[Federal Register Volume 64, Number 149 (Wednesday, August 4, 1999)]
[Rules and Regulations]
[Pages 42530-42549]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-19433]
[[Page 42529]]
_______________________________________________________________________
Part III
Environmental Protection Agency
_______________________________________________________________________
40 CFR Part 58
Air Quality Index Reporting; Final Rule
Federal Register / Vol. 64, No. 149 / Wednesday, August 4, 1999 /
Rules and Regulations
[[Page 42530]]
ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 58
[FRL-6409-7]
RIN 2060-AH92
Air Quality Index Reporting
AGENCY: Environmental Protection Agency (EPA).
ACTION: Final rule.
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SUMMARY: Today, EPA adopts revisions to the uniform air quality index
used by States for daily air quality reporting to the general public in
accordance with section 319 of the Clean Air Act (Act). These changes
include the addition of the following elements: a new category
described as ``unhealthy for sensitive groups;'' two new requirements,
first, to report a pollutant-specific sensitive group statement when
the index is above 100, and second, to use specific colors if the index
is reported in a color format; new breakpoints for the ozone
(03) sub-index in terms of 8-hour average 03
concentrations; a new sub-index for fine particulate matter
(PM2.5); and conforming changes to the sub-indices for
coarse particulate matter (PM10), carbon monoxide (CO), and
sulfur dioxide (SO2). In addition, EPA is changing the name
of the index from the Pollutant Standards Index (PSI) to the Air
Quality Index (AQI). This document discusses the development of related
informational materials on pollutant-specific health effects and
sensitive groups and on precautionary actions that can be taken by
individuals to reduce exposures of concern. This document also
discusses the interrelationship between the uniform air quality index
and other programs that provide air quality information and related
health information to the general public, including State and local
real-time air quality data mapping and community action programs.
EFFECTIVE DATE: October 4, 1999.
ADDRESSES: A docket containing information relating to EPA's revisions
of the air quality index (Docket No. A-98-20) is available for public
inspection in the Air and Radiation Docket and Information Center, U.S.
Environmental Protection Agency, South Conference Center, Room M-1500,
401 M St., SW, Washington, DC 20460, telephone (202) 260-7548. The
docket may be inspected between 8 a.m. and 5:30 p.m. on weekdays, and a
reasonable fee may be charged for copying. For the availability of
related information, see SUPPLEMENTARY INFORMATION.
FOR FURTHER INFORMATION CONTACT: Terence Fitz-Simons, EPA (MD-14),
Research Triangle Park, NC 27711, telephone (919) 541-0889, e-mail
fitz-simons.terence@epa.gov. For health effects information, contact
Susan Lyon Stone, EPA (MD-15), Research Triangle Park, NC 27711,
telephone (919) 541-1146, e-mail stone.susan@epa.gov.
SUPPLEMENTARY INFORMATION: In compliance with President Clinton's June
1, 1998 Executive Memorandum on Plain Language in government writing,
this package is written using plain language. Thus, the use of ``we''
or ``us'' in this package refers to EPA. The use of ``you'' refers to
the reader and may include industry, State and local agencies,
environmental groups and other interested individuals.
Availability of Related Information
Certain documents are available from the U.S. Department of
Commerce, National Technical Information Service, 5285 Port Royal Road,
Springfield, VA 22161. Available documents include:
(1) The Review of the National Ambient Air Quality Standards for
Ozone: Assessment of Scientific and Technical Information (``Staff
Paper'') (EPA-452/R-96-007, June 1996, NTIS # PB-96-203435, $67.00
paper copy and $21.50 microfiche). (Add a $3.00 handling charge per
order.)
(2) Review of the National Ambient Air Quality Standards for
Particulate Matter: Policy Assessment of Scientific and Technical
Information (``Staff Paper'') (EPA-452/R-96-013, July 1996, NTIS # PB-
97-115406, $47.00 paper copy and $19.50 microfiche). (Add a $3.00
handling charge per order.)
The guidance documents associated with this rulemaking are
available from EPA's Office of Air Quality Planning and Standards in
Research Triangle Park, NC. Requests for these publications can be
mailed to: Terence Fitz-Simons, EPA (MD-14), Research Triangle Park, NC
27711. Your request may also be phoned in to Terence Fitz-Simons at
919-541-0889, or sent by e-mail to fitz-simons.terence@epa.gov.
(1) Guideline for Public Reporting of Daily Air Quality--Air
Quality Index (AQI) (EPA-454/R-99-010).
(2) Guideline for Developing an Ozone Forecasting Program (EPA-454/
R-99-009).
The following document is available from EPA's Office of Mobile
Sources (OMS) in Ann Arbor, MI. Requests for this publication can be
mailed to: Michael Ball, US EPA--National Vehicle and Fuel Emissions
Laboratory (NVFEL), 2000 Traverwood Dr., Ann Arbor, MI 48103. Your
request may also be phoned in to Michael Ball at 734-214-4897, or sent
by e-mail to ball.michael@epa.gov.
(1) Community Action Programs: Blueprint for Program Design (EPA
420-R-98-003).
Table of Contents
I. Background
A. What Are the Legislative Requirements?
B. What Is the History of the Air Quality Index?
C. What Programs Are Related to the AQI?
1. Ozone and Particulate Matter NAAQS Revisions
2. Real-Time Data Reporting Initiative (Ozone Mapping Project)
3. Community Action Programs
II. Rationale for Final Revisions
A. What Revisions Did We Propose?
1. What Were the Proposed General Changes?
2. What Were the Proposed Changes to the Sub-Indices?
B. What Were the Significant Comments and Our Responses?
1. Comments and Responses on General Changes
2. Comments and Responses on Changes to the Sub-Indices
C. What Are the Final Revisions?
1. What Are the General Changes?
2. What Are the Changes to the Sub-Indices?
D. What Are the Related Informational Materials?
III. Regulatory and Environmental Impact Analyses
A. Executive Order 12866: OMB Review of ``Significant Actions''
B. Regulatory Flexibility Analysis/Small Business Regulatory
Enforcement Fairness Act
C. Unfunded Mandates Reform Act
D. Paperwork Reduction Act
E. Executive Order 13045: Children's Health
F. Executive Order 12848: Environmental Justice
G. Executive Order 12875: Enhancing Intergovernmental
Partnerships
H. Executive Order 13084: Consultation and Coordination with
Indian Tribal Governments
I. National Technology Transfer and Advancement Act
J. Congressional Review Act
IV. References
I. Background
A. What Are the Legislative Requirements?
Section 319 of the Act governs the establishment of a uniform air
quality index for reporting of air quality. This section directs the
Administrator to ``promulgate regulations establishing an air quality
monitoring system throughout the United States which utilizes uniform
air quality monitoring criteria and methodology and measures such air
quality according to a uniform air quality index'' and ``provides for
daily analysis and reporting of air
[[Page 42531]]
quality based upon such uniform air quality index * * *''.
B. What Is the History of the Air Quality Index?
In 1976, we established a nationally uniform AQI, called the
Pollutant Standards Index (PSI), for use by State and local agencies on
a voluntary basis (41 FR 37660). This uniform index was established in
light of a study conducted by EPA and the President's Council on
Environmental Quality (CEQ, 1976). This study found that the 55 urban
areas in the U.S. and Canada reporting an index of air quality used 14
different indices, in conjunction with different cautionary messages,
such that in essence 55 different indices were being used to report air
quality. This diversity of indices sent a confusing message about air
quality to the public. Based in part on this study, we developed an
index to meet the needs of State and local agencies that has the
following advantages: it sends a clear and consistent message to the
public by providing nationally uniform information on air quality; it
is keyed as appropriate to the national ambient air quality standards
(NAAQS) and the significant harm level (SHL) 1 which have a
scientific basis relating air quality and public health; it is simple
and easily understood by the public; it provides a framework for
reflecting changes to the NAAQS; and it can be forecasted to provide
advance information on air quality.
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\1\ Significant harm levels are those ambient concentrations of
air pollutants that present an imminent and substantial endangerment
to public health or welfare, or to the environment, as established
in 40 CFR 51.151.
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The PSI, which is also commonly referred to by some State and local
agencies as the AQI, includes sub-indices for O3, PM, CO,
SO2, and nitrogen oxide (NO2), which relate
ambient pollutant concentrations to index values on a scale from 0
through 500. This represents a very broad range of air quality, from
pristine air to air pollution levels that present imminent and
substantial endangerment to the public. The index has historically been
normalized across pollutants by defining an index value of 100 as the
numerical level of the short-term (i.e., averaging time of 24-hours or
less) primary NAAQS for each pollutant and an index value of 500 as the
SHL.2 Such index values serve to divide the index into
categories, with each category being identified by a simple informative
descriptor. The descriptors are intended to convey to the public
information about how air quality within each category relates to
public health, with increasing public health concerns being conveyed as
the categories range to the upper end of the scale. Additional
information about the general health effects associated with each
category, and precautions that sensitive groups and the general public
can take to avoid exposures of concern, has been made available through
an informational booklet, updated as appropriate, that also presents
and explains the PSI (EPA, 1994).
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\2\ Intermediate index values of 200, 300, and 400 were defined
and are the basis for the Alert, Warning, and Emergency episode
levels included in 40 CFR part 51, appendix L, as part of the
Prevention of Air Pollution Emergency Episodes program. This program
requires specified areas to have contingency plans in place and to
implement these plans during episodes when high levels of air
pollution, approaching the SHL, are in danger of being reached.
Changes to this emergency episode program will be proposed in the
near future.
Below an index value of 100, historically an intermediate value
of 50 was defined either as the level of the annual standard if an
annual standard has been established (for PM10 and
SO2), or as a concentration equal to one-half the value
of the short-term standard used to define an index value of 100 (for
O3 and CO). Coarse or inhalable particulate matter,
PM10, refers to particles with an aerodynamic diameter
less than or equal to a nominal 10 micrometers.
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In 1979, we made changes to the AQI, in part to reflect revisions
to the NAAQS for O3, and to establish requirements for AQI
reporting (44 FR 27598). The requirement for State and local agencies
to report the AQI appears in 40 CFR part 58.50, and the specific
requirements (e.g., what to report, how to report, reporting frequency,
calculations) are in appendix G to 40 CFR part 58.
C. What Programs Are Related to the AQI?
Historically, State and local agencies have used primarily the AQI,
or other AQIs, to provide general information to the public about air
quality and its relationship to public health. In recent years, many
States and local agencies, as well as EPA, have been developing new and
innovative programs and initiatives to provide more information to the
public, in a more timely way. These initiatives, including real-time
data reporting through the Ozone Mapping Project and community action
programs, can serve to provide useful, up-to-date, and timely
information to the public about air pollution and its effects. Such
information will help individuals take actions to avoid or reduce
exposures of concern and can encourage the public to take actions that
will reduce air pollution on days when levels are projected to be in
air quality categories of concern to local communities. Thus, these
programs are significantly broadening the ways in which State and local
agencies can meet the nationally uniform AQI reporting requirements,
and are contributing to State and local efforts to provide community
health protection and to attain or maintain compliance with the NAAQS.
We and State and local agencies recognize that these programs are
interrelated with AQI reporting and with the information on the effects
of air pollution on public health that is generated through the
periodic review, and revision when appropriate, of the NAAQS.
The most recent revisions to the O3 and PM NAAQS, the
Ozone Mapping Project, and community action programs are discussed
briefly below. In light of the interrelationships among these programs,
we have developed today's revisions to the uniform AQI with the goal of
creating a revised AQI that can effectively serve as a nationally
uniform link across these programs. In so doing, we intend to support
and encourage State and local participation in real-time data reporting
initiatives and the development and implementation of community action
programs that serve public education and health protection goals.
1. Ozone and Particulate Matter NAAQS Revisions
On July 18, 1997, we revised the primary NAAQS for O3
and PM based on a thorough review of the scientific evidence linking
exposures to ambient concentrations of these pollutants to adverse
health effects at levels allowed by the previous NAAQS. In particular,
we replaced the 1-hour O3 NAAQS with an 8-hour O3
NAAQS and supplemented the PM NAAQS with 24-hour and annual standards
for fine particulate matter (measured as
PM2.5 3). These decisions were challenged in the
U.S. Court of Appeals for the District of Columbia Circuit, and on May
14, 1999, the Court remanded them to the Agency for further
consideration, principally in light of constitutional concerns
regarding section 109 of the Act as interpreted by EPA. American
Trucking Associations v. EPA, Nos. 97-1440, 97-1441 (D.C. Cir. May 14,
1999). On June 28, 1999, the U.S. Department of Justice on behalf of
EPA filed a petition for rehearing seeking review of the Court's
decision by the entire Court of Appeals. The EPA is continuing to
assess what further legal or administrative proceedings may be
appropriate in response to the Court's decision, as well
[[Page 42532]]
as its relevance to other rulemakings such as this one.
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\3\ PM2.5 refers to particles with an aerodynamic
diameter less than or equal to a nominal 2.5 micrometers.
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With respect to the present rulemaking, we have concluded that it
is appropriate to proceed with final action on the proposed AQI
revisions. As indicated previously, section 319 of the Act requires the
Agency to establish a uniform air quality index, and this requirement
is independent of the statutory provisions governing establishment and
revision of the NAAQS. Moreover, there is no statutory requirement that
the AQI be linked to the NAAQS, although EPA has used NAAQS levels in
the past as reference points for the establishment of specific
breakpoints within sub-indices. Nothing in the Court's opinion alters
the conclusions EPA reached in revising the air quality criteria for PM
and O3 under section 108 of the Act, or in the NAAQS
rulemakings, concerning the occurrence of specific health effects at
varying concentrations of PM and O3 in the air. Regardless
of the outcome of the remand as to the NAAQS themselves, we believe the
scientific record and conclusions underlying them are more than
sufficient as a basis for decisions on the levels at which the public
should be notified about health risks associated with daily air
quality.4
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\4\ Under section 319, the levels that are appropriate for this
purpose do not necessarily depend on the NAAQS levels that may be
appropriate under section 109. Depending on how the Agency chose to
set an ambient standard, for example, it might conclude that the
standard does not need to preclude certain effects falling below the
level of public health concern, and at the same time set the AQI in
such a way as to assure that sensitive individuals who might
experience those effects receive notification and advice on actions
they might take to avoid them. Similarly, AQI values might be set
that are higher than the standard would permit but that would
require more serious health warnings. This is not to say, however,
that the levels of the 1997 NAAQS are irrelevant to decisions on the
AQI breakpoints. To the contrary, the levels of the 1997 NAAQS are
useful surrogates for a series of scientific conclusions reached in
the NAAQS rulemakings, based on the revised air quality criteria,
regarding the nature, extent, and severity of health effects
associated with varying concentrations of PM and O3 in
the air. Accordingly, later sections of this notice make reference
as appropriate to relevant levels of the 1997 NAAQS.
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We do not regard this notification function as involving the
constitutional concerns raised in the Court's opinion. The AQI has no
bearing on pollution control requirements for specific sources; nor
does it serve to implement the NAAQS involved in the litigation.
Rather, it provides information on air quality and health that will
help individual citizens take prudent, self-protective actions to avoid
or reduce exposures of concern and to avoid contributing to air
pollution on days when unhealthy air quality is projected. In this
regard, the AQI is essentially a way of conveying scientific/medical
advice to the public in an easily understood form.
As indicated below, there was broad support in public comments for
modifying and expanding the use of the AQI to take into account the
expanded understanding of air quality-health relationships that
resulted from EPA's review of the latest scientific information on the
effects of PM and O3. Other proposed revisions were designed
to enhance the effectiveness of the AQI generally. The function the AQI
serves of conveying to the public information on daily air quality and
associated health risks is clearly important, and the season of higher
pollution levels is imminent. For all the above reasons, we see no
reason to delay final action on the proposed revisions of the AQI. The
remainder of this section discusses aspects of the O3 and PM
NAAQS rulemakings as they relate to today's action.
As a result of the reviews of the scientific information upon which
the 1997 NAAQS for O3 and PM are based, an expanded
understanding emerged as to the nature of the relationships between
exposure to ambient concentrations of these pollutants and the health
effects likely to be experienced, especially near the level of the
NAAQS. We and the Clean Air Scientific Advisory Committee (CASAC)
5 recognized that for these pollutants there may be no
thresholds below which health effects are not likely to occur, but
rather a continuum of effects potentially extending down to background
levels. As ambient concentrations increase, the proportion of
individuals likely to experience effects and the seriousness of the
health effects increase. Thus, the 1997 standards were not considered
risk free. While the standards were intended to protect public health
with an adequate margin of safety, in accordance with section 109(b) of
the Act, including the health of sensitive groups, exposures to ambient
concentrations just below the numerical level of the standards may
result in exposures of concern for the most sensitive individuals.
Conversely, exposures to ambient concentrations just above the
numerical level of the standards are not likely to result in exposures
of concern for most healthy people. This expanded understanding is
reflected in the forms of the new standards, which allow for multiple
days above the numerical level of the standards.
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\5\ CASAC is a scientific advisory committee established under
the Act to review the scientific criteria and standards and to
advise the Administrator on revision of the NAAQS, as appropriate.
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These understandings were also reflected in CASAC's advice to the
Administrator during the O3 NAAQS review, urging expansion
of the public health advisory system (i.e., a uniform AQI) and
communication to the public of the apparent nonthreshold nature of the
health effects. More specifically, a number of CASAC panel members
recommended ``that an expanded air pollution warning system be
initiated so that sensitive individuals can take appropriate `exposure
avoidance' behavior'' (Wolff, 1995). Consistent with this advice, in
the preamble to the proposed revisions to the O3 NAAQS (61
FR 65733-65734), the Administrator requested comment on the usefulness
of providing specific health effects information when ambient
concentrations are around the numerical level of the standard, the
appropriateness of using the AQI to convey such information to the
public, the possible addition of two new AQI categories (one just above
and one just below the numerical level of the standard) and associated
descriptors and levels, as well as related health effects and
cautionary statements.
Broad support for modifying the AQI was received in public comments
on this aspect of the O3 NAAQS proposal, as discussed in the
final rule establishing revisions to the O3 NAAQS (62 FR
38873-38874). Commenters overwhelmingly endorsed expanding the use of
the AQI for various reasons, although many expressed concern with the
possible category descriptors suggested in the proposal (i.e.,
``moderately good'' and ``moderately unhealthful''). Many commenters
felt that an expanded AQI could help particularly sensitive people take
action to minimize their exposures, and that the AQI could be combined
with community action programs to reduce ambient concentrations when
the numerical level of the standard was forecasted to be exceeded. Some
commenters endorsed increasing the specificity of health and cautionary
statements related to the AQI categories. Commenters from State and
local agencies encouraged us to develop any approaches to revising the
AQI in consultation with them, specifically in the areas of sharing
real-time monitoring data, risk communication with the public, and
coordination of a national program.
2. Real-time Data Reporting Initiative (Ozone Mapping Project)
The Ozone Mapping Project is part of EPA's Environmental Monitoring
for
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Public Access and Community Tracking (EMPACT) initiative--a new
approach to providing timely environmental information to communities.
It is a cooperative effort of the EPA, State and local air pollution
control agencies, and regional organizations including the Mid-Atlantic
Regional Air Management Association (MARAMA), the Northeast States for
Coordinated Air Use Management (NESCAUM), the northeast Ozone Transport
Commission (OTC), the Lake Michigan Air Directors Consortium (LADCO),
SouthEast States Air Resource Managers (SESARM), and Central States Air
Resource Agencies (CenSARA). During the summer of 1998, EPA's Office of
Air Quality Planning and Standards assumed coordination of the project.
The Ozone Map provides simple and timely information about ground-
level O3. During the 1998 O3 season it was
available on EPA's AIRNOW web site (http://www.epa.gov/airnow) and on
some local television and news reports. It is an animated contour map
that shows concentrations of O3, in categories ranging from
good to moderate to varying degrees of unhealthy, based on AQI values,
as they develop across the eastern United States. In 1998, the map was
created from real-time, hourly O3 data provided by a network
of more than 400 air monitoring stations from South Carolina to
Wisconsin and Maine. When accessed on a computer, cautionary statements
for each category could be displayed by running a cursor over the
legend. Also available on the AIRNOW web site were still maps of
maximum values and forecasted values, and archived animated maps. In
1999, the ozone mapping coverage is being expanded to include 31 States
and over 1500 monitors across the eastern and central U.S., and
California. In addition, TV weather service providers are planning to
carry the Ozone Map and forecasts as part of their traditional weather
packages for local TV stations.
Along with the Ozone Map, the AIRNOW web site contains information
about O3 health effects in the ``Health Facts'' section, and
emission reduction activities in the ``What You Can Do'' section. It
also provides links to real-time data, and community action program web
sites, that are maintained by State and local agencies around the
country. The goals of the web site are to: (1) Provide real-time air
pollution data in an understandable, visual format, (2) provide
information about the public health and environmental effects of air
pollution, and (3) provide the public with information about ways in
which they can protect their health and actions they can take to reduce
pollution.
3. Community Action Programs
The implementation of community action programs (also referred to
as voluntary action programs or episodic emission control programs) is
becoming increasingly popular across the country as an innovative
approach used to reduce emissions of O3 precursors, CO, and
PM. Motivation for implementation of this type of program often stems
from local government and business concerns about the NAAQS attainment
status of the area and the restrictions, additional controls, and costs
associated with being classified as a nonattainment area. Many areas
are also motivated by public health concerns and believe that
increasing the amount of air quality information available to sensitive
populations raises awareness and results in significant health
benefits. Specific goals which are usually associated with community
action programs include: (1) Educate the public and enhance protection
of public health; (2) attain or maintain NAAQS attainment status and
the associated economic benefits; (3) meet specific emission reduction
targets; and (4) manage/reduce traffic congestion.
Community action programs are usually voluntary and generally
provide multiple steps that the public, business, and industry can take
to reduce emissions when higher levels of air pollution are forecast to
occur, including in particular transportation-related measures such as
trip reduction, postponement of certain activities such as vehicle
refueling, and maintenance of cars. The programs emphasize educating
the public about the impact of individual activities on local air
quality and the basics of air pollution. The educational component of
these programs also helps to create a strong link between environmental
goals and associated public health benefits.
Most of these programs are based on the categories of the AQI and
make use of the AQI descriptors and related health effects and
cautionary statements on action days. By linking action days to the
AQI, local control programs hope to alter individual behavior to reduce
emissions and to reduce exposures to the population. In addition to
reduced pollutant exposure of the general population due to improved
air quality, there are other health benefits directly associated with
community action programs that can be enhanced by linkage to the AQI.
Different population groups are more sensitive to the harmful effects
of the different air pollutants included in the AQI, and the revisions
to the AQI being adopted today, together with related informational
materials, will significantly improve the effectiveness of
communications with these groups. Public education, or programs
directly targeting these groups, may provide the most significant
benefits of a community action program. Forecasting days with elevated
pollution levels, and then communicating effectively about air quality
and associated health effects, may help these groups selectively limit
their outdoor activities and, therefore, limit their potential for
exposures of concern.
We are committed to providing States and local agencies with
support in their efforts to meet air quality standards, to inform the
public about air quality, and to educate the public about the impacts
of air pollution. The revisions to the AQI being adopted today have as
a goal the creation of a revised AQI that can effectively serve as a
nationally uniform link across the range of programs (e.g., real-time
data reporting initiatives, community action programs) that have these
functions.
In support of community action programs, we have developed
informational materials related to the AQI, including the health
effects and cautionary statements associated with each category and
more detailed health effects information (see section II.D.), available
on the AIRNOW web site, that State and local agencies may use to
enhance their community action programs. Focusing on transportation
measures that are often a major component of community action programs,
EPA's OMS has developed a report entitled, ``Community Action Programs:
Blueprint for Program Design.'' This document describes the major steps
needed to put together a successful episodic control program and
provides criteria that State and local agencies can use to examine and
evaluate their own programs. The report is available from OMS (see
Availability of Related Information).
II. Rationale for Final Revisions
In developing the revisions to the AQI that are being adopted
today, we sought extensive input from State and local agencies and from
the public. We sponsored a workshop with State and local agencies,
participated in numerous meetings, prepared and made available a staff
draft revision to the AQI sub-index for O3 for use during
the 1998 O3 season, and conducted several focus groups
across the nation to obtain public input on the effectiveness of draft
revisions to the AQI and related O3 maps and informational
materials. A
[[Page 42534]]
detailed history of the process leading to the proposal and the
rationale for the proposed revisions are described more fully in the
December 9, 1998 proposal notice (63 FR 67818-67834). The sub-sections
below contain a description of the revisions we proposed, a discussion
of the significant comments we received and our responses to them, and
a summary of the AQI we are adopting today.
A. What Revisions Did We Propose?
The primary consideration that shaped the proposed revisions was
the importance of providing nationally uniform health information
associated with daily ambient levels of the air pollutants included in
the index, consistent with the requirement of section 319 of the Act
for an index to achieve national uniformity in daily air quality
reporting. More specifically, the proposed changes to the AQI sub-
indices for O3 and PM reflected the 1997 revisions to the
O3 and PM NAAQS. The proposed general changes to the
structure of the AQI were based on the expanded understanding that
emerged during the O3 and PM reviews as to the nature of the
relationships between exposure to ambient concentrations of these
pollutants and the health effects likely to be experienced,
consideration of the implications of changes for the other pollutants,
and broad input from State and local agencies and the public. The
proposed general changes to the AQI, together with related
informational materials, were intended to expand the use of the AQI to
provide more pollutant-specific health information, especially when
ambient concentrations are close to the level of the primary NAAQS.
1. What Were the Proposed General Changes?
a. Categories and related descriptors, index values and colors. The
AQI currently incorporates the pollutants O3, PM, CO,
SO2, and NO2. Index values range from 0 to 500
6, and the index is segmented into five categories named by
descriptor words that were chosen to characterize the relationship
between daily air quality and public health. To reflect better the
current understanding of the health effects associated with exposure to
these air pollutants, we proposed to revise the AQI categories and
descriptors, and to associate specific colors with the categories as
shown below in Table 1.
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\6\ For NO2, the index ranges from 200 to 500, since
there is no short-term NAAQS for this pollutant.
Table 1.--Proposed Category Index Values, Descriptors, and Colors
------------------------------------------------------------------------
Index values Descriptor Color
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0-50.................... Good.................. Green
51-100.................. Moderate.............. Yellow
101-150................. Unhealthy for Orange
sensitive groups.
151-200................. Unhealthy............. Red
201-300................. Very unhealthy........ Purple
301-500................. Hazardous............. Maroon
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These proposed changes reflected the addition of a new category
above an AQI of 100, created by dividing the current ``unhealthful''
category into two categories.
When air quality is in the ``unhealthy for sensitive groups''
range, people that are in the sensitive group, whether the sensitivity
is due to medical conditions, exposure conditions, or inherent
sensitivity, may experience exposures of concern. However, exposures to
ambient concentrations in this range are not likely to result in
exposures of concern for most healthy people. The descriptor
``unhealthy for sensitive groups'' was chosen to convey this message
clearly. Participants in focus groups (SAIC 1998) clearly understood
that ``sensitive groups'' does not refer to the general public,
indicating that this descriptor effectively communicates the intended
health message. This category would include a caution that while
perhaps of interest to all citizens, would be of particular interest to
individuals and families of individuals who are members of sensitive
groups.
As air quality moves into the ``unhealthy'' range, exposures are
associated with an increase in the number of individuals who could
potentially experience effects and includes a greater proportion of
members of the general public. Based on input received in the
development of the proposal, the descriptor ``unhealthy'' appropriately
characterizes air quality in this range.
In addition to an increasing number of exposures of concern, when
air quality moves into the ``unhealthy'' range and above, individuals
who were affected at lower levels, typically members of sensitive
groups, are likely to experience more serious health effects than
members of the general public. To reflect this understanding, it is
appropriate to convey two messages in the cautionary statements for
both the ``unhealthy'' and ``very unhealthy'' categories. One message
is directed to members of sensitive groups, and the other is directed
to the general public. The use of a distinct cautionary message for
members of sensitive groups is entirely consistent with an original
goal that the index be based on the relationships between pollutant
concentrations and adverse health effects within various groups, e.g.,
aggravation of disease in people with respiratory disease and incidence
of respiratory effects in healthy people. Guidance on pollutant-
specific cautionary statements related to the categories of the AQI is
discussed below in section II.D.
Consistent with the overarching goal of national uniformity in the
reporting of air quality, we proposed that the specific colors listed
in Table 1 be associated with each category. While the AQI can be
reported without the use of colors (through text and numbers alone),
when the index is reported using colors, we proposed to require that
only these specified colors be used. Three examples of AQI reports that
use color are the color bars that appear in many newspapers, the color
scales on State and local agency web sites, and the color contours of
the Ozone Map. We participated in many discussions with State and local
agencies and associations regarding which specific colors should be
associated with the AQI categories, particularly above an index value
of 100. These discussions typically were in the context of either the
Ozone Mapping Project or community action programs. It was clear that
the color associated with a category can be part of the health effects
and cautionary message being conveyed. Were various State and local
agencies to use different colors to represent the same category, and
thus the same level of air quality, it could well send a confusing
message about air quality and associated health effects to the public.
As an alternative to requiring the use of specified colors, we
solicited comment on the option of recommending, rather than requiring,
the use of these colors when reporting agencies choose to report the
AQI in color format. In soliciting comment on this alternative, we
sought to allow communities maximum flexibility in AQI reporting, while
still preserving a nationally uniform AQI. We, therefore, requested
that commenters addressing this issue discuss how this more flexible
approach would satisfy the statutory language requiring a nationally
uniform AQI if different colors may be used across the nation to
represent the same range of air quality.
b. Reporting requirements. We proposed to change 40 CFR part 58.50
to require reporting of the AQI in all
[[Page 42535]]
Metropolitan Statistical Areas (MSAs) 7 with a population
over 350,000, instead of all urbanized areas with a population over
200,000. This change was proposed for consistency with the other
monitoring regulations in part 58, which are or will be based on MSAs.
This proposed change would not, however, have a significant impact on
who is required to report, since virtually the same number of cities
would be covered under the proposed reporting requirement as are
covered under the existing requirement.
---------------------------------------------------------------------------
\7\ A complete list of MSAs and their boundaries can be found in
the Statistical Abstract of the United States (1998).
---------------------------------------------------------------------------
Consistent with early input from State and local agencies, we
proposed to change the rounding conventions used to calculate index
values corresponding to pollutant concentrations at and above the
numerical level of the NAAQS to be consistent with the rounding
conventions used in defining the NAAQS for each pollutant. This would
avoid situations where a health advisory could be issued that describes
the air as unhealthy, when in fact the numerical level of the standard
has not been exceeded.
The proposed rule retained the requirements to identify the area
for which the AQI is being reported, the time period covered by the
report, the ``critical'' pollutant for which the reported AQI value was
derived, the AQI value, and the associated category descriptor.
Recognizing that many agencies use a color format to report the AQI,
the proposed rule added the requirement to report the associated
category color if a color format is used. Because different sensitive
groups are at-risk from different pollutants, issuing advisories for
all sensitive groups who may be affected at AQI values greater than 100
clearly improves public health protection. Therefore, the proposed rule
encouraged, but did not require, that AQI reports include: appropriate
health effects and cautionary statements, all AQI values greater than
100, the AQI for sub-divisions of the MSA (if there are important
differences in air quality across sub-divisions of the MSA), possible
causes for high index values, and the actual pollutant concentrations.
These topics were also discussed in our draft ``Guideline for Public
Reporting of Daily Air Quality--Pollutant Standards Index (PSI)'' that
was made available on the AIRLINKS web site.
The proposed rule emphasized the importance of forecasting the AQI
by specifying that forecasted values should be reported, when possible,
but did not require that forecasted values be reported. Given the
importance of the O3 sub-index in a large number of MSAs,
and the use of an 8-hour averaging time for calculating the
O3 sub-index value, forecasting the O3 index
value is now more beneficial than before. For a health advisory system
to be effective, people need to be notified as early as possible to be
able to avoid exposures of concern. Because the O3 sub-index
is based on 8-hour O3 averages, forecasting O3
concentrations clearly would have increased value in providing
cautionary statements to the public. We recognized that many State and
local air agencies are already issuing health advisories based on
forecasted O3 concentrations. Since we have determined that
forecasting would add much to the benefits of AQI reporting, we
indicated that we would be making available guidance on starting a
forecasting program (EPA 1999b) in an area or MSA where forecasting is
not presently done. Included in the document is guidance on using
hourly O3 concentrations as predictors for 8-hour averages.
c. Index name. Many State and local agencies encouraged us to
change the name of the PSI to the Air Quality Index, or AQI, since many
agencies already use the name AQI when reporting the AQI value to the
public. Most participants in the focus groups preferred the name AQI,
commenting that it more clearly identified the index as relating to the
quality of the air rather than to environmental pollution in general.
Based on these considerations, we solicited comment on changing the
index name from Pollutant Standards Index (PSI) to Air Quality Index
(AQI).
2. What Were the Proposed Changes to the Sub-Indices?
To conform to the proposed general changes to the AQI discussed
above, and to reflect the recent revisions to the O3 and PM
NAAQS, we proposed changes to the sub-indices for O3, PM,
CO, and SO2; no conforming changes are necessary for the
NO2 sub-index. The proposed sub-indices are summarized below
in Table 2, in terms of pollutant concentrations that correspond to
breakpoints in the index, and are discussed in the following sections.
Table 2.--Proposed Breakpoints for O3, PM2.5, PM10, CO, and SO2 Sub-indices
--------------------------------------------------------------------------------------------------------------------------------------------------------
O3 PM
-------------------------------------------------------------------------------------
AQI value PM2.5, 24-hr PM10, 24-hr CO, 8-hr SO2, 24-hr
8-hr (ppm) 1-hr (ppm) (g/ (g/ (ppm) (ppm)
m\3\) m\3\)
--------------------------------------------------------------------------------------------------------------------------------------------------------
50................................. 0.07............................... .............. 15 50 4 0.03
100................................ 0.08............................... 0.12 65 150 9 0.14
150................................ 0.10............................... 0.16 * 100 250 12 0.22
200................................ 0.12............................... 0.20 * 150 350 15 0.30
300................................ 0.40 (1-hr)........................ 0.40 * 250 420 30 0.60
400................................ 0.50 (1-hr)........................ 0.50 * 350 500 40 0.80
500................................ 0.60 (1-hr)........................ 0.60 * 500 600 50 1.00
--------------------------------------------------------------------------------------------------------------------------------------------------------
* If a different SHL for PM2.5 is promulgated, these numbers will be revised accordingly.
a. Proposed ozone sub-index. On July 18, 1997, we revised the
O3 primary NAAQS to replace the 1-hour standard with a new
standard with an 8-hour average at a level of 0.08 ppm and a form based
on the 3-year average of the annual fourth-highest daily maximum 8-hour
average O3 concentrations measured at each monitor within an
area (62 FR 38856-38896). These proposed revisions were based on
findings from the most recent review of the NAAQS indicating that the
new primary standard will provide increased protection to the public,
especially children active outdoors and other sensitive groups, against
a wide range of O3-induced health effects, including
decreased lung function; increased respiratory symptoms; hospital
admissions and emergency room visits
[[Page 42536]]
for respiratory causes, among children and adults with pre-existing
respiratory disease such as asthma; inflammation of the lung; and
possible long-term damage to the lungs. In setting this standard, we
recognized that there is no apparent threshold below which health
effects do not occur, that the standard is not risk free, and, thus,
that exposures of concern are possible below the numerical level of the
standard for some extremely sensitive individuals.
We proposed to set an index value of 100 equal to the level of the
8-hour O3 standard. Recognizing the continuum of health
effects, we considered the results of a quantitative risk assessment
(Whitfield et al., 1996) in selecting 8-hour O3
concentrations to correspond to index values of 50, 150 and 200. Since
no human health effects information was available for 8-hour average
O3 concentrations at significantly higher levels, we
proposed to retain the breakpoints at the upper end of the AQI scale
(between the ``very unhealthy'' and ``hazardous'' categories and the
SHL which corresponds to the top of the PSI scale of 500) in terms of
the existing 1-hour average concentrations.
These proposed revisions reflect the new 8-hour O3 NAAQS
and will in almost all areas result in a more precautionary index than
the current 1-hour sub-index. However, we recognized that a very small
number of areas in the U.S. have atypical air quality patterns, with
very high 1-hour daily peak O3 concentrations relative to
the associated 8-hour average concentrations. In such areas, the use of
the current 1-hour sub-index may be more precautionary on a given day
than the proposed 8-hour sub-index. To allow for the reporting of the
more precautionary sub-index value, we proposed to retain the 1-hour
sub-index at and above AQI values of 100 and to allow the reporting of
the higher of the two O3 sub-index values. Thus, both the
new 8-hour and the current 1-hour sub-indices, as shown in Table 2,
were included in the proposed appendix G. Since for the large majority
of areas the 8-hour sub-index will be more precautionary, we did not
propose to require all areas to calculate both sub-index values.
Rather, we proposed to allow areas the flexibility to calculate both
sub-index values and, when both sub-index values are calculated, to
require that the higher value be reported. We specifically solicited
comment on this proposed approach.
b. Proposed PM sub-index. On July 18, 1997, we revised the PM NAAQS
by adding a new set of standards for fine particles, or
PM2.5, set at levels of 15 g/m\3\ (annual) and 65
g/m\3\ (24-hour average) (62 FR 38652-38760). These revisions
were based on findings from the most recent review of the PM NAAQS that
recently published studies have indicated that serious health effects
were more closely associated with the levels of the smaller particle
subset of PM10. These health effects include premature
mortality and increased hospital admissions and emergency room visits,
primarily in the elderly and individuals with cardiopulmonary disease;
increased respiratory symptoms and disease in children and individuals
with cardiopulmonary disease; decreased lung function, particularly in
children and individuals with asthma; and alterations in respiratory
tract defense mechanisms. In addition, PM10 standards were
retained at the same levels of 50 g/m\3\ (annual) and 150
g/m\3\ (24-hour average) to continue to provide protection
against health effects associated with the coarse particle subset of
PM10, including aggravation of asthma and respiratory
infections. To reflect these revisions to the PM NAAQS, we proposed to
add a new sub-index for PM2.5, and to make conforming
changes to the sub-index for PM10, consistent with the
proposed general changes to the AQI. The proposed sub-indices are
summarized in Table 2 and discussed below.
Proposed new PM2.5 sub-index. Consistent with the
historical method of selecting breakpoints of the AQI, we proposed to
set an index value of 100 at the level of the 24-hour PM2.5
NAAQS, 65 g/m\3\, and an index value of 50 at the level of the
annual NAAQS, 15 g/m\3\. Also consistent with the basic
structure of the AQI, the proposed upper bound index value of 500
corresponds to the SHL, established in section 51.16 of the CFR under
the Prevention of Air Pollution Emergency Episodes program. The SHL is
set at a level that represents an imminent and substantial endangerment
to public health. When we propose revisions to the Prevention of Air
Pollution Emergency Episodes program, the proposal will include a SHL
for PM2.5. In the interim, we proposed to establish a
PM2.5 concentration of 500 g/m\3\ to be associated
with a PM2.5 index value of 500.
For intermediate breakpoints in the AQI between values of 100 and
500, PM2.5 concentrations were proposed that generally
reflect a linear relationship between increasing index values and
increasing PM2.5 values. The available scientific evidence
of health effects related to population exposures to PM2.5
concentrations between the 24-hour NAAQS level and the proposed
PM2.5 concentration to be associated with a PM2.5
index value of 500 suggest a continuum of effects in this range, with
increasing PM2.5 concentrations being associated with
increasingly larger numbers of people likely experiencing serious
health effects (62 FR 38675; Staff Paper, p. VII-27). The proposed
generally linear relationship between AQI values and PM2.5
concentrations in this range, rounded to increments of 50 g/
m\3\ to reflect the approximate nature of such a relationship, is
consistent with this evidence.
Proposed conforming changes to the PM10 sub-index.
Consistent with the retention of the levels of the PM10
NAAQS, we proposed to retain the PM10 sub-index generally
and to add a new breakpoint at an index value of 150 to conform to the
proposed additional AQI category. We proposed that this breakpoint be
set at a PM10 24-hour average concentration of 250
g/m\3\, the mid-point between the breakpoints associated with
index values of 100 and 200. We believe that the PM10 sub-
index, with this conforming change, remains appropriate for the public
health protection purposes of the AQI.
c. Proposed conforming changes to the CO and SO2 sub-
indices. Since the current AQI sub-indices reflect the current NAAQS
for CO and SO2, the only change we proposed for these sub-
indices was to add a breakpoint to each sub-index at an index value of
150 to conform to the proposed additional AQI category. We proposed
that these breakpoints be set at concentrations at the mid-points
between the breakpoints associated with index values of 100 and 200,
consistent with the approach described above for conforming changes to
both the 1-hour O3 sub-index and the PM10 sub-
index. These proposed breakpoints are summarized in Table 2 and will be
reviewed in conjunction with the future reviews of the CO and
SO2 NAAQS.
B. What Were the Significant Comments and Our Responses?
This section describes the significant comments we received on
proposed revisions to the index and our general responses to them. More
detailed comment summaries and responses are contained in a Response to
Comments Document that is available in the docket (see Addresses).
1. Comments and Responses on General Changes
a. Categories and related descriptors, index values and colors.
With regard to the proposed changes to the general structure of the
index, we received comments that focused on two major
[[Page 42537]]
issues. The first major issue was whether to add a category above or
below the standard, or both. In addition, related to that issue were
comments about the proposed descriptor for the category we proposed to
add above the level of the standard. The second major issue regarded
the particular colors, listed in Table 1, we proposed to associate with
each category.
With regard to the general structure of the index, most commenters
supported our proposal to add a category above the level of the
standard. However, commenters from environmental groups and several
States suggested adding a category below the level of the standard to
provide additional caution for members of sensitive groups, instead of,
or in addition to one above. These commenters expressed the view that
the proposed sub-indices, that added a category above the standard, did
not sufficiently caution members of sensitive groups about health
effects occurring below the level of the standard. Specifically, their
comments were in reference only to potential health effects occurring
below the 8-hour O3 and 24-hour PM2.5 standards.
Regarding health effects below the PM2.5 standard, one State
commenter took exception with the statement in the proposal that an
additional category below the standard, while perhaps meaningful for
O3, would not be an appropriate distinction for the other
pollutants in the index. This commenter noted that ``such a distinction
would be more imperative for other pollutants, especially for PM where
the level of the 24-hour standard may be less protective of sensitive
groups than the ozone standard.'' (Docket No. A-98-20, IV-D-19).
Agreeing with the importance of cautioning sensitive groups below the
level of the 24-hour PM2.5 standard, another commenter noted
``We believe that adding a category below the level of the standard is
of particular importance with respect to fine particles.'' (Docket No.
A-98-20, IV-D-11). Regarding the O3 sub-index, some of the
States and the environmental groups that endorsed adding a category
below the level of the standard supported that position by noting that
we and CASAC stated that extremely sensitive individuals may be
affected down to background levels of O3. One comment from
an environmental group noted that:
The CASAC recognized that for O3 and fine particle
pollution, ``there are no discernible thresholds below which health
effects are not likely to occur in the most sensitive individuals'
as it was advising EPA to set new health standards. We agree with
CASAC and support the idea of setting ``an expanded air pollution
warning system (to) be initiated so that sensitive individuals can
take appropriate exposure avoidance behavior,'' however EPA has
misrepresented the health threat with the levels it has proposed.
(Docket No. A-98-20, IV-D-17).
A State commenter that supported adding a category below the level
of the standard observed that adding such a category would be
consistent with EPA's conclusion ``that exposures to ambient
concentrations just below the numerical level of the standard may
result in exposures of concern for the most sensitive individuals.''
(Docket No. A-98-20, IV-D-19).
We understand and agree with the issues related to communication of
risk below the levels of the 24-hour PM2.5 and 8-hour
O3 standards. For the PM2.5 sub-index, we have
addressed concerns about health effects below the level of the 24-hour
PM2.5 standard by revising the PM2.5 sub-index so
sensitive groups are cautioned below the 24-hour PM2.5
standard. Based on review of the suggested revisions to the
PM2.5 sub-index that we received in comments, we believe
this approach fully addresses their concerns. The revision is discussed
in section II.B.2 below.
For better communication of health risk below the 8-hour
O3 standard, we have addressed the issues raised by
commenters by revising the O3 sub-index. We have expanded
the ``moderate'' range of the 8-hour O3 sub-index to make it
more precautionary. When air quality is in the ``moderate'' range of
the 8-hour O3 sub-index, we have provided health effects and
cautionary statements, available in our AQI Reporting Guidance document
(EPA, 1999a) (discussed in section II.D), that may be used by State and
local agencies to caution unusually sensitive individuals below the
level of the 8-hour O3 standard. This revision is discussed
in section II.B.2 below.
We do not believe it is necessary or appropriate to change the
general structure of the index by adding a new category below the level
of the standard to caution extremely sensitive individuals. Based on
the concerns of State and local agencies that the addition of two new
categories would unduly complicate the index, we are adding just one
new category to maintain the degree of simplicity strongly supported by
State and local agencies, none of whom advocated the addition of two
new categories. As described in section II.A.1 above, we believe that
adding a category above the level of the standard makes a distinction
that is useful for members of sensitive groups without alarming the
general public. As noted by one State commenter:
We are satisfied and support the proposed category index values,
descriptors and colors. [We] believe that the Air Quality Index * *
* has been a very effective communication tool during the ozone
season. It has been our experience that a category above the
standard provides the proper communication to the affected
populations without alarming or desensitizing others. (Docket No. A-
98-20, IV-G-04).
Further, given the changes we have made to the PM2.5
sub-index, and the expanded ``moderate'' range and the cautionary
statements we have made available in guidance for use below the level
of the 8-hour O3 standard, we do not believe a category
below the level of the standard to caution members of sensitive groups
would be an appropriate distinction for any of the pollutants included
in the index. We believe that the approach we have adopted retains the
simplicity of the index while allowing for more detailed cautionary
information to be made available to the public when appropriate.
With regard to the descriptor ``unhealthy for sensitive groups,''
some commenters expressed the view that this descriptor is misleading
because it encompasses a large segment of the population. In addition,
they argued, the public will not know that for certain pollutants
healthy people, especially healthy children, are members of sensitive
groups. Noting that it is prudent policy to assume that most risk
communication regarding air quality impacts will be limited to the
general descriptors, some of these commenters requested that if we
continue to distinguish sensitive groups from the general population,
that the descriptor be changed from ``unhealthy for sensitive groups''
to ``unhealthy for children and other sensitive groups,'' so that the
public would receive a clear message that children are members of a
sensitive group that may be at increased risk from exposure to ozone.
(Docket No. A-98-20, IV-D-2, IV-D-4 and IV-D-11). We agree with the
view of these commenters, based on the responses of participants in the
focus groups, that the public will not know that healthy people,
including healthy children, may be at risk when air quality is in the
``unhealthy for sensitive groups'' range. The suggested descriptor,
however, is only appropriate for pollutants for which children are a
sensitive group. Since the sensitive groups differ from one pollutant
to another, and children are only part of the sensitive group for
O3, PM2.5 and NO2, this descriptor is
not appropriate for the other pollutants. For
[[Page 42538]]
example, the descriptor ``unhealthy for children and other sensitive
groups'' would not be appropriate for use in the CO sub-index, where
people with heart disease are the group most at-risk. Use of this
descriptor when CO levels are above an index value of 100 could lead to
confusion about the health effects associated with high levels of CO.
Therefore, we do not believe it would be useful or prudent to adopt the
descriptor ``unhealthy for children and other sensitive groups.'' To
increase public awareness that healthy children are members of the
sensitive group for O3, we are adding the requirement that
when the AQI value is above 100, reporting agencies include in their
published report a statement describing the sensitive group for that
particular pollutant. The reporting requirement for pollutant-specific
statements describing sensitive groups is discussed below in section
II.C.1.b on reporting requirements, and listed in appendix G. We
believe that the requirement for agencies to report the pollutant-
specific statements identifying the groups at risk, when air quality is
above an index value of 100, will more effectively communicate the risk
associated with specific air pollutants, and thereby better help
members of the public reduce personal exposure. To the extent possible
with AQI reporting, this requirement will also ensure that the public
is informed that children are part of the sensitive group for
O3. This requirement will not only improve protection for
healthy children, but also healthy adults, the elderly, and people with
heart and lung disease. We believe that another good way to address
this lack of awareness is to educate the public, and the media and
health care professionals that inform the public, about the health
effects message associated with the category ``unhealthy for sensitive
groups.'' To help accomplish the goal of educating the public, we will
be expanding the development of education and outreach materials and
activities as described in section II.D below.
With regard to the colors listed in Table 1, we received comments
concerning both the particular colors associated with the different
categories and whether specific colors should be required or
recommended. The majority of commenters, including most State and local
agencies commenting, supported our proposed color scheme. Many of those
(commenters that did support it), had used the same or a similar color
scheme associated with either community action programs or ozone maps.
Commenters that had used the same or a similar color scheme noted that
it effectively and appropriately portrayed the full range of local air
quality values. On the other hand, some environmental groups and
several States commented that the color red should be used for the
category just above standard, instead of the color orange that we
proposed. Primarily, these commenters expressed the view that the color
orange would not send a sufficiently strong message that the standard
has been exceeded. In the proposal we indicated that because the color
red sends a strong cautionary message, it is most appropriately used
when effects are likely to occur in the general population, and when
more serious effects are likely in members of sensitive groups. Many of
these commenters noted that since up to 30 percent of the population
could be considered to be in the sensitive group for O3,
when the standard is exceeded the general public should be alerted.
These commenters expressed the view that it is appropriate to use the
color red just above the level of the standard both to alert the public
of potential health risks and to encourage emission reduction actions.
An environmental group commented:
While individuals that are sensitive to poor air quality may
look at the daily listing in the newspaper or call a message
recorded by the state or local air agency, we know from experience
that air quality does not receive broad public attention until it is
predicted or reaches the level of ``code red.'' At that point, the
television and radio media announces that people should restrict
outdoor activity and take steps to not add more pollution to the air
by carpooling, using less electricity, or using mass transit.
(Docket No. A-98-20, IV-D-17).
Another commenter from a State agency noted:
Considering that the definition of sensitive individuals for
ozone includes healthy active children and outdoor workers, a clear
unambiguous message needs to be sent to the public so that they can
respond accordingly. For parents of active children, a message which
states that air quality is unhealthy, and displays it using the
color red, sends a clear message--even though it may carry with it
the risk that individuals not in the sensitive population might also
take exposure avoidance measures. Issuing a message that air quality
is unhealthy for sensitive individuals and displays it with a code
orange runs the risk of having sensitive individuals, or those
guiding sensitive individuals (i.e., doctors and parents) not
prescribe any avoidance action because of the ambiguity of the
message. (Docket No. A-98-20, IV-G-19).
Additionally, these commenters suggested that the color orange be
used for the category they wanted us to add below the level of the
standard, as described above.
In considering these comments, we recognize that the NAAQS are set
to protect public health with an adequate margin of safety, including
the health of sensitive groups. When the standards are met, public
health is protected. Exposures to ambient concentrations just above the
numerical level of the standards are not likely to result in exposures
of concern for most healthy people. This is especially true for the 8-
hour O3 standard, which has a concentration-based form
designed to offer more protection from higher concentrations than from
multiple smaller exceedances of the standard. The form of the 8-hour
O3 standard allows for multiple days above the level of the
standard, provided the 3-year average of the fourth-highest maximum
concentrations does not exceed the level of the standard. This means
that public health is protected, even when there are multiple days each
year when ambient O3 concentrations are above the level of
the standard, as long as the standard is met. Therefore, it is
inappropriate on any given day to express a high level of concern when
air quality just exceeds the level of the standard. Besides sending an
inaccurate health effects message by using the color red with the
category ``unhealthy for sensitive groups,'' another concern is the
potential loss of credibility that could result from repeatedly sending
a signal disproportionate to the expected incidence of noticeable
symptoms. If this were to happen, the AQI could lose the power to
influence people's behavior to protect their health. One commenter from
a State agency expressed this concern:
One of our key concerns * * * is that the general public will
become ambivalent if we forecasted 20, 30, or more Code Red days
over the course of an ozone season. Under this scenario, people may
not take adequate precautions to protect themselves when an actual
unhealthy level is reached. (Docket No. A-98-20, IV-G-05).
A commenter from another State agency expressed a similar view:
It is important to make sure that this general message is not
jeopardized by treating the new 85 ppb, 8-hour standard as the
bright line between healthy and unhealthy. The Code Red message will
not be considered credible if it is issued between 40 to 60 times a
summer in our area. Last year there were 54 days * * * where the 8-
hour standard was exceeded. (Docket No. A-98-20, IV-G-13).
From the comments we have received and from our focus group
research, we believe that the color red sends too strong a message for
use in the
[[Page 42539]]
``unhealthy for sensitive groups category.'' Additionally, based on the
comments of State and local agencies that have used the same or a
similar color scheme, we believe that the color orange sends an
appropriate health message and yet a strong message that the standard
has been exceeded. One State commenter noted that their environmental
agency:
has been using a green/yellow/orange/red communication system since
1993. The media has used the red, orange and yellow air quality
codes to convey a ``the air is not clean'' message. In general, the
media has used Code Red to convey a message that air pollution is or
will be at a near emergency level. Code Orange has connoted ``very
dirty.'' Code Yellow has, in general, been used to characterize air
pollution as not too bad--but still not clean. (Docket No. A-98-20,
IV-G-13).
Another State commenter noted:
We disagree, however, with * * * [the] assertion that the ``Code
Orange'' message in the PSI does not adequately protect public
health. Our experience * * * has been that the health message can be
effectively delivered for Code Orange levels. We have received much
feedback from the general public about our ozone action day program,
and the resounding message has been: Thank you for this program, I
can now plan my day to avoid exposure to high levels of ozone.
(Docket No. A-98-20, IV-G-05).
In addition, ozone mapping projects have successfully represented
air quality using the full AQI color scheme. In the Ozone Mapping
Project, described in section I.C.2, the proposed AQI color scheme was
used successfully during the 1998 O3 season. Participating
State and local agencies and regional organizations have selected the
same color scheme for use in the 1999 O3 season. Having used
the proposed color scheme in their local O3 map, one
metropolitan air agency noted that ``EPA's proposed color scheme
communicates clearly in a logical progression which in our experience
is already understood by the public and the media.'' (Docket No. A-98-
20, IV-G-11).
Because we believe the proposed color scheme effectively and
appropriately communicates the health effects message that was the
basis for setting the O3 and PM standards, we have adopted
the color scheme as proposed. However, we strongly agree with the views
expressed by commenters that it is important for the health effects
message associated with the category ``unhealthy for sensitive groups''
to be effectively communicated to the public, health care providers and
the media. It is very important that members of sensitive groups, which
for some pollutants includes healthy children and adults, be alerted to
potential health risks and that the general public be motivated to take
emissions reductions measures when air quality is above the level of
the standard. In response to the concerns expressed by these
commenters, we are planning to significantly step up the development of
education and outreach materials and increase activities to get this
message out, as discussed in section II.D below.
Only two commenters recommended against requiring specific colors.
The first commenter did so on the grounds that requiring specific
colors would be unenforceable, and may lead to frustration and
conflict. While applauding our goal of establishing a consistent
message, and agreeing that it is good to have as much national
consistency as possible, this commenter noted that efforts to legislate
aesthetics are uncomfortable, unwieldy and ultimately unnecessary.
(Docket No. A-98-20, IV-D-11). The second commenter noted that some
States may elect to use Code Red for ozone action programs at levels
other than what is being proposed and the regulation should not
preclude them from doing that. (Docket No. A-98-20, IV-D-19). On the
other hand, there was very strong support in the comments for us to
require that agencies that use color, use specific colors in AQI
reporting. All of the other commenters that addressed this issue,
including a commenter from an environmental organization, supported
requiring specific colors for all State/local agencies using a color
format. The commenter from an environmental group noted:
EPA states that revisions to the PSI have as a goal the creation
of a nationally uniform link across a range of programs. We urge
that this uniformity be achieved through the use of a national
public health warning system that is clear to the public. To this
end, we do support the EPA requiring that when colors are used by a
state in its PSI, that the same color system incorporated in the
PSI, and not variants, be utilized by such state. (Docket No. A-98-
20, IV-D-21).
One of the many State commenters agreeing with us that such a
requirement was necessary for national uniformity, noted that
``Specific colors * * * associated with each category should be
required for national uniformity and ease of understanding. Anything
less would defeat the purpose of a national index for comparing air
quality in different locales.'' (Docket No. A-98-20, IV-D-07). Another
State commenter made the point that ``Consistency of message is
important, especially if the regional nature of many air pollution
problems is to be communicated effectively.'' (Docket No. A-98-20, IV-
D-01).
In response to the first commenter's objections, we do not believe
that requiring specific colors presents any particular enforceability
problems. This requirement is one of many contained in the 40 CFR part
58 Ambient Air Quality Surveillance requirements and would be
enforceable in the same manner and to the same extent as any other
requirement of this section. As such, we believe there is no difference
in enforceability between this and a requirement for the use of
particular descriptors or air quality index values. We expect to work
with EPA Regional Offices to ensure that they monitor State
implementation of the revised AQI and work with the States to encourage
compliance.
With regard to comments that our requirement would preclude States
from using other color schemes and action levels in their voluntary
programs, it is important to note that the AQI addresses the reporting
of measured air quality and does not impose any requirements or
limitations on community action programs based on air quality
forecasts. We recognize that a nationally uniform color scheme for AQI
reporting will, as a practical matter, complicate a State's efforts to
use other color schemes in action programs based on predicted air
quality, but they remain free to do so under our regulations.
Because it is the fundamental goal of the AQI to provide nationally
uniform information about daily air quality and the public health
messages that are appropriately associated with various daily air
quality levels, in a format that is timely and easily understood, we
continue to believe that requiring specified colors when the AQI
categories are reported in color format is both necessary and
appropriate. Neither of the commenters opposing this requirement
addressed how a more flexible approach of recommending specific colors,
thereby allowing the use of different colors to represent the same
range of air quality, would satisfy the statutory language requiring a
nationally uniform air quality index. Therefore, we are adopting the
requirement, as specified in appendix G below, that when State and
local agencies report the AQI in a color format, that the specific
colors listed in Table 1 be associated with each category.
b. Reporting requirements. We received significant comments on
several issues related to the reporting requirements, including the
population threshold and other aspects of the reporting requirements,
the appropriate
[[Page 42540]]
method of monitoring and reporting the PM sub-indices, the effect of
AQI changes relative to the SHL program, and the effective date of the
final rule. Since we received no significant comments on our proposal
to change the rounding conventions for calculating the index to make
them consistent with the rounding conventions used in defining the
NAAQS, we are adopting that revision as proposed. With regard to the
population threshold, one commenter expressed the view that the change
from requiring AQI reporting in urbanized areas with a population
greater than 200,000, to requiring reporting in MSAs with populations
greater than 350,000, would raise the threshold for the requirement and
appear to mean that large segments of the U.S. population would not
have access to AQI reporting. (Docket No. A-98-20, IV-D-03). We have
adopted the requirement for AQI reporting in MSAs with populations
greater than 350,000 to be consistent with the State/Local Air
Monitoring Stations (SLAMs) monitoring regulations in 40 CFR part 58,
since AQI reporting is based on information from SLAMS monitors that
are located and reported within the context of MSAs. The use of MSAs
also provides for more stable reporting areas since MSAs are usually
defined by county boundaries that typically do not change, whereas the
boundaries for urbanized areas are very irregular, may include parts of
counties, and may change with each census. In selecting the MSA
population threshold of 350,000, we tried to make the new reporting
requirement equivalent to the old one. Under the new requirement,
virtually the same number of cities will be required to report the AQI
as were previously. Because urbanized areas and MSAs are not
equivalent, we realize that some areas will be required to report the
AQI that were not required to do so before this rulemaking, and vice
versa. The regulation does not preclude any area from reporting the
AQI, and we encourage State and local air agencies to report the AQI
whenever possible so that people will be informed about local air
quality.
Another commenter noted that some MSAs fall within the boundaries
of more than one State, and requested that we identify which of the two
or more reporting agencies would be responsible for reporting the AQI
for the MSA. (Docket No. A-98-20, IV-G-15). We expect that decisions
about AQI reporting in multi-State MSAs will be made by participating
agencies in the same manner as decisions about activities to implement
the standards through the State Implementation Plans (SIPs). Guidance
for air quality planning and implementation in MSAs that fall within
the boundaries of more than one State generally calls for the
participating State and local agencies to identify, in the SIPs for
those States, who will be responsible for the preparation and
submission of the required elements, including AQI reports. Where a
local or regional planning organization has been designated to carry
out such requirements, such an organization is the appropriate one to
report the AQI. In any case, we encourage AQI reporting on the sub-MSA
level, especially where the AQI differs within the MSA.
Another commenter urged us to expand the requirement for AQI
reporting to areas with populations less than 350,000, if these areas
are likely not to be in attainment for the 8-hour O3
standard. To support this position, the commenter noted that
O3 can be transported long distances downwind from where it
is generated, resulting in serious air quality problems in downwind
rural and smaller urban areas. (Docket No. A-98-20, IV-G-27). We agree
with this commenter that downwind areas may be significantly affected
by transport of O3 and precursors. In section 5 of appendix
G, we encourage States to evaluate air quality in affected areas
downwind of MSAs to identify the potential for significant transport-
related air quality impacts and to expand their AQI reporting to
address these situations. We have also changed the language in this
section such that the affected area need not be contiguous to the
reporting MSA.
On a related topic, one commenter noted an example in which a MSA
with a population greater than 350,000, has not registered AQI values
in excess of 50 (such that AQI reporting would be discretionary),
although values above 100 are registered infrequently at a national
monument within the larger air basin. (Docket No. A-98-20, IV-G-17).
This commenter requested that we revise the reporting requirements to
add an air quality consideration to the population threshold as a
second component of AQI reporting. To address one part of this comment,
we encourage State and local air agencies to report the AQI and issue
forecasts for national parks or monuments whenever possible, since
these are places people go to for activities that often involve
prolonged or vigorous exertion, thereby increasing the risk from air
pollution. We have worked with the National Park Service to develop
appropriate guidance for visitors and staff to use when index values
are expected to be above 100 for O3. To address the other
part of this comment, section 8 of appendix G describes exceptions
under which AQI reporting becomes discretionary, either for one
pollutant or the entire index, for areas with good air quality.
Regarding these exceptions, a State commenter suggested that we require
a minimum of 2 years at an AQI value lower than 50 before allowing
agencies to ``opt out'' of reporting the AQI for a particular
pollutant, so that for example, one unusually good O3 season
would not make it possible for an agency to avoid reporting high index
values in subsequent O3 seasons. (Docket No. A-98-20, IV-D-
06). We believe that requiring 2 years of index values lower than 50
before allowing State and local agencies discretion in reporting, while
appropriate in some situations, may be unnecessary in others. We agree
with this commenter that it is appropriate to require reporting of
higher index values, even if air quality has been good throughout the
previous year. Therefore, we have revised section 8 of appendix G, such
that when the criteria for an exemption are no longer met, the
responsible agency is required to report the AQI. Another commenter
expressed the view that we should strengthen the minimum notification
requirements, so that when the AQI value exceeds 100, State and local
agencies are required to report the index to all three media (print,
radio and television) to help ensure that the public is informed that
the standard has been exceeded. (A-98-20, IV-E-3) We agree that it is
important to inform the public when the AQI is above 100, and therefore
have strengthened the reporting provisions in section 6 of appendix G.
In particular, when the AQI exceeds 100, reporting agencies should
expand reporting to all major news media, and at a minimum, should
include notification to the media with the largest market coverages for
the area in question.
Looking at these reporting provisions more broadly, we believe that
it would be very beneficial for reporting agencies to educate the media
about alternative sources for this information, such as web sites and
community action programs. Many State and local agencies have web sites
that provide quick access to timely and accurate air quality and
related information. For State and local agencies participating in the
Ozone Mapping Project, the media could be directed to the AIRNOW web
site as a source of information about O3 air quality and
associated health effects for yesterday, today and tomorrow. In
addition, this web site provides in-depth information about
O3 health effects, sources of emissions and simple
[[Page 42541]]
measures people can take to improve air quality. Community action
programs also provide timely and accurate information, and are often
used to inform the public when air quality is predicted to be above an
index value of 100. Tools and programs such as these can significantly
improve the timeliness of AQI reporting and provide additional useful
information. We believe that, in the near future, the AQI will be
reported by the regional and national media in ways, such as the Ozone
Map, that will not be limited to specific MSAs. This type of approach
will help provide AQI reporting for areas that would otherwise not be
covered, including, in some cases, rural and small urban areas and
national parks.
Regarding reporting the PM sub-indices, one commenter requested
that we clarify whether PM2.5 and PM10 should be
treated as one pollutant (e.g., reported simply as PM) or two different
pollutants (e.g., reported separately). (Docket No. A-98-20, IV-D-19).
We expect State and local air agencies to report PM2.5 and
PM10 separately, since there are two separate sub-indices
with different sensitive groups, and different health effects and
cautionary statements. In response to this comment, we have added
clarifying language to section 9 in appendix G. In addition, many
commenters noted that at the present time there is very little
monitoring for PM (both PM2.5 and PM10) that is
suitable for use in daily AQI reports, and requested guidance for the
use of non-reference methods for the purpose of AQI reporting. Since PM
is often measured at intervals longer than every 24-hours, State and
local agencies are encouraged to use monitoring data from continuous PM
monitors for use in AQI reporting, whenever possible. As noted by
commenters, due to the lack of appropriate monitoring information, at
this time it may not be possible to report the AQI for PM in many
locations. To assist State and local agencies in the use of non-
reference methods, we have added language to section 10 of appendix G
stating that non-reference methods may be used for the purpose of AQI
reporting if it is possible to demonstrate a simple linear relationship
between the non-reference and the reference methods.
Regarding the effect of changes to the AQI on the SHL program, we
received two significant comments. One commenter noted that our
proposed changes to the categories, to standardize them such that the
upper bound falls on an even number, rounded to 50 (e.g., 200), and
lower bound falls on an odd number (e.g., 201), resulted in the AQI
breakpoint of 200 being the upper bound of the ``unhealthy'' category,
rather than the lower bound of the ``very unhealthy'' category, as it
has been historically. Since the AQI breakpoint of 200 is also commonly
used as the ``Alert Level,'' or the first stage of an air pollution
emergency episode in example guidance associated with the SHL program,
this commenter requested that we leave the AQI value of 200 as the
lower breakpoint of the ``very unhealthy'' category, so that emergency
episodes would start when air quality is classified as ``very
unhealthy'' and include appropriate-sounding health effects and
cautionary statements. (Docket No. A-98-20, IV-D-22). We are adopting
the breakpoints as proposed, because we believe that it is important to
be consistent in the treatment of the category boundaries (e.g., 51 to
100, 101 to 150, 151 to 200, etc.). When we propose revisions to the
requirements of the SHL program, we plan to change all references to
the ``Alert Level'' so they will refer to air quality that exceeds the
``Alert Level,'' rather than to air quality that reaches the ``Alert
Level.'' However, State and local agencies should not change their
emergency episode plans at this point simply because we are adopting
this consistent approach to setting AQI breakpoints. Eventually, some
agencies may have to revise emergency episode plans because we have
revised the AQI value of 200 for the 8-hour O3 sub-index.
But we do not expect States to make any revisions to their emergency
episode plans until we promulgate the revised requirements. Finally,
several commenters noted that in the proposal, we did not specify an
effective date for the final revisions. Some of these commenters
suggested that we extend the effective date, with suggestions ranging
from 60 days to more than a year after publication. We are adopting an
effective date of 60 days after publication. We believe that this will
allow adequate time for State and local agencies to revise daily AQI
reports. We recognize that it may take longer to revise related
informational materials, such as printed documents, or related programs
that agencies may want to revise. However, since this rulemaking
applies only to the requirements for daily reporting of air quality, we
believe an effective date of 60 days is adequate.
c. Index name. All commenters that expressed a view on the index
name supported changing the name of the index from the Pollutant
Standards Index (PSI) to the Air Quality Index (AQI), because this name
clearly identifies the index as relating to the quality of the air.
Accordingly, we are changing the name of the index to the Air Quality
Index, or AQI.
2. Comments and Responses on Changes to the Sub-Indices.
All of the comments we received on proposed changes to the sub-
indices focused on the sub-indices that were added for O3
(8-hour) and PM2.5. Since we did not receive specific
comments on the conforming changes we proposed to the CO,
SO2 and PM10 sub-indices, we are adopting these
sub-indices as proposed.
a. Ozone sub-index. We received significant comments on two issues
related to the O3 sub-index. The first group of comments was
in response to our request for comment on retaining the 1-hour
O3 sub-index in addition to the 8-hour O3 sub-
index. The second group of comments focused on the appropriateness of
providing precautionary language below the level of the 8-hour
O3 standard. Regarding the 1-hour sub-index, almost all of
the comments that addressed this issue supported retaining the 1-hour
O3 sub-index. However, one State commenter expressed the
view that the proposal was unclear regarding how areas that have not
attained the 1-hour O3 standard are to use the new 8-hour
O3 sub-index. This commenter also noted that it might be
confusing to report the AQI based on the 8-hour O3 sub-index
in an area where the 1-hour O3 standard had not yet been
attained. (Docket No. A-98-20, IV-D-07). We are requiring that all
State and local agencies that report the AQI for O3
calculate the 8-hour O3 sub-index, even if the reporting
area has not attained the 1-hour standard. In addition to calculating
the 8-hour O3 sub-index, which is required, the reporting
agency may also calculate the 1-hour O3 sub-index, but this
is not required. However, if the reporting agency calculates both
O3 sub-index values, it is required to report the higher
index value of the two. The AQI does not relate to attainment status;
rather, it is a tool for reporting daily air quality and associated
health information. We are retaining the 1-hour O3 sub-index
only because we recognize that there are a very small number of areas
in the U.S. that have atypical air quality patterns, with very high 1-
hour daily peak O3 concentrations relative to 8-hour average
concentrations. In such areas, an index value greater than 100 might be
calculated using the 1-hour sub-index, even when the 8-hour sub-index
might be below 100. For these areas, the use of the 1-hour sub-index is
clearly more precautionary. Because our major interest is that
appropriate precautionary messages be issued, we
[[Page 42542]]
are not retaining a complete 1-hour O3 sub-index with
``good'' and ``moderate'' categories. Likewise, when ambient 8-hour
O3 concentrations are greater than 0.374 ppm, reporting
agencies must calculate the index value using the 1-hour O3
sub-index. This is because no human health effects information is
available for higher 8-hour average O3 concentrations to use
as a basis for selecting 8-hour breakpoints and for developing
appropriate health effects and cautionary statements. We believe that
since State and local agencies are required to report the name of the
pollutant responsible for an index value greater than 100, but not the
associated averaging period, using the 8-hour O3 sub-index
should not be confusing in areas that have not yet attained the 1-hour
O3 standard.
Regarding the issue of alerting sensitive individuals below the
level of the 8-hour O3 standard, some commenters not only
suggested adding a category below the level of the standard, but also
suggested reducing the lower bound of the ``moderate'' category.
(Docket No. A-98-20, IV-D-11, IV-D-17, IV-D-19, IV-G-21). We are not
adding a category below the level of the standard as discussed in
section II.B.1. above. However, to be somewhat more precautionary, we
have expanded the ``moderate'' range by reducing the lower bound of
this category from 0.070 ppm to 0.065 ppm O3, 8-hour
average. We believe that setting the breakpoint between the ``good''
and ``moderate'' categories at this lower level, is appropriate, based
in part on risk estimates done in conjunction with the review of the
O3 NAAQS which suggested that risk to healthy people likely
becomes negligible at this level (Whitfield et al., 1996). This change
is also responsive to comments from State agencies that the proposed
range of the ``moderate'' category was so narrow (spanning only 15 ppb
O3, as compared to 20 ppb range used in the Ozone Map in
1998) that it would be more difficult to forecast accurately and also
would provide too quick a transition from good to unhealthy. (Docket
No. A-98-20, IV-D-10, IV-G-04). Conversely, an industry group and a
State commenter took exception to issuing a ``limited health notice''
for O3 that we proposed as the purpose of the ``moderate''
category. (Docket No. A-98-20, IV-D-12, IV-G-14). The State commenter
objected to the use of the term ``health notice'' below the level of
the standard because it implies that the standard is not protective of
public health. In addition to stating that the ``limited health
notice'' associated with moderate air quality is inconsistent with the
8-hour O3 standard because the standard is intended to
protect public health, even the health of sensitive populations, with
an adequate margin of safety, the industry commenter expressed the view
that we should omit from our materials the health effects and
cautionary statements suggesting that air quality meeting the level of
the standard is a threat to health. We agree with the industry and
State commenters that since the 8-hour O3 standard is
intended to protect public health, including the health of sensitive
groups, with an adequate margin of safety, that the term ``limited
health notice'' may be misleading. However, we continue to believe that
it is appropriate to provide guidance with cautionary language for
extremely sensitive individuals, not populations or groups, below the
level of the standard. This approach is consistent with the advice of
CASAC, and the way we discussed expanding the use of the AQI,
specifically to caution extremely sensitive individuals below the level
of the O3 standard, in the O3 proposal and final
decision notices.
b. PM2.5 sub-index. We received a number of comments
regarding the PM2.5 sub-index, almost all of them focusing
on our proposal to set the index value of 100 at the level of the 24-
hour standard (65 g/m3). Some commenters
recommended setting an index value of 100, or otherwise providing for
cautionary messages, at concentrations lower than 65 g/
m3. One commenter, for example, stated that under the
proposal ``many areas of the country will likely violate the annual
standard of 15 g/m3 without ever (or hardly ever)
reaching a PSI of 100 or a category indicating some degree of
unhealthfulness. This situation will result in an inconsistent and
inappropriate message to the public, especially given the severe health
effects associated with fine particles.'' (Docket No. A-98-20, IV-D-
11).
In light of these comments, we have reexamined the basis for
selecting PM2.5 AQI breakpoints and agree that the sub-index
as proposed would not adequately caution sensitive groups about
potential risks associated with short-term exposures to
PM2.5. This is essentially because the proposed
PM2.5 sub-index was developed using the Agency's historical
approach to selecting index breakpoints, which on examination does not
correspond well with the way the PM2.5 standards were
intended to function. The historical practice has been simply to set
the AQI value of 100 at the level of the short-term standard for a
pollutant (in this case, the 24-hour PM2.5 standard) and the
AQI value of 50 at the level of the annual standard, if there is one,
or at one-half the level of the short-term standard.8 This
method of structuring the index is appropriate for a ``typical'' suite
of air-quality standards, which includes a short-term standard designed
to protect against the health effects associated with short-term
exposures and an annual standard designed to protect against health
effects associated with long-term exposures. In such cases, the short-
term standard in effect defines the level of health protection provided
against short-term risks and thus is a useful benchmark against which
to compare daily air-quality concentrations.
---------------------------------------------------------------------------
\8\ See 63 FR 67819, 67829 (Dec. 9, 1998).
---------------------------------------------------------------------------
In the case of the PM2.5 standards, however, EPA took a
different approach to protecting against health risks associated with
short-term exposures. For reasons discussed in the preamble to the
final standards, the annual and 24-hour PM2.5 standards were
designed to work together for this purpose, and the intended level of
protection against short-term risk is not defined by the 24-hour
standard but by the combination of the two standards working in
concert. Indeed, the annual PM2.5 level of 15 g/
m3 was intended to serve as the principal vehicle for
protection against short-term PM2.5 exposures (by reducing
the entire distribution of PM2.5 concentrations in an area),
with the short-term standard serving essentially to provide
supplemental protection in special situations. 9 Given the
respective roles of the two standards, setting the AQI value of 100 at
the level of the 24-hour standard would not reflect the short-term
health risks associated with lower concentrations, which the annual
standard was designed to address. Accordingly, we agree that it is
appropriate to caution members of sensitive groups below the level of
the 24-hour standard and believe this should be done in a way that
reflects the intended roles of both standards in protecting against
short-term risks.
---------------------------------------------------------------------------
\9\ See 62 FR 38669-71, 38676-77 (July 18, 1997).
---------------------------------------------------------------------------
It would also be inappropriate to compare daily air-quality
concentrations directly with the level of the annual standard (by
setting the AQI value of 100 at that level), because the annual
standard represents an average of many daily concentrations rather than
daily values per se. In the circumstances, we believe the guiding
principle for PM2.5 should be to set the AQI value of 100 in
a way that, at least conceptually, reflects the general level of health
protection against short-term risks
[[Page 42543]]
provided by the annual and 24-hour standards in combination. This
approach, although inexact, is consistent with the historical approach,
in that the underlying logic of that approach, as applied to a typical
suite of standards, is also to set the AQI value of 100 in a way that
reflects the level of protection provided against short-term risks--
that is, by setting it at the level of the short-term standard that
provides the protection. In the case of PM2.5, as indicated
above, the level of the 24-hour standard (65 g/m3)
is too high to reflect the intended level of protection, and the level
of the annual standard (15 g/m3) is too low.
Between the two values, the available health studies indicate a
continuum of risks associated with increasing PM concentrations,
although with significant uncertainties as to the extent of the risk
associated with single peak exposures.10 Consistent with
EPA's general practice of setting AQI breakpoints in symmetrical
fashion where health effects information does not suggest particular
levels,11 we concluded that it is appropriate to set the AQI
value of 100 at the mid-point of the range between the annual and the
24-hour PM2.5 standards (40 g/m3). Given
that decision, we also concluded that it is appropriate to retain the
level of the annual standard for an AQI value of 50, as proposed, and
to set the AQI level of 150 at the level of the 24-hour standard.
---------------------------------------------------------------------------
\10\ See 62 FR 38670, 38677 (July 18, 1997).
\11\ See 63 FR 67824, 67832 (Dec. 9, 1998).
---------------------------------------------------------------------------
To reiterate, the purpose of setting the AQI value of 100 somewhat
below the level of the 24-hour standard was to reflect the dual role of
the annual and 24-hour PM2.5 standards in protecting against
short-term risks, and the aim was to select a breakpoint that would
serve as a rough surrogate for the general level of protection provided
by the two standards in combination. Given the nature of the standards
and the available health information, a more exact approach was not
possible. In this regard, setting the breakpoint at the mid-point of
the range between the annual and 24-hour standards, as opposed to a
level somewhat higher or lower within that range, simply reflected
EPA's general practice of setting symmetrical breakpoints as indicated
above, and does not imply any sort of health-effects threshold. In
particular, it does not reflect a judgment about the extent of the risk
associated with single peak concentrations of PM2.5, as to
which the available health information is inconclusive, or the level at
which EPA might set a 24-hour standard if the annual standard did not
serve as the primary vehicle for protection against such
concentrations. As with other AQI breakpoints, it also has no effect on
the degree of control required of specific sources.
In short, EPA's decision to treat the annual standard as the
principal vehicle for protecting against short-term PM2.5
concentrations, although judged to be the best approach based on the
available health information, does present a different situation than
that involved in previous AQI rulemakings. As discussed in the preamble
to the final standards, the annual standard was intended to reduce all
PM2.5 concentrations, including short-term peaks, in an area
sufficiently to protect public health with an adequate margin of
safety, aside from special situations which the 24-hour standard was
designed to address. As one commenter suggested, however, it would be
possible for an area to violate the annual standard without ever
experiencing (or seldom experiencing) daily peaks that exceeded the
level of the 24-hour standard. Moreover, it might be difficult, if not
impossible, to predict in advance whether the annual standard will be
attained in a given area. For these reasons, as well as the
uncertainties in the available health information, it is inherently
difficult to judge the significance of single peak concentrations when
they occur. In view of the various uncertainties involved, particularly
sensitive individuals may wish to avoid exposure to such
concentrations, especially concentrations that approach the level of
the 24-hour standard. To facilitate such choices, consistent with the
purposes of the AQI and the advice of CASAC, we believe that cautioning
members of sensitive groups in the range of 40 to 65 g/
m3 is appropriate.
We did not receive any comments on the proposal to establish a
concentration of 500 g/m3 to be associated with a
PM2.5 index value of 500, or our method of selecting the
intermediate breakpoints. Therefore, we are adopting 500 g/
m3 as the upper bound of the index.12 For
intermediate breakpoints in the AQI between values of 150 and 500, we
have adopted PM2.5 concentrations that generally reflect a
linear relationship between increasing index values and increasing
PM2.5 values. As discussed in the proposal, the generally
linear relationship between AQI values and PM2.5
concentrations in this range, rounded to increments of 50 g/
m3 to reflect the approximate nature of such a relationship,
is consistent with the health effects evidence that was the basis for
the PM standards.
---------------------------------------------------------------------------
\12\ As discussed in the proposal, should the final SHL for
PM2.5, when promulgated, be different from this
concentration, we will revise this PM2.5 sub-index
accordingly.
---------------------------------------------------------------------------
C. What Are the Final Revisions?
The sub-sections below only summarize changes to the regulatory
text. They do not describe all aspects of 40 CFR part 58.50 or appendix
G.
1. What Are the General Changes?
Based on the proposed structure of the AQI, the comments we
received and our responses to them, as discussed above, we are adopting
the following changes to the general structure and reporting
requirements to the AQI.
a. Categories and related descriptors, index values and colors. We
are adopting the index values, descriptors and associated colors listed
in Table 1 above.
b. Reporting requirements. We are revising 40 CFR 58.50 to require
reporting of the AQI in all MSAs with a population over 350,000. In
appendix G, we are adopting rounding conventions to be used to
calculate index values that are consistent with the rounding
conventions used in defining the NAAQS for each pollutant.
The final rule retains the requirements to identify the area for
which the AQI is being reported, the time period covered by the report,
the ``critical'' pollutant for which the reported AQI value was
derived, the AQI value, and the associated category descriptor. The
final rule adds two requirements: (1) To report the associated category
color if a color format is used and, (2) to report the pollutant-
specific sensitive group for any reported index value greater than 100.
The final rule encourages, but does not require, that AQI reports
include: appropriate health effects and cautionary statements, all AQI
values greater than 100, the AQI for sub-divisions of the MSA (if there
are important differences in air quality across sub-divisions of the
MSA), possible causes for high index values, and the actual pollutant
concentrations.
In the case of rural or small urban areas that are significantly
affected by pollutants transported from a MSA where the AQI is
reported, the final rule recommends that the MSA report the AQI for the
affected areas as well. In addition, when the AQI is greater than 100,
reporting agencies should expand AQI reporting to include all major
news media. The final rule continues to allow agencies to discontinue
reporting for any pollutant, if index values for that pollutant have
been below 50 for an entire season or a year. However, if in subsequent
years pollutant levels rise
[[Page 42544]]
such that index values for that pollutant would be above 50, then the
final rule requires that AQI reporting for that pollutant resume. The
final rule emphasizes the importance of forecasting the AQI by
specifying that forecasted values should be reported, when possible,
but does not require that forecasted values be reported.
c. Index name. We are adopting the name the Air Quality Index or
AQI.
2. What Are the Changes to the Sub-Indices?
Based on the proposed sub-indices, the comments we received and our
responses to them, as discussed above, we are adopting new sub-indices
corresponding to the 8-hour O3 standard and the
PM2.5 standards, as well as conforming changes to the CO, 1-
hour O3, PM10, and SO2 sub-indices.
The adopted breakpoints for the O3 (8-hour and 1-hour)
PM2.5, PM10, CO and SO2 sub-indices
are listed in Table 3.
Table 3.--Breakpoints for O3, PM2.5, PM10, CO, and SO2 Sub-indices
--------------------------------------------------------------------------------------------------------------------------------------------------------
O3 PM
-------------------------------------------------------------------------------------
AQI value PM2.5, 24-hr PM10, 24-hr CO, 8-hr (ppm) SO2, 24-hr
8-hr (ppm) 1-hr (ppm) (g/ (g/ (ppm)
m3) m3)
--------------------------------------------------------------------------------------------------------------------------------------------------------
50................................. 0.06............................... .............. 15 50 4 0.03
100................................ 0.08............................... 0.12 40 150 9 0.14
150................................ 0.10............................... 0.16 65 250 12 0.22
200................................ 0.12............................... 0.20 * 150 350 15 0.30
300................................ 0.40 (1-hr)........................ 0.40 * 250 420 30 0.60
400................................ 0.50 (1-hr)........................ 0.50 * 350 500 40 0.80
500................................ 0.60 (1-hr)........................ 0.60 * 500 600 50 1.00
--------------------------------------------------------------------------------------------------------------------------------------------------------
* If a different SHL for PM2.5 is promulgated, these numbers will be revised accordingly.
These sub-indices are presented in more detail in appendix G to
reflect the changes to the numerical rounding conventions for
calculating index values.
D. What Are the Related Informational Materials?
The primary documents associated with the AQI and this rulemaking,
are our guidance on AQI reporting, ``Guideline for Public Reporting of
Daily Air Quality--Air Quality Index (AQI)'' (EPA 1999a), and our
guidance on AQI forecasting, ``Guideline for Developing an Ozone
Forecasting Program'' (EPA 1999b). These documents are available on
AIRLINKS (http://www.epa.gov/airlinks). The AQI Reporting document
contains information regarding the AQI requirements and
recommendations, example AQI reports, and a list of MSAs required to
report the AQI. It also includes pollutant-specific health effects and
cautionary statements for use with the index, for O3,
PM2.5, PM10, CO, and SO2. The AQI
Forecasting document explains the steps necessary to start an air
pollution forecasting program. Included in the document is guidance on
using hourly O3 concentrations as predictors for 8-hour
averages.
Other related informational materials are also available. The
brochure ``The Pollutant Standards Index'' (EPA 1994) contained general
information about the health effects and air quality, and general
precautions that sensitive groups and the general public can take to
avoid exposures of concern. It is being revised to be consistent with
the new name (i.e., the Air Quality Index brochure), with final
revisions to the AQI, and will identify sensitive groups in the health
effects statements for each of the pollutants, and include the
pollutant-specific health effects and cautionary statements discussed
above. A colorful fact sheet, called the ``Air Quality Guide,''
provides information about the AQI, O3 health effects and
the sources of ground-level O3 is available on the AIRNOW
web site. A revised booklet, ``SMOG--Who Does It Hurt?,'' provides
information for the general public about O3 health effects
and is based on scientific information gained in the recent review of
the O3 standard. ``SMOG--Who Does It Hurt?'' was designed to
provide, in simple language, enough detail for individuals to
understand who is at most risk from O3 exposure and why, the
nature of O3 health effects, and a detailed explanation of
how individuals can reduce the likelihood of exposure using common
everyday activities as examples. We are also developing a shorter,
summary pamphlet about O3 health effects to complement the
``SMOG--Who Does It Hurt?'' booklet. We expect the AQI brochure,
``SMOG--Who Does It Hurt?'' and the shorter summary pamphlet about
O3 health effects to be available in paper format and on the
AIRNOW web site early in the 1999 ozone season. In addition, we will
translate the Air Quality Guide, the AQI brochure, ``SMOG--Who Does It
Hurt?'', and the shorter summary pamphlet into Spanish. These materials
will be available on a Spanish page on the AIRNOW web site.
There are other materials available on the AIRNOW web site that
provide general information about O3. Information about
ground-level as contrasted to stratospheric O3 may be found
in EPA's publication ``Ozone: Good Up High, Bad Nearby.'' The EPA's
video, ``Ozone Double Trouble'' also provides information about ground-
level and stratospheric O3 and the health effects associated
with exposure to ground-level O3, or smog.
In addition to the products discussed above, to address the
concerns of commenters that when air quality is in the ``unhealthy for
sensitive groups'' range the public will not understand that the
standard has been exceeded or who is at risk, we are going to
significantly increase education and outreach related to the AQI. At
this point, we are still in the process of planning specific new
products or activities, but have decided what general direction these
efforts will take. First, we plan to increase our contacts with the
news providers to better inform them about the importance of including
accurate, timely and understandable information in their broadcasts and
reporting, and to enlist them as full partners in the implementation of
the AQI. Second, we plan to form new associations with health care
providers to keep them informed about air pollution health effects,
since these professionals are the most trusted source of health effects
information. Third, we plan to increase direct outreach to the public
through a variety of means, including materials tailored to school-age
children, the Spanish-speaking community, and others. Finally, we plan
to work with public health interest organizations to support
[[Page 42545]]
their efforts to provide more immediate and interactive education and
outreach to all of these groups.
III. Regulatory and Environmental Impact Analyses
A. Executive Order 12866: OMB Review of ``Significant Actions''
Under Executive Order 12866, the Agency must determine whether a
regulatory action is ``significant'' and, therefore, subject to Office
of Management and Budget (OMB) review and the requirements of the
Executive Order. The order defines ``significant regulatory action'' as
one that may:
(1) Have an annual effect on the economy of $100 million or more or
adversely affect in a material way the economy, a sector of the
economy, productivity, competition, jobs, the environment, public
health or safety, or State, local, or tribal governments or
communities;
(2) Create a serious inconsistency or otherwise interfere with an
action taken or planned by another Agency;
(3) Materially alter the budgetary impact of entitlements, grants,
user fees, or loan programs or the rights and obligations or recipients
thereof; or
(4) Raise novel legal or policy issues arising out of legal
mandates, the President's priorities, or the principles set forth in
the Executive Order. The EPA has determined that the revisions to air
quality index reporting in this final rule would not have an annual
effect on the economy of $100 million or more or adversely affect in a
material way the economy, a sector of the economy, productivity,
competition, jobs, the environment, public health or safety, or State,
local, or tribal governments or communities, and therefore did not
prepare a regulatory impact assessment. The OMB has advised us this
final decision should be construed as a ``significant regulatory
action'' within the meaning of Executive Order 12866. Accordingly, this
action was submitted to the OMB for review. Any changes made in
response to OMB suggestions or recommendations will be documented in
the public record and made available for public inspection at EPA's Air
and Radiation Docket Information Center (Docket No. A-98-20).
B. Regulatory Flexibility Analysis/Small Business Regulatory
Enforcement Fairness Act
Under the Regulatory Flexibility Act (RFA), 5 U.S.C. 601 et seq.,
EPA must prepare a regulatory flexibility analysis assessing the impact
of any proposed or final rule on small entities. Under 6 U.S.C. 605(b),
this requirement may be waived if EPA certifies that the rule will not
have a significant economic impact on a substantial number of small
entities. Small entities include small businesses, small not-for-profit
enterprises, and governmental entities with jurisdiction over
populations less than 50,000 people.
Today's final decision to revise the AQI program modifies existing
air quality reporting requirements for MSA's with populations over
350,000 people. Today's final decision will not establish any new
regulatory requirements affecting small entities. On the basis of the
above considerations, EPA certifies that today's final decision will
not have a significant economic impact on a substantial number of small
entities within the meaning of the RFA. Based on the same
considerations, EPA also certifies that the new small-entity provisions
in section 244 of the Small Business Regulatory Enforcement Fairness
Act (SBREFA) do not apply.
C. Unfunded Mandates Reform Act
Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), Public
Law 104-4, establishes requirements for Federal agencies to assess the
effects of their regulatory actions on State, local, and tribal
governments and the private sector. Under section 202 of the UMRA, EPA
generally must prepare a written statement, including a cost-benefit
analysis, for proposed and final rules with ``Federal mandates'' that
may result in expenditures to State, local and tribal governments, in
the aggregate, or to the private sector, of $100 million or more in any
1 year. In addition, before EPA establishes any regulatory requirements
that may significantly or uniquely affect small governments, including
tribal governments, it must have developed under section 203 of the
UMRA a small government agency plan. The plan must provide for
notifying potentially affected small governments, enabling officials of
affected small governments to have meaningful and timely input in the
development of EPA regulatory proposals with significant Federal
intergovernmental mandates, and informing, educating, and advising
small governments on compliance with the regulatory requirements.
The EPA has determined that today's final decision would not
include a Federal mandate that may result in estimated costs of $100
million in any 1 year to either State, local, or tribal governments, in
the aggregate, or to the private sector. Accordingly, EPA has
determined that the provisions of section 202 of the UMRA do not apply
to this rulemaking. With regard to section 203 of the UMRA, EPA has
determined that this rule contains no regulatory requirements that
might significantly or uniquely affect small governments. This rule
requires reporting of the Air Quality Index only in MSAs with
populations greater than 350,000, and therefore does not affect small
governments.
D. Paperwork Reduction Act
Today's final decision does not establish any new information
collection requirements beyond those which are currently required under
the Ambient Air Quality Surveillance Regulations in 40 CFR part 58 (OMB
#2060-0084, EPA ICR No. 0940.15). Therefore, the requirements of the
Paperwork Reduction Act do not apply to today's action.
E. Executive Order 13045: Children's Health
Executive Order 13045, entitled ``Protection of Children from
Environmental Health Risks and Safety Risks'' (62 FR 19885, April 23,
1997), requires Federal agencies to ensure that their policies,
programs, activities, and standards identify and assess environmental
health and safety risks that may disproportionately affect children. To
respond to this order, agencies must explain why the regulation is
preferable to other potentially effective and reasonably feasible
alternatives considered by the agency. In today's final decision, EPA
identified children as one of the sensitive groups which may be at
increased risk of experiencing the effects of concern following
exposure to O3, PM2.5 and NO2.5. The
AQI categories, descriptors, and health effects and cautionary
statements as proposed, for the first time reflect consideration of the
increased health risk to children which may result from such exposures.
Promulgation of the proposed AQI is one potentially effective
alternative that was considered. However, based on comments that the
public may not be aware that healthy, active children are included in
the sensitive groups for O3, PM2.5 and
NO2, we have adopted the additional requirement that
reporting agencies must include a pollutant-specific statement of the
sensitive groups when an index value of 100 is exceeded. For example,
when reporting an AQI value of 110 for ozone, the reporting agency must
include a statement that children and people with asthma are the groups
most at risk. Whenever the AQI value is above 100 for a pollutant, and
children are one of the sensitive groups for that pollutant, the AQI
report must include a statement
[[Page 42546]]
that children are at risk. Therefore, today's action does comply with
the requirements of E.O. 13045.
F. Executive Order 12848: Environmental Justice
Executive Order 12848 requires that each Federal agency make
achieving environmental justice part of its mission by identifying and
addressing, as appropriate, disproportionately high and adverse human
health or environmental effects of its programs, policies, and
activities on minorities and low-income populations in the United
States.
The nature of today's action is to inform the general public,
including minorities and low-income populations, about the nature of
the air pollution in the areas in which they live. Today's action
establishes a uniform tool for States to use to develop programs which
will caution particularly sensitive people to minimize their exposures
and educate the public about general health effects associated with
exposure to different pollution levels. States may also use information
established as part of the AQI to trigger programs designed to reduce
emissions to avoid exceedances of the NAAQS. Therefore, today's action
will help facilitate public participation, outreach, and communication
in areas where environmental justice issues are present.
G. Executive Order 12875: Enhancing Intergovernmental Partnerships
Under Executive Order 12875, EPA may not issue a regulation that is
not required by statute and that creates a mandate upon a State, local
or tribal government, unless the Federal government provides the funds
necessary to pay the direct compliance costs incurred by those
governments, or we will consult with those governments. If EPA complies
by consulting, Executive Order 12875 requires us to provide to OMB a
description of the extent of our prior consultation with
representatives of affected State, local and tribal governments, the
nature of their concerns, copies of any written communications from the
governments, and a statement supporting the need to issue the
regulation. In addition, Executive Order 12875 requires us to develop
an effective process permitting elected officials and other
representatives of State, local and tribal governments ``to provide
meaningful and timely input in the development of regulatory proposals
containing significant unfunded mandates.''
Today's rule implements requirements set forth in section 319 of
the Act and thus is required by statute. This rule does not establish a
wholly new requirement but rather modifies existing reporting
requirements which State and local governments have been implementing
for approximately 20 years. While these changes are significant in many
ways, they are not expected to result in a significant increase in
reporting burdens. Nonetheless, EPA engaged in extensive consultation
with State and local governments in the development of the proposed and
final rules, and this consultation is discussed and documented
elsewhere in today's notice and in the notice of proposed rulemaking.
H. Executive Order 13084: Consultation and Coordination With Indian
Tribal Governments
Under Executive Order 13084, EPA may not issue a regulation that is
not required by statute, that significantly or uniquely affects the
communities of Indian tribal governments, and that imposes substantial
direct compliance costs on those communities, unless the Federal
government provides the funds necessary to pay the direct compliance
costs incurred by the tribal governments, or EPA will consult with
those governments. If EPA complies by consulting, Executive Order 13084
requires us to provide to OMB, in a separately identified section of
the preamble to the rule, a description of the extent of our prior
consultation with representatives of affected tribal governments, a
summary of the nature of their concerns, and a statement supporting the
need to issue the regulation. In addition, Executive Order 13084
requires us to develop an effective process permitting elected
officials and other representatives of Indian tribal governments ``to
provide meaningful and timely input in the development of regulatory
policies on matters that significantly or uniquely affect their
communities.''
Today's rule implements requirements specifically set forth by the
Congress in section 319 of the Act without the exercise of any
discretion by us. Accordingly, the requirements of section 3(b) of
Executive Order 13084 do not apply to this rule.
This rule governs the reporting of air quality by States for MSAs
and, in some cases, areas that are significantly affected by transport
of pollutants from MSAs. In extensive public and intergovermental
coordination efforts during the development of the proposal, EPA
received no information which would suggest that the rule will impose
new requirements on Indian tribal governments nor will it significantly
or uniquely affect communities of Indian tribal governments. To the
extent that air pollution from upwind MSAs significantly affects any
lands within Indian country, this impact is not a result of, or
affected by, today's rule and would be addressed under existing
requirements governing the implementation of air quality standards.
I. National Technology Transfer and Advancement Act
Section 12(d) of the National Technology Transfer and Advancement
Act of 1995 (NTTAA), Public Law 104-113, section 12(d) (15 U.S.C. 272
note) directs EPA to use voluntary consensus standards in its
regulatory activities unless to do so would be inconsistent with
applicable law or otherwise impractical. Voluntary consensus standards
are technical standards (e.g., materials specifications, test methods,
sampling procedures, and business practices) that are developed or
adopted by voluntary consensus standards bodies. The NTTAA directs EPA
to provide Congress, through OMB, explanations when the Agency decides
not to use available and applicable voluntary consensus standards. This
action does not involve technical standards. Therefore, EPA did not
consider the use of any voluntary consensus standards.
J. Congressional Review Act
The Congressional Review Act, 5 U.S.C. 801 et seq., as added by the
Small Business Regulatory Enforcement Fairness Act of 1996, generally
provides that before a rule may take effect, the agency promulgating
the rule must submit a rule report, which includes a copy of the rule,
to each House of the Congress and to the Comptroller General of the
United States. The EPA will submit a report containing this rule and
other required information to the U.S. Senate, the U.S. House of
Representatives, and the Comptroller General of the United States prior
to the publication of the rule in the Federal Register. This rule is
not a ``major rule'' as defined by 5 U.S.C. 804(2).
IV. References
CEQ, (1976) A Recommended Air Pollution Index, report prepared by
the Federal Interagency Task Force on Air Quality Indicators,
Council on Environmental Quality, Environmental Protection Agency,
and Department of Commerce.
EPA, (1994) Measuring Air Quality: The Pollutant Standards Index,
U.S. Environmental Protection Agency, Office of Air Quality Planning
and Standards (MD-10), Research Triangle Park, NC, 27711, EPA 451/K-
94-001.
[[Page 42547]]
EPA, (1999a) Guideline for Public Reporting of Daily Air Quality--
Air Quality Index (AQI), U.S. Environmental Protection Agency,
Office of Air Quality Planning and Standards, Research Triangle
Park, NC, 27711, EPA-454/R-99-010.
EPA, (1999b) Guideline for Developing an Ozone Forecasting Program,
U.S. Environmental Protection Agency, Office of Air Quality Planning
and Standards, Research Triangle Park, NC, 27711, EPA-454/R-99-009.
EPA, (1999c) The Air Quality Index, U.S. Environmental Protection
Agency, Office of Air Quality Planning and Standards, Research
Triangle Park, NC, 27711, in preparation.
Science Applications International Corporation, (1998) Report of
Eight Focus Groups on the Ozone Map, the Pollutant Standards Sub-
index for Ozone, and the Ozone Health Effects Booklet, Science
Applications International Corporation, McLean, VA.
U.S. Department of Commerce, (1998) Statistical Abstract of the
United States, U.S. Bureau of the Census.
Whitfield, R.G.; Biller, W.F.; Jusko, M.J.; Keisler, JM (1996) A
probabilistic assessment of health risks associated with short-term
exposure to tropospheric ozone. Report prepared for U.S. EPA, OAQPS.
Argonne National Laboratory; Argonne, IL.
Wolff, G.T., (1995) Letter from Chairman of the Clean Air Scientific
Advisory Committee to the EPA Administrator, dated November 30,
1995. EPA-SAB-CASAC-LTR-96-002.
List of Subjects in 40 CFR Part 58
Environmental protection, Air pollution control, Intergovernmental
relations, Reporting and recordkeeping requirements.
Dated: July 23, 1999.
Carol M. Browner,
Administrator.
Accordingly, 40 CFR part 58 is amended as follows:
PART 58--AMBIENT AIR QUALITY SURVEILLANCE
1. The authority citation for part 58 continues to read as follows:
Authority: 42 U.S.C. 7410, 7601(a), 7613, and 7619.
2. Section 58.50 is revised to read as follows:
Sec. 58.50 Index reporting.
(a) The State shall report to the general public through prominent
notice an air quality index in accordance with the requirements of
appendix G to this part.
(b) Reporting is required by all Metropolitan Statistical Areas
with a population exceeding 350,000.
(c) The population of a Metropolitan Statistical Area for purposes
of index reporting is the most recent decennial U.S. census population.
3. Appendix G to part 58 is revised to read as follows:
Appendix G to Part 58--Uniform Air Quality Index (AQI) and Daily
Reporting
General Requirements
1. What is the AQI?
2. Why report the AQI?
3. Must I report the AQI?
4. What goes into my AQI report?
5. Is my AQI report for my MSA only?
6. How do I get my AQI report to the public?
7. How often must I report the AQI?
8. May I make exceptions to these reporting requirements?
Calculation
9. How does the AQI relate to air pollution levels?
10. Where do I get the pollutant concentrations to calculate the
AQI?
11. Do I have to forecast the AQI?
12. How do I calculate the AQI?
Background and Reference Materials
13. What additional information should I know?
General Requirements
1. What Is the AQI?
The AQI is a tool that simplifies reporting air quality to the
general public. The AQI incorporates into a single index
concentrations of 5 criteria pollutants: ozone (O3),
particulate matter (PM), carbon monoxide (CO), sulfur dioxide
(SO2), and nitrogen dioxide (NO2). The scale
of the index is divided into general categories that are associated
with health messages.
2. Why Report the AQI?
The AQI offers various advantages:
a. It is simple to create and understand.
b. It conveys the health implications of air quality.
c. It promotes uniform use throughout the country.
3. Must I Report the AQI?
You must report the AQI daily if yours is a metropolitan
statistical area (MSA) with a population over 350,000.
4. What Goes Into My AQI Report?
i. Your AQI report must contain the following:
a. The reporting area(s) (the MSA or subdivision of the MSA).
b. The reporting period (the day for which the AQI is reported).
c. The critical pollutant (the pollutant with the highest index
value).
d. The AQI (the highest index value).
e. The category descriptor and index value associated with the
AQI and, if you choose to report in a color format, the associated
color. Use only the following descriptors and colors for the six AQI
categories:
Table 1.--AQI Categories
------------------------------------------------------------------------
For this AQI Use this descriptor And this color
----------------------------------------------------------------1-------
0 to 50.......................... ``Good''............ Green.
------------------------------------------------------------------------
51 to 100........................ ``Moderate''........ Yellow.
------------------------------------------------------------------------
101 to 150....................... ``Unhealthy for Orange.
Sensitive Groups''.
------------------------------------------------------------------------
151 to 200....................... ``Unhealthy''....... Red.
------------------------------------------------------------------------
201 to 300....................... ``Very Unhealthy''.. Purple.
------------------------------------------------------------------------
301 and above.................... ``Hazardous''....... Maroon.\1\
------------------------------------------------------------------------
1 Specific colors can be found in the most recent reporting guidance
(Guideline for Public Reporting of Daily Air Quality--Air Quality
Index (AQI)).
f. The pollutant specific sensitive groups for any reported
index value greater than 100. Use the following sensitive groups for
each pollutant:
------------------------------------------------------------------------
When this pollutant has an index value Report these sensitive groups *
above 100 * * * * *
------------------------------------------------------------------------
Ozone.................................. Children and people with asthma
are the groups most at risk.
------------------------------------------------------------------------
PM2.5.................................. People with respiratory or
heart disease, the elderly and
children are the groups most
at risk.
------------------------------------------------------------------------
PM10................................... People with respiratory disease
are the group most at risk.
------------------------------------------------------------------------
CO..................................... People with heart disease are
the group most at risk.
------------------------------------------------------------------------
SO2.................................... People with asthma are the
group most at risk.
------------------------------------------------------------------------
[[Page 42548]]
NO2.................................... Children and people with
respiratory disease are the
groups most at risk.
------------------------------------------------------------------------
ii. When appropriate, your AQI report may also contain the
following:
a. Appropriate health and cautionary statements.
b. The name and index value for other pollutants, particularly
those with an index value greater than 100.
c. The index values for sub-areas of your MSA.
d. Causes for unusual AQI values.
e. Actual pollutant concentrations.
5. Is My AQI Report for My MSA Only?
Generally, your AQI report applies to your MSA only. However, if
a significant air quality problem exists (AQI greater than 100) in
areas significantly impacted by your MSA but not in it (for example,
O3 concentrations are often highest downwind and outside
an urban area), you should identify these areas and report the AQI
for these areas as well.
6. How Do I Get My AQI Report to the Public?
You must furnish the daily report to the appropriate news media
(radio, television, and newspapers). You must make the daily report
publicly available at one or more places of public access, or by any
other means, including a recorded phone message, a public Internet
site, or facsimile transmission. When the AQI value is greater than
100, it is particularly critical that the reporting to the various
news media be as extensive as possible. At a minimum, it should
include notification to the media with the largest market coverages
for the area in question.
7. How Often Must I Report the AQI?
You must report the AQI at least 5 days per week. Exceptions to
this requirement are in section 8 of this appendix.
8. May I Make Exceptions to These Reporting Requirements?
i. If the index value for a particular pollutant remains below
50 for a season or year, then you may exclude the pollutant from
your calculation of the AQI in section 12.
ii. If all index values remain below 50 for a year, then you may
report the AQI at your discretion. In subsequent years, if pollutant
levels rise to where the AQI would be above 50, then the AQI must be
reported as required in sections 3, 4, 6, and 7 of this appendix.
Calculation
9. How Does the AQI Relate to Air Pollution Levels?
For each pollutant, the AQI transforms ambient concentrations to
a scale from 0 to 500. The AQI is keyed as appropriate to the
national ambient air quality standards (NAAQS) for each pollutant.
In most cases, the index value of 100 is associated with the
numerical level of the short-term standard (i.e., averaging time of
24-hours or less) for each pollutant. Different approaches are taken
for NO2, for which no short-term standard has been
established, and for PM2.5, for which the annual standard
is the principal vehicle for protecting against short-term
concentrations. The index value of 50 is associated with the
numerical level of the annual standard for a pollutant, if there is
one, at one-half the level of the short-term standard for the
pollutant, or at the level at which it is appropriate to begin to
provide guidance on cautionary language. Higher categories of the
index are based on increasingly serious health effects and
increasing proportions of the population that are likely to be
affected. The index is related to other air pollution concentrations
through linear interpolation based on these levels. The AQI is equal
to the highest of the numbers corresponding to each pollutant. For
the purposes of reporting the AQI, the sub-indexes for
PM10 and PM2.5 are to be considered
separately. The pollutant responsible for the highest index value
(the reported AQI) is called the ``critical'' pollutant.
10. Where Do I Get the Pollutant Concentrations To Calculate the
AQI?
You must use concentration data from population-oriented State/
Local Air Monitoring Station (SLAMS) or parts of the SLAMS required
under 40 CFR 58.20 for each pollutant except PM. For PM, you need
only calculate and report the AQI on days for which you have
measured air quality data (e.g., particulate monitors often report
values only every sixth day). You may use particulate measurements
from monitors that are not reference or equivalent methods (for
example, continuous PM10 or PM2.5 monitors) if
you can relate these measurements by statistical linear regression
to reference or equivalent method measurements.
11. Do I Have to Forecast the AQI?
You should forecast the AQI to provide timely air quality
information to the public, but this is not required. If you choose
to forecast the AQI, then you may consider both long-term and short-
term forecasts. You can forecast the AQI at least 24-hours in
advance using the most accurate and reasonable procedures
considering meteorology, topography, availability of data, and
forecasting expertise. The document ``Guideline for Developing an
Ozone Forecasting Program'' (the Forecasting Guidance) will help you
start a forecasting program. You can also issue short-term forecasts
by predicting 8-hour ozone values from 1-hour ozone values using
methods suggested in the Reporting Guidance, ``Guideline for Public
Reporting of Daily Air Quality.''
12. How Do I Calculate the AQI?
i. The AQI is the highest value calculated for each pollutant as
follows:
a. Identify the highest concentration among all of the monitors
within each reporting area and truncate the pollutant concentration
to one more than the significant digits used to express the level of
the NAAQS for that pollutant. This is equivalent to the rounding
conventions used in the NAAQS.
b. Using Table 2, find the two breakpoints that contain the
concentration.
c. Using Equation 1, calculate the index.
d. Round the index to the nearest integer.
Table 2.--Breakpoints for the AQI
--------------------------------------------------------------------------------------------------------------------------------------------------------
These breakpoints Equal these AQIs * *
-----------------------------------------------------------------------------------------------------------------------*-----------
PM10 Category
O3 (ppm) 8-hour O3 (ppm) 1- PM2.5 (g/ CO (ppm) SO2 (ppm) NO2 (ppm) AQI
hour 1 m>g/m3) m3)
--------------------------------------------------------------------------------------------------------------------------------------------------------
0.000-0.064...................... ............ 0.0-15.4 0-54 0.0-4.4 0.000-0.034 (2) 0-50 Good.
0.065-0.084...................... ............ 15.5-40.4 55-154 4.5-9.4 0.035-0.144 (2) 51-100 Moderate.
0.085-0.104...................... 0.125-0.164 40.5-65.4 155-254 9.5-12.4 0.145-0.224 (2) 101-150 Unhealthy for
sensitive groups.
0.105-0.124...................... 0.165-0.204 4 65.5-150.4 255-354 12.5-15.4 0.225-0.304 (2) 151-200 Unhealthy.
0.125-0.374...................... 0.205-0.404 4 150.5-250.4 355-424 15.5-30.4 0.305-0.604 0.65-1.24 201-300 Very unhealthy.
(3).............................. 0.405-0.504 4 250.5-350.4 425-504 30.5-40.4 0.605-0.804 1.25-1.64 301-400 ....................
(3).............................. 0.505-0.604 4 350.5-500.4 505-604 40.5-50.4 0.805-1.004 1.65-2.04 401-500 Hazardous.
--------------------------------------------------------------------------------------------------------------------------------------------------------
1 Areas are generally required to report the AQI based on 8-hour ozone values. However, there are a small number of areas where an AQI based on 1-hour
ozone values would be more precautionary. In these cases, in addition to calculating the 8-hour ozone index value, the 1-hour ozone index value may be
calculated, and the maximum of the two values reported.
[[Page 42549]]
2 NO2 has no short-term NAAQS and can generate an AQI only above an AQI value of 200.
3 8-hour O3 values do not define higher AQI values ( 301). AQI values of 301 or higher are calculated with 1-hour O3 concentrations.
4 If a different SHL for PM2.5 is promulgated, these numbers will change accordingly.
ii. If the concentration is equal to a breakpoint, then the
index is equal to the corresponding index value in Table 2. However,
Equation 1 can still be used. The results will be equal. If the
concentration is between two breakpoints, then calculate the index
of that pollutant with Equation 1. You must also note that in some
areas, the AQI based on 1-hour O3 will be more
precautionary than using 8-hour values (see footnote 1 to Table 2).
In these cases, you may use 1-hour values as well as 8-hour values
to calculate index values and then use the maximum index value as
the AQI for O3.
[GRAPHIC] [TIFF OMITTED] TR04AU99.044
Where:
Ip = the index value for pollutantp
Cp = the truncated concentration of
pollutantp
BPHi = the breakpoint that is greater than or equal to
Cp
BPLo = the breakpoint that is less than or equal to
Cp
IHi = the AQI value corresponding to BPHi
Ilo = the AQI value corresponding to BPLo.
iii. If the concentration is larger than the highest breakpoint
in Table 2 then you may use the last two breakpoints in Table 2 when
you apply Equation 1.
Example
iv. Using Table 2 and Equation 1, calculate the index value for
each of the pollutants measured and select the one that produces the
highest index value for the AQI. For example, if you observe a
PM10 value of 210 g/m3, a 1-hour
O3 value of 0.156 ppm, and an 8-hour O3 value
of 0.130 ppm, then do this:
a. Find the breakpoints for PM10 at 210 g/
m3 as 155 g/m3 and 254 g/
m3, corresponding to index values 101 and 150;
b. Find the breakpoints for 1-hour O3 at 0.156 ppm as
0.125 ppm and 0.164 ppm, corresponding to index values 101 and 150;
c. Find the breakpoints for 8-hour O3 at 0.130 ppm as
0.125 ppm and 0.374 ppm, corresponding to index values 201 and 300;
d. Apply Equation 1 for 210 g/m3,
PM10:
[GRAPHIC] [TIFF OMITTED] TR04AU99.045
e. Apply Equation 1 for 0.156 ppm, 1-hour O3:
[GRAPHIC] [TIFF OMITTED] TR04AU99.046
f. Apply Equation 1 for 0.130 ppm, 8-hour O3:
[GRAPHIC] [TIFF OMITTED] TR04AU99.047
g. Find the maximum, 203. This is the AQI. The minimal AQI
report would read:
v. Today, the AQI for my city is 203 which is very unhealthy,
due to ozone. Children and people with asthma are the groups most at
risk.
Background and Reference Materials
13. What Additional Information Should I Know?
The EPA has developed a computer program to calculate the AQI
for you. The program works with Windows 95, it prompts for inputs,
and it displays all the pertinent information for the AQI (the index
value, color, category, sensitive group, health effects, and
cautionary language). The EPA has also prepared a brochure on the
AQI that explains the index in detail (The Air Quality Index),
Reporting Guidance (Guideline for Public Reporting of Daily Air
Quality) that provides associated health effects and cautionary
statements, and Forecasting Guidance (Guideline for Developing an
Ozone Forecasting Program) that explains the steps necessary to
start an air pollution forecasting program. You can download the
program and the guidance documents at www.epa.gov/airnow.
[FR Doc. 99-19433 Filed 8-3-99; 8:45 am]
BILLING CODE 6560-50-P
