do show positive associations between
particulate air pollution and adverse health effects for those with
pre-existing respiratory or cardiovascular disease; and as mentioned
earlier, there is a large body of evidence showing that respiratory
diseases classified as COPD are significantly more prevalent among
miners than in the general population. It also appears that PM exposure
may exacerbate existing respiratory infections and asthma, increasing
the risk of severe outcomes in individuals who have such conditions
(EPA, 1996).
III.2.d. Mechanisms of Toxicity
As described in Part II, the particulate fraction of diesel exhaust
is made up of aggregated soot particles. Each soot particle consists of
an insoluble, elemental carbon core and an adsorbed, surface coating of
relatively soluble organic compounds, such as polycyclic aromatic
hydrocarbons (PAH's). When released into an atmosphere, the soot
particles formed during combustion tend to aggregate into larger
particles.
The literature on deposition of fine particles in the respiratory
tract is reviewed in Green and Watson (1995) and U.S. EPA (1996). The
mechanisms responsible for the broad range of potential particle-
related health effects will vary depending on the site of deposition.
Once deposited, the particles may be cleared from the lung,
translocated into the interstitium, sequestered in the lymph nodes,
metabolized, or be otherwise transformed by various mechanisms.
As suggested by Figure II-1 of this preamble, most of the
aggregated particles making up dpm never get any larger than one
micrometer in diameter. Particles this small are able to penetrate into
the deepest regions of the lungs, called alveoli. In the alveoli, the
particles can mix with and be dispersed by a substance called
surfactant, which is secreted by cells lining the alveolar surfaces.
MSHA would welcome any additional information, not already covered
in the surveys cited above, on fine particle deposition in the
respiratory tract, especially as it might pertain to lung loading in
miners exposed to a combination of diesel particulate and other dusts.
Any such additional information will be placed into the public record
and considered by MSHA before a final rule is adopted.
III.2.d.i. Effects Other than Cancer. A number of controlled animal
studies have been undertaken to ascertain the toxic effects of exposure
to diesel exhaust and its components. Watson and Green (1995) reviewed
approximately 50 reports describing noncancerous effects in animals
resulting from the inhalation of diesel exhaust. While most of the
studies were conducted with rats or hamsters, some information was also
available from studies conducted using cats, guinea pigs, and monkeys.
The authors also correlated reported effects with different descriptors
of dose. From their review of these studies, Watson and Green concluded
that:
(a) Animals exposed to diesel exhaust exhibit a number of
noncancerous pulmonary effects, including chronic inflammation,
epithelial cell hyperplasia, metaplasia, alterations in connective
tissue, pulmonary fibrosis, and compromised pulmonary function.
(b) Cumulative weekly exposure to diesel exhaust of 70 to 80
mghr/m3 or greater are associated with the presence
of chronic inflammation, epithelial cell proliferation, and depressed
alveolar clearance in chronically exposed rats.
(c) The extrapolation of responses in animals to noncancer
endpoints in humans is uncertain. Rats were the most sensitive animal
species studied.
Subsequent to the review by Watson and Green, there have been a
number of animal studies on allergic immune responses to dpm. Takano et
al. (1997) investigated the effects of dpm injected into mice through
an intratracheal tube and found manifestations of allergic asthma,
including enhanced antigen-induced airway inflammation, increased local
expression of cytokine proteins, and increased production of antigen-
specific immunoglobulins. The authors concluded that the study
demonstrated dpm's enhancing effects on allergic asthma and that the
results suggest that dpm is ``implicated in the increasing prevalence
of allergic asthma in recent years.'' Similarly, Ichinose et al. (1997)
found that five different strains of mice injected intratracheally with
dpm exhibited manifestations of allergic asthma, as expressed by
enhanced airway inflammation, which were correlated with an increased
production of antigen-specific immunoglobulin due to the dpm. The
authors concluded that dpm enhances manifestations of allergic airway
inflammation and that ``* * * the cause of individual differences in
humans at the onset of allergic asthma may be related to differences in
antigen-induced immune responses * * *.''
Several laboratory animal studies have been performed to ascertain
whether the effects of diesel exhaust are attributable specifically to
the particulate fraction. (Heinrich et al., 1986; Iwai et al., 1986;
Brightwell et al., 1986). These studies compare the effects of chronic
exposure to whole diesel exhaust with the effects of filtered exhaust
containing no particles. The studies demonstrate that when the exhaust
is sufficiently diluted to nullify the effects of gaseous irritants
(NO2 and SO2), irritant vapors (aldehydes), CO,
and other systemic toxicants, diesel particles are the prime etiologic
agents of noncancer health effects. Exposure to dpm produced changes in
the lung that were much more prominent than those evoked by the gaseous
fraction alone. Marked differences in the effects of whole and filtered
diesel exhaust were also evident from general toxicological indices,
such as body weight, lung weight, and pulmonary histopathology. This
provides strong evidence that the toxic component in diesel emissions
producing the effects noted in other animal studies is due to the
particulate fraction.
The mechanisms that may lead to adverse health effects in humans
from inhaling fine particulates are not fully understood, but potential
mechanisms that have been hypothesized for non-cancerous outcomes are
summarized in Table III-6. A comprehensive review of the toxicity
literature is provided in U.S. EPA (1996).
Deposition of particulates in the human respiratory tract could
initiate events leading to increased airflow obstruction, impaired
clearance, impaired host defenses, or increased epithelial
permeability. Airflow obstruction could result from laryngeal
constriction or bronchoconstriction secondary to stimulation of
receptors in extrathoracic or intrathoracic airways. In addition to
reflex airway narrowing, reflex or local stimulation of mucus secretion
could lead to mucus hypersecretion and could eventually lead to mucus
plugging in small airways.
Pulmonary changes that contribute to cardiovascular responses
include a
[[Page 17536]]
variety of mechanisms that can lead to hypoxemia, including
bronchoconstriction, apnea, impaired diffusion, and production of
inflammatory mediators. Hypoxia can lead to cardiac arrhythmias and
other cardiac electrophysiologic responses that, in turn, may lead to
ventricular fibrillation and ultimately cardiac arrest. Furthermore,
many respiratory receptors have direct cardiovascular effects. For
example, stimulation of C-fibers leads to bradycardia and hypertension,
and stimulation of laryngeal receptors can result in hypertension,
cardiac arrhythmia, bradycardia, apnea, and even cardiac arrest. Nasal
receptor or pulmonary J-receptor stimulation can lead to vagally
mediated bradycardia and hypertension (Widdicombe, 1988).
In addition to possible acute toxicity of particles in the
respiratory tract, chronic exposure to particles that deposit in the
lung may induce inflammation. Inflammatory responses can lead to
increased permeability and possibly diffusion abnormality. Furthermore,
mediators released during an inflammatory response could cause release
of factors in the clotting cascade that may lead to an increased risk
of thrombus formation in the vascular system (Seaton, 1995). Persistent
inflammation, or repeated cycles of acute lung injury and healing, can
induce chronic lung injury. Retention of the particles may be
associated with the initiation and/or progression of COPD.
III.2.d.ii. Lung Cancer.
III.2.d.ii.A. Genotoxicological Evidence. Many studies have shown
that diesel soot, or its organic component, can increase the likelihood
of genetic mutations during the biological process of cell division and
replication. A survey of the applicable scientific literature is
provided in Shirname-More (1995). What makes this body of research
relevant to the risk of cancer is that mutations in critical genes can
sometimes initiate, promote, or advance a process of carcinogenesis.
The determination of genotoxicity has frequently been made by
treating diesel soot with organic solvents such as dichloromethane and
dimethyl sulfoxide. The solvent removes the organic compounds from the
carbon core. After the solvent evaporates, the mutagenic potential of
the extracted organic material is tested by applying it to bacterial,
mammalian, or human cells propagated in a laboratory culture. In
general, the results of these studies have shown that various
components of the organic material can induce mutations and chromosomal
aberrations.
A critical issue is whether whole diesel particulate is mutagenic
when dispersed by substances present in the lung. Since the laboratory
procedure for extracting organic material with solvents bears little
resemblance to the physiological environment of the lung, it is
important to establish whether dpm as a whole is genotoxic, without
solvent extraction. Early research indicated that this was not the case
and, therefore, that the active genotoxic materials adhering to the
carbon core of diesel particles might not be biologically damaging or
even available to cells in the lung (Brooks et al., 1980; King et al.,
1981; Siak et al., 1981). A number of more recent research papers,
however, have shown that dpm, without solvent extraction, can cause DNA
damage when the soot is dispersed in the pulmonary surfactant that
coats the surface of the alveoli (Wallace et al., 1987; Keane et al.,
1991; Gu et al., 1991; Gu et al., 1992). From these studies, NIOSH has
concluded:
* * * the solvent extract of diesel soot and the surfactant
dispersion of diesel soot particles were found to be active in
procaryotic cell and eukaryotic cell in vitro genotoxicity assays.
The cited data indicate that respired diesel soot particles on the
surface of the lung alveoli and respiratory bronchioles can be
dispersed in the surfactant-rich aqueous phase lining the surfaces,
and that genotoxic material associated with such dispersed soot
particles is biologically available and genotoxically active.
Therefore, this research demonstrates the biological availability of
active genotoxic materials without organic solvent interaction.
[Cover letter to NIOSH response to ANPRM.]
From this conclusion, it follows that dpm itself, and not only its
organic extract, can cause genetic mutations when dispersed by a
substance present in the lung.
The biological availability of the genotoxic components is also
supported directly by studies showing genotoxic effects of exposure to
whole dpm. The formation of DNA adducts is an important indicator of
genotoxicity and potential carcinogenicity. If DNA adducts are not
repaired, then a mutation or chromosomal aberration can occur during
normal mitosis (i.e., cell replication). Hemminki et al. (1994) found
that DNA adducts were significantly elevated in nonsmoking bus
maintenance and truck terminal workers, as compared to a control group
of hospital mechanics, with the highest adduct levels found among
garage and forklift workers. Similarly, Nielsen et al. (1996) found
that DNA adducts were significantly increased in bus garage workers and
mechanics exposed to dpm as compared to a control group.
III.2.d.ii.B. Evidence from Animal Studies. Bond et al. (1990)
investigated differences in peripheral lung DNA adduct formation among
rats, hamsters, mice, and monkeys exposed to dpm at a concentration of
8100 g/m3 for 12 weeks. Mice and hamsters showed no
increase of DNA adducts in their peripheral lung tissue, whereas rats
and monkeys showed a 60 to 80% increase. The increased prevalence of
lung DNA adducts in monkeys suggests that, with respect to DNA adduct
formation, the human lungs' response to dpm inhalation may more closely
resemble that of the rat than that of the hamster or mouse.
Mauderly (1992) and Busby and Newberne (1995) provide reviews of
the scientific literature relating to excess lung cancers observed
among laboratory animals chronically exposed to filtered and unfiltered
diesel exhaust. The experimental data demonstrate that chronic exposure
to whole diesel exhaust increases the risk of lung cancer in rats and
that dpm is the causative agent. This carcinogenic effect has been
confirmed in two strains of rats and in at least five laboratories.
Experimental results for animal species other than the rat, however,
are either inconclusive or, in the case of Syrian hamsters, suggestive
of no carcinogenic effect. This is consistent with the observation,
mentioned above, that lung DNA adduct formation is increased among
exposed rats but not among exposed hamsters or mice.
The conflicting results for rats and hamsters indicate that the
carcinogenic effects of dpm exposure may be species-dependent. Indeed,
monkey lungs have been reported to respond quite differently than rat
lungs to both diesel exhaust and coal dust (Nikula, 1997). Therefore,
the results from rat experiments do not, by themselves, infer any
excess risk due to dpm exposure for humans. The human epidemiological
data, however, indicate that humans comprise a species that, like rats
and unlike hamsters, suffer a carcinogenic response to dpm exposure.
Therefore, MSHA considers the rat studies at least relevant to an
evaluation of the risk for humans.
When dpm is inhaled, a number of adverse effects that may
contribute to carcinogenesis are discernable by microscopic and
biochemical analysis. For a comprehensive review of these effects, see
Watson and Green (1995). In brief, these effects begin with
phagocytosis, which is essentially an attack on the diesel particles by
cells called alveolar macrophages. The macrophages engulf and ingest
the diesel particles, subjecting them to detoxifying enzymes. Although
this is a normal physiological response to the
[[Page 17537]]
inhalation of foreign substances, the process can produce various
chemical byproducts injurious to normal cells. In attacking the diesel
particles, the activated macrophages release chemical agents that
attract neutrophils (a type of white blood cell that destroys
microorganisms) and additional alveolar macrophages. As the lung burden
of diesel particles increases, aggregations of particle-laden
macrophages form in alveoli adjacent to terminal bronchioles, the
number of Type II cells lining particle-laden alveoli increases, and
particles lodge within alveolar and peribronchial tissues and
associated lymph nodes. The neutrophils and macrophages release
mediators of inflammation and oxygen radicals, which have been
implicated in causing various forms of chromosomal damage, genetic
mutations, and malignant transformation of cells (Weitzman and Gordon,
1990). Eventually, the particle-laden macrophages are functionally
altered, resulting in decreased viability and impaired phagocytosis and
clearance of particles. This series of events may result in pulmonary
inflammatory, fibrotic, or emphysematous lesions that can ultimately
develop into cancerous tumors.
Such reactions have also been observed in rats exposed to high
concentrations of fine particles with no organic component (Mauderly et
al., 1994; Heinrich et al., 1994 and 1995; Nikula et al., 1995). Rats
exposed to titanium dioxide or pure carbon (``carbon-black'')
particles, which are not considered to be genotoxic, developed lung
cancers at about the same rate as rats exposed to whole diesel exhaust.
Therefore, it appears that the toxicity of dpm, at least in some
species, may result largely from a biochemical response to the particle
itself rather than from specific effects of the adsorbed organic
compounds.
Some researchers have interpreted the carbon-black and titanium
dioxide studies as also suggesting that (1) the carcinogenic mechanism
in rats depends on massive overloading of the lung and (2) that this
may provide a mechanism of carcinogenesis specific to rats which does
not occur in other rodents or in humans (Oberdorster, 1994; Watson and
Valberg, 1996). Some commenters on the ANPRM cited the lack of any link
between lung cancer and coal dust or carbon black exposure as evidence
that carbon particles, by themselves, are not carcinogenic in humans.
Coal mine dust, however, consists almost entirely of particles larger
than those forming the carbon core of dpm or used in the carbon-black
and titanium dioxide rat studies. Furthermore, although there have been
eight studies \14\ reporting no excess risk of lung cancer among coal
miners (Liddell, 1973; Costello et al., 1974; Armstrong et al., 1979;
Rooke et al., 1979; Ames et al., 1983; Atuhaire et al., 1985; Miller
and Jacobsen, 1985; Kuempel et al., 1995), five studies have reported
an elevated risk of lung cancer for those exposed to coal dust
(Enterline, 1972; Rockette, 1977; Correa et al., 1984; Levin et al.,
1988; Morfeld et al., 1997). The positive results in two of these
studies (Enterline, 1972; Rockette, 1977) were statistically
significant. Furthermore, excess lung cancers have been reported among
carbon black production workers (Hodgson and Jones, 1985; Siemiatycki,
1991; Parent et al., 1996). MSHA is not aware of any evidence that a
mechanism of carcinogenesis due to fine particle overload is
inapplicable to humans. Studies carried out on rodents certainly do not
provide such evidence.
---------------------------------------------------------------------------
\14\ The Agency has recently learned of another report, from the
University of Newcastle, Australia, that found no elevated risk of
lung cancer among coal miners. Although the Agency has not been able
to acquire this report in time to include it in the present risk
assessment, it will be reviewed and considered in the risk
assessment prior to any final action. The Agency would also welcome
information on any additional studies or reports on this issue of
which it is not currently aware.
---------------------------------------------------------------------------
The carbon-black and titanium dioxide studies indicate that lung
cancers in rats exposed to dpm may be induced by a mechanism that does
not require the bioavailability of genotoxic organic compounds adsorbed
on the elemental carbon particles. These studies do not, however, prove
that the only significant agent of carcinogenesis in rats exposed to
diesel particulate is the non-soluble carbon core. Nor do the carbon-
black studies prove that the only significant mechanism of
carcinogenesis due to diesel particulate is lung overload. Due to the
relatively high doses administered in the rat studies, it is
conceivable that an overload phenomenon masks or parallels other
potential routes to cancer. It may be that effects of the genotoxic
organic compounds are merely masked or displaced by overloading in the
rat studies. Gallagher et al. (1994) exposed different groups of rats
to diesel exhaust, carbon black, or titanium dioxide and detected
species of lung DNA adducts in the rats exposed to dpm that were not
found in the controls or rats exposed to carbon black or titanium
dioxide.
Particle overload may provide the dominant route to lung cancer at
very high concentrations of fine particulate, while genotoxic
mechanisms may provide the primary route under lower-level exposure
conditions. In humans exposed over a working lifetime to doses
insufficient to cause overload, carcinogenic mechanisms unrelated to
overload may dominate, as indicated by the human epidemiological
studies and the data on human DNA adducts cited above. Therefore, the
carbon black results observed in the rat studies do not preclude the
possibility that the organic component of dpm has important genotoxic
effects in humans (Nauss et al., 1995).
Even if the genotoxic organic compounds in dpm were biologically
unavailable and played no role in human carcinogenesis, this would not
rule out the possibility of a genotoxic route to lung cancer (even for
rats) due to the presence of dpm particles themselves. For example, as
a byproduct of the biochemical response to the presence of dpm in the
alveoli, free oxidant radicals may be released as macrophages attempt
to digest the particles. There is evidence that dpm can both induce
production of active oxygen agents and also depress the activity of
naturally occurring antioxidant enzymes (Mori, 1996; Sagai, 1993).
Oxidants can induce carcinogenesis either by reacting directly with
DNA, or by stimulating cell replication, or both (Weitzman and Gordon,
1990). This would provide a mutagenic route to lung cancer with no
threshold. Therefore, the carbon black and titanium dioxide studies
cited above do not prove that dpm exposure has no incremental,
genotoxic effects or that there is a threshold below which dpm exposure
poses no risk of causing lung cancer.
It is noteworthy, however, that dpm exposure levels recorded in
some mines have been almost as high as laboratory exposures
administered to rats showing a clearly positive response. Intermittent,
occupational exposure levels greater than about 500 g/m\3\ dpm
may overwhelm the human lung clearance mechanism (Nauss et al., 1995).
Therefore, concentrations at levels currently observed in some mines
could be expected to cause overload in some humans, possibly inducing
lung cancer by a mechanism similar to what occurs in rats. MSHA would
like to receive additional scientific information on this issue,
especially as it relates to lung loading in miners exposed to a
combination of diesel particulate and other dusts.
As suggested above, such a mechanism would not necessarily be the
only route to carcinogenesis in humans and, therefore, would not imply
that dpm concentrations too low to
[[Page 17538]]
cause overload are safe for humans. Furthermore, a proportion of
exposed individuals can always be expected to be more susceptible than
normal. Therefore, at lower dpm concentrations, particle overload may
still provide a route to lung cancer in susceptible humans. At even
lower concentrations, other routes to carcinogenesis in humans may
predominate, possibly involving genotoxic effects.
III.3. Characterization of Risk
Having reviewed the evidence of health effects associated with
exposure to dpm, MSHA has evaluated that evidence to ascertain whether
exposure levels currently existing in mines warrant regulatory action
pursuant to the Mine Act. The criteria for this evaluation are
established by the Mine Act and related court decisions. Section
101(a)(6)(A) provides that:
The Secretary, in promulgating mandatory standards dealing with
toxic materials or harmful physical agents under this subsection,
shall set standards which most adequately assure on the basis of the
best available evidence that no miner will suffer material
impairment of health or functional capacity even if such miner has
regular exposure to the hazards dealt with by such standard for the
period of his working life.
Based on court interpretations of similar language under the
Occupational Safety and Health Act, there are three questions that need
to be addressed: (1) whether health effects associated with dpm
exposure constitute a ``material impairment'' to miner health or
functional capacity; (2) whether exposed miners are at significant
excess risk of incurring any of these material impairments; and (3)
whether the proposed rule will substantially reduce such risks.
The criteria for evaluating the health effects evidence do not
require scientific certainty. As noted by Justice Stevens in an
important case on risk involving the Occupational Safety and Health
Administration, the need to evaluate risk does not mean an agency is
placed into a ``mathematical straightjacket.'' [Industrial Union
Department, AFL-CIO v. American Petroleum Institute, 448 U.S. 607, 100
S.Ct. 2844 (1980), hereinafter designated the ``Benzene'' case]. When
regulating on the edge of scientific knowledge, certainty may not be
possible; and--
so long as they are supported by a body of reputable scientific
thought, the Agency is free to use conservative assumptions in
interpreting the data * * * risking error on the side of
overprotection rather than underprotection. [Id. at 656].
The statutory criteria for evaluating the health evidence do not
require MSHA to wait for absolute precision. In fact, MSHA is required
to use the ``best available evidence.'' (Emphasis added).
III.3.a. Material Impairments to Miner Health or Functional Capacity
From its review of the literature cited in Part III.2, MSHA has
tentatively concluded that underground miners exposed to current levels
of dpm are at excess risk of incurring the following three kinds of
material impairment: (i) sensory irritations and respiratory symptoms;
(ii) death from cardiovascular, cardiopulmonary, or respiratory causes;
and (iii) lung cancer. The basis for linking these with dpm exposure is
summarized in the following three subsections.
III.3.a.i. Sensory Irritations and Respiratory Symptoms. Kahn et
al. (1988), Battigelli (1965), Gamble et al. (1987a) and Rudell et al.
(1996) identified a number of debilitating acute responses to diesel
exhaust exposure: irritation of the eyes, nose and throat; headaches,
nausea, and vomiting; chest tightness and wheeze. These symptoms were
also reported by miners at the 1995 workshops. In addition, Ulfvarson
et al. (1987, 1990) found evidence of reduced lung function in workers
exposed to dpm for a single shift.
Although there is evidence that such symptoms subside within one to
three days of no occupational exposure, a miner who must be exposed to
dpm day after day in order to earn a living may not have time to
recover from such effects. Hence, the opportunity for a so-called
``reversible'' health effect to reverse itself may not be present for
many miners. Furthermore, effects such as stinging, itching and burning
of the eyes, tearing, wheezing, and other types of sensory irritation
can cause severe discomfort and can, in some cases, be seriously
disabling. Also, workers experiencing sufficiently severe sensory
irritations can be distracted as a result of their symptoms, thereby
endangering other workers and increasing the risk of accidents. For
these reasons, MSHA considers such irritations to constitute ``material
impairments'' of health or functional capacity within the meaning of
the Act, regardless of whether or not they are reversible. Further
discussion of why MSHA believes reversible effects can constitute
material impairments can be found earlier in this risk assessment, in
the section entitled ``Relevance of Health Effects that are
Reversible.''
The best available evidence also points to more severe respiratory
consequences of exposure to dpm. Significant associations have been
detected between acute environmental exposures to fine particulates and
debilitating respiratory impairments in adults, as measured by lost
work days, hospital admissions, and emergency room visits. Short-term
exposures to fine particulates, or particulate air pollution in
general, have been associated with significant increases in the risk of
hospitalization for both pneumonia and COPD (EPA, 1996).
The risk of severe respiratory effects is exemplified by specific
cases of persistent asthma linked to diesel exposure (Wade and Newman,
1993). There is considerable evidence for a causal connection between
dpm exposure and increased manifestations of allergic asthma and other
allergic respiratory diseases, coming from recent experiments on
animals and human cells (Peterson and Saxon, 1996; Diaz-Sanchez, 1997;
Takano et al., 1997; Ichinose et al., 1997). Such health outcomes are
clearly ``material impairments'' of health or functional capacity
within the meaning of the Act.
III.3.a.ii. Excess Risk of Death from Cardiovascular,
Cardiopulmonary, or Respiratory Causes. The evidence from air pollution
studies identifies death, largely from cardiovascular or respiratory
causes, as an endpoint significantly associated with acute exposures to
fine particulates. The weight of epidemiological evidence indicates
that short-term ambient exposure to particulate air pollution
contributes to an increased risk of daily mortality. Time-series
analyses strongly suggest a positive effect on daily mortality across
the entire range of ambient particulate pollution levels. Relative risk
estimates for daily mortality in relation to daily ambient particulate
concentration are consistently positive and statistically significant
across a variety of statistical modeling approaches and methods of
adjustment for effects of relevant covariates such as season, weather,
and co-pollutants. After thoroughly reviewing this body of evidence,
the U.S. Environmental Protection Agency (EPA) concluded:
It is extremely unlikely that study designs not yet employed,
covariates not yet identified, or statistical techniques not yet
developed could wholly negate the large and consistent body of
epidemiological evidence * * *.
There is also substantial evidence of a relationship between
chronic exposure to fine particulates and an excess (age-adjusted) risk
of mortality, especially from cardiopulmonary diseases. The Six Cities
and ACS studies of ambient air particulates both found a significant
association between chronic exposure to fine particles and excess
mortality. In
[[Page 17539]]
both studies, after adjusting for smoking habits, a statistically
significant excess risk of cardiopulmonary mortality was found in the
city with the highest average concentration of fine particulate (i.e.,
PM2.5) as compared to the city with the lowest. Both studies
also found excess deaths due to lung cancer in the cities with the
higher average level of PM2.5, but these results were not
statistically significant (EPA, 1996). The EPA concluded that--
* * * the chronic exposure studies, taken together, suggest
there may be increases in mortality in disease categories that are
consistent with long-term exposure to airborne particles and that at
least some fraction of these deaths reflect cumulative PM impacts
above and beyond those exerted by acute exposure events* * * There
tends to be an increasing correlation of long-term mortality with PM
indicators as they become more reflective of fine particle levels
(EPA, 1996).
Whether associated with acute or chronic exposures, the excess risk
of death that has been linked to pollution of the air with fine
particles like dpm is clearly a ``material impairment'' of health or
functional capacity within the meaning of the Act.
III.3.a.iii. Lung Cancer. It is clear that lung cancer constitutes
a ``material impairment'' of health or functional capacity within the
meaning of the Act. Questions have been raised however, as to whether
the evidence linking dpm exposure with an excess risk of lung cancer
demonstrates a causal connection (Stober and Abel, 1996; Watson and
Valberg, 1996; Cox, 1997; Morgan et al., 1997; Silverman, 1998).
MSHA recognizes that no single one of the existing epidemiological
studies, viewed in isolation, provides conclusive evidence of a causal
connection between dpm exposure and an elevated risk of lung cancer in
humans. Consistency and coherency of results, however, do provide such
evidence. Although no epidemiological study is flawless, studies of
both cohort and case-control design have quite consistently shown that
chronic exposure to diesel exhaust, in a variety of occupational
circumstances, is associated with an increased risk of lung cancer.
With only rare exceptions, involving too few workers and/or observation
periods too short to have a good chance of detecting excess cancer
risk, the human studies have shown a greater risk of lung cancer among
exposed workers than among comparable unexposed workers.
Lipsett and Alexeeff (1998) performed a comprehensive statistical
meta-analysis of the epidemiological literature on lung cancer and dpm
exposure. This analysis systematically combined the results of the
studies summarized in Tables III-4 and III-5. Some studies were
eliminated because they did not allow for a period of at least 10 years
for the development of clinically detectable lung cancer. Others were
eliminated because of bias resulting from incomplete ascertainment of
lung cancer cases in cohort studies or because they examined the same
cohort population as another study. One study was excluded because
standard errors could not be calculated from the data presented. The
remaining 30 studies were analyzed using both a fixed-effects and a
random-effect analysis of variance (ANOVA) model. Sources of
heterogeneity in results were investigated by subset analysis; using
categorical variables to characterize each study's design; target
population (general or industry-specific); occupational group; source
of control or reference population; latency; duration of exposure;
method of ascertaining occupation; location (North America or Europe);
covariate adjustments (age, smoking, and/or asbestos exposure); and
absence or presence of a clear healthy worker effect (as manifested by
lower than expected all-cause mortality in the occupational population
under study).
Sensitivity analyses were conducted to evaluate the sensitivity of
results to inclusion criteria and to various assumptions used in the
analysis. This included substitution of excluded ``redundant'' studies
of same cohort population for the included studies and exclusion of
studies involving questionable exposure to dpm. An influence analysis
was also conducted to examine the effect of dropping one study at a
time, to determine if any individual study had a disproportionate
effect on the ANOVA. Potential effects of publication bias were also
investigated. The authors concluded:
The results of this meta-analysis indicate a consistent positive
association between occupations involving diesel exhaust exposure
and the development of lung cancer. Although substantial
heterogeneity existed in the initial pooled analysis, stratification
on several factors identified a relationship that persisted
throughout various influence and sensitivity analyses * * *.
This meta-analysis provides evidence consistent with the
hypothesis that exposure to diesel exhaust is associated with an
increased risk of lung cancer. The pooled estimates clearly reflect
the existence of a positive relationship between diesel exhaust and
lung cancer in a variety of diesel-exposed occupations, which is
supported when the most important confounder, cigarette smoking, is
measured and controlled. There is suggestive evidence of an
exposure-response relationship in the smoking adjusted studies as
well. Many of the subset analyses indicated the presence of
substantial heterogeneity among the pooled estimates. Much of the
heterogeneity observed, however, is due to the presence or absence
of adjustment for smoking in the individual study risk estimates, to
occupation-specific influences on exposure, to potential selection
biases, and other aspects of study design.
A second, independent meta-analysis of epidemiological studies
published in peer-reviewed journals was conducted by Bhatia et al.
(1998).\15\ In this analysis, studies were excluded if actual work with
diesel equipment ``could not be confirmed or reliably inferred'' or if
an inadequate latency period was allowed for cancer to develop, as
indicated by less than 10 years from time of first exposure to end of
follow-up. Studies of miners were also excluded, because of potential
exposure to radon and silica. Likewise, studies were excluded if they
exhibited selection bias or examined the same cohort population as a
study published later. A total of 29 independent studies from 23
published sources were identified as meeting the inclusion criteria.
After assigning each of these 29 studies a weight proportional to its
estimated precision, pooled relative risks were calculated based on the
following groups of studies: all 29 studies; all case-control studies;
all cohort studies; cohort studies using internal reference
populations; cohort studies making external comparisons; studies
adjusted for smoking; studies not adjusted for smoking; and studies
grouped by occupation (railroad workers, equipment operators, truck
drivers, and bus workers). Elevated risks were shown for exposed
workers overall and within every individual group of studies analyzed.
A positive duration-response relationship was observed in those studies
presenting results according to employment duration. The weighted,
pooled estimates of relative risk were identical for case-control and
cohort studies and nearly identical for studies with or without smoking
adjustments. Based on their stratified analysis, the authors argued
that--
---------------------------------------------------------------------------
\15\ To address potential publication bias, the authors
identified several unpublished studies on truck drivers and noted
that elevated risks for exposed workers observed in these studies
were similar to those in the published studies utilized. Based on
this and a `'funnel plot'' for the included studies, the authors
concluded that there was no indication of publication bias.
the heterogeneity in observed relative risk estimates may be
explained by differences between studies in methods, in populations
studied and comparison groups used, in latency intervals, in
intensity and duration of
[[Page 17540]]
exposure, and in the chemical and physical characteristics of diesel
exhaust.
They concluded that the elevated risk of lung cancer observed among
exposed workers was unlikely to be due to chance, that confounding from
smoking is unlikely to explain all of the excess risk, and that ``this
meta-analysis supports a causal association between increased risks for
lung cancer and exposure to diesel exhaust.''
As discussed earlier in the section entitled ``Mechanisms of
Toxicity,'' animal studies have confirmed that diesel exhaust can
increase the risk of lung cancer in some species and shown that dpm
(rather than the gaseous fraction of diesel exhaust) is the causal
agent. MSHA, however, views results from animal studies as subordinate
to the results obtained from human studies. Since the human studies
show increased risk of lung cancer at dpm levels lower than what might
be expected to cause overload, they provide evidence that overload may
not be the only mechanism at work among humans. The fact that dpm has
been proven to cause lung cancer in laboratory rats is of interest
primarily in supporting the plausibility of a causal interpretation for
relationships observed in the human studies.
Similarly, the genotoxicological evidence provides additional
support for a causal interpretation of associations observed in the
epidemiological studies. This evidence shows that dpm dispersed by
alveolar surfactant can have mutagenic effects, thereby providing a
genotoxic route to carcinogenesis independent of overloading the lung
with particles. Chemical byproducts of phagocytosis may provide another
genotoxic route. Inhalation of diesel emissions has been shown to cause
DNA adduct formation in peripheral lung cells of rats and monkeys, and
increased levels of human DNA adducts have been found in association
with occupational exposures. Therefore, there is little basis for
postulating that a threshold exists, demarcating overload, below which
dpm would not be expected to induce lung cancers in humans.
Results from the epidemiological studies, the animal studies, and
the genotoxicological studies are coherent and mutually reinforcing.
After considering all these results, MSHA has concluded that the
epidemiological studies, supported by the experimental data
establishing the plausibility of a causal connection, provide strong
evidence that chronic occupational dpm exposure increases the risk of
lung cancer in humans.
III.3.b. Significance of the Risk of Material Impairment to Miners
The fact that there is substantial evidence that dpm exposure can
materially impair miner health in several ways does not imply that
miners will necessarily suffer such impairments. This section will
consider the significance of the risk faced by miners exposed to dpm.
III.3.b.i. Definition of a Significant Risk. The benzene case,
referred to earlier in this section, provides the starting point for
MSHA's analysis of this issue. Soon after its enactment in 1970, OSHA
adopted a ``consensus'' standard on exposure to benzene, as required
and authorized by the OSH Act. The basic part of the standard was an
average exposure limit of 10 parts per million over an 8-hour workday.
The consensus standard had been established over time to deal with
concerns about poisoning from this substance (448 U.S. 607, 617).
Several years later, NIOSH recommended that OSHA alter the standard to
take into account evidence suggesting that benzene was also a
carcinogen. (Id., at 619 et seq.). Although the ``evidence in the
administrative record of adverse effects of benzene exposure at 10 ppm
is sketchy at best,'' OSHA was operating under a policy that there was
no safe exposure level to a carcinogen. (Id., at 631). Once the
evidence was adequate to reach a conclusion that a substance was a
carcinogen, the policy required the agency to set the limit at the
lowest level feasible for the industry. (Id., at 613). Accordingly, the
Agency proposed lowering the permissible exposure limit to 1 ppm.
The Supreme Court rejected this approach. Noting that the OSH Act
requires ``safe or healthful employment,'' the court stated that--
* * * `safe' is not the equivalent of `risk-free' * * * a
workplace can hardly be considered `unsafe' unless it threatens the
workers with a significant risk of harm. Therefore, before he can
promulgate any permanent health or safety standard, the Secretary is
required to make a threshold finding that a place of employment is
unsafe--in the sense that significant risks are present and can be
eliminated or lessened by a change in practices. [Id., at 642,
italics in original.]
The court went on to explain that it is the Agency that determines how
to make such a threshold finding:
First, the requirement that a `significant' risk be identified
is not a mathematical straitjacket. It is the Agency's
responsibility to determine, in the first instance, what it
considered to be a `significant' risk. Some risks are plainly
acceptable and others are plainly unacceptable. If, for example, the
odds are one in a billion that a person will die from cancer by
taking a drink of chlorinated water, the risk clearly could not be
considered significant. On the other hand, if the odds are one in a
thousand that regular inhalation of gasoline vapors that are 2%
benzene will be fatal, a reasonable person might well consider the
risk significant and take appropriate steps to decrease or eliminate
it. Although the Agency has no duty to calculate the exact
probability of harm, it does have an obligation to find that a
significant risk is present before it can characterize a place of
employment as `unsafe.' [Id., at 655.]
The court noted that the Agency's ``* * * determination that a
particular level of risk is `significant' will be based largely on
policy considerations.'' (Id., note 62.)
III.3.b.ii. Evidence of Significant Risk at Current Exposure
Levels. In evaluating the significance of the risks to miners, a key
factor is the very high concentrations of diesel particulate to which a
number of those miners are currently exposed--compared to ambient
atmospheric levels in even the most polluted urban environments, and to
workers in diesel-related occupations for which positive
epidemiological results have been observed. Figure III-4 compared the
range of median dpm exposures measured for mine workers at various
mines to the range of geometric means (i.e., estimated medians)
reported for other occupations, as well as to ambient environmental
levels. Figure III-5 presents a similar comparison, based on the
highest mean dpm level observed at any individual mine, the highest
mean level reported for any occupational group other than mining, and
the highest monthly mean concentration of dpm estimated for ambient air
at any site in the Los Angeles basin.\16\ As shown in Figure III-5,
underground miners are currently exposed at mean levels up to 10 times
higher than the highest mean exposure reported for other occupations,
and up to 100 times higher than comparable environmental levels of
diesel particulate.
\16\ For comparability with occupational lifetime exposure
levels, the environmental ambient air concentration has been
multiplied by a factor of approximately 4.7. This factor reflects a
45-year occupational lifetime with 240 working days per year, as
opposed to a 70-year environmental lifetime with 365-days per year,
and assumes that air inhaled during a work shift comprises half the
total air inhaled during a 24-hour day.
[[Page 17541]]
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Given the significantly increased mortality and other acute,
adverse health effects associated with increments of 25 g/m\3\
in fine particulate concentration (Table III-3), the relative risk for
some miners, especially those already suffering respiratory problems,
appears to be extremely high. Acute responses to dpm exposures have
been detected in studies of stevedores, whose exposure was likely to
have been less than one-tenth the exposure of some miners on the job.
Both existing meta-analyses of human studies relating dpm exposure
and lung cancer suggest that, on average, occupational exposure is
responsible for a 30- to 40-percent increase in lung cancer risk across
all industries studied (Lipsett and Alexeeff, 1998; Bhatia et al.,
1998). Moreover, the epidemiological studies providing the evidence of
this increased risk involved average exposure levels estimated to be
far below levels to which some underground miners are currently
exposed. Specifically, the elevated risk of lung cancer observed in the
two most extensively studied industries--trucking (including dock
workers) and railroads--was associated with average exposure levels
estimated to be far below levels observed in underground mines. The
highest average concentration of dpm reported for dock workers--the
most highly exposed occupational group within the trucking industry--is
about 55 g/m\3\ total elemental carbon at an individual dock
(NIOSH, 1990). This translates, on average, to no more than about 110
g/m\3\ of dpm. Published measurements of dpm for railworkers
have generally been less than 140 g/m\3\ (measured as
respirable particulate matter other than cigarette smoke). The reported
mean of 224 g/m\3\ for hostlers displayed in Figure III-5
represents only the worst case occupational subgroup (Woskie et al.,
1988). Indeed, although MSHA views extrapolations from animal studies
as subordinate to results obtained from human studies, it is noteworthy
that dpm exposure levels recorded in some underground mines (Figures
III-1 and III-2) have been well within the exposure range that produced
tumors in rats (Nauss et al., 1995).
The significance of the lung cancer risk to exposed underground
miners is also supported by a recent NIOSH report (Stayner et al.,
1998), which summarizes a number of published quantitative risk
assessments. These assessments are broadly divided into those based on
human studies and those based on animal studies. Depending on the
particular studies, assumptions, and methods of assessment used,
estimates of the exact degree of risk vary widely even within each
broad category. MSHA
[[Page 17542]]
recognizes that a conclusive assessment of the quantitative
relationship between lung cancer risk and specific exposure levels is
not possible at this time, given the limitations in currently available
epidemiological data and questions about the applicability to humans of
responses observed in rats. However, all of the very different
approaches and methods published so far, as described in Stayner et al.
1998, have produced results indicating that levels of dpm exposure
measured at some underground mines present an unacceptably high risk of
lung cancer for miners--a risk significantly greater than the risk they
would experience without the dpm exposure.
Quantitative risk estimates based on the human studies were
generally higher than those based on analyses of the rat inhalation
studies. As indicated by Tables 3 and 4 of Stayner et al. 1998, a
working lifetime of exposure to dpm at 500 g/m\3\ yields
estimates of excess lung cancer risk ranging from about 1 to 200 excess
cases of lung cancer per thousand workers based on the rat inhalation
studies and from about 50 to 800 per 1000 based on the epidemiological
assessments. Even the lowest of these estimates indicates a risk that
is clearly significant under the quantitative rule of thumb established
in the benzene case. [Industrial Union vs. American Petroleum; 448 U.S.
607, 100 S.Ct. 2844 (1980)].
Stayner et al. 1998 concluded their report by stating:
The risk estimates derived from these different models vary by
approximately three orders of magnitude, and there are substantial
uncertainties surrounding each of these approaches. Nonetheless, the
results from applying these methods are consistent in predicting
relatively large risks of lung cancer for miners who have long-term
exposures to high concentrations of DEP [i.e., dpm]. This is not
surprising given the fact that miners may be exposed to DEP [dpm]
concentrations that are similar to those that induced lung cancer in
rats and mice, and substantially higher than the exposure
concentrations in the positive epidemiologic studies of other worker
populations.
The Agency is also aware that a number of other governmental and
nongovernmental bodies have concluded that the risks of dpm are of
sufficient significance that exposure should be limited:
(1) In 1988, after a thorough review of the literature, the
National Institute for Occupational Safety and Health (NIOSH)
recommended that whole diesel exhaust be regarded as a potential
occupational carcinogen and controlled to the lowest feasible
exposure level. The document did not contain a recommended exposure
limit.
(2) In 1995, the American Conference of Governmental Industrial
Hygienists placed on the Notice of Intended Changes in their
Threshold Limit Values (TLV's) for Chemical Substances and Physical
Agents and Biological Exposure Indices Handbook a recommended TLV of
150 g/m\3\ for exposure to whole diesel particulate.
(3) The Federal Republic of Germany has determined that diesel
exhaust has proven to be carcinogenic in animals and classified it
as an A2 in their carcinogenic classification scheme. An A2
classification is assigned to those substances shown to be clearly
carcinogenic only in animals but under conditions indicative of
carcinogenic potential at the workplace. Based on that
classification, technical exposure limits for dpm have been
established, as described in part II of this preamble. These are the
minimum limits thought to be feasible in Germany with current
technology and serve as a guide for providing protective measures at
the workplace.
(4) The Canada Centre for Mineral and Energy Technology (CANMET)
currently has an interim recommendation of 1000 g/m\3\
respirable combustible dust. The recommendation was made by an Ad
hoc committee made up of mine operators, equipment manufacturers,
mining inspectorates and research agencies. As discussed in part II
of this preamble, the committee has presently established a goal of
500 g/m\3\ as the recommended limit.
(5) Already noted in this preamble is the U.S. Environmental
Protection Agency's recently enacted regulation of fine particulate
matter, in light of the significantly increased health risks
associated with environmental exposure to such particulates. In some
of the areas studied, fine particulate is composed primarily of dpm;
and significant mortality and morbidity effects were also noted in
those areas.
(6) The California Environmental Protection Agency (CALEPA) has
tentatively concluded that diesel exhaust appears to meet the
definition of a toxic air contaminant (as stated in their Health and
Safety Code, Section 39655). According to that section, a toxic air
contaminant is an air pollutant which may cause or contribute to an
increase in mortality or in serious illness, or which may pose a
present or potential hazard to human health. At the present time,
this tentative conclusion is still subject to revision.
(7) The International Programme on Chemical Safety (IPCS), which
is a joint venture of the World Health Organization, the
International Labour Organisation, and the United Nations
Environment Programme, has issued a health criteria document on
diesel fuel and exhaust emissions (IPCS, 1996). This document states
that the data support a conclusion that inhalation of diesel exhaust
is of concern with respect to both neoplastic and non-neoplastic
diseases. It also states that the particulate phase appears to have
the greatest effect on health, and both the particle core and the
associated organic materials have biological activity, although the
gas-phase components cannot be disregarded.
Based on both the epidemiological and toxicological evidence,
the IPCS criteria document concluded that diesel exhaust is
``probably carcinogenic to humans'' and recommended that ``in the
occupational environment, good work practices should be encouraged,
and adequate ventilation must be provided to prevent excessive
exposure.'' Quantitative relationships between human lung cancer
risk and dpm exposure were derived using a dosimetric model that
accounted for differences between experimental animals and humans,
lung deposition efficiency, lung particle clearance rates, lung
surface area, ventilation, and elution rates of organic chemicals
from the particle surface.
As the Supreme Court pointed out in the benzene case, the
appropriate definition of significance also depends on policy
considerations of the Agency involved. In the case of MSHA, those
policy considerations include special attention to the history of the
Mine Act. That history is intertwined with the toll to the mining
community due to silicosis and coal miners' pneumoconiosis (``black
lung''), along with billions of dollars in Federal expenditures.
At one of the 1995 workshops on diesel particulate cosponsored by
MSHA, a miner noted:
People, they get complacent with things like this. They begin to
believe, well, the government has got so many regulations on so many
things. If this stuff was really hurting us, they wouldn't allow it
in our coal mines * * * (dpm Workshop; Beckley, WV, 1995).
Referring to some commenters' position that further scientific study
was necessary before a limit on dpm exposure could be justified,
another miner said:
* * * if I understand the Mine Act, it requires MSHA to set the
rules based on the best set of available evidence, not possible
evidence * * * Is it going to take us 10 more years before we kill
out, or are we going to do something now * * *? (dpm Workshop;
Beckley, WV, 1995).
Concern with the risk of waiting for additional scientific evidence to
support regulation of dpm was also expressed by another miner who
testified:
What are the consequences that the threshold limit values are
too high and it's loss of human lives, sickness, whatever, compared
to what are the consequences that the values are too low? I mean,
you don't lose nothing if they're too low, maybe a little money. But
* * * I got the indication that the diesel studies in rats could no
way be compared to humans because their lungs are not the same * * *
But * * * if we don't set the limits, if you remember probably last
year when these reports come out how the government used human
guinea pigs for radiation, shots, and all this, and aren't we doing
the same thing by using coal miners as guinea pigs to set the value?
(dpm Workshop; Beckley, WV, 1995).
[[Page 17543]]
III.3.c. Substantial Reduction of Risk by Proposed Rule
A review of the best available evidence indicates that reducing the
very high exposures currently existing in underground mines can
substantially reduce health risks to miners--and that greater
reductions in exposure would result in even lower levels of risk.
Although there are substantial uncertainties involved in converting 24-
hour environmental exposures to 8-hour occupational exposures, Table
III-3 suggests that reducing occupational dpm concentrations by as
little as 75 g/m3 (corresponding to a reduction of
25 g/m3 in 24-hour ambient atmospheric
concentration) could lead to significant reductions in the risk of
various adverse acute responses, ranging from respiratory irritations
to mortality. The Agency recognizes that a conclusive, quantitative
dose-response relationship has not been established between dpm and
lung cancer in humans. However, the epidemiological studies relating
dpm exposure to excess lung cancer were conducted on populations whose
average exposure is estimated to be less than 200 g/
m3 and less than one tenth of average exposures observed in
some underground mines. Therefore, the best available evidence
indicates that lifetime occupational exposure at levels currently
existing in some underground mines presents a significant excess risk
of lung cancer.
In the case of underground coal mines, calculations by the Agency
indicate that the filtration required by the proposed rule would reduce
dpm concentrations to below 200 g/m3 in most
underground coal mines.\17\ The Agency recognizes that although health
risks would be substantially reduced, the best available evidence
indicates a significant risk of adverse health effects could remain.
However, as explained in Part V of this preamble, MSHA has tentatively
concluded that, because of both technology and cost considerations, the
underground coal mining sector as a whole cannot feasibly reduce dpm
concentrations further at this time.
---------------------------------------------------------------------------
\17\ These calculations are discussed in detail in Part V, which
reviews the extent to which the proposed rule meets the Agency's
statutory obligation to attain the highest degree of health and
safety protection feasible for a miner.
---------------------------------------------------------------------------
Conclusions
MSHA has reviewed a considerable body of evidence to ascertain
whether and to what level dpm should be controlled. It has evaluated
the information in light of the legal requirements governing regulatory
action under the Mine Act. Particular attention was paid to issues and
questions raised by the mining community in response to the Agency's
Advance Notice of Proposed Rulemaking and at workshops on dpm held in
1995. Based on its review of the record as a whole to date, the agency
has tentatively determined that the best available evidence warrants
the following conclusions:
1. The health effects associated with exposure to dpm can
materially impair miner health or functional capacity. These
material impairments include sensory irritations and respiratory
symptoms; death from cardiovascular, cardiopulmonary, or respiratory
causes; and lung cancer.
2. At exposure levels currently observed in underground mines,
many miners are presently at significant risk of incurring these
material impairments over a working lifetime.
3. The proposed rule for underground coal mines is justified
because the reduction in dpm exposure levels that would result from
implementation of the proposed rule would substantially reduce the
significant health risks currently faced by underground miners
exposed to dpm.
Table III-2.--Studies of Acute Health Effects Using Filter Based Optical Indicators of Fine Particles in the Ambient Air
--------------------------------------------------------------------------------------------------------------------------------------------------------
City Study years Indicator* Reference
--------------------------------------------------------------------------------------------------------------------------------------------------------
Acute Mortality
--------------------------------------------------------------------------------------------------------------------------------------------------------
London.............................. 1963-1972, winters....................... BS Thurston et al., 1989.
1965-1972, winters....................... ..................... Ito et al., 1993.
1975-1987................................ ..................... Katsouyanni et al., 1990.
Athens.............................. July, 1987............................... BS Katsouyanni et al., 1993.
1984-1988................................ ..................... Touloumi et al., 1994.
1970-1979................................ ..................... Shumway et al., 1988.
Los Angeles......................... 1970-1979................................ KM Kinney and Ozkaynak, 1991.
Santa Clara......................... 1980-1986, winters....................... COH Fairley, 1990.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Increased Hospitalization
--------------------------------------------------------------------------------------------------------------------------------------------------------
Barcelona........................... 1985-1989................................ BS Sunyer et al., 1993.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Acute Change in Pulmonary Function
--------------------------------------------------------------------------------------------------------------------------------------------------------
Wageningen, Netherlands............. ......................................... BS Hoek and Brunkreef, 1993.
Netherlands......................... ......................................... BS Roemer et al., 1993.
--------------------------------------------------------------------------------------------------------------------------------------------------------
*BS (black smoke), KM (carbonaceous material), and COH (coefficient of haze) are optical measurements that are most directly related to elemental carbon
concentrations, but only indirectly to mass. Site specific calibrations and/or comparisons of such optical measurements with gravimetric mass
measurements in the same time and city are needed to make inferences about particle mass. However, all three of these indicators preferentially
measure carbon particles found in the fine fraction of total airborne particulate matter. (EPA, 1996).
Table III-3.--Studies of Acute Health Effects Using Gravimetric Indicators of Fine Particles in the Ambient Air
----------------------------------------------------------------------------------------------------------------
RR( CI)/25
Indicator g/m3 PM Mean PM levels (min/
increase max)
----------------------------------------------------------------------------------------------------------------
Acute Mortality
----------------------------------------------------------------------------------------------------------------
Six CitiesA
[[Page 17544]]
Portage, WI................ PM2.5.................. 1.030 (0.993,1.071).... 11.2 (7.8)
Topeka, KS................. PM2.5.................. 1.020 (0.951,1.092).... 12.2 (7.4)
Boston, MA................. PM2.5.................. 1.056 (1.038,1.0711)... 15.7 (9.2)
St. Louis, MO.............. PM2.5.................. 1.028 (1.010,1.043).... 18.7 (10.5)
Kingston/Knoxville, TN..... PM2.5.................. 1.035 (1.005,1.066).... 20.8 (9.6)
Steubenville, OH........... PM2.5.................. 1.025 (0.998,1.053).... 29.6 (21.9)
----------------------------------------------------------------------------------------------------------------
Increased Hospitalization
----------------------------------------------------------------------------------------------------------------
Ontario, CANB.................. SO4=................... 1.03 (1.02,1.04)....... Min/Max = 3.1-8.2
Ontario, CANC.................. SO4=................... 1.03 (1.02,1.04)....... Min/Max = 2.0-7.7
O3..................... 1.03 (1.02,1.05) .............................
NYC/Buffalo, NYD............... SO4=................... 1.05 (1.01,1.10)....... NR
Toronto, CAND.................. H+ (Nmol/m3)........... 1.16 (1.03,1.30)\1\.... 28.8 (NR/391)
SO4=................... 1.12 (1.00,1.24)....... 7.6 (NR, 48.7)
PM2.5.................. 1.15 (1.02,1.78)....... 18.6 (NR, 66.0)
----------------------------------------------------------------------------------------------------------------
Increased Respiratory Symptoms
----------------------------------------------------------------------------------------------------------------
Southern CaliforniaF........... SO4=................... 1.48 (1.14,1.91)....... R = 2-37
Six CitiesG.................... PM2.5.................. 1.19 (1.01,1.42)\2\.... 18.0 (7.2,37)\3\
(Cough).................... PM2.5 Sulfur........... 1.23 (0.95,1.59)\2\.... 2.5 (3.1,61)\3\
H+..................... 1.06 (0.87,1.29)\2\.... 18.1 (0.8,5.9)\3\
Six CitiesG.................... PM2.5.................. 1.44 (1.15-1.82)\2\.... 18.0 (7.2,37)\3\
(Lower Resp. Symp.)........ PM2.5 Sulfur........... 1.82 (1.28-2.59)\2\.... 2.5 (0.8,5.9)\3\
H+..................... 1.05 (0.25-1.30)\3\.... 18.1 (3.1,61)\3\
Denver, COP.................... PM2.5.................. 0.0012 (0.0043)\3\..... 0.41-73
(Cough, adult asthmatics).. SO4=................... 0.0042 (0.00035)\3\.... 0.12-12
H+..................... 0.0076 (0.0038)\3\..... 2.0-41
----------------------------------------------------------------------------------------------------------------
Decreased Lung Function
----------------------------------------------------------------------------------------------------------------
Uniontown, PAE................. PM2.5.................. PEFR 23.1 (-0.3,36.9) 25/88 (NR/88)
(per 25 g/m3).
Seattle, WAQ................... bext................... FEV1 42 ml (12,73)..... 5/45
Asthmatics................. calibrated by PM2.5.... FVC 45 ml (20,70)
----------------------------------------------------------------------------------------------------------------
(EPA, 1996)
A Schwartz et al. (1996a).
B Burnett et al. (1994).
C Burnett et al. (1995).
D Thurston et al. (1992, 1994).
E Neas et al. (1995).
F Ostro et al. (1993).
G Schwartz et al. (1994).
Q Koenig et al. (1993).
P Ostro et al. (1991).
Min/Max 24-h PM indicator level shown in parentheses unless otherwise noted as (S.D.), 10
and 90 percentile (10,90).
* Change per 100 nmoles/m3.
** Change per 20 g/m3 for PM2.5; per 5 g/m3 for PM2.5 sulfur; per 25 nmoles/m3 for H+.
*** 50th percentile value (10,90 percentile).
**** Coefficient and SE in parenthesis.
BILLING CODE 4510-431-P
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BILLING CODE 4510-43-C
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Table III-6.--Hypothesized Mechanisms of Particulate Toxicity a
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Response Description
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Increased Airflow Obstruction.......... PM exposure may aggravate existing respiratory symptoms which feature
airway obstruction. PM-induced airway narrowing or airway obstruction
from increased mucous secretion may increase abnormal ventilation/
perfusion ratios in the lung and create hypoxia. Hypoxia may lead to
cardiac arrhythmias and other cardiac electrophysiologic responses
that in turn may lead to ventricular fibrillation and ultimately
cardiac arrest. For those experiencing airflow obstruction, increased
airflow into non-obstructed areas of the lung may lead to increased
particle deposition and subsequent deleterious effects on remaining
lung tissue, further exacerbating existing disease processes. More
frequent and severe symptoms may be present or more rapid loss of
function.
Impaired Clearance..................... PM exposure may impair clearance by promoting hypersecretion of mucus
which in turn results in plugging of airways. Alterations in clearance
may also extend the time that particles or potentially harmful
biogenic aerosols reside in the tracheobronchial region of the lung.
Consequently alterations in clearance from either disturbance of the
mucociliary escalator or of macrophage function may increase
susceptibility to infection, produce an inflammatory response, or
amplify the response to increased burdens of PM. Acid aerosols impair
mucociliary clearance.
Altered Host Defense................... Responses to an immunological challenge (e.g., infection), may enhance
the subsequent response to inhalation of nonspecific material (e.g.,
PM). PM exposure may also act directly on macrophage function which
may not only affect clearance of particles but also increase
susceptibility and severity of infection by altering their
immunological function. Therefore, depression or over-activation of
the immune system, caused by exposure to PM, may be involved in the
pathogenesis of lung disease. Decreased respiratory defense may result
in increased risk of mortality from pneumonia and increased morbidity
(e.g., infection).
Cardiovascular Perturbation............ Pulmonary responses to PM exposure may include hypoxia,
bronchoconstriction, apnea, impaired diffusion, and production of
inflammatory mediators that can contribute to cardiovascular
perturbation. Inhaled particles could act at the level of the
pulmonary vasculature by increasing pulmonary vascular resistance and
further increase ventilation/perfusion abnormalities and hypoxia.
Generalized hypoxia could result in pulmonary hypertension and
interstitial edema that would impose further workload on the heart. In
addition, mediators released during an inflammatory response could
cause release of factors in the clotting cascade that may lead to
increased risk of thrombus formation in the vascular system. Finally,
direct stimulation by PM of respiratory receptors found throughout the
respiratory tract may have direct cardiovascular effects (e.g.,
bradycardia, hypertension, arrhythmia, apnea and cardiac arrest).
Epithelial Lining Changes.............. PM or its pathophysiological reaction products may act at the alveolar
capillary membrane by increasing the diffusion distances across the
respiratory membrane (by increasing its thickness) and causing
abnormal ventilation/perfusion ratios. Inflammation caused by PM may
increase ``leakiness'' in pulmonary capillaries leading eventually to
increased fluid transudation and possibly to interstitial edema in
susceptible individuals. PM induced changes in the surfactant layer
leading to increased surface tension would have the same effect.
Inflammatory Response.................. Diseases which increase susceptibility to PM toxicity involve
inflammatory response (e.g., asthma, COPD, and infection). PM may
induce or enhance inflammatory responses in the lung which may lead to
increased permeability, diffusion abnormality, or increased risk of
thrombus formation in vascular system. Inflammation from PM exposure
may also decrease phagocytosis by alveolar macrophages and therefore
reduce particle clearance. (See discussions above for other
inflammatory effects from PM exposure.)
----------------------------------------------------------------------------------------------------------------
a This table reproduces Table V-2 of the EPA staff paper. The citation in the staff paper indicates the table is
derived from information in the EPA criteria document on particulate matter (p. 13-67 to 72; p. 11-179 to 185)
and information in Appendix D of EPA staff paper.
IV. Discussion of Proposed Rule
This part of the preamble explains, section-by-section, the
provisions of the proposed rule. As appropriate, this part references
discussions in other parts of this preamble: in particular, the
background discussions on measurement methods and controls in part II,
and the feasibility discussions in part V.
The proposed rule would add a new subpart to 30 CFR part 72,
Subpart D--Diesel Particulate Matter--Underground, and would also add
two new sections (Secs. 72.500 and 72.510). The proposal would also
amend existing Sec. 75.371 in 30 CFR part 75.
Sec. 72.500 Diesel Particulate Filtration Systems
Summary
The proposed rule would require the installation and maintenance of
high-efficiency particulate filters on the most polluting types of
diesel equipment in underground coal mines.
Proposed Sec. 72.500(a) would require that beginning 18 months
after the date the rule is promulgated, any piece of permissible
diesel-powered equipment operated in an underground coal mine must be
equipped with a system capable of removing, on average, at least 95% of
the mass of the dpm emitted from the engine.
Paragraph (b) would require that beginning 30 months after the rule
is promulgated, any nonpermissible piece of ``heavy duty'' diesel-
powered equipment operated in an underground coal mine be equipped with
a system capable of removing, on average, at least 95% of the mass of
the dpm emitted from the engine. ``Heavy duty'' for this purpose is
defined by existing Sec. 75.1908(a).
Paragraph (c) would require that any exhaust aftertreatment device
installed to reduce the emission of dpm be maintained in accordance
with manufacturer specifications.
Paragraph (d) would set forth the Agency's requirements for
determining whether a system is capable of removing, on average, at
least 95% of diesel particulate matter by mass. It states that a
filtration system would be tested by comparing the results of emission
tests of an engine with and without the filtration system in place,
using the test cycle specified in Table E-3 of 30 CFR 7.89, ``Tests to
Determine
[[Page 17556]]
Particulate Index.'' The proposed rule would also require that the
filtration system submitted for testing be representative of those
actually intended for mining use.
Discussion of Alternatives
Alternative approaches for this sector considered by the Agency are
discussed in detail in part V of this preamble concerning feasibility.
MSHA's decision to propose an approach requiring a technology capable
of reducing engine emissions by a specified amount was driven by
several considerations.
First, the Agency is not confident that there is a measurement
method for dpm that will provide accurate, consistent and verifiable
results at lower concentration levels in underground coal mines. The
available measurement methods for determining dpm concentrations in
underground coal mines were carefully evaluated by the Agency,
including field testing, before the Agency reached this conclusion. The
problems are discussed in detail in part II of this preamble. The
Agency is continuing to collect data and is consulting with NIOSH to
resolve questions about the measurement of dpm in underground coal
mines. If at some future time it can be established that a particular
measurable component of dpm (e.g., the elemental carbon component of
dpm) can be used to accurately quantify the level of dpm, the Agency
would reevaluate the question of measurement at underground coal mines
in that light.
Second, filtration systems for the diesel equipment used in this
sector are available at a reasonable cost, and if properly maintained
can provide generally consistent, highly effective elimination of dpm
from underground mine atmospheres.
Finally, the Agency believes that alternative approaches that would
require each combination of engine plus filtration system to meet a
defined dpm emissions requirement might well provide inadequate
protection. The statute requires the Agency to adopt the feasible
approach that provides maximum protection.
Types of Equipment To Be Filtered
MSHA's field data on dpm emissions in underground coal mines is
reviewed in part III of this preamble. The data indicates that it is
currently the permissible equipment used for face haulage that
contributes most to high dpm levels, but heavy-duty outby equipment can
also generate significant dpm emissions.
Because of its statutory obligation to attain the highest degree of
safety and health protection for miners, with feasibility a
consideration, the Agency explored the implications of requiring all
diesel-powered equipment to be filtered; but as discussed in part V of
the preamble, the Agency has tentatively concluded that the high costs
of filtering all light-duty outby equipment may not be feasible for
this sector at this time.
However, MSHA welcomes information about light-duty equipment which
may be making a significant contribution to dpm emissions in particular
mines or particular situations, and MSHA may consider including in the
final rule filtration requirements to address any such problems. The
Agency would also welcome comment on whether it would be feasible for
this sector to implement a requirement that any new light-duty
equipment added to a mine's fleet be filtered. By way of a rough cost
estimate, if turnover is only 10% a year, for example, the cost of such
an approach would be only about a tenth of that for filtering all
light-duty outby. To the extent there may be technological restraints
on filtering light-duty equipment with 95% filters, the Agency would
welcome comment on the feasibility of requiring that 60-90% filtration
be used on some or all of the light-duty fleet. And the agency is
interested in comments as to whether it is likely that, in response to
the market for high-efficiency filters on other types of equipment,
there will soon be developed high-efficiency ceramic filters suitable
for light-duty equipment. MSHA welcomes comment on these and other
approaches dealing with light-duty equipment in underground coal mines,
and will continue to study this issue in light of the record.
Timeframe for Implementation
On permissible equipment, the filters can simply be installed
directly on the tailpipes; accordingly, the rule would require these
filters to be installed within 18 months. In the case of outby
equipment, scrubbers and cooling system upgrades will need to be added
to cool the exhaust before the filters are installed, or a dry
technology system utilized. Accordingly, an additional year is provided
for such equipment.
95% Effective
The proposed rule would define effectiveness of a filtration system
in removing dpm mass by reference to a laboratory test, using an engine
for the test representative of those to be actually used in mining. The
test involves: (a) measuring the average dpm mass of the emissions from
the engine (under steady state load conditions specified in Table E-3
of section 7.89 of title 30 of the Code of Federal Regulations) before
the filtration system is added; (b) measuring again after the
filtration system is added; and (c) determining the efficiency of the
filtration system by comparing the results.
As discussed in the background materials in part II of this
preamble (including MSHA's toolbox, reprinted as an Appendix at the end
of this document), there are several systems presently on the market
capable of achieving such reductions. Current permissible engines used
in underground coal mines are equipped with power packages that protect
the engine against fire and explosion hazards. Power packages are
installed with either water scrubbers (wet systems) or with heat
exchanger technology (dry systems). For both cases, paper filters have
been installed on these systems. The paper filter can be used on
permissible equipment due to the limitation of the exhaust gas
temperature to below 302 deg.F; above that temperature, the paper could
catch fire and burn.
Information concerning the particulate removal capability of these
filters has been well documented in field studies and laboratory tests.
Overall, the paper filters, when attached to a dry system and when
tested in the laboratory on an engine dynamometer using the test cycle
specified in the proposed rule, achieve greater than 95% diesel
particulate removal (Gautam, dpm Workshop; Beckley, WV, 1995). Field
studies have indicated diesel particulate removal using the paper
filters on wet systems up to 90% using a wet permissible system (BOM RI
9508).
Nonpermissible equipment can utilize such paper filters if the
exhaust is cooled through the addition of heat exchangers or other
devices. Dry technology can also be utilized.
As noted in part II, ceramic filters may in the future be capable
of achieving reductions of at least 95% in dpm mass. MSHA would welcome
information on the development of ceramic filters which can or will
soon meet such capabilities. Ceramic filters can be used directly on
hot emissions, and hence might be a particularly attractive alternative
for nonpermissible equipment. But whether paper, ceramic or some other
media, the same test would be utilized to determine particulate removal
capabilities.
Maintenance
The proposed rule would require that any filtration system
installed to reduce the emission of dpm be maintained in
[[Page 17557]]
accordance with manufacturer specifications (e.g., changing disposable
filters at the proper interval), ensuring cooling devices added to
nonpermissible equipment are maintained.
Enforcement
Since a concentration limit is not being established, the proposed
rule does not require environmental monitoring of dpm concentrations by
either operators or by MSHA specialists. Enforcement of the proposed
underground coal requirements would be through observation by MSHA
inspectors. Inspectors would observe whether an aftertreatment device
that passed the effectiveness test is actually installed on each piece
of equipment on which one is required, and whether diesel equipment was
emitting black smoke during changes in acceleration or otherwise
suggesting lack of required maintenance.
It should be noted that the training and qualifications of those
who perform maintenance of diesel-powered equipment is governed by 30
CFR 75.1915, pursuant to MSHA's diesel equipment rule.
Sec. 72.510 Miner Health Training
Paragraph (a) of this section requires hazard awareness training of
underground coal miners who can reasonably be expected to be exposed to
dpm. Paragraph (b) includes provisions on records retention, access and
transfer.
To ensure miners can better contribute to dpm reduction efforts,
underground coal miners who can reasonably be expected to be exposed to
diesel emissions must be annually trained about the hazards associated
with that exposure and in the controls being used by the operator to
limit dpm concentrations.
Proposed Sec. 72.510(a) would require any underground coal miner
``who can reasonably be expected to be exposed to diesel emissions'' to
be trained annually in: (a) the health risks associated with dpm
exposure; (b) the methods used in the mine to control dpm
concentrations; (c) identification of the personnel responsible for
maintaining those controls; and (d) actions miners must take to ensure
the controls operate as intended.
The purpose of the proposed requirement is to promote miner
awareness. Exposure to diesel particulate is associated with a number
of harmful effects as discussed in part III of this preamble, and the
safe level is unknown. Miners who work in mines where they are exposed
to this risk ought to be reminded of the hazard often enough to make
them active and committed partners in implementing actions that will
reduce that risk.
The training need only be provided to underground coal miners who
can reasonably be expected to be exposed at the mine. The training is
to be provided by operators; hence, it is to be without fee to the
miner.
The rule places no constraints on the operator as to how to
accomplish this training. MSHA believes that the required training can
be provided at minimal cost and with minimal disruption. The proposal
would not require any special qualifications for instructors, nor would
it specify the hours of instruction.
Instruction could take place at safety meetings before the shift
begins, devoting one of those meetings to the topic of dpm would be a
very easy way to convey the necessary information. Simply providing
miners with a copy of MSHA's ``toolbox,'' and reviewing how to use it
in an individual mine, can cover several of the training requirements.
One-on-one discussions that cover the required topics is another
approach that can be used.
Operators could also choose to include a discussion on diesel
emissions in their part 48 training, provided the plan is approved by
MSHA. There is no existing requirement that part 48 training include a
discussion of the hazards and control of diesel emissions. While mine
operators are free to cover additional topics during the part 48
training sessions, the topics that must be covered during the required
time frame may make it impracticable to cover other matters within the
prescribed time limits. Where the time is available in mines using
diesel-powered equipment, operators would be free to include the dpm
instruction in their part 48 training plans. The Agency does not
believe special language in the proposed rule is required to permit
this action under part 48, but welcomes comment in this regard.
To assist mine operators with the proposed training requirement, it
is MSHA's intent to develop an instruction outline that mine operators
can use as a guide for training personnel. Instruction materials will
be provided with the outline.
The proposal does not require the mine operator to separately
certify the completion of the dpm training, but some evidence that the
training took place would have to be produced upon request. A serial
log with the employee's signature is an acceptable practice.
Proposed Sec. 72.510(b)(1) would require that any log or record
produced signifying that the training had taken place would be retained
at the mine site for one year.
The records need to be where an inspector can view them during the
course of an inspection, as the information in the records may
determine how the inspection proceeds. But if the mine site has a fax
machine or computer terminal, MSHA would permit the records to be
maintained elsewhere so long as they are readily accessible. MSHA's
approach in this regard is consistent with Office of Management and
Budget Circular A-130.
Under proposed paragraph (b)(2) mine operators must promptly
provide access to the training records upon request from an authorized
representative of the Secretary of Labor, the Secretary of Health and
Human Services, or from an authorized representative of miners. If an
operator ceases to do business, all training records of employees are
expected to be transferred to any successor operator. The successor
operator will be expected to maintain those training records for the
required one year period unless the successor operator has undertaken
to retrain the employees.
Amendment to Sec. 75.371 Ventilation Plan Modification
The proposed rule would amend existing Sec. 75.371 to add one new
requirement to an underground coal mine's ventilation control plan. The
information is limited, but is critical to the control of dpm. The
proposed added paragraph (qq) would require the ventilation plan to
contain a list of the diesel-powered units used by the mine operator
together with information about any unit's emission control or
filtration system. Included in that information should be details
relative to the efficiency of the system and the method(s) used to
establish the efficiency of the system for removing dpm. Any amendments
to a mine's ventilation plan must, of course, be accomplished pursuant
to the requirements of 30 CFR 75.370.
General Effective Date
The proposed rule provides that unless otherwise specified, its
provisions take effect 60 days after the date of promulgation of the
final rule.
Some provisions of the proposed rule contain delayed effective
dates that provide more time for technical assistance to mine
operators. For example, the first filtration requirements
[[Page 17558]]
for underground coal mining equipment would be delayed for 18 months.
V. Adequacy of protection and feasibility of proposed rule
The Mine Act requires that in promulgating a standard, the
Secretary, based on the best available evidence, shall attain the
highest degree of health and safety protection for the miner with
feasibility a consideration.
Overview
This part begins with a summary of the pertinent legal
requirements, followed by a general profile of the economic health and
prospects of the coal mining industry.
The discussion then turns to the rule being proposed by the Agency
for underground coal mines. MSHA is proposing to require that mine
operators utilize a particular technological approach to reduce the
levels of dpm which result from the emissions generated by diesel
equipment engines. No specific concentration limit for dpm would be
established for the underground coal sector. Miner hazard awareness
training would also be required by the proposal.
This part evaluates the proposed rule for underground coal mines to
ascertain if, as required by the statute, it achieves the highest
degree of protection for underground coal miners that it is feasible,
both technologically and economically, for underground coal mine
operators to provide.
Regulatory alternatives to the proposed rule are also reviewed in
this regard, for example, establishing a dpm concentration limit for
underground coal mines, with operator flexibility on choice of control
technologies. After review and considerable study of these
alternatives, the Agency has tentatively concluded that compliance with
these alternatives discussed below are not technologically or
economically feasible for underground coal mine operators at this time.
MSHA has also tentatively concluded that the approach being proposed is
both economically and technologically feasible for this sector.
Pertinent Legal Requirements
Section 101(a)(6)(A) of the
Federal Mine Safety and Health Act of 1977 (Mine Act) states that
MSHA's promulgation of health standards must:
* * * [A]dequately assure, on the basis of the best available
evidence, that no miner will suffer material impairment of health or
functional capacity even if such miner has regular exposure to the
hazards dealt with by such standard for the period of his working
life.
The Mine Act also specifies that the Secretary of Labor
(Secretary), in promulgating mandatory standards pertaining to toxic
materials or harmful physical agents, base such standards upon:
* * * [R]esearch, demonstrations, experiments, and such other
information as may be appropriate. In addition to the attainment of
the highest degree of health and safety protection for the miner,
other considerations shall be the latest available scientific data
in the field, the feasibility of the standards, and experience
gained under this and other health and safety laws. Whenever
practicable, the mandatory health or safety standard promulgated
shall be expressed in terms of objective criteria and of the
performance desired. [Section 101(a)(6)(A)].
Thus, the Mine Act requires that the Secretary, in promulgating a
standard, based on the best available evidence, attain the highest
degree of health and safety protection for the miner with feasibility a
consideration.
In relation to feasibility, the legislative history of the Mine Act
states that:
* * * This section further provides that ``other
considerations'' in the setting of health standards are ``the latest
available scientific data in the field, the feasibility of the
standards, and experience gained under this and other health and
safety laws.'' While feasibility of the standard may be taken into
consideration with respect to engineering controls, this factor
should have a substantially less significant role. Thus, the
Secretary may appropriately consider the state of the engineering
art in industry at the time the standard is promulgated. However, as
the circuit courts of appeal have recognized, occupational safety
and health statutes should be viewed as ``technology-forcing''
legislation, and a proposed health standard should not be rejected
as infeasible when the necessary technology looms in today's
horizon. AFL-CIO v. Brennan, 530 F.2d 109 (1975); Society of the
Plastics Industry v. OSHA, 509 F.2d 1301, cert. denied, 427 U.S. 992
(1975).
Similarly, information on the economic impact of a health
standard which is provided to the Secretary of Labor at a hearing or
during the public comment period, may be given weight by the
Secretary. In adopting the language of [this section], the Committee
wishes to emphasize that it rejects the view that cost benefit
ratios alone may be the basis for depriving miners of the health
protection which the law was intended to insure. S. Rep. No. 95-181,
95th Cong., 1st Sess. 21 (1977).
Court decisions have clarified the meaning of feasibility. The
Supreme Court, in American Textile Manufacturers' Institute v. Donovan
(OSHA Cotton Dust), 452 U.S. 490, 101 S.Ct. 2478 (1981), defined the
word ``feasible'' as ``capable of being done, executed, or effected.''
The Court stated that a standard would not be considered economically
feasible if an entire industry's competitive structure was threatened.
According to the Court, the appropriate inquiry into a standard's
economic feasibility is whether the standard is capable of being
achieved.
Courts do not expect hard and precise predictions from agencies
regarding feasibility. Congress intended for the ``arbitrary and
capricious standard'' to be applied in judicial review of MSHA
rulemaking (S.Rep. No. 95-181, at 21.) Under this standard, MSHA need
only base its predictions on reasonable inferences drawn from the
existing facts. MSHA is required to produce reasonable assessment of
the likely range of costs that a new standard will have on an industry.
The agency must also show that a reasonable probability exists that the
typical firm in an industry will be able to develop and install
controls that will meet the standard. See, Citizens to Preserve Overton
Park v. Volpe, 401 U.S. 402, 91 S.Ct. 814 (1971); Baltimore Gas &
Electric Co. v. NRDC, 462 U.S. 87 103 S.Ct. 2246, (1983); Motor Vehicle
Manufacturers Assn. v. State Farm Mutual Automobile Insurance Co., 463
U.S. 29, 103 S.Ct. 2856 (1983); International Ladies' Garment Workers'
Union v. Donovan, 722 F.2d 795, 232 U.S. App. D.C. 309 (1983), cert.
denied, 469 U.S. 820 (1984); Bowen v. American Hospital Assn., 476 U.S.
610, 106 S.Ct. 2101 (1986).
In developing a health standard, MSHA must also show that modern
technology has at least conceived some industrial strategies or devices
that are likely to be capable of meeting the standard, and which
industry is generally capable of adopting. United Steelworkers of
America v. Marshall, 647 F.2d 1189, 1272 (1980). If only the most
technologically advanced companies in an industry are capable of
meeting the standard, then that would be sufficient demonstration of
feasibility (this would be true even if only some of the operations met
the standard for some of the time). American Iron and Steel Institute
v. OSHA, 577 F.2d 825 (3d Cir. 1978); see also, Industrial Union
Department, AFL-CIO v. Hodgson, 499 F.2d 467 (1974).
Industry Profile
The industry profile provides background information describing the
structure and economic characteristics of the coal mining industry.
This information was considered by MSHA as appropriate in reaching
tentative conclusions about the economic feasibility of various
regulatory alternatives. MSHA welcomes the
[[Page 17559]]
submission of additional economic information about the coal mining
industry, and about underground coal mining in particular, that will
help it make final determinations about the economic feasibility of the
proposed rule.
This profile provides data on the number of mines, their size, the
number of employees in each segment, as well as selected market
characteristics. This profile does not provide information about the
use of diesel engines in the industry; information in that regard was
provided in the first section of part II of this preamble.
Although this particular rulemaking does not apply to the surface
coal sector, information about surface coal mines is provided here in
order to give context for the discussions on underground mining.
Overall Mining Industry
MSHA divides the mining industry into two major segments based on
commodity, the coal mining industry and the metal and nonmetal (M&NM)
mining industry. These major industry segments are further divided
based on type of operation (underground mines, surface mines, and
independent mills, plants, shops, and yards). MSHA maintains its own
data on mine type, size, and employment. MSHA also collects data on the
number of contractors and contractor employees by major industry
segment.
With respect to mine size, the mining community has traditionally
regarded a ``small'' mine as being one with less than 20 miners. This
has been a useful dividing line for a number of purposes, including
rulemaking, because the nature of the safety and health issues facing
such entities tends to be different than for larger mines. MSHA
recognizes, however, that the definition of ``small entity'' used by
the Small Business Administration in the mining sector is different--
500 employees or less. In order to accommodate both perspectives when
analyzing the impact of this proposed rule on the mining industry, MSHA
has prepared its Preliminary Regulatory Economic Analysis (PREA) in
such a way as to focus on the special impacts of both size categories--
those with less than 20 employees, and those with less than 500
employees (basically all mines). In this profile, however, the term
``small mine'' refers to one with less than 20 miners.
Table V-1 presents the number of small and large coal mines and the
corresponding number of miners, excluding contractors, by major
industry segment and mine type. Table V-2 presents MSHA data on the
numbers of independent contractors and the corresponding numbers of
employees by major industry segment and the size of the operation based
on employment.
Table V-1.--Distribution of Operations and Employment (Excluding Contractors) by Mine Type, Commodity, and Size
----------------------------------------------------------------------------------------------------------------
Small (<20 ees)="" large="">20 Total
-------------------------- EES) -------------------------
Mine type --------------------------
Number of Number of Number of Number of Number of Number of
mines miners mines miners mines miners
----------------------------------------------------------------------------------------------------------------
Coal:
Underground................... 426 4,371 545 46,206 971 50,577
Surface....................... 776 4,705 370 28,314 1,146 33,019
Shp/Yrd/Mll/Plnt.............. 399 2,538 128 5,010 527 7,548
Office workers................ ........... 657 ........... 4,500 ........... 5,157
-----------------------------------------------------------------------------
Total coal mines.......... 1,601 12,271 1,043 84,030 2,644 96,301
----------------------------------------------------------------------------------------------------------------
Source: U.S. Department of Labor, Mine Safety and Health Administration, Office of Standards, Regulations, and
Variances, based on preliminary 1996 MIS data (quarter 1-quarter 4, 1996). MSHA estimates assume that office
workers are distributed between large and small operations the same as non-office workers.
Table V-2.--Distribution of Contractors (Contr) and Contractor Employees (Miners) by Major Industry Segment and
Size of Operation
----------------------------------------------------------------------------------------------------------------
Small (<20) large="">20) Total
Contractors -----------------------------------------------------------------------------
No. contr No. miners No. contr No. miners No. contr No. miners
----------------------------------------------------------------------------------------------------------------
Coal:
Other than office............. 3,606 13,954 297 13,792 3,903 27,746
Office workers................ ........... 1,034 ........... 1,022 ........... 2,056
-----------------------------------------------------------------------------
Total coal................ 3,606 14,988 297 14,814 3,903 29,802
----------------------------------------------------------------------------------------------------------------
Source: U.S. Department of Labor, Mine Safety and Health Administration, Office of Standards, Regulations, and
Variances, based on preliminary 1996 MIS data (quarter 1--quarter 4, 1996). MSHA estimates assume that office
workers are distributed between large and small contractors the same as non-office workers.
MSHA separates the U.S. coal mining industry into two major
commodity groups, bituminous and anthracite. The bituminous group
includes the mining of subbituminous coal and lignite. Bituminous
operations represent over 93% of the coal mining operations, employ
over 98% of the coal miners, and account for over 99% of the coal
production. About 60% of the bituminous operations are small; whereas,
about 90% of the anthracite operations are small.
Underground bituminous mines are more mechanized than anthracite
mines in that most, if not all, underground anthracite mines still
hand-load. Over 70% of the underground bituminous mines use continuous
mining and longwall mining methods. The remaining use drills, cutters,
and scoops. As noted in the first section of part II of this preamble,
although underground coal mines generally use electrical powered
equipment, a growing number of underground coal
[[Page 17560]]
mines use diesel-powered equipment. (See Table II-1).
Surface mining methods include drilling, blasting, and hauling and
are similar for all commodity types. Most surface mines use front-end
loaders, bulldozers, shovels, or trucks for coal haulage. A few still
use rail haulage. Although some coal may be crushed to facilitate
cleaning or mixing, coal processing usually involves cleaning, sizing,
and grading. As noted in section 1 of part II of this preamble, diesel
power is used extensively in surface mines for all these operations.
Preliminary data for 1996 (MSHA/DMIS, Coal, CM-441, 1996) indicate
that there are about 2,650 active coal mines of which 1,600 are small
mines (about 60% of the total) and 1,050 are large mines (about 40% of
the total). These data indicate employment at coal mines to be about
96,300 of which 12,275 (13% of the total) worked at small mines and
84,025 (87% of the total) worked at large mines. (Ibid.). MSHA
estimates that the average employment is 8 miners at small coal mines
and 81 miners at large coal mines.
The U.S. Department of Energy, Energy Information Administration,
reported that the U.S. coal industry produced a record 1.06 billion
tons of coal in 1996 with a value of approximately $20 billion. Of the
several different types of coal commodities, bituminous and
subbituminous coal account for 91% of all coal production (about 940
million tons). The remainder of U.S. coal production is lignite (86
million tons) and anthracite (4 million tons). Although anthracite
offers superior burning qualities, it contributes only a small and
diminishing share of total coal production. Less than 0.4% of U.S. coal
production in 1996 was anthracite (DOE/EIA, 1997, p. 209).
Mines east of the Mississippi account for about 53% of the current
U.S. coal production. For the period 1949 through 1996, coal production
east of the Mississippi River fluctuated from a low of 395 million tons
in 1954 to 630 million tons in 1990. During this same period, however,
coal production west of the Mississippi increased each year from a low
of 20 million tons in 1959 to a record 505 million tons in 1996.
(Ibid.). The growth in western coal is due in part to environmental
concerns that led to increased demand for low-sulfur coal, which is
concentrated in the West. In addition, surface mining which is more
prevalent in the West has increased in productivity due to the
technological developments of oversized power shovels and draglines.
The 1996 estimate of the average value of coal at the point of
production is about $19 per ton for bituminous coal and lignite.
(Ibid., at 221). MSHA chose to use $19 per ton as the value for all
coal production because anthracite contributes such a small amount to
total production that the higher value per ton of anthracite does not
greatly impact the total value. The total value of coal production in
1996 was approximately $20 billion of which about $0.9 billion was
produced by small mines and $19.1 billion was produced by large mines.
Coal is used for several purposes including the production of
electricity. The predominant consumer of U.S. coal is the electric
utility industry which used 898 million tons of coal in 1996 or 84% of
the coal produced. Other coal consumers include coke plants (31 million
tons), residential and commercial consumption (6 million tons), and
miscellaneous other industrial uses (71 million tons). This last
category includes the use of coal products in the manufacturing of
other products, such as plastics, dyes, drugs, explosives, solvents,
refrigerants, and fertilizers. (Ibid., at 205).
The U.S. coal industry enjoys a fairly constant domestic demand due
to electric utility usage of coal. MSHA does not expect a substantial
change in coal demand by utilities in the near future because of the
high conversion costs of changing a fuel source in the electric utility
industry. Energy experts predict that coal will continue to be the
dominant fuel source of choice for power plants built in the future.
Adequacy of Miner Protection Provided by the Proposed Rule for
Underground Coal Mines
In evaluating the protection provided by the proposed rule, it
should be remembered that MSHA has measured dpm concentrations in
production areas and haulageways of underground coal mines as high as
3,650DPM g/m3 with a mean concentration
of 644DPM g/m3. See Table III-1 and
Figure III-1 in part III of this preamble. As discussed in detail in
part III of the preamble, these concentrations place underground coal
miners at significant risk of material impairment of their health, and
the evidence supports the proposition that reducing the exposure
reduces the risk. Therefore, to address this risk, the Agency is
proposing to develop requirements which reduce these concentrations as
much as is both technologically and economically feasible for this
sector as a whole.
The proposed rule would require the installation of high-efficiency
filters on all permissible and heavy-duty outby diesel-powered
equipment in underground coal mines. Operators would have 18 months to
install these filters on permissible diesel equipment, and an
additional 12 months to do the same for heavy-duty nonpermissible
diesel equipment (as defined by 30 CFR 75.1908(a)).
As an example of what filtration can achieve, take the case of a
single-section mine with three Ramcars (94hp, indirect injection) and a
section airflow of 45,000 cfm. MSHA measured concentrations of dpm in
this mine at 610DPM g/m3. Of this
amount, 25DPM g/m3 was coming from the
intake to the section, and the remaining 585DPM g/
m3 was emitted by the engines. Reducing the engine emissions
by 95% through the use of aftertreatment filters would reduce the dpm
emitted to 29DPM g/m3. With an intake
amount of 25DPM g/m3, the ambient
concentration would be about 54DPM g/m3.
Similarly, dramatic results can be achieved in almost any situation if
the filters achieve in practice the predicted reduction in particulate
matter; and as the coal fleet turns over, in accordance with the
existing diesel equipment rule, to the exclusive use of approved
engines, the combination of that change and the use of 95% filters
should keep ambient dpm concentrations at much lower levels than at
present.
There are some reasons for caution. MSHA's experience with the
high-efficiency filters is limited. While they are capable in
laboratory tests of achieving a 95% reduction in dpm mass, and this has
been confirmed in some field tests, the Agency has not tested them
under a variety of actual mining conditions. As discussed in part IV,
determination of the efficiency of any filter media is greatly
dependent upon the test used to determine efficiency or collection
capacity. Therefore, actual performance may be different in the field
due to individual mining conditions (e.g., ventilation changes),
changes of the equipment due to maintenance, and the type of engine
used.
Two factors that come into play are the ventilation rate and the
ambient dpm intake into the section. If ventilation levels drop below
the nameplate requirements for gaseous emissions, or if many pieces of
equipment throughout the mine create a high ambient level of dpm,
implementation of the proposed rule may not bring concentrations down
as effectively as suggested in the prior example. On the other hand, if
the ventilation rate is maintained at a higher level, the engine
emissions would be better diluted and the ambient
[[Page 17561]]
concentration could offset any decrease in filter efficiency under
actual mining conditions.
Table V-3 summarizes information from a series of simulations
designed to illustrate these variables. The simulations were performed
using the tool discussed in the Appendix to this part (MSHA's
``Estimator'') for a mine section with a 94 horsepower engine, with a
0.3 gm/hp-hr dpm emission rate and a nameplate airflow, 5500 cfm. The
engine was operated during an eight hour shift. The estimator was used
to calculate the values. The same results would be obtained for
multiple pieces of equipment provided that the nameplate airflow is
additive for each piece of equipment.
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In Table V-3, the intake dpm (second column) increases after every
fourth row. Within each group of four rows, the ventilation (first
column) increases from one row to the next. The last 3 columns display
the ambient dpm concentration with a particular filter efficiency. The
first four rows represent a situation where there is no intake dpm. If
the mine is ventilated with four times the nameplate airflow (row 4),
the ambient dpm concentration using a filter operating at 95% (last
column) is reduced to 38DPM g/m\3\. If the filter
in this situation only works in practice at 85% efficiency in removing
dpm, the ambient dpm concentration is only reduced to 113DPM
g/m\3\. And if the ventilation is reduced to the nameplate
airflow (first column) and the filter is only 85% efficient, the
ambient dpm climbs to 452DPM g/m\3\. The last four
rows display the parallel situation but with an ambient intake
concentration to the section of 75DPM g/m\3\. In
this situation, depending on ventilation and filter effectiveness, the
ambient dpm concentration ranges from 113DPM to
527DPM g/m\3\.
In the example discussed above--a single section mine with three 94
hp Ramcars--the airflow of 45,000 cfm represents three times the
current nameplate requirements. If this airflow were reduced to the
current nameplate requirements, the ambient dpm would have been
1620DPM g/m\3\, and would have been reduced by 95%
effective filters to 105DPM g/m\3\.
It should be remembered that the proposed rule does not require the
filtration of light-duty equipment; hence, mines with significant light
duty equipment will have this exhaust as an ``intake'' in such
calculations. Also, many underground coal mines may use more than the
nameplate ventilation to lower methane concentrations at the face.
Based on its experience as to the general effects of mining
conditions on the expected efficiency of equipment, and on ventilation
rates, MSHA believes that the proposed rule for this sector will
substantially reduce the concentrations of dpm to which underground
coal miners are exposed. But in order to ensure that the maximum
protection feasible is being provided, the Agency has considered some
alternatives.
(1) Establish a Concentration Limit in Coal
Under such an approach, a diesel particulate concentration limit
would be phased in and operators could select any combination of
controls that keep ambient dpm concentrations below the limit.
After careful analysis, the agency has determined that it is not
yet ready to conclude that it is technologically feasible to establish
a dpm concentration limit for underground coal mines. The problem, as
discussed in part IV, is that significant questions remain as to
whether there is a sampling and analytical system that can provide
consistent and accurate measurements of dpm in areas of underground
coal mines where there is a heavy concentration of coal dust. The
Agency is continuing to work on the technical issues involved, and
should it determine that these technological problems have been
resolved, it will notify the mining community and proceed accordingly.
(2) Alternatives to 95% Filters on Permissible and Heavy-duty Equipment
In part IV of this preamble, the agency outlines some approaches
that might be considered as alternatives to the requirement in the
proposal that all permissible and heavy-duty equipment must have a 95%
aftertreatment filter installed and properly maintained.
The first alternative would in essence provide some credit in
filter selection to those operators who use engines that significantly
reduce ambient mine dpm concentration. Under this approach, the engine
and aftertreatment filter would be bench tested as a unit; and if the
emissions from the unit are below a certain level (e.g.,
120DPM g/m\3\, using 50% of the name plate
ventilation, the emissions limit applicable under Pennsylvania law),
the package would be acceptable without regard to the efficiency of
just the filter component. The second option would also provide credit
in filter selection for extra ventilation used in an underground coal
mine. If the bench test of the combined engine and filter package was
conducted at the name plate ventilation, a mine's use of more than that
level of ventilation would be factored into the calculation of what
package would be acceptable.
One practical effect of these approaches would be to permit some
operators to save the costs of installing heat exchangers or other
exhaust-cooling devices on nonpermissible heavy-duty equipment. Such
devices are necessary in order for this equipment to be fitted with
paper filters--and at the moment, these are the only filters on the
market capable of providing 95% and more filtration capability. (It is
not out of the realm of possibility that once a market develops for 95%
filters, makers of ceramic filters will develop models that reach this
level of efficiency--hence obviating the need for the heat exchangers
or other exhaust cooling technology on the outby equipment; information
or comment on this point would be welcome).
It is not clear to the Agency, however, that it would be
appropriate, under the statute, to take such an approach. With the
proper equipment to cool the exhaust, a 95% paper filter can be
installed on any piece of heavy-duty equipment in coal mines--and of
course directly on any permissible piece of equipment. And, as
indicated herein, the Agency is tentatively concluding that such an
approach is economically feasible as well. Installing a 95% efficient
filter on an engine lowers the dpm concentration in the mine more than
would installing a less efficient filter. Hence for engines which, with
a 95% filter, can reduce emissions below 120DPM g/
m\3\ (or whatever emissions limit is set), the alternative approach
would seem to provide miners with less protection.
In some cases, however, use of such an alternative approach could
actually result in a reduction of mine dpm--by forcing out certain
older, high-polluting engines. It is not clear to MSHA that 95%
filtration of the engines used on the majority of permissible machines
in underground coal mines can meet an emissions limit of
120DPM g/m\3\ using MSHA's name plate ventilation.
The engines involved just produce too much diesel particulate.
Accordingly, adopting a rule with an emissions limit of
120DPM g/m\3\ would in effect require these
existing permissible engines to be replaced with cleaner engines. Of
course, it follows that such a rule would be more costly than the one
proposed, because it would require the 95% filters plus the replacement
of these engines.
The second alternative (emissions limit plus credit for
ventilation) appears to be less protective in all cases. To provide
mines who need extra ventilation for other reasons (e.g., to keep
methane in check) with a credit for this fact in determining the
required filter efficiency would not reduce dpm concentrations as much
as simply requiring a 95% filter.
The Agency welcomes comments on these approaches and information
that will help it assess them in light of the requirements of the Mine
Act.
MSHA recognizes that a specification standard does not allow for
the use of future alternative technologies that might provide the same
or enhanced protection at the same or lower cost. MSHA welcomes comment
as to whether and how the proposed rule can be modified to enhance its
flexibility in this regard.
[[Page 17564]]
(3) Accelerate the Time-Frame for Installation of Filters on
Underground Coal Equipment
This approach would not change the level of protection ultimately
provided to miners when the proposed rule is fully implemented. But it
would ensure miners are protected more quickly, and therefore, needs to
be considered.
Under the first phase of the proposed rule, 95% effective filters
are required on all permissible equipment after 18 months. This
equipment constitutes only about 19% of the 2,950 pieces of diesel-
powered equipment estimated to be present in underground coal mines;
but because of where and how it is used (production areas), it produces
extensive amounts of particulate matter.
Cutting the 18 month time-frame does not appear to be practicable
for the industry. Eighteen months to obtain and install a relatively
new technology is a reasonable time. Time is needed for operators to
familiarize themselves with this technology. Also, mine personnel have
to be trained in how to maintain control devices in working order.
The second stage of the proposal requires the installation of 95%
filters on heavy-duty nonpermissible equipment after 30 months--a year
after the permissible equipment must be filtered. Again, speeding up
this timeframe may not be practicable. If paper filters indeed have to
be used, this equipment would need to be first equipped with water
scrubbers, heat exchangers or other systems to cool the exhaust before
the filtration can be installed, or dry technology installed. Providing
another year also allows additional time for possible perfection of
ceramic filtration, with the potential cost savings associated with
that approach, or other improvements in filtration that could better
protect miners. MSHA believes that providing the industry an extra year
to phase in controls for the heavy-duty outby equipment is reasonable.
(4) Require High Efficiency Filters on Any Diesel Equipment in
Underground Coal Mines
The proposed rule does not apply to approximately 65% of the
equipment in the fleet--light-duty outby. While this equipment does not
pollute as heavily as the equipment being covered by MSHA's proposal,
it does contribute to the total particulate concentration in
underground coal mines. And, as noted above, the Agency at this time
lacks confidence in a measurement system that can detect localized
concentrations even in outby areas. Accordingly, MSHA has considered
the possibility of requiring filtration for such equipment.
The Commonwealth of Pennsylvania has recently adopted legislation
for universal high-efficiency filtration based on an agreement in the
mining community of that state. The Pennsylvania law requires the use
of 95% efficiency filters on all diesel-powered equipment introduced in
the future into underground coal mines in that state (in addition to
other requirements). Since, however, the State did not allow the use of
diesel-powered equipment in underground coal mines prior to enactment
of this legislation, in practice the new law achieves a goal of
universal filtration.
The Agency decided to consider what it would take to bring the rest
of the industry up to the standard established under the Pennsylvania
agreement of universal high-efficiency filtration. MSHA has calculated
that such a requirement would cost the underground coal industry an
additional $17 million a year. This would increase by 70% the costs per
operator for the underground coal mining industry. This added cost
raises questions because for those mines with permissible and heavy-
duty equipment, filtering that equipment can achieve significant
reductions in existing dpm concentrations. Given the economic profile
of the coal sector, MSHA has tentatively concluded that such a
requirement may not be feasible for the underground coal sector at this
time.
MSHA welcomes information about light-duty equipment which may be
making a particular significant contribution to dpm emissions in
particular mines or particular situations, and which is likely to
continue to do so after full implementation of the approval
requirements of the diesel equipment rule. MSHA will consider including
in the final rule filtration requirements that may be necessary to
address any such identified problem. The Agency would also welcome
comment on whether it would be feasible for this sector to implement a
requirement that any new light-duty equipment added to a mine's fleet
be filtered. By way of a rough cost estimate, if turnover is only 10% a
year, for example, the cost of such an approach would be only about a
tenth of that for filtering all light-duty outby. To the extent there
may be technological restraints on filtering light-duty equipment with
95% filters, the Agency would welcome comment on the feasibility of
requiring that 60-90% filtration be used on some or all of the light-
duty fleet. And the agency is interested in comments as to whether it
is likely that, in response to the market for high-efficiency filters
on other types of equipment, there will soon develop high-efficiency
ceramic filters suitable for light-duty equipment. MSHA welcomes
comment on these and other approaches to dealing with light-duty
equipment in underground coal mines, and will continue to study this
issue in light of the record.
(5) Requiring Certain Engines to Meet Defined Particulate Emission
Standards
As discussed in part II of this preamble, the Mine Safety and
Health Advisory Committee on Standards and Regulations for Diesel-
Powered Equipment in Underground Coal Mines recommended the
establishment of a particulate index (PI), and MSHA did so in its
diesel equipment rule. Under that rule, the PI establishes the amount
of air required to dilute the dpm produced by an engine (as determined
during its approval test under subpart E of part 7) to 1000 g/
m\3\. In the preamble of the diesel equipment rule, MSHA explicitly
deferred until this rulemaking the question of whether to require
engines used in mining environments to meet a particular PI. It noted
that mine operators and machine manufacturers would find it useful to
consider the engine PI in selecting and purchasing decisions.
Since the publication of the PI is a relatively new requirement,
the agency does not believe it has enough information at this time to
evaluate the feasibility of a requirement that certain engines must
meet a particular PI to be used in underground coal mines. Presumably,
coupling such a requirement with a requirement for a 95% filter would
provide more protection to miners than requiring only the 95% filter;
but without information about what is technologically available for any
type of engines, the Agency would have difficulty in selecting the PI
to require.
MSHA solicits comments on whether it should limit the PI or the PI
per horsepower of engines used in underground coal mines.
Feasibility of proposed rule for underground coal mining sector.
The Agency has carefully considered both the technological and economic
feasibility of the proposed rule for the underground coal mining sector
as a whole.
The technology exists to implement the proposed rule's requirements
for 95% filtration of permissible and ``heavy-duty'' equipment. As
widely recognized now by the mining community (see, e.g., MSHA's
``Toolbox''), there are disposable paper
[[Page 17565]]
filters available for permissible coal mine equipment equipped with
water scrubbers that meet the proposed rule's requirements for
efficiency. In addition, a dry technology (known as the DST)
of very high efficiency is also available for this type of equipment.
Based on its long experience with diesel-powered outby equipment, the
Agency is also confident that the disposable paper filters can be used
on this equipment too--once the equipment is equipped with water
scrubbers, heat exchangers, or other systems to first cool the exhaust
enough so the paper filters will not burn. The dry technology used on
permissible equipment can also work on the outby equipment. MSHA
understands that filtration systems that meet the efficiency
requirements in the proposed rule, and which are specifically designed
to fit on outby equipment are under development; additional information
in this regard would be welcome.
The total costs for the proposed rule for underground coal mines
are about $10 million per year beyond the $10.3 million per year costs
this sector is already absorbing to implement the requirements of
MSHA's recent diesel equipment rule. The costs per dieselized mine are
expected to be about $58,000 a year (the diesel equipment rule costs
per dieselized mine are about $59,000 a year). The proposed rule
provides adequate time for equipment purchase, installation, and
training. MSHA has calculated that the costs of the proposed rule
amount to less than one-half of one percent of the revenues of the
underground coal mining sector at this time. (The methodology for this
calculation is discussed in part V of the Agency's PREA). After
reviewing the economic profile of that sector, and taking into account
the cost of implementing the related diesel equipment rule, MSHA has
concluded that the proposed rule is economically feasible for this
sector as a whole.
Conclusion: Underground Coal Mines
Based on the best evidence available to it at this time, the Agency
has concluded that the proposed rule for the underground coal sector
meets the statutory requirement that it attain the highest degree of
health and safety protection for the miners in that sector, with
feasibility a consideration.
Appendix to Part V: Diesel Emission Control Estimator
As noted in the text of this part, MSHA has developed a model that
can help it estimate the impact on dpm concentrations of various
control variables. The model also permits the estimation of actual dpm
concentrations based upon equipment specifications. This model, or
simulator, is called the ``Diesel Emission Control Estimator'' (or the
``Estimator'').
The model is capable only of simulating conditions in production or
other confined areas of an underground mine. Air flow distribution
makes modeling of larger areas more complex. The Estimator can be used
in any type of underground mine.
While the calculations involved in this model can be done by hand,
use of a computer spreadsheet system facilitates prompt comparison of
the results of alternative combinations of controls. Changing a
particular entry instantly changes all dependent outputs. Accordingly,
MSHA developed the Estimator as a spreadsheet format. It can be used in
any standard spreadsheet program.
A paper discussing this model has been presented and published as
an SME Preprint (98-146) in March 1998 at the Society for Mining and
Exploration Annual Meeting. It was demonstrated at a workshop at the
Sixth International Mine Ventilation Congress, Pittsburgh, Pa., in June
1997. The Agency is making available to the mining community the
software and instructions necessary to enable it to perform simulations
for specific mining situations. Copies may be obtained by contacting:
Dust Division, MSHA, Pittsburgh Safety and Health Technology Center,
Cochrans Mill Road, P.O. Box 18233, Pittsburgh, Pa. 15236. The Agency
welcomes comments on the proposed rule that include information
obtained by using the Estimator. The Agency also welcomes comments on
the model itself, and suggestions for improvements.
Determining the Current DPM Concentration
The Estimator was designed to provide an indication of what dpm
concentration will remain in a production area once a particular
combination of controls is applied. Its baseline is the current dpm
concentration, which of course reflects actual equipment and work
practices.
If the actual ambient dpm concentration is known, this information
provides the best baseline for determining the outcome from applying
control technologies. Any method that can reliably determine ambient
dpm concentrations under the conditions involved can be utilized. A
description of various methods available to the mining community is
described in part II of the preamble.
If the exact dpm concentration is not known, estimates can be
obtained in several ways. One way is to take a percentage of the
respirable dust concentration in the area. Studies have shown that dpm
can range from 50-90% of the respirable dust concentration, depending
on the specific operation, the size distribution of the dust and the
level of controls in place. Another method is simply to choose a value
of 644 for an underground coal mine, or 830 for an underground metal or
nonmetal mine. These values correspond to the average mean
concentration which MSHA sampling to date has measured in such
underground mines. Or, depending upon mine conditions, some other value
from the range of mean mine concentrations displayed in part III of
this preamble might be an appropriate baseline--for example, an average
similar to that of mine sections like the one for which controls are
required.
Moreover, the Estimator has been designed to automatically compute
another estimate of current ambient dpm concentration, and to provide
outputs using this estimate even when the actual ambient dpm
concentration is available and used in the model. This is done by using
emissions data for the engines involved--specific manufacturer
emissions data where available, or an average using the known range of
emissions for each type of engine being used.
As with other estimates of current ambient dpm concentration, using
engine data to derive this baseline measure does not produce the same
results as actual dpm measurements. The Agency's experience is that the
use of published engine emissions rates provides a good estimate of dpm
exposures when the engines involved are used under heavy duty cycle
conditions; for light duty cycle equipment, the published emission
rates will generally overestimate the ambient particulate exposures.
Also, such an approach assumes that the average ambient concentration
derived is representative of the workplace where miners actually work
or travel.
Columns
An example of a full spreadsheet from the Estimator is displayed as
Figure V-5. The example here involves the application of various
controls in an underground metal and nonmetal mine. As illustrated in
the discussion in this part, the Estimator can be used equally well to
ascertain what happens to dpm concentrations in an underground coal
mine when the high-efficiency filters required by the proposed rule are
used
[[Page 17566]]
under various ventilation and section dpm intake conditions.
Underground coal mine operators who are interested in ascertaining what
impact it might have on dpm concentrations in their mines if the
proposed rule permitted the use of alternative controls, or required
the use of additional controls (e.g. filters on light duty equipment),
can use the Estimator for this purpose as well.
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A full spreadsheet from the Estimator has two columns, labeled A
and B. Column A displays information on computations where the baseline
is the measured ambient dpm concentration, or whose baselines are
estimated as a percentage of respirable dust or by using the mean
concentration for the sector. Column B displays information on
computations in which the baseline itself was derived from engine
emission information entered into the Estimator.
Sections. The Estimator spreadsheet is divided into 6 sections.
Sections 1 through 4 contain information on the baseline situation in
the mine section. Section 5 contains information on proposed new
controls, and Section 6 displays the dpm concentration expected to
remain after the application of those new controls. Table V-4
summarizes the information in each section of the Estimator.
Table V-4.--Information Needed for or Provided by Each Section of the Estimator Model
----------------------------------------------------------------------------------------------------------------
Spreadsheet section Input/output Mine information
----------------------------------------------------------------------------------------------------------------
SECTION 1..................... INPUT.............................. MEASURED DP LEVEL, g/m3.
SECTION 2..................... INPUT.............................. ENGINE EMISSIONS, gm/hp-hr.
ENGINE HORSEPOWER, hp.
OPERATION TIMES, hr.
SHIFT DURATION, hr.
SECTION 3..................... INPUT.............................. SECTION AIRFLOW, cfm.
INTAKE DP LEVEL, g/m3.
SECTION 4..................... OUTPUT............................. CURRENT DP LEVEL, g/m3.
SECTION 5..................... INPUT.............................. DP CONTROLS:
AIRFLOW, cfm.
OXID. CAT. CONVERTER, percent.
ENGINE EMISSIONS, gm/hp-hr.
AFTER-FILTERS, percent.
CABS, percent.
SECTION 6..................... OUTPUT............................. PROJECTED DP LEVEL, g/m3.
----------------------------------------------------------------------------------------------------------------
Section 1. This is the place to enter data on baseline dpm
concentrations if obtained by actual measurement or estimate based on
respirable dust concentration or mean concentration in the mining
sector. Measurements should be entered in terms of whole diesel
particulate matter for consistency with engine information. Information
need not be entered in this section, in which case only engine-emission
derived estimates will be produced by the Estimator (in Column B).
Sections 2 and 3. Section 2 is the place to enter data about the
existing engines and engine use, and section 3 is the place to enter
data about current ventilation practices. This information is used in
two ways. First, the Estimator uses this information to derive an
estimated baseline dpm concentration (for column B). Second, by
comparing this information with that in section 5 on proposed controls
that would change engines, engine use, or ventilation practices, the
Estimator calculates the improvement in dpm that would result.
The first information entered in section 2 is the dpm emission rate
(in gm/hp-hr) for each vehicle. The Estimator in its current form
provides room to enter appropriate identification information for up to
four vehicles. However, when multiple engines of the same type are
used, the spreadsheet can be simplified and the number of entries
conserved by combining the horsepower of these engines. For example,
two 97 hp, 0.5 gm/hp-hr engines can be entered as a single 194 hp, 0.5
gm/hp-hr engine. However, if the estimate is to involve
[[Page 17569]]
the use of different controls for each engine, the data for each engine
must be entered separately. In order to account for the duty cycle, the
engine operating time for each piece of equipment must then be entered
in section 2, along with the length of the shift.
The last item in section 2, the ``average total shift particulate
output'' in grams, is calculated by the Estimator based on the measured
concentration entered in section 1 (for column A, or the engine
emission rates for column B), the intake concentration, engine
horsepower, engine operating time, and airflow. For column A, the
average total shift diesel particulate output is calculated from the
formula:
E(a) = (DPM(m) -I) x (Q(I) / 35200) / [Sum ( Hp(I) x To(I))]
Where:
E(a) = Average engine output, gm/hp-hr
DPM(m) = Measured concentration of diesel particulate, g/
m3
Q(I) = Initial section ventilation, cfm
I = Intake concentration, g/m3
Hp(I) = Individual engine Horsepower, hp
To(I) = Individual engine operating times, hours
For column B, the average total shift diesel particulate output is
calculated from the formula:
E(a) = [Sum (E(I) x Hp(I) x To(I))] / [Sum (Hp(I))] / Ts
Where:
E(a) = Average engine output, gm/hp-hr
E(I) = Individual engine emission rates, gm/hp-hr
Hp(I) = Individual engine Horsepower, hp
To(I) = Individual engine operating times, hours
Ts = Shift length, hours
The ``average total shift particulate'' provides useful information in
determining what types of controls would be most useful. If the average
output is less than 0.3, controls such as cabs and afterfilters would
have a large impact on dpm. If the average output is greater than 0.3,
new engines would have a large impact on dpm.
There are two data elements concerning existing ventilation in the
section that must be entered into section 3 of the Estimator: the full
shift intake dpm concentration, the section air quantity. The former
can be measured, or an estimate can be used. Based upon MSHA
measurements to date, an estimate of between 25 and 100 micrograms of
dpm per cubic meter would account for the dpm contribution coming into
the section from the rest of the mine.
The last item in section 3, the airflow per horsepower, is
calculated by the Estimator from the information entered on these two
items in sections 2 and 3, as an indication of ventilation system
performance. If the value is less than 125 cfm/hp, consideration should
be given to increasing the airflow. If the value is greater than 200
cfm/hp, primary consideration would focus on controls other than
increased airflow.
Section 4. Section 4 only displays information in Column B. Using
the individual engine emissions, horsepower, operating time, section
airflow, intake DPM and shift length, the Estimator calculates a
presumed dpm concentration. The presumed dpm concentration is
calculated by the formula:
DPM(a) = {[[Sum (E(I) x Hp(I) x To(I))] x 35,300 / Q(I)]+I} x [Ts / 8]
Where:
35,300 is a metric conversion factor
DPM(a) = Shift weighted average concentration of diesel particulate,
g/m3.
E(I) = Individual engine emission rates, gm/hp-hr
Hp(I) = Individual engine Horsepower, hp
To(I) = Operating time hours
Ts = Shift length, hours
Q(I) = Initial section ventilation, cfm
I = Intake concentration, g/m3.
Section 5. Information about any combination of controls likely to
be used to reduce dpm emissions in underground mines--changes in
airflow, the addition of oxygen catalytic converters, the use of an
engine that has a lower dpm emission rate, and the addition of either a
cab or aftertreatment filter--is entered into Section 5. Information is
entered here, however, only if it involves a change to the baseline
conditions entered into Sections 2 and 3. Entries are cumulative.
The first possible control would be to increase the system air
quantity. The minimum airflow should be either the summation of the
Particulate Index (PI) for all heavy duty engines in the area of the
mine, or 200 cfm/hp. The spreadsheet displays the ratio between the air
quantity in section 5 and that in section 3, and the airflow per
horsepower.
The second possible control would be to add an oxidation catalytic
converter to one or more engines if not initially present. When such
converters are used, a dpm reduction of up to 20 percent can be
obtained (as noted in MSHA's toolbox, reprinted as an Appendix to the
end of this document. The third possible control would be to change one
or more engines to newer models to reduce emissions. As noted in part
II of this preamble, clean engine technology has emissions as low as
0.1 and 0.2 gm/hp-hr.
Finally, each piece of equipment could be equipped with either a
cab and an aftertreatment filter. But since MSHA considers it unlikely
an operator would use both controls, the Estimator is designed to
assume that no more than one of these two possible controls would be
used on a particular engine. Ceramic aftertreatment filters that can
reduce emissions by 65-80% are currently on the market; MSHA is
soliciting information about the potential for future improvements in
ceramic filtration efficiency. Paper filters can remove up to 95% or
more of dpm, but these can only be used on equipment whose exhaust is
appropriately cooled to avoid igniting the paper (i.e., permissible
coal equipment, or other equipment equipped with a water scrubber or
other cooling device). Air conditioned cabs can reduce the exposure of
the equipment operator by anywhere from 50-80%. (See part II, section
6, for information on filters and cabs). But while the Estimator will
produce an estimate of the full shift dpm concentration that includes
the effects of using such cabs, it should be remembered that such an
estimate is only directly relevant to equipment operators. Thus, cabs
are a viable control for sections where the miners are all equipment
operators, but they will not impact the dpm concentrations to which
other miners are exposed.
Section 6. The Estimator displays in this section an estimated full
shift dpm concentration. If a measured baseline dpm concentration was
entered in section 1, this information will be displayed in column A.
Column B displays an estimate based on the engine emissions data.
Here is how the computations are performed.
The effect of control application is calculated in Section 6,
Column A from the following formula:
DPM(c) = {Sum [(To(I) / Ts) x 1000 x [(E(a) / 60) x Hp(I) x (35300 /
Q(I)) x (Q(I) / Q(f)) x (1-R(o)) x (1-R(f)) x (1-R(e))]} + I
Where:
DPM(c) = Diesel particulate concentration after control application/
g/m3,
E(a) = Average engine emission rate, gm/hp-hr,
Hp(I) = Individual engine Horsepower, hp.
To(I) = Operating time hours,
I = Intake DPM concentration, g/m3,
Q(I) = Initial section ventilation, cfm,
[[Page 17570]]
Q(f) = Final section ventilation, cfm,
R(o) = Efficiency of oxidation catalytic converter, decimal
R(f) = Efficiency of after filters or cab, decimal,
R(e) = Reduction for new engine technology, decimal, and
R(e) = (Ei--Ef) / Ei
Where:
R(e) = Reduction for new engine technology, decimal,
E(i) = Initial engine emission rates, gm/hp-hr,
E(f) = New engine emission rates, gm/hp-hr,
The effect of control application is calculated in Section 6,
Column B from the following formula:
DPM(c) = {Sum[(E(I) x Hp(I) x To(I)) x (35,300 / Q(I)) x (1-R(o)) x (1-
R(f)) x (1-R(e))] x [Q(I) / Q(f)]}+I
Where:
DPM(c) = Diesel particulate concentration after control application/
g/m3,
E(I) = Individual engine emission rates, gm/hp-hr,
Hp(I) = Individual engine Horsepower, hp,
To(I) = Operating time hours,
I = Intake DPM concentration, g/m3,
Q(I) = Initial section ventilation, cfm,
Q(f ) = Final section ventilation, cfm,
R(o) = Efficiency of oxidation catalytic converter, decimal,
R(f) = Efficiency of after filters or cab, decimal,
R(e) = Reduction for new engine technology, decimal, and
R(e) = (Ei--Ef) / Ei
Where:
R(e) = Reduction for new engine technology, decimal,
(i) = Initial engine emission rates, gm/hp-hr,
E(f) = New engine emission rates, gm/hp-hr.
VI. Impact Analyses
This part of the preamble reviews several impact analyses which the
Agency is required to provide in connection with proposed rulemaking.
The full text of these analyses can be found in the Agency's PREA.
(A) Costs and Benefits: Executive Order 12866
In accordance with Executive Order 12866, MSHA has prepared a
Preliminary Regulatory Economic Analysis (PREA) of the estimated costs
and benefits associated with the proposed rule for the underground coal
sector.
The key conclusions of the PREA are summarized, together with cost
tables, in part I of this preamble (see Question and Answer 5). The
complete PREA is part of the record of this rulemaking, and is
available from MSHA.
The Agency considers this rulemaking ``significant'' under section
3(f) of Executive Order 12866, and has so designated the rule in its
semiannual regulatory agenda (RIN 1219-AA74). However, based upon the
PREA, MSHA has determined that the proposed rule does not constitute an
``economically significant'' regulatory action pursuant to section
3(f)(1) of Executive Order 12866.
(B) Regulatory Flexibility Certification
Introduction
Pursuant to the Regulatory Flexibility Act of 1980, MSHA has
analyzed the impact of this rule upon small businesses. Further, MSHA
has made a preliminary determination with respect to whether or not it
can certify that this proposal will not have a significant economic
impact on a substantial number of small entities. Under the Small
Business Regulatory Enforcement Fairness Act (SBREFA) amendments to the
RFA, MSHA must include in the proposal a factual basis for this
certification. If the proposed rule does have a significant economic
impact on a substantial number of small entities, then the Agency must
develop an initial regulatory flexibility analysis.
Based upon MSHA's analysis, the Agency has determined that the
proposed rule will not have a significant economic impact on a
substantial number of small underground coal mine operators, and has so
certified to the Small Business Administration (SBA). MSHA specifically
solicits comments on the cost data and assumptions concerning the
regulatory flexibility certification statement for underground coal
mine operators.
To facilitate public participation in the rulemaking process, MSHA
will mail a copy of the proposed rule and this preamble to every
underground coal mine operator. In addition, the regulatory flexibility
certification, including its factual basis, is reprinted here.
Definition of Small Mine
Under SBREFA, in analyzing the impact of a proposed rule on small
entities, MSHA must use the SBA definition for a small entity or, after
consultation with the SBA Office of Advocacy, establish an alternative
definition for the mining industry by publishing that definition in the
Federal Register for notice and comment. MSHA has not taken such an
action, and hence is required to use the SBA definition.
The SBA defines a small mining entity as an establishment with 500
employees or less (13 CFR 121.201). MSHA's use of the 500 or less
employees includes all employees (miners and office workers). Almost
all mines (including underground coal mines) fall into this category
and hence, can be viewed as sharing the special regulatory concerns
which the RFA was designed to address. That is why MSHA has, for
example, committed to providing to all underground coal mine operators
a copy of a compliance guide explaining provisions of this rule.
The Agency is concerned, however, that looking only at the impacts
of the proposed rule on all the mines in this sector does not provide
the Agency with a very complete picture on which to make decisions.
Traditionally, the Agency has also looked at the impacts of its
proposed rules on what the mining community refers to as ``small
mines''--those with fewer than 20 miners. The way these small mines
perform mining operations is generally recognized as being different
from the way other mines operate, which has led to special attention by
the Agency and the mining community.
This analysis complies with the legal requirements of the RFA for
an analysis of the impacts on ``small entities'' while continuing
MSHA's traditional look at ``small mines''. In concluding that it can
certify that the proposed rule has no significant economic impact on a
substantial number of small entities in the underground coal sector,
the Agency determined that this is the case both for underground coal
mines with 500 or fewer miners and for underground coal mines with 20
or fewer miners.
The Underground Coal Mines: Factual Basis for Certification
The Agency's analysis of impacts on ``small entities'' and ``small
mines'' begins with a ``screening'' analysis. The screening compares
the estimated compliance costs of the proposed rule for small mine
operators in each affected sector to the estimated revenues for that
sector. When estimated compliance costs are less than 1 percent of
estimated revenues, (at both of the size categories considered), the
Agency believes it is generally appropriate to conclude that there is
no significant economic impact on a substantial number of small
entities. When estimated compliance costs approach or exceed 1 percent
of revenues, it tends to indicate that further analysis may be
warranted. The Agency welcomes comment on its approach in this regard.
[[Page 17571]]
Derivation of Costs and Revenues for Screening Analysis
In the case of this proposed rule, because the compliance costs
must be absorbed by underground coal mines only, the agency focused its
attention exclusively on the relationship between costs and revenues
for underground coal mines, rather than looking at the coal sector as a
whole.
The compliance costs for this analysis are presented earlier along
with an explanation of how they were derived. In deriving compliance
costs, there were areas where different assumptions had to be made for
small mines in order to account for the fact that the mining operations
of small mines are not the same as those of large mines. For example,
assumptions used to derive compliance costs concerning: the number of
production shifts per mine, and the number of days the mine operates on
an annual basis were different depending on whether the mine was
classified as either a large or small mining operation. In determining
revenues for underground coal mines, MSHA multiplied underground coal
production data (in tons) for underground coal mines in specific size
categories (reported to MSHA quarterly) by $19 per ton (the average
rounded price per ton). The Agency welcomes comment on alternative data
sources that can help it more accurately estimate revenues for the
final rule.
Results of Screening Analysis
With respect to underground coal mine operators, as can be seen in
Table VI-1, when the definition of a small mine operator is fewer than
20 employees, then estimated average per year costs of the proposed
rule are $8,000 per small mine operator and estimated costs as a
percentage of revenues are 0.04 percent for small mine operators. When
the definition of a small mine operator is fewer than 500 employees,
then estimated average per year costs of the proposed rule are $57,650
per small mine operator and estimated costs as a percentage of revenues
are 0.13 percent for small mine operators.
In both cases, the impact of the proposed costs is less than 1
percent of revenues, well below the level suggesting that the proposed
rule might have a significant impact on a substantial number of small
entities. Accordingly, MSHA has certified that there is no such impact
for small entities that mine underground coal.
Table VI-1.--Underground Coal Mines
----------------------------------------------------------------------------------------------------------------
Estimated Estimated Estimated
costs revenue cost per Costs as %
(thous.) (million) mine of revenue
----------------------------------------------------------------------------------------------------------------
Small <20................................................... $120="" $287="" $8,000="" 0.04="" small=""><500.................................................. 9,624="" 7,359="" 57,650="" 0.13="" ----------------------------------------------------------------------------------------------------------------="" as="" required="" under="" the="" law,="" msha="" is="" complying="" with="" its="" obligation="" to="" consult="" with="" the="" chief="" counsel="" for="" advocacy="" on="" this="" proposed="" rule,="" and="" on="" the="" agency's="" certification="" of="" no="" significant="" economic="" impact="" in="" underground="" coal.="" consistent="" with="" agency="" practice,="" notes="" of="" any="" meetings="" with="" the="" chief="" counsel's="" office="" on="" this="" rule,="" or="" any="" written="" communications,="" will="" be="" placed="" in="" the="" rulemaking="" record.="" the="" agency="" will="" continue="" to="" consult="" with="" the="" chief="" counsel's="" office="" as="" the="" rulemaking="" process="" proceeds.="" (c)="" unfunded="" mandates="" reform="" act="" of="" 1995="" msha="" has="" determined="" that,="" for="" purposes="" of="" section="" 202="" of="" the="" unfunded="" mandates="" reform="" act="" of="" 1995,="" this="" proposed="" rule="" does="" not="" include="" any="" federal="" mandate="" that="" may="" result="" in="" increased="" expenditures="" by="" state,="" local,="" or="" tribal="" governments="" in="" the="" aggregate="" of="" more="" than="" $100="" million,="" or="" increased="" expenditures="" by="" the="" private="" sector="" of="" more="" than="" $100="" million.="" moreover,="" the="" agency="" has="" determined="" that="" for="" purposes="" of="" section="" 203="" of="" that="" act,="" this="" proposed="" rule="" does="" not="" significantly="" or="" uniquely="" affect="" small="" governments.="" the="" unfunded="" mandates="" reform="" act="" was="" enacted="" in="" 1995.="" while="" much="" of="" the="" act="" is="" designed="" to="" assist="" the="" congress="" in="" determining="" whether="" its="" actions="" will="" impose="" costly="" new="" mandates="" on="" state,="" local,="" and="" tribal="" governments,="" the="" act="" also="" includes="" requirements="" to="" assist="" federal="" agencies="" to="" make="" this="" same="" determination="" with="" respect="" to="" regulatory="" actions.="" based="" on="" the="" analysis="" in="" the="" agency's="" preliminary="" regulatory="" economic="" statement,="" the="" compliance="" costs="" of="" this="" proposed="" rule="" for="" the="" underground="" coal="" mining="" industry="" are="" about="" $10="" million="" per="" year.="" accordingly,="" there="" is="" no="" need="" for="" further="" analysis="" under="" section="" 202="" of="" the="" unfunded="" mandates="" reform="" act.="" msha="" has="" concluded="" that="" small="" governmental="" entities="" are="" not="" significantly="" or="" uniquely="" impacted="" by="" the="" proposed="" regulation.="" the="" proposed="" rule="" affects="" only="" underground="" coal="" mines,="" and="" msha="" is="" not="" aware="" of="" any="" state,="" local="" or="" tribal="" government="" ownership="" interest="" in="" underground="" coal="" mines.="" msha="" seeks="" comments="" of="" any="" state,="" local,="" and="" tribal="" government="" which="" believes="" that="" they="" may="" be="" affected="" by="" this="" rulemaking.="" (d)="" paperwork="" reduction="" act="" of="" 1995="" (pra)="" this="" proposed="" rule="" contains="" information="" collections="" which="" are="" subject="" to="" review="" by="" the="" office="" of="" management="" and="" budget="" (omb)="" under="" the="" paperwork="" reduction="" act="" of="" 1995="" (pra95).="" tables="" vi-1="" and="" vi-2="" show="" the="" estimated="" annual="" reporting="" burden="" hours="" associated="" with="" each="" proposed="" information="" collection="" requirement.="" these="" burden="" hour="" estimates="" are="" an="" approximation="" of="" the="" average="" time="" expected="" to="" be="" necessary="" for="" a="" collection="" of="" information,="" and="" are="" based="" on="" the="" information="" currently="" available="" to="" msha.="" included="" in="" the="" estimates="" are="" the="" time="" for="" reviewing="" instructions,="" gathering="" and="" maintaining="" the="" data="" needed,="" and="" completing="" and="" reviewing="" the="" collection="" of="" information.="" msha="" invites="" comments="" on:="" (1)="" whether="" any="" proposed="" collection="" of="" information="" presented="" here="" (and="" further="" detailed="" in="" the="" agency's="" prea)="" is="" necessary="" for="" proper="" performance="" of="" msha's="" functions,="" including="" whether="" the="" information="" will="" have="" practical="" utility;="" (2)="" the="" accuracy="" of="" msha's="" estimate="" of="" the="" burden="" of="" the="" proposed="" collection="" of="" information,="" including="" the="" validity="" of="" the="" methodology="" and="" assumptions="" used;="" (3)="" ways="" to="" enhance="" the="" quality,="" utility,="" and="" clarity="" of="" information="" to="" be="" collected;="" and="" (4)="" ways="" to="" minimize="" the="" burden="" of="" the="" collection="" of="" information="" on="" respondents,="" including="" through="" the="" use="" of="" automated="" collection="" techniques,="" when="" appropriate,="" and="" other="" forms="" of="" information="" technology.="" submission="" the="" agency="" has="" submitted="" a="" copy="" of="" this="" proposed="" rule="" to="" omb="" for="" its="" review="" and="" approval="" of="" these="" information="" [[page="" 17572]]="" collections.="" interested="" persons="" are="" requested="" to="" send="" comments="" regarding="" this="" information="" collection,="" including="" suggestions="" for="" reducing="" this="" burden,="" to="" the="" office="" of="" information="" and="" regulatory="" affairs,="" omb="" new="" executive="" office="" bldg.,="" 725="" 17th="" st.="" nw.,="" rm.="" 10235,="" washington,="" dc="" 20503,="" attn:="" desk="" officer="" for="" msha.="" submit="" written="" comments="" on="" the="" information="" collection="" not="" later="" than="" april="" 7,="" 1998.="" the="" agency's="" complete="" paperwork="" submission="" is="" contained="" in="" the="" prea,="" and="" includes="" the="" estimated="" costs="" and="" assumptions="" for="" each="" proposed="" paperwork="" requirement="" (these="" costs="" are="" also="" included="" in="" the="" agency's="" cost="" and="" benefit="" analyses="" for="" the="" proposed="" rule).="" a="" copy="" of="" the="" prea="" is="" available="" from="" the="" agency.="" these="" paperwork="" requirements="" have="" been="" submitted="" to="" the="" office="" of="" management="" and="" budget="" for="" review="" under="" section="" 3504(h)="" of="" the="" paperwork="" reduction="" act="" of="" 1995.="" respondents="" are="" not="" required="" to="" respond="" to="" any="" collection="" of="" information="" unless="" it="" displays="" a="" current="" valid="" omb="" control="" number.="" description="" of="" respondents="" those="" required="" to="" provide="" the="" information="" are="" mine="" operators="" and="" diesel="" equipment="" manufacturers.="" description="" the="" proposed="" rule="" would="" result="" in="" additional="" burden="" hours="" associated="" with:="" the="" additional="" training="" that="" will="" be="" required="" for="" diesel="" equipment="" operators="" under="" sec.="" 75.1915;="" the="" additional="" changes="" required="" to="" be="" included="" in="" the="" mine="" ventilation="" plans="" under="" secs.="" 75.370="" and="" 75.371;="" the="" new="" training="" requirements="" in="" proposed="" sec.="" 72.510;="" and="" the="" additional="" burden="" hours="" for="" equipment="" manufacturers="" under="" part="" 36="" in="" connection="" with="" the="" approval="" of="" filtration="" systems="" that="" would="" be="" required="" by="" this="" rule.="" tables="" vi-2="" and="" vi-3="" summarize="" the="" burden="" hours="" for="" mine="" operators="" and="" manufacturers="" by="" section.="" table="" vi-2.--underground="" coal="" mines="" burden="" hours="" ------------------------------------------------------------------------="" detail="" large="" small="" total="" ------------------------------------------------------------------------="" 75.370.......................................="" 93="" 9="" 102="" 75.371.......................................="" 158="" 8="" 166="" 75.1915......................................="" 12="" 1="" 13="" 72.510.......................................="" 347="" 5="" 352="" --------------------------="" total....................................="" 610="" 23="" 633="" ------------------------------------------------------------------------="" table="" vi-3.--diesel="" equipment="" manufacturers="" burden="" hours="" 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[[Page 17577]]
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Supplementary References
Below is a list of supplemental references that MSHA reviewed
and considered in the development of the proposed rule. These
documents are not specifically cited in the preamble discussion, but
are applicable to MSHA's findings:
Bice, D.E., et al., ``Effects of Inhaled Diesel Exhaust on Immune
Responses after Lung Immunization,'' Fundamental and Applied
Toxicology, 5:1075-1086, 1985.
Diaz-Sanchez, D., et al., ``Enhanced Nasal Cytokine Production in
Human Beings After In Vivo Challenge with Diesel Exhaust
Particles,'' Journal of Allergy Clinical Immunology, 98:114-123,
1996.
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IgE Production in Vivo and Alter the Pattern of IgE Messenger RNA
Isoforms,'' Journal of Clinical Investigation, 94(4):1417-1425,
1994.
Enya, Takeji, et al., ``3 Nitrobenzanthrone, a Powerful Bacterial
Mutagen and Suspected Human Carcinogen Found in Diesel Exhaust and
Airborne Particulates,'' Environmental Science and Technology,
31:2772-2776, 1997.
Fischer, Torkel, and Bolli Bjarnason, ``Sensitizing and Irritant
Properties of 3 Environmental Classes of Diesel Oil and Their
Indicator Dyes,'' Contact Dermatitis, 34:309-315, 1996.
Frew, A.J., and S.S. Salvi, ``Diesel Exhaust Particles and
Respiratory Allergy,'' Clinical and Experimental Allergy, 27:237-
239, 1997.
Fujimaki, Hidekazu, et al., ``Intranasal Instillation of Diesel
Exhaust Particles and Antigen in Mice Modulated Cytokine Productions
in Cervical Lymph Node Cells,'' International Archives of Allergy
and Immunology, 108:268-273, 1995.
Fujimaki, Hidekazu, et al., ``IL-4 Production in Mediastinal Lymph
Node Cells in Mice Intratracheally Instilled with Diesel Exhaust
Particles and Antigen,'' Toxicology, 92:261-268, 1994.
Fujimaki, Hidekazu, et al., ``Inhalation of Diesel Exhaust Enhances
Antigen-Specific IgE Antibody Production in Mice,'' Toxicology,
116:227-233, 1997.
Ikeda, Masahiko, et al., ``Impairment of Endothelium-Dependent
Relaxation by Diesel Exhaust Particles in Rat Thoracic Aorta,''
Japanese Journal of Pharmacology, 68:183-189, 1995.
Lovik, Martinus, et al., ``Diesel Exhaust Particles and Carbon Black
Have Adjuvant Activity on the Local Lymph Node Response and Systemic
IgE Production to Ovalbumin,'' Toxicology, 121:165-178, 1997.
Muranaka, Masaharu, et al., ``Adjuvant Activity of Diesel-Exhaust
Particles for the Production of IgE Antibody in Mice,'' J Allergy
Clin Immunology, 77:616-623, 1986.
Takafuji, Shigeru, et al., ``Diesel-Exhaust Particulates Inoculated
by the Intranasal Route Have an Adjuvant Activity for IgE Production
in Mice,'' J Allergy Clin Immunol, 79:639-645, 1987.
Takenaka, Hiroshi, et al., ``Enhanced Human IgE Production Results
from Exposure to the Aromatic Hydrocarbons from Diesel Exhaust:
Direct Effects on B-Cell IgE Production,'' J Allergy Clin Immunol,
95-103-115, 1995.
Terada, Nobushisa, et al., ``Diesel Exhaust Particulates Enhance
Eosinophil Adhesion to Nasal Epithelial Cells and Cause
Degranulation,'' International Archives of Allergy and Immunology,
114:167-174, 1997.
Tsien, Albert, et al., ``The Organic Component of Diesel Exhaust
Particles and Phenanthrene, a Major Polyaromatic Hydrocarbon
Constituent, Enhances IgE Production by IgE-Secreting EBV-
Transformed Human B Cells in Vitro,'' Toxicology and Applied
Pharmacology, 142:256-263, 1997.
Yang, Hui-Min, et al., ``Effects of Diesel Exhaust Particles on the
Release of Interleukin-1 and Tumor Necrosis Factor-Alpha from Rat
Alveolar Macrophages,'' Experimental Lung Research, 23:269-284,
1997.
List of Subjects
30 CFR Part 72
Coal, Health standards, Mine safety and health, Underground mines,
Diesel particulate matter.
30 CFR Part 75
Mine safety and health, Underground coal mines, Ventilation.
Dated: March 31, 1998.
J. Davitt McAteer,
Assistant Secretary for Mine Safety and Health.
It is proposed to amend Chapter I of Title 30 of the Code of
Federal Regulations as follows:
PART 72--[AMENDED]
1. The authority citation for Part 72 continues to read as follows:
Authority: 30 U.S.C. 811, 813(h), 957, 961.
2. Part 72 is amended by adding Subpart D to read as follows:
Subpart D--Diesel Particulate Matter--Underground
72.500 Diesel particulate filtration systems.
72.510 Miner health training.
Subpart D--Diesel Particulate Matter--Underground
Sec. 72.500 Diesel particulate filtration systems.
(a) As of [insert the date 18 months after the date of publication
of the final rule], any piece of permissible diesel-powered equipment
operated in an underground coal mine shall be equipped with a system
capable of removing, on average, at least 95% of diesel particulate
matter by mass.
(b) As of [insert the date 30 months after the date of publication
of the final rule], any nonpermissible piece of heavy duty diesel-
powered equipment (as defined by Sec. 75.1908(a) of this title)
operated in an underground coal mine shall be equipped with a system
capable of removing, on average, at least 95% of diesel particulate
matter by mass.
(c) The systems required by this section shall be maintained in
accordance with manufacturer specifications.
(d) In determining, for the purposes of this section, whether a
filtration system is capable of removing, on average, at least 95% of
diesel particulate matter by mass, emission tests shall be performed to
compare the mass of diesel particulate matter emitted from an engine
with and without the filtration system in place. Such tests shall be
performed using the test cycle specified in Table E-3 of Sec. 7.89 of
this title. The filtration system tested shall be representative of the
system intended to be used in mining.
Sec. 72.510 Miner health training.
(a) All miners at a mine covered by this subpart who can reasonably
be expected to be exposed to diesel emissions on that property shall be
trained annually in--
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(1) The health risks associated with exposure to diesel particulate
matter;
(2) The methods used in the mine to control diesel particulate
matter concentrations;
(3) Identification of the personnel responsible for maintaining
those controls; and
(4) Actions miners must take to ensure the controls operate as
intended.
(b)(1) An operator shall retain at the mine site a record that the
training required by this section has been provided for one year after
completion of the training. Such record may be retained elsewhere if
the record is immediately accessible from the mine site by electronic
transmission.
(2) Upon request from an authorized representative of the Secretary
of Labor, the Secretary of Health and Human Services, or from the
authorized representative of miners, mine operators shall promptly
provide access to any such training record. Whenever an operator ceases
to do business, that operator shall transfer such records, or a copy
thereof, to any successor operator who shall receive these records and
maintain them for the required period.
PART 75--[AMENDED]
3. The authority citation for part 75 continues to read as follows:
Authority: 30 U.S.C. 811.
4. Section 75.371 is amended by adding paragraph (qq) to read as
follows:
75.371 Mine ventilation plans; contents.
* * * * *
(qq) A list of diesel-powered units used by the mine operator
together with information about any unit's emission control or
filtration system.
BILLING CODE 4510-43-P
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Appendix to Preamble--Background Discussion MSHA's Toolbox
Note: This appendix will not appear in the Code of Federal
Regulations. It is provided here as a guide.
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[FR Doc. 98-8756 Filed 4-8-98; 8:45 am]
BILLING CODE 4510-43-C
