[Federal Register Volume 64, Number 38 (Friday, February 26, 1999)]
[Notices]
[Pages 9560-9599]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-4416]
[[Page 9559]]
_______________________________________________________________________
Part II
Environmental Protection Agency
_______________________________________________________________________
Radon in Drinking Water Health Risk Reduction and Cost Analysis; Notice
Federal Register / Vol. 64, No. 38 / Friday, February 26, 1999 /
Notices
[[Page 9560]]
ENVIRONMENTAL PROTECTION AGENCY
[FRL-6304-3]
Radon in Drinking Water Health Risk Reduction and Cost Analysis
AGENCY: Environmental Protection Agency.
ACTION: Notice and request for public comments and announcement of
stakeholder meeting.
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SUMMARY: The Safe Drinking Water Act (SDWA), as amended in 1996,
requires the U.S. Environmental Protection Agency (EPA) to publish a
health risk reduction and cost analysis (HRRCA) for radon in drinking
water for public comment. The purpose of this notice is to provide the
public with the HRRCA for radon and to request comments on the
document. As required by SDWA, EPA will publish a response to all
significant comments to the HRRCA in the preamble to the proposed
National Primary Drinking Water Regulation (NPDWR) for radon, due in
August, 1999.
The goal of the HRRCA is to provide a neutral and factual analysis
of the costs, benefits, and other impacts of controlling radon levels
in drinking water. The HRRCA is intended to support future decision
making during development of the radon NPDWR. The HRRCA evaluates radon
levels in drinking water of 100, 300, 500, 700, 1000, 2000, and 4000
pCi/L. The HRRCA also presents information on the costs and benefits of
implementing multimedia mitigation (MMM) programs to reduce the risks
of radon exposure in indoor air. The SDWA, as amended, provides for
development of an Alternative Maximum Contaminant Level (AMCL), which
public systems may comply with if their State has an EPA approved MMM
program to reduce radon in indoor air. The concept behind the AMCL and
MMM option is to reduce radon health risks by addressing the larger
source of exposure (air levels in homes) compared to drinking water. If
a State chooses to employ a MMM program to reduce radon risk, it would
implement a State program to reduce indoor air levels and require
public water systems to control water radon levels to the AMCL. If a
State does not choose a MMM program option, a public water system may
propose a MMM program for EPA approval. Today's notice does not include
any decisions regarding the choice of a Maximum Contaminant Level (MCL)
for radon in drinking water. Today's notice also announces a
stakeholder meeting on the HRRCA and framework for the MMM program.
DATES: The Agency must receive comments on the HRRCA on or before April
12, 1999. EPA will hold a one day public meeting on Tuesday, March 16,
1999 from 9 a.m. to 5:30 p.m. EST.
ADDRESSES: Send written comments on HRRCA to the Comment Clerk, docket
number W-98-30, Water Docket (MC4101), USEPA, 401 M St., SW,
Washington, DC 20460. Please submit an original and three copies of
your comments and enclosures (including references).
Commenters who want EPA to acknowledge receipt of their comments
should enclose a self-addressed, stamped envelope. No facsimiles
(faxes) will be accepted. Comments may also be submitted electronically
to ow-docket@epa.gov. Electronic comments must be submitted as an
ASCII, WP6.1, or WP8 file avoiding the use of special characters and
any form of encryption. Electronic comments must be identified by the
docket number W-98-30. Comments and data will also be accepted on disks
in WP6.1, WP8, or ASCII file format. Electronic comments on this notice
may be filed online at many Federal Depository Libraries.
The record for this notice has been established under docket number
W-98-30, and includes supporting documentation as well as printed,
paper versions of electronic comments. The full record is available for
inspection from 9 a.m. to 4 p.m. EST Monday through Friday, excluding
legal holidays at the Water Docket, Room EB57, USEPA Headquarters, 401
M St., SW, Washington, DC 20460. For access to docket materials, please
call 202-260-3027 to schedule an appointment.
The stakeholder meeting on the HRRCA and multimedia mitigation
framework will be held at the offices of at RESOLVE, Inc., 1255 23rd
Street, N.W,. Suite 275, Washington, DC 20037. Check-in will begin at
8:30 a.m.
FOR FURTHER INFORMATION CONTACT: For general information, please
contact the EPA Safe Drinking Water Hotline at 1-800-426-4791 or 703-
285-1093 between 9 a.m. and 5:30 p.m. EST. (For information on radon in
indoor air, contact the National Safety Council's National Radon
Hotline at 1-800-SOS-RADON.) The HRRCA, including the appendices, can
also be accessed on the internet at http://www.epa.gov/safewater/
standard/pp/radonpp/html. For specific information and technical
inquiries, contact Michael Osinski at 202-260-6252 or
osinski.michael@epa.gov.
For general information on meeting logistics, please contact Sheri
Jobe at RESOLVE, Inc., at 202-965-6382 or Email: sjobe@resolv.org.
SUPPLEMENTARY INFORMATION: The purpose of the March 16, 1999
stakeholder meeting is to cover the following key issues, including:
(1) Discussion of the Health Risk Reduction and Cost Analysis published
in this notice; and (2) present information and discuss issues related
to status of development of a framework for multimedia mitigation
programs. This upcoming meeting is the fifth of a series of
stakeholders meetings on the NPDWR for radon, intended to seek input
from State and Tribal drinking water and radon programs, the regulated
community (public water systems), public health and safety
organizations, environmental and public interest groups, and other
stakeholders. EPA encourages the full participation of stakeholders
throughout this process.
To register for the meeting, please contact Sheri Jobe at RESOLVE,
Inc., 1255 23rd Street, N.W,. Suite 275, Washington, DC 20037, Phone:
202-965-6382, Fax: 202-338-1264, Email: sjobe@resolv.org. Please
provide your name, affiliation/organization, address, phone, fax and
email if you would like to be on the mailing list to receive further
information about the meeting (including agenda and meeting summary). A
limited number of tele-conference lines will be available. Please
indicate whether you would like to participate by phone. Those
registered for the meeting by February 26, 1999 will receive an agenda,
logistics sheet, and other information prior to the meeting.
Dated: January 5, 1999.
Dana D. Minerva,
Acting Assistant Administrator, Office of Water, Environmental
Protection Agency.
Radon in Drinking Water Health Risk Reduction and Cost Analysis
Table of Contents
1. Executive Summary
2. Introduction
2.1 Background
2.2 Regulatory History
2.3 Safe Drinking Water Act Amendments of 1996
2.4 Specific Requirements for the Health Risk Reduction and Cost
Analysis
2.5 Radon Levels Evaluated
2.6 Document Structure
3. Health Effects From Radon Exposure
3.1 Radon Occurrence and Exposure Pathways
3.1.1 Occurrence
3.1.2 Exposure Pathways
3.2 Nature of Health Impacts
3.3 Impacts on Sensitive Subpopulations
[[Page 9561]]
3.4 Risk Reduction Model for Radon in Drinking Water
3.5 Risks from Existing Radon Exposures
3.6 Potential for Risk Reductions Associated with Removal of Co-
Occurring Contaminants
3.7 Potential for Risk Increases from Other Contaminants
Associated with Radon Removal
3.8 Risk for Ever-Smokers and Never-Smokers
4. Benefits of Reduced Radon Exposure
4.1 Nature of Regulatory Impacts
4.1.1 Quantifiable Benefits
4.1.2 Non-Quantifiable Benefits
4.2 Monetization of Benefits
4.2.1 Estimation of Fatal and Non-Fatal Cancer Risk Reduction
4.2.2 Value of Statistical Life for Fatal Cancers Avoided
4.2.3 Costs of Illness and Lost Time for Non-Fatal Cancers
4.2.4 Willingness to Pay to Avoid Non-Fatal Cancers
4.3 Treatment of Monetized Benefits Over Time
5. Costs of Radon Treatment Measures
5.1 Drinking Water Treatment Technologies and Costs
5.1.1 Aeration
5.1.2 Granular Activated Carbon (GAC)
5.1.3 Storage
5.1.4 Regionalization
5.1.5 Radon Removal Efficiencies
5.1.6 Pre-Treatment to Reduce Iron and Manganese Levels
5.1.7 Post-Treatment--Disinfection
5.2 Monitoring Costs
5.3 Water Treatment Technologies Currently In Use
5.4 Cost of Technologies as a Function of Flow Rates and Radon
Removal Efficiency
5.5 Choice of Treatment Responses
5.6 Cost Estimation
5.6.1 Site and System Costs
5.6.2 Aggregate National Costs
5.6.3 Costs to Community Water Systems
5.6.4 Costs to Consumers/Households
5.6.5 Costs to Non-Transient Non-Community Systems
5.7 Application of Radon Related Costs to Other Rules
6. Results: Costs and Benefits of Reducing Radon in Drinking Water
6.1 Overview of Analytical Approach
6.2 Health Risk Reduction and Monetized Health Benefits
6.3 Costs of Radon Mitigation
6.4 Incremental Costs and Benefits of Radon Removal
6.5 Costs to Community Water Systems
6.6 Costs and Impacts to Households
6.7 Summary of Cost and Benefit Analysis
6.8 Sensitivities and Uncertainties
6.8.1 Uncertainties in Risk Reduction and Health Benefits
Calculations
6.8.2 Uncertainty in Cost and Impact Calculations
7. Implementation Scenarios--Multimedia Mitigation Programs
7.1 Multimedia Mitigation Programs
7.2 Implementation Scenarios Evaluated
7.3 Multimedia Mitigation Cost and Benefit Assumptions
7.4 Annual Costs and Benefits of Multimedia Mitigation Program
Implementation
7.6 Sensitivities and Uncertainties
List of Tables and Figures
Table 3-1. Radon Distributions by Region
Table 3-2. Radon Distribution in Public Water Systems
Table 3-3. Population Exposed Above Various Radon Levels By System
Size
Table 3-4. Estimated Radon Unit Lifetime Fatal Cancer Risks in
Community Water Systems
Table 3-5. Radon Treatment Assumptions to Calculate Residual Fatal
Cancer Risks
Table 3-6. Annual Fatal Cancer Risks for Exposures to Radon from
Community Water Systems
Table 3-7. Radon Risk Reductions Across Various Effluent Levels and
Percent Removals
Table 3-8. Radon Risk Reduction from Treatment Compared to DBP Risks
Table 3-9. Annual Lung Cancer Death Risks Estimates from Radon
Progeny for Ever-Smokers, Never-Smokers, and the General Population
Table 4-1. Proportion of Fatal Cancers by Exposure Pathway and
Estimated Mortality
Table 4-2. Estimated Medical Care and Lost-Time Costs Per Case for
Survivors of Lung Cancer
Table 4-3. Estimated Medical Care and Lost-time Costs Per Case for
Survivors of Stomach Cancer
Table 5-1. Unit Treatment Costs by Removal Efficiency and System
Size
Table 5-2. Estimated Proportions of Ground Water Systems With Water
Treatment Technologies Already in Place
Table 5-3. Decision Matrix For Selection of Treatment Technology
Options
Table 5-4. Number of Sites per Ground Water System by System Size
Table 6-1. Risk Reduction and Residual Cancer Risk from Reducing
Radon in Drinking Water
Table 6-2. Estimated Monetized Health Benefits from Reducing Radon
in Drinking Water
Table 6-3. Risk Reduction and Monetized Benefits Estimates For Ever-
Smokers
Table 6-4. Risk Reduction and Monetized Benefits Estimates For
Never-Smokers
Table 6-5. Estimated Annualized National Costs of Reducing Radon
Exposures
Table 6-6. Capital and O&M Costs of Mitigating Radon in Drinking
Water
Table 6-7. Estimates of the Annual Incremental Costs and Benefits of
Reducing Radon in Drinking Water
Table 6-8. Number of Community Water Systems Exceeding Various Radon
Levels
Table 6-9. Average Annual Cost Per System
Table 6-10. Annual Costs per Household for Community Water Systems
Table 6-11. Per Household Impact by Community Water System as a
Percentage of Median Household Income
Table 6-12. Estimated National Annual Costs and Benefits of Reducing
Radon Exposures--Central Tendency Estimate
Table 6-13. Total Annual Costs and Fatal Cancers Avoided by System
Size
Table 6-14. Annual Monetized Health Benefits by System Size
Table 7-1. Central Tendency Estimates of Annualized Costs and
Benefits of Reducing Radon Exposures with 50% of States Selecting
the MMM/AMCL Option
Table 7-2. Central Tendency Estimates of Annualized Costs and
Benefits of Reducing Radon Exposures with 100% of States Selecting
the MMM/AMCL Option
Figure 3-1. General Patterns of Radon Occurrence in Ground Water
Figure 3-2. EPA Map of Radon Zones in Indoor Air
Figure 6-1. Sensitivity Analysis of Water Mitigation Costs
Figure 7-1. Sensitivity Analysis to Changes in MMM Cost Estimates
Abbreviations Used in This Document
AF: Average Flow
AMCL: Alternative Maximum Contaminant Level
AWWA: American Water Works Association
BAT: Best Available Technology
CWS: Community Water System
DA: Diffused-Bubble Aeration
DBP: Disinfection By-Products
DF: Design Flow
GAC: Granular Activated Carbon
EPA: US Environmental Protection Agency
FACA: Federal Advisory Committee Act
HRRCA: Health Risk Reduction and Cost Analysis
MCL: Maximum Contaminant Level
MCLG: Maximum Contaminant Level Goal
MMM: Multimedia Mitigation program
MSBA: Multi-Stage Diffused Bubble Aeration
NAS: National Academy of Sciences
NDWAC: National Drinking Water Advisory Council
NIRS: National Inorganics and Radionuclides Survey
NPDWR: National Primary Drinking Water Regulation
NTNCWS: Non-Transient Non-Community Water System
OGWDW: Office of Ground Water and Drinking Water
O&M: Operation and Maintenance
OMB: Office of Management and Budget
pCi/l: Picocurie Per Liter
POE GAC: Point-of-Entry Granular Activated Carbon
PTA: Packed Tower Aeration
RIA: Regulatory Impact Analysis
SAB: Science Advisory Board
SDWA: Safe Drinking Water Act, as amended in 1986 and 1996
SDWIS: Safe Drinking Water Inventory System
THM: Trihalomethane
VSL: Value of a Statistical Life
WTP: Willingness To Pay
1. Executive Summary
This document constitutes the Health Risk Reduction and Cost
Analysis (HRRCA) in support of development of a National Primary
Drinking Water Regulation (NPDWR) for radon in drinking water, as
required by Section 1412(b)(13) of the 1996 Amendments to
[[Page 9562]]
the Safe Drinking Water Act (SDWA). The goal of the HRRCA is to provide
a neutral and fact-based analysis of the costs, benefits, and other
impacts of controlling radon levels in drinking water to support future
decision making during development of the radon NPDWR. The document
addresses the various requirements for the analysis of benefits, costs,
and other elements specified by Section 1412(b)(13) of the SDWA, as
amended.
This is the first time the Environmental Protection Agency (EPA)
has prepared a HRRCA under the SDWA, as amended. As such, the EPA is
very interested in seeking comment on the techniques, assumptions, and
data inputs upon which the analysis is based. The Agency recognizes
that there may be other methods of conducting the analysis and
presenting the data required for this HRRCA, and encourages meaningful
input from all stakeholders during the public comment period.
Therefore, the specific analysis and findings presented here are
intended as an initial effort to frame an analysis that can support
development of the NPDWR. Since the HRRCA is a cost-benefit tool to
analyze an array of radon levels during development of the NPDWR, many
of the issues to be addressed in the regulatory development process
(e.g. the selection of a Maximum Contaminant Level (MCL), Best
Available Technology (BAT), and monitoring framework) are not analyzed
here, but will be presented in the proposed rule.
The HRRCA evaluates radon levels in ground water supplies of 100,
300, 500, 700, 1000, 2000, and 4000 pCi/l. The HRRCA also presents
information on the costs and benefits of implementing multimedia
mitigation (MMM) programs. The scenarios evaluated are described in
detail in Section 2.5. This executive summary presents a background on
the radon in drinking water problem, followed by a summary of findings
arranged according to each provision for HRRCAs as specified by the
SDWA, as amended.
Background: Radon Health Risks, Occurrence, and Regulatory History
Radon is a naturally occurring volatile gas formed from the normal
radioactive decay of uranium. It is colorless, odorless, tasteless,
chemically inert, and radioactive. Uranium is present in small amounts
in most rocks and soil, where it decays to other products including
radium, then to radon. Some of the radon moves through air or water-
filled pores in the soil to the soil surface and enters the air, and
can enter buildings through cracks and other holes in the foundation.
Some radon remains below the surface and dissolves in ground water
(water that collects and flows under the ground's surface). Due to
their very long half-life (the time required for half of a given amount
of a radionuclide to decay), uranium and radium persist in rock and
soil.
Exposure to radon and its progeny is believed to be associated with
increased risks of several kinds of cancer. When radon or its progeny
are inhaled, lung cancer accounts for most of the total incremental
cancer risk. Ingestion of radon in water is suspected of being
associated with increased risk of tumors of several internal organs,
primarily the stomach. As required by the SDWA, EPA arranged for the
National Academy of Sciences (NAS) to assess the health risks of radon
in drinking water. The NAS released the ``Report on the Risks of Radon
in Drinking Water,''(NAS Report) in September 1998 (NAS 1998B). The NAS
Report represents a comprehensive assessment of scientific data
gathered to date on radon in drinking water. The report, in general,
confirms earlier EPA scientific conclusions and analyses of radon in
drinking water (US EPA,1994C).
NAS recently estimated individual lifetime unit fatal cancer risks
associated with exposure to radon from domestic water use for ingestion
and inhalation pathways (Table 3-4). The results show that inhalation
of radon progeny accounts for most (approximately 89 percent) of the
individual risk associated with domestic water use, with almost all of
the remainder (11 percent) resulting from directly ingesting radon in
drinking water. Inhalation of radon progeny is associated primarily
with increased risk of lung cancer, while ingestion exposure is
associated primarily with elevated risk of stomach cancer.
The NAS Report confirmed that indoor air contamination arising from
soil gas typically account for the bulk of total individual risk due to
radon exposure. Usually, most radon gas enters indoor air by diffusion
from soils through basement walls or foundation cracks or openings.
Radon in domestic water generally contributes a small proportion of the
total radon in indoor air.
The NAS Report is one of the most important inputs used by EPA in
the HRRCA. EPA has used the NAS's assessment of the cancer risks from
radon in drinking water to estimate both the health risks posed by
existing levels of radon in drinking water and also the cancer deaths
prevented by reducing radon levels.
In updating key analyses and developing the framework for the cost-
benefit analysis presented in the HRRCA, EPA has consulted with a broad
range of stakeholders and technical experts. Participants in a series
of stakeholder meetings held in 1997 and 1998 included representatives
of public water systems, State drinking water and indoor air programs,
Tribal water utilities and governments, environmental and public health
groups, and other federal agencies.
The HRRCA builds on several technical components, including
estimates of radon occurrence in drinking water, analytical methods for
detecting and measuring radon levels, and treatment technologies.
Extensive analyses of these issues were undertaken by the Agency in the
course of previous rulemaking efforts for radon and other
radionuclides. Using data provided by stakeholders, and from published
literature, the EPA has updated these technical analyses to take into
account the best currently available information and to respond to
comments on the 1991 proposed NPDWR for radon. As required by the 1996
Safe Drinking Water Act (SDWA), EPA has withdrawn the proposed NPDWR
for radon (US EPA 1997B) and will propose a new regulation by August,
1999. The HRRCA does not include any decisions regarding the choice of
a Maximum Contaminant Level (MCL) for radon in drinking water.
The analysis presented in this HRRCA uses updated estimates of the
number of active public drinking water systems obtained from EPA's Safe
Drinking Water Information System (SDWIS). Treatment costs for the
removal of radon from drinking water have also been updated. The HRRCA
follows current EPA policies with regard to the methods and assumptions
used in cost and benefit assessment.
As part of the regulatory development process, EPA has updated and
refined its analysis of radon occurrence patterns in ground water
supplies in the United States (US EPA 1998L). This new analysis
incorporates information from the EPA's 1985 National Inorganic and
Radionuclides Survey (NIRS) of 1000 community ground water systems
throughout the United States, along with supplemental data provided by
the States, water utilities, and academic research. The new study also
addressed a number of issues raised by public comments in the previous
occurrence analysis that accompanied the 1991 proposed NPDWR, including
characterization of regional and temporal variability in radon levels,
and
[[Page 9563]]
the impact of sampling point for monitoring compliance.
In general, radon levels in ground water in the United States have
been found to be the highest in New England and the Appalachian uplands
of the Middle Atlantic and Southeastern states (Figure 3-1). There are
also isolated areas in the Rocky Mountains, California, Texas, and the
upper Midwest where radon levels in ground water tend to be higher than
the United States average. The lowest ground water radon levels tend to
be found in the Mississippi Valley, lower Midwest, and Plains states.
When comparing radon levels in ground water to radon levels in indoor
air at the State level, the distribution of radon concentrations in
indoor air (Figure 3-2) do not always mirror distributions of radon in
ground water.
In addition, the 1996 Amendments to the SDWA introduce two new
elements into the radon in drinking water rule: (1) an Alternative
Maximum Contaminant Level (AMCL) and (2) multimedia radon mitigation
(MMM) programs. The SDWA, as amended, provides for development of an
AMCL, which public water systems may comply with if their State has an
EPA approved MMM program to reduce radon in indoor air. The NAS Report
estimated that the AMCL would be about 4,000 pCi/L, based on SDWA
requirements. The concept behind the AMCL and MMM option is to reduce
radon health risks by addressing the larger source of exposure (air
levels in homes) compared to drinking water. If a State chooses to
employ a MMM program to reduce radon risk, it would implement a State
program to reduce indoor air levels and require public water systems to
control radon levels in drinking water to the AMCL. If a State does not
choose a MMM program option, a public water system may propose a MMM
program for EPA approval.
Summary of Findings
Quantifiable and Non-Quantifiable Costs
The capital and operating and maintenance (O&M) costs of mitigating
radon in Community Water Systems (CWSs) were estimated for each of the
radon levels evaluated. The costs of reducing radon in ground water to
specific target levels were calculated using the cost curves discussed
in Section 5.4 and the matrix of treatment options presented in Section
5.5. For each radon level and system size stratum, the number of
systems that need to reduce radon levels by up to 50 percent, 80
percent and 99 percent were calculated. Then, the cost curves for the
distributions of technologies dictated by the treatment matrix were
applied to the appropriate proportions of the systems. Capital and O&M
costs were then calculated for each system, based on typical estimated
design and average flow rates. These flow rates were calculated on
spreadsheets using equations from EPA's Safe Drinking Water Suite Model
(US EPA 1998N). The equations and parameter values relating system size
to flow rates are presented in Appendix C. The technologies addressed
in the cost estimation included a number of aeration and granular
activated carbon (GAC) technologies described in Section 5.1, as well
as storage, regionalization, and disinfection as a post-treatment. To
estimate costs, water systems were assumed, with a few exceptions, to
select the technology that could reduce radon to the selected target
level at the lowest cost. CWSs were also assumed to treat separately at
every source from which water was obtained and delivered into the
distribution system.
The costs of reducing radon to various levels are summarized in
Table 6-5, which shows that, as expected, aggregate radon mitigation
costs increase with decreasing radon levels. The cost ranges presented
in the table represent plausible upper and lower bounds of 50 percent
above to 50 percent below the central tendency estimates. For CWSs, the
costs per system do not vary substantially across the different radon
levels evaluated. This is because the menu of mitigation technologies
for systems with various influent radon levels remains relatively
constant.
Quantifiable and Non-Quantifiable Health Benefits
The quantifiable health benefits of reducing radon exposures in
drinking water are attributable to the reduced incidence of fatal and
non-fatal cancers, primarily of the lung and stomach. Table 6-1 shows
the health risk reductions (number of fatal and non-fatal cancers
avoided) and the residual health risk (number of remaining cancer
cases) at various radon in water levels. Since preparing the
prepublication edition of the NAS Report, the NAS has reviewed and
slightly revised their unit risk estimates. EPA uses these updated unit
risk estimates in calculating the baseline risks, health risk
reductions, and residual risks. Under baseline assumptions (no control
of radon exposure), approximately 160 fatal cancers and 9.2 non-fatal
cancers per year are associated with radon exposures through CWSs. At a
radon level of 4,000 pCi/l, approximately 2.2 fatal cancers and 0.1
non-fatal cancers per year are prevented. At the lowest level evaluated
(100 pCi/l), approximately 115 fatal and 6.6 non-fatal cancers per year
would be prevented.
The Agency has developed monetized estimates of the health benefits
associated with the risk reductions from radon exposures. The SDWA, as
amended, requires that a cost-benefit analysis be conducted for each
NPDWR, and places a high priority on better analysis to support
rulemaking. The Agency is interested in refining its approach to both
the cost and benefit analysis, and in particular recognizes that there
are different approaches to monetizing health benefits. In the past,
the Agency has presented benefits as cost per life saved, as in Table
6-5. An alternative approach presented here for consideration as one
measure of potential benefits is the monetary value of a statistical
life (VSL) applied to each fatal cancer avoided. Since this approach is
relatively new to the development of NPDWRs, EPA is interested in
comments on these alternative approaches to valuing benefits, and will
have to weigh the value of these approaches for future use.
Estimating the VSL involves inferring individuals' implicit
tradeoffs between small changes in mortality risk and monetary
compensation. In the HRRCA, a central tendency estimate of $5.8 million
(1997$) is used in the monetary benefits calculations, with low- and
high-end values of $700,000 (1997$) and $16.3 million (1997$),
respectively, used for the purposes of sensitivity analysis. These
figures span the range of VSL estimates from 26 studies reviewed in
EPA's recent draft guidance on benefits assessment (US EPA 1998E),
which is currently under review by the Agency's Science Advisory Board
(SAB) and the Office of Management and Budget (OMB).
It is important to recognize the limitations of existing VSL
estimates and to consider whether factors such as differences in the
demographic characteristics of the populations and differences in the
nature of the risks being valued have a significant impact on the value
of mortality risk reduction benefits. Also, medical care or lost-time
costs are not separately included in the benefits estimate for fatal
cancers, since it is assumed that these costs are captured in the VSL
for fatal cancers.
For non-fatal cancers, willingness to pay (WTP) data to avoid
chronic bronchitis is used as a surrogate to estimate the WTP to avoid
non-fatal lung and stomach cancers. The use of
[[Page 9564]]
such WTP estimates is supported in the SDWA, as amended, at Section
1412(b)(3)(C)(iii): ``The Administrator may identify valid approaches
for the measurement and valuation of benefits under this subparagraph,
including approaches to identify consumer willingness to pay for
reductions in health risks from drinking water contaminants.''
A WTP central tendency estimate of $536,000 is used to monetize the
benefits of avoiding non-fatal cancers (Viscusi et al. 1991), with a
range between $169,000 and $1.05 million (1997$). The combined fatal
and non-fatal health benefits are summarized in Table 6-2. The annual
health benefits range from $13 million for a radon level of 4000 pCi/l
to $673 million at 100 pCi/l. The ranges in the last column of Table 6-
2 illustrate how benefits vary when the upper and lower bound estimates
of the VSL and WTP measures are used.
Reductions in radon exposures might also be associated with non-
quantifiable benefits. EPA has identified several potential non-
quantifiable benefits associated with regulating radon in drinking
water. These benefits may include any peace of mind benefits specific
to reduction of radon risks that may not be adequately captured in the
VSL estimate. In addition, treating radon in drinking water with
aeration oxidizes arsenic into a less soluble form that is easier to
remove with conventional removal technologies. In terms of reducing
radon exposures in indoor air, it has also been suggested that
provision of information to households on the risks of radon in indoor
air and available options to reduce exposure is a non-quantifiable
benefit that can be attributed to some components of a MMM program.
Providing such information might allow households to make informed
choices about the appropriate level of risk reduction given their
specific circumstances and concerns. These potential benefits are
difficult to quantify because of the uncertainty surrounding their
estimation. However, they are likely to be somewhat less significant
relative to the monetized benefits estimates.
Incremental Costs and Benefits of Radon Removal
Table 6-7 summarizes the central tendency and the upper and lower
bound estimates of the incremental costs and benefits of radon exposure
reduction. Both the annual incremental costs and benefits increase as
the radon level decreases from 4000 pCi/l down to 100 pCi/l.
Incremental costs and benefits are within 10 percent of each other at
radon levels of 1000, 700, and 500 pCi/l. The table also illustrates
the wide ranges of potential incremental costs and benefits due to the
uncertainty inherent in the estimates. There is substantial overlap
between the incremental costs and benefits at each radon level.
Impacts on Households
The cost impact of reducing radon in drinking water at the
household level was also assessed. As expected, costs per household
increase as system size decreases (Table 6-10). Costs to households are
higher for households served by smaller systems than larger systems for
two reasons. First, smaller systems serve far fewer households than
larger systems and, consequently, each household must bear a greater
percentage share of the capital and O&M costs. Second, smaller systems
tend to have higher influent radon concentrations that, on a per-capita
or per-household basis, require more expensive treatment methods (e.g.,
one that has an 85 percent removal efficiency rather than 50 percent)
to achieve the applicable radon level.
Another significant finding is that, like the per system costs,
costs per household (which are a function of per system costs) are
relatively constant across different radon levels within each system
size category. For example, there is less than one dollar per year
variation in household costs, regardless of the radon level being
considered for households served by large public or private systems
(between $6 and $7 annually), by medium public or private systems
(between $10 and $11), and by small public or private systems (between
$19 and $20 annually). Similarly, for very small systems (501-3300
people), the cost per household is consistently about $34 annually for
public systems and about $40 annually for private systems, varying
little with the target radon level. Only for very very small systems is
there a noticeable variation in household costs across radon levels.
The range for per household costs for public CWSs serving 25-500 people
is $87 per year (at 4,000 pCi/l) to $135 per year (at 100 pCi/l). The
corresponding range for private CWSs is $139 to $238 per year. For
households served by the smallest public systems (25-100 people) the
range of cost per household ranges from $292 per year at 4,000 pCi/l to
$398 per year at 100 pCi/l. For private systems, the range is $364 per
year to $489 per year, respectively.
Summary of Annual Costs and Benefits
Table 6-12 reveals that at a radon level of 4000pCi/l (equivalent
to the AMCL estimated in the NAS Report), annual costs are
approximately twice the annual monetized benefits. For radon levels of
1000pCi/l to 300 pCi/l, the central tendency estimates of annual costs
are above the central tendency estimates of the monetized benefits,
although they are within 10 percent of each other. However, as shown in
Tables 6-2 and 6-5, due to the uncertainty in the cost and benefit
estimates, there is a very broad possible range of potential costs and
benefits that overlap across all of the radon levels evaluated.
Benefits From the Reduction of Co-Occurring Contaminants
The occurrence patterns of other industrial pollutants are
difficult to clearly define at the national level relative to a
naturally occurring contaminant such as radon. Similarly, the Agency's
re-evaluation of radon occurrence has revealed that the geographic
patterns of radon occurrence are not significantly correlated with
other naturally occurring inorganic contaminants that may pose health
risks. Thus, it is not likely that a clear relationship exists between
the need to install radon treatment technologies and treatments to
remove other contaminants. On the other hand, technologies used to
reduce radon levels in drinking water have the potential to reduce
concentrations of other pollutants as well. Aeration technologies will
also remove volatile organic contaminants from contaminated ground
water. Similarly, granular activated carbon (GAC) treatment for radon
removal effectively reduces the concentrations of organic (both
volatile and nonvolatile) chemicals and some inorganic contaminants.
Aeration also tends to oxidize dissolved arsenic (a known carcinogen)
to a less soluble form that is more easily removed from water. The
frequency and extent that radon treatment would also reduce risks from
other contaminants has not been quantitatively evaluated.
Impacts on Sensitive Subpopulations
The SDWA, as amended, includes specific provisions in Section
1412(b)(3)(C)(i)(V) to assess the effects of the contaminant on the
general population and on groups within the general population such as
children, pregnant women, the elderly, individuals with a history of
serious illness, or other subpopulations that are
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identified as likely to be at greater risk of adverse health effects
due to exposure to contaminants in drinking water than the general
population. The NAS Report concluded that there is insufficient
scientific information to permit separate cancer risk estimates for
potential subpopulations such as pregnant women, the elderly, children,
and seriously ill persons. The NAS Report did note, however, that
according to the NAS model for the cancer risk from ingested radon,
which accounts for 11% of the total fatal cancer risk from radon in
drinking water, approximately 30% of the fatal lifetime cancer risk is
attributed to exposure between ages 0 to 10.
The NAS Report identified smokers as the only group that is more
susceptible to inhalation exposure to radon progeny (NAS 1998A, 1998B).
Inhalation of cigarette smoke and radon progeny result in a greater
increased risk than if the two exposures act independently to induce
lung cancer. NAS estimates that ``ever smokers'' (more than 100
cigarettes over a lifetime) may be more than five times as sensitive to
radon progeny as ``never smokers'' (less than 100 cigarettes over a
lifetime). Using current smoking prevalence data, EPA's preliminary
estimate for the purposes of the HRRCA is that approximately 85 percent
of the cases of radon-induced cancer will occur among current and
former smokers. This population of current and former smokers, which
consists of 58 percent of the male and 42 percent of the female
population (US EPA 1999A), will also experience the bulk of the risk
reduction from radon exposure reduction in drinking water supplies.
Risk Increases From Other Contaminants Associated With Radon Exposure
Reduction
As discussed in Section 5.1, the need to install radon treatment
technologies may require some systems that currently do not disinfect
to do so. Case studies (US EPA 199D) of twenty-nine small to medium
water systems that installed treatment (24 aeration, 5 GAC) to remove
radon from drinking water revealed only two systems that reported
adding disinfection (both aeration) with radon treatment (the systems
either had disinfection already in place or did not add it). In
practice, the tendency to add disinfection may be much more significant
than these case studies indicate. EPA also realizes that the addition
of chlorination for disinfection may result in risk-risk tradeoffs,
since, for example, the disinfection technology reduces potential for
infectious disease risk, but at the same time can result in increased
exposures to disinfection by-products (DBPs). This risk-risk trade-off
is addressed by the recently promulgated Disinfectants and Disinfection
By-Products NPDWR (US EPA 1998I). This rule identified MCLs for the
major DBPs, which all CWSs and NTNCWSs must comply. These MCLs set a
risk ceiling from DBPs that water systems adding disinfection in
conjunction with treatment for radon removal could face. The formation
of DBPs is proportional to the concentration of organic precursor
contaminants, which tend to be much lower in ground water than in
surface water.
The NAS Report addressed several important potential risk-risk
tradeoffs associated with reducing radon levels in drinking water,
including the trade-off between risk reduction from radon treatment
that includes post-disinfection with the increased potential for DBP
formation (NAS 1998B). The report concluded that, based upon median and
average total trihalomethane (THM) levels taken from EPA's 1981
Community Water System Survey, a typical ground water CWS would face
incremental individual lifetime cancer risk due to chlorination
byproducts of 5 x 10-5. It should be emphasized that this
risk is based on average and median THM occurrence information that
does not segregate systems that disinfect from those that do. Further,
the NAS Report points out that this average DBP risk is smaller than
the average individual lifetime fatal cancer risk associated with
baseline radon exposures from ground water (untreated for radon), which
is estimated at 1.2 x 10-4 using a mean radon concentration
of 213 pCi/l.
A more meaningful comparison is to look at the trade-off between
risk reduction from radon treatment in cases where disinfection is
added with the added risks from DBP formation. This trade-off will
affect only a minority of systems since a majority of ground water
systems already have disinfection in place. For the smallest systems
size category, approximately half of all CWSs already have disinfection
in place. The proportion of systems having disinfection in place
increases as the size categories increase, up to >95% for large systems
(Table 5-2). In addition, although EPA is using the conservative
costing assumption that all systems adding aeration or GAC would
disinfect, not all systems adding aeration or GAC would have to add
post-disinfection or, if disinfecting, may use a disinfection
technology that does not forms DBPs. For those ground water systems
adding treatment with disinfection, this trade-off tends to be
favorable since the combined risk reduction from radon removal and
microbial risk reduction outweigh the added risk from DBP formation.
An estimate of the risk reduction due to treatment of radon in
water for various removal percentages and finished water concentrations
is provided in Table 3.7. As noted by the NAS Report, these risk
reductions outweigh the increased risk from DBP exposure for those
systems that chlorinate as a result of adding radon treatment.
The ratios between risk reduction from radon removal and the risks
from THMs at levels equal their MCLs (a conservative assumption) are
shown in Table 3.8. The data indicate that the risk ratios are
favorable for treatment with disinfection, ignoring microbial risk
reduction, even assuming the worst case scenario that ground water
systems have THM levels at the MCL. It is worth noting that there is
the possibility that accounting quantitatively for the increased risk
from DBP exposure for systems adding chlorination in conjunction with
treatment for radon may somewhat decrease the monetized benefits
estimates.
Other Factors: Uncertainty in Risk, Benefit, and Cost Estimates
Estimates of health benefits from radon reduction are uncertain. A
few of the variables affecting the uncertainty in the benefit estimates
include the distribution of radon in ground water systems, the NAS's
risk models for ingestion and inhalation risks, and the transfer factor
used to estimate indoor air radon activity levels. EPA plans to include
an uncertainty analysis of radon in drinking water risks with the
proposed rule. Monetary benefit estimates are also strongly affected by
the VSL estimate that is used for fatal cancers. The WTP valuation for
non-fatal cancers has less impact on benefit estimates because it
contributes less than 1 percent to the total benefits estimates, due to
the fact that there are few non-fatal cancers relative to fatal
cancers.
Estimates of the regulatory costs also have associated uncertainty.
The major factors affecting this uncertainty include assumptions
regarding the distribution of radon levels among ground water systems
and among treatment sites within systems, uncertainties in unit cost
models, the assumed prevalence of the various compliance decisions, and
the exclusion of NTNCWSs in the HRRCA's national cost estimates.
To deal with a lack of information regarding the intra-system
variability of
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radon levels between treatment sites (source wells), the national cost
estimates are based on the assumption that all CWSs above a target
radon level, as estimated by system-level average radon occurrence
predictions from the occurrence model, will install separate treatment
systems at each site. Ideally, occurrence information at each treatment
site will provide a better estimate of national costs, since the wells
within a water system would exhibit a range of radon occurrence levels,
some of which may be below the target radon level, others above this
level. Since it is not obvious whether the system-level approach will
lead to either a positive or negative bias in the national cost
estimates, EPA is in the process of performing an analysis of the
intra-system variability for radon occurrence and will include this
analysis in support of the upcoming proposed rule.
There are also significant uncertainties in estimated treatment
unit costs and in the decision-trees that are used to model national
level compliance decisions that will by made by the system-size
stratified universe of drinking water systems in response to a range of
radon influent levels. It is possible to estimate the uncertainties in
both the unit costs and the decision-tree by performing sensitivity
analyses for the factors affecting costs. Regarding unit costs, this
analysis leads to a spread in costs that adequately resembles the
``real-world'' as shown by ranges in treatment cost case studies.
Regarding the uncertainty in the decision-tree, it is unfortunately not
possible to verify results in this way. However, since there are so few
technologies to mitigate radon in water, the decision-tree is fairly
robust.
Other Impacts: Costs and Benefits of Multimedia Mitigation Program
Implementation Scenarios
In addition to evaluating the costs and benefits across a range of
radon levels, two scenarios were evaluated that reduce radon exposure
through the use of MMM programs. The two scenarios evaluated assume:
(1) 50 percent of States (all water systems in those States) select MMM
implementation; and (2) 100 percent of States select MMM. These two
scenarios are described in detail in Section 7. For the MMM
implementation analysis, systems were assumed to mitigate water to the
4,000 pCi/l Alternative Maximum Contaminant Level (AMCL), if necessary,
and that equivalent risk reduction between the AMCL and the radon level
under evaluation would be achieved through a MMM program. Therefore,
the actual number of cancer cases avoided is the same for the MMM
implementation scenarios as for the water mitigation only scenario.
In calculating the cost of MMM programs, the cost per fatal cancer
case avoided was estimated at $700,000 (1997$). This value was
originally estimated by EPA in 1992 using 1991 data. The same nominal
value is used in the HRRCA based on anecdotal evidence from EPA's
Office of Radiation and Indoor Air (ORIA) that there has been an
equivalent offset between a decrease in testing and mitigation costs
since 1991 and the expected increase due to inflation in the years
1992-1997. This dollar amount reflects that real testing and mitigation
costs have decreased, while nominal costs have remained approximately
constant.
Tables 7-2 and 7-3 illustrate that, as expected, the costs of
reducing radon exposures decrease with increasing numbers of States
(i.e. CWSs) selecting the MMM implementation scenario. Also, as would
be expected, the annual costs of implementing MMM are, on average,
lower compared to reducing radon exposures in drinking water alone.
Central tendency estimates of the total annualized benefits exceed the
annualized costs for both the 50 and 100 percent MMM participation
scenarios over all radon levels. The cost per fatal cancer case avoided
is also lower for both the 50 and 100 percent MMM implementation
scenarios compared to the scenario in which no States elect to develop
a MMM program. In addition, the cost per fatal cancer case avoided is
significantly lower for the MMM scenario with 100 percent of the States
electing the MMM program compared to when 50 percent of the States
choose the MMM scenario, especially at the lower radon levels. The
costs and benefits estimates are also broken out into their respective
MMM and water mitigation components. With the exception of 4000pCi/l
(the NAS estimated AMCL), annual monetized benefits are significantly
larger than annual costs for the MMM component of the total costs. For
the water mitigation component, the annual costs are larger than the
annual monetized benefits across all radon levels.
2. Introduction
2.1 Background
This Health Risk Reduction and Cost Analysis (HRRCA) provides the
Environmental Protection Agency's (EPA) analysis of potential costs and
benefits of different target levels for radon in drinking water. The
HRRCA builds on several technical components, including estimates of
radon occurrence in drinking water supplies, analytical methods for
detecting and measuring radon levels, and treatment technologies.
Extensive analyses of these issues were undertaken by the Agency in the
course of previous rulemaking efforts for radon and other
radionuclides. Using data provided by stakeholders, and from published
literature, the EPA has updated these technical analyses to take into
account the best currently available information and to respond to
comments on the 1991 proposed regulation for radon in drinking water.
As required by the 1996 Safe Drinking Water Act (SDWA), EPA has
withdrawn the proposed regulation for radon in drinking water (US EPA
1997B) and will propose a new regulation by August, 1999.
One of the most important inputs used by EPA in the HRRCA is the
National Academy of Sciences (NAS) September 1998 report ``Risk
Assessment of Radon in Drinking Water'' (NAS Report). EPA has used the
NAS assessment of the cancer risks from radon in drinking water to
estimate both the health risks posed by existing levels of radon in
drinking water and also the estimated cancer deaths potentially
prevented by reducing radon levels. The NAS Report is the most
comprehensive accumulation of scientific data gathered to date on radon
in drinking water. SDWA required the NAS assessment, which generally
affirms EPA's earlier scientific conclusions and analyses on the risks
of exposure to radon and progeny in drinking water.
The analysis presented in this HRRCA uses updated estimates of the
number of active public drinking water systems obtained from EPA's Safe
Drinking Water Information System (SDWIS). Treatment costs for the
removal of radon from drinking water also have been updated. The HRRCA
follows EPA policies with regard to the methods and assumptions used in
cost and benefit assessment.
In updating key analyses and developing the framework for the cost-
benefit analysis presented in the HRRCA, EPA has consulted with a broad
range of stakeholders and technical experts. Participants in a series
of stakeholder meetings held in 1997 and 1998 included representatives
of public water systems, State drinking water and indoor air programs,
tribal water utilities and governments, environmental and public health
groups, and other federal agencies. EPA convened an expert panel in
Denver in November of 1997 to review treatment technology costing
approaches. The panel made a number of
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recommendations for modification to EPA cost estimating protocols that
have been incorporated into the radon cost estimates. EPA also
consulted with a subgroup of the National Drinking Water Advisory
Council (NDWAC) on evaluating the benefits of drinking water
regulations. The NDWAC was formed in accordance with the Federal
Advisory Committee Act (FACA) to assist and advise EPA. A variety of
stakeholders participated in the NDWAC benefits working group,
including utility company staff, environmentalists, health
professionals, State water program staff, a local elected official,
economists, and members of the general public.
The American Water Works Association (AWWA) convened a ``Radon
Technical Work Group,'' in 1998 that provided technical input on EPA's
update of technical analyses (occurrence, analytical methods, and
treatment technology), and discussed conceptual issues related to
developing guidelines for multimedia mitigation programs. Members of
the Radon Technical Work Group included representatives from State
drinking water and indoor air programs, public water systems, drinking
water testing laboratories, environmental groups and the U.S.
Geological Survey. EPA also held a series of conference calls with
State drinking water and indoor air programs, to discuss issues related
to developing guidelines for multimedia mitigation programs.
2.2 Regulatory History
Section 1412 of the Safe Drinking Water Act (SDWA), as amended in
1986, requires the EPA to publish Maximum Contaminant Level Goals
(MCLGs) and to promulgate National Primary Drinking Water Regulations
(NPDWRs) for contaminants that may cause an adverse effect on human
health and that are known or anticipated to occur in public water
supplies. In response to this charge, the EPA proposed NPDWRs for
radionuclides, including radon, in 1991 (US EPA 1991). The proposed
rule included a maximum contaminant level (MCL) of 300 pCi/l for radon
in drinking water, applicable to both community water systems and non-
transient non-community water systems. A community water system (CWS)
is defined as a public water system with at least 15 or more service
connections or that regularly serves at least 25 year-round residents.
A non-transient non-community system (NTNCWS) is a public water system
that is not a CWS and that regularly serves at least 25 of the same
persons for at least six months per year. Examples of NTNCWSs include
those that serve schools, offices, and commercial buildings. Under the
proposed rule, all CWSs and NTNCWSs relying on ground water would have
been required to monitor radon levels quarterly at each point of entry
to the distribution system. Compliance monitoring requirements were
based on the arithmetic average of four quarterly samples. The 1991
proposed rule required systems with one or more points of entry out of
compliance to treat influent water to reduce radon levels below the MCL
or to secure water from another source below the MCL.
The proposed rule was accompanied by an assessment of regulatory
costs and economic impacts, as well as an assessment of the risk
reduction associated with implementation of the MCL. The Agency
received substantial comments on the proposal and its supporting
analyses from States, water utilities, and other stakeholder groups.
Comments from the water industry questioned EPA's estimates of the
number of systems that would be out of compliance with the proposed
MCL, as well as the cost of radon mitigation. EPA's Science Advisory
Board (SAB) provided extensive comments on the risk assessment used by
the Agency to support the proposed MCL. The SAB recommended that EPA
expand the analysis of the uncertainty associated with the risk and
risk reduction estimates. In response to these comments, the assessment
was revised twice, once in 1993 and again in 1995 (US EPA 1995). Both
of the revised risk analyses provided detailed quantitative uncertainty
analysis.
2.3 Safe Drinking Water Act Amendments of 1996
In the 1996 Amendments to the Safe Drinking Water Act, Congress
established a new charter for public water systems, States, and EPA to
protect the safety of drinking water supplies. Among other mandates,
amended Section 1412(b)(13) directed EPA to withdraw the drinking water
standards proposed for radon in 1991 and to propose a new MCLG and
NPDWR for radon by no later than August 6, 1999. As noted above, the
amendments require NAS to conduct a risk assessment for radon in
drinking water and an assessment of risk reduction benefits from
various mitigation measures to reduce radon in indoor air (Section
1412(b)(13)(B)). In addition, the amendments introduce two new elements
into the radon in drinking water rule: (1) An Alternative Maximum
Contaminant Level (AMCL) and (2) multimedia radon mitigation (MMM)
program.
If the MCL established for radon in drinking water is more
stringent than necessary to reduce the contribution to radon in indoor
air from drinking water to a concentration that is equivalent to the
national average concentration of radon in outdoor air, EPA is required
to simultaneously establish an AMCL that would result in a contribution
of radon from drinking water to radon levels in indoor air equivalent
to the national average concentration of radon in outdoor air (Section
1412(b)(13)(F)). If an AMCL is established, EPA is to publish
guidelines for State programs, including criteria for multimedia
measures to mitigate radon levels in indoor air, to comply with the
AMCL.
States may develop and submit to EPA for approval an MMM program to
decrease radon levels in indoor air (Section 1412(b)(13)(G)). These
programs may rely on a variety of mitigation measures, including public
education, testing, training, technical assistance, remediation grants
and loan or incentive programs, or other regulatory and non-regulatory
measures. EPA shall approve a State's program if it is expected to
achieve equal or greater health risk reduction benefits than would be
achieved by compliance with the more stringent MCL. If EPA does not
approve a State program, or a State does not propose a program, public
water supply systems may propose their own MMM programs to EPA,
following the same procedures outlined for States. Once the MMM
programs are established, EPA is required to re-evaluate them no less
than every five years.
2.4 Specific Requirements for the Health Risk Reduction and Cost
Analysis
Section 1412(b)(13)(C) of the 1996 Amendments requires EPA to
prepare a Health Risk Reduction and Cost Analysis (HRRCA) to be used to
support the development of the radon NPDWR. SDWA requires the HRRCA be
published for public comment by February 6, 1999, six months before the
rule is to be proposed. In the preamble of the proposed rule, EPA must
include a response to all significant public comments on the HRRCA.
The HRRCA must also satisfy the requirements established in Section
1412(b)(3)(C) of the amended SDWA. According to these requirements, EPA
must analyze each of the following when proposing an NPDWR that
includes a MCL: (1) Quantifiable and non-quantifiable health risk
reduction benefits for which there is a factual basis in the rulemaking
record to conclude that such benefits are likely to
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occur as the result of treatment to comply with each level; (2)
quantifiable and non-quantifiable health risk reduction benefits for
which there is a factual basis in the rulemaking record to conclude
that such benefits are likely to occur from reductions in co-occurring
contaminants that may be attributed solely to compliance with the MCL,
excluding benefits resulting from compliance with other proposed or
promulgated regulations; (3) quantifiable and non-quantifiable costs
for which there is a factual basis in the rulemaking record to conclude
that such costs are likely to occur solely as a result of compliance
with the MCL, including monitoring, treatment, and other costs, and
excluding costs resulting from compliance with other proposed or
promulgated regulations; (4) The incremental costs and benefits
associated with each alternative MCL considered; (5) the effects of the
contaminant on the general population and on groups within the general
population, such as infants, children, pregnant women, the elderly,
individuals with a history of serious illness, or other subpopulations
that are identified as likely to be at greater risk of adverse health
effects due to exposure to contaminants in drinking water than the
general population; (6) any increased health risk that may occur as the
result of compliance, including risks associated with co-occurring
contaminants; and (7) other relevant factors, including the quality and
extent of the information, the uncertainties in the analysis, and
factors with respect to the degree and nature of the risk.
To the extent possible, this HRRCA follows the new cost-benefit
framework being developed by the Office of Ground Water and Drinking
Water (OGWDW) . As provided in the SDWA, as amended, the HRRCA
discusses the costs and benefits associated with a variety of radon
levels. Summary tables and figures are presented that characterize
aggregate costs and benefits, impacts on affected entities, and
tradeoffs between risk reduction and compliance costs. More in-depth
discussions of input data and assumptions will be provided in a
companion ``Analytical Support Document'' and an in-depth presentation
and discussion of the results will appear in a separate ``Cost/Benefit
Document'' that will accompany the proposed rule. The HRRCA by itself
does not constitute the complete Regulatory Impact Analysis (RIA), but
serves as a foundation upon which the RIA can be developed for the
proposed rule.
2.5 Radon Levels Evaluated
The HRRCA is intended to present preliminary estimates of the
potential costs and benefits of various levels of controlling radon in
drinking water. The HRRCA assumes that all systems drawing water from
sources above a defined radon level will employ treatment technologies
to meet the target level or ``regionalize'' to obtain water from
another source with lower radon levels. This analysis evaluates radon
levels of 100, 300, 500, 700, 1,000, 2,000, and 4,000 pCi/l. The
analysis did not include any provisions for exemptions or phased
compliance and assumed that a simple quarterly monitoring scheme would
be used to determine the need for mitigation and ongoing compliance.
The HRRCA also evaluates national costs and benefits of MMM
implementation scenarios, with States choosing to reduce radon exposure
in drinking water through an Alternative Maximum Contaminant Level
(AMCL) and radon risks in indoor air through MMM programs. Based on NAS
recommendations, the AMCL level that is evaluated is 4,000 pCi/l. Under
the scenarios that include an AMCL, the HRRCA assumes that a portion of
the States would adopt an AMCL supplemented with MMM programs to
address indoor air radon risks. In the absence of information
concerning the number of States that would choose to implement radon
risk reduction through the use of AMCL plus multimedia programs, the
HRRCA assumes that either 50 or 100 percent of the systems in the
United States would choose to implement MMM programs and comply with
the AMCL. For the MMM implementation scenarios, a single multimedia
cost estimate is used, based on the cost-effectiveness of current
voluntary mitigation efforts. These issues are discussed in more detail
in Section 7.
2.6 Document Structure
The HRRCA is organized into 7 sections and a number of appendices.
The appendices, while not included in this Federal Register Notice, are
available in the docket for review and can be downloaded from the web
at www.epa.gov/safewater/standard/pp/radonpp/html. Section 3 discusses
the health effects of exposure to radon. Section 4 describes the
assumptions and methods for estimating quantifiable benefits and
assessing non-quantifiable benefits. Section 5 discusses the water
treatment and MMM methods used to calculate the national costs of the
various radon levels examined. Section 6 presents the results of the
cost and benefit analysis of reducing radon levels in drinking water,
and evaluates economic impacts on households. In addition, the major
sources of uncertainty associated with the estimates of costs,
benefits, and economic impacts are identified. Section 7 estimates the
costs and benefits of two different implementation scenarios in which
States and water systems elect to develop and implement a MMM program
and comply with the AMCL. Appendices provide details of the risk
calculations, cost curves for treatment technologies, methods used to
calculate system flows, and detailed breakdown summaries of the cost,
benefit and impact calculations.
3. Health Effects of Radon Exposure
This Section presents an overview of the major issues and
assumptions addressed in order to characterize the health impacts and
potential benefits of reductions in radon exposures. The methods that
have been used to characterize risk and benefits in the HRRCA are also
described. The assumptions and methods presented below are used in
Section 4 to derive detailed estimates of the health reduction benefits
of different radon levels in ground water supplies.
3.1 Radon Occurrence and Exposure Pathways
As part of the regulatory development process, EPA has updated and
refined its analysis of radon occurrence patterns in ground water
supplies in the United States (US EPA 1998L). This new analysis
incorporates information from the EPA 1985 National Inorganic and
Radionuclides Survey (NIRS) of 1000 community ground water systems
throughout the United States, along with supplemental data provided by
the States, water utilities, and academic researchers.
The new study also addressed a number of issues raised by public
comments on the previous occurrence analysis. These include
characterization of regional and temporal variability in radon levels,
variability in radon levels across different-sized water systems,
impact of sampling point, and the proper statistical techniques for
evaluating the data.
3.1.1 Occurrence
Radon is a naturally occurring volatile gas formed from the normal
radioactive decay of uranium. It is colorless, odorless, tasteless,
chemically inert, and radioactive. Uranium is present in small amounts
in most rocks and soil, where it decays to other products including
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radium, then to radon. Some of the radon moves through air or water-
filled pores in the soil to the soil surface and enters the air, while
some remains below the surface and dissolves in ground water (water
that collects and flows under the ground's surface). Due to their very
long half-life (the time required for half of a given amount of a
radionuclide to decay), uranium and radium persist in rock and soil.
Radon itself undergoes radioactive decay and has a radioactive
half-life of about four days. When radon atoms decay they emit
radiation in the form of alpha particles, and transform into decay
products, or progeny, which also decay. Unlike radon gas, these progeny
easily attach to and can be transported by dust and other particles in
air. The decay of progeny continues until stable, non-radioactive
progeny are formed. At each step in the decay process, radiation is
released. The term radon, as commonly used, refers to radon-222 as well
as its radioactive decay products.
In general, radon levels in ground water in the United States have
been found to be the highest in New England and the Appalachian uplands
of the Middle Atlantic and Southeastern States (Figure 3-1). There are
also isolated areas in the Rocky Mountains, California, Texas, and the
upper Midwest where radon levels in ground water tend to be higher than
the United States average. The lowest ground water radon levels tend to
be found in the Mississippi Valley, lower Midwest, and Plains States.
When comparing radon levels in ground water to radon levels in indoor
air at the State level, the distribution of radon concentrations in
indoor air (Figure 3-2) do not always mirror distributions of radon in
ground water.
In addition to large-scale regional variation, radon levels in
ground water also vary significantly over smaller distance scales.
Local differences in geology tend to greatly influence the patterns of
radon levels observed at specific locations (e.g., not all radon levels
in New England are high; not all radon levels in the Gulf Coast region
are low). Over small distances, there is often no consistent
relationship between measured radon levels in ground water and radium
levels in the ground water or in the parent bedrock (Davis and Watson
1989). Similarly, no significant national correlation has been found
between radon levels in individual ground water systems and the levels
of other inorganic contaminants or conventional geochemical parameters.
Potential correlations between radon levels and levels of organic
contaminants in ground water have not been investigated, but there is
little reason to believe any would be found. Radon's volatility is
rather high compared to its solubility in water. Thus, radon
volatilizes rapidly from surface water, and measured radon levels in
surface water supplies are generally insignificant compared to those
found in ground water.
Figure 3-1. General Patterns of Radon Occurrence in Groundwater in
the United States
Figure 3-1 is not printed in the Federal Register. It is available
in the Water Docket at the address listed in the ADDRESSES section.
Figure 3-2. EPA Map of Radon Zones in Indoor Air
Figure 3-2 is not printed in the Federal Register. It is available
in the Water Docket at the address listed in the ADDRESSES section.
Because of its short half life, there are relatively few man-made
sources of radon exposure in ground water. The most common man-made
sources of radon ground water contamination are phosphate or uranium
mining or milling operations and wastes from thorium or radium
processing. Releases from these sources can result in high ground water
exposures, but generally only to very limited populations; for
instance, to persons using a domestic well in a contaminated aquifer as
a source of potable water (US EPA 1994B).
Table 3-1 summarizes the regional patterns of radon in drinking
water supplies as seen in the NIRS database. This survey of 1,000
ground water systems, undertaken by EPA in 1985, provides the most
representative national characterization of radon levels in drinking
water.
However, the NIRS has the disadvantage that the samples were all
taken from within the water distribution systems, making estimation of
the naturally occurring influent radon levels difficult. In addition,
the NIRS data provide no information to allow analysis of the
variability of radon levels over time or within individual systems.
Table 3-1.--Radon Distributions by Region (All System Sizes)
----------------------------------------------------------------------------------------------------------------
Geometric
Arithmetic Geometric Mean standard
Region mean (pCi/l) \1\ (pCi/l) deviation \2\
(pCi/l)
----------------------------------------------------------------------------------------------------------------
Appalachian..................................................... 1,127 333 4.76
California...................................................... 629 333 3.09
Gulf Coast...................................................... 263 125 3.38
Great Lakes..................................................... 278 151 3.01
New England..................................................... 2,933 1,214 3.77
Northwest....................................................... 222 161 2.23
Plains.......................................................... 213 132 2.65
Rocky Mountains................................................. 607 361 2.77
----------------------------------------------------------------------------------------------------------------
\1\ The geometric mean is the anti-log of the average of the logarithms (log base e) of the observations.
\2\ The geometric standard deviation is the anti-log of the standard deviation of the logarithms (log base e) of
the observations.
Source: US EPA 1998L. The values given are not population-weighted, but reflect averages across systems.
The NIRS data illustrate the wide regional variations in radon
levels in ground water. The arithmetic mean and geometric mean radon
levels are substantially higher in New England and the Appalachian
region (in this analysis, all the States on the east coast between New
York and Florida) than in other regions of the United States. The large
differences between the geometric (anti-log of the average of the
logarithms (log base e) of the observations) and arithmetic means
indicate how ``skewed'' (i.e., ``stretched'' in a positive direction; a
bell-shaped curve with a tail out to the right) the radon distributions
are. The Agency selected a lognormal model as the best approach to
evaluating these data.
EPA's current re-evaluation of radon occurrence in ground water
uses data from a number of additional sources to supplement the NIRS
information and to develop estimates of the national
[[Page 9570]]
distribution of radon in ground water systems of different sizes. Data
from 17 States were used to evaluate the differences between radon
levels in ground water and radon levels in distribution systems in the
same regions. The results of these comparisons were used to estimate
national distributions of radon occurrence in ground water. Table 3-2
summarizes EPA's latest characterization of the distributions of radon
levels in ground water supplies of different sizes and populations
exposed to radon through CWSs.
In this table, radon levels and populations are presented for
systems serving various population ranges from 25 to greater than
100,000. For purpose of estimating costs and benefits, the CWSs are
aggregated to be consistent with the following system size categories
identified in the 1996 SDWA, as amended: very very small systems (25-
500 people), further subdivided into 25-100 and 101-500; very small
systems (501-3,300 people); small systems (3,301-10,000 people); medium
systems (10,001-100,000 people); and large systems (greater than
100,000 people).
In the updated occurrence analysis, insufficient data were
available to accurately assess radon levels in the highest CWSs size
stratum. Thus, data from the two largest size strata were pooled to
develop exposure estimates for the risk and benefits assessments.
The Agency estimates that approximately 89.7 million people are
served by community ground water systems in the United States based on
an EPA analysis of SDWIS data in 1998). The data in Table 3-2 show that
systems serving more than 500 people account for approximately 95
percent of the population served by ground water systems, even though
they represent only 40 percent the total active systems (USEPA 1997A).
The estimated system geometric mean radon levels range from
approximately 120 pCi/l for the largest systems to 312 pCi/l for the
smallest systems. Arithmetic mean values for the various size
categories range from 175 pCi/l to 578 pCi/l, and the population-
weighted arithmetic mean radon level across all the community ground
water supplies is 213 pCi/l.
Table 3-2.--Radon Distributions in Public Water Systems
----------------------------------------------------------------------------------------------------------------
System size (population served)
----------------------------------------------------------------
25-100 101-500 501-3,300 3,301- >10,000
-------------------------------------------------------------------------------------------10,000---------------
Total Systems.................................. 14,651 14,896 10,286 2,538 1,536
Geometric Mean Radon Level, pCi/l.............. 312 259 122 124 132
Geometric Standard Deviation................... 3.0 3.3 3.2 2.3 2.3
Population Served (Millions)................... 0.87 4.18 14.2 14.5 65.9
----------------------------------------------------------------------------------------------------------------
Radon Level, pCi/l............................. Proportions of Systems Exceeding Radon Levels (percent)
----------------------------------------------------------------------------------------------------------------
100............................................ 84.7 78.7 56.9 60.4 62.9
300............................................ 51.4 45.1 22.1 14.3 16.2
500............................................ 33.6 29.1 11.4 4.6 5.5
700............................................ 23.4 20.3 6.8 1.8 2.3
1000........................................... 14.7 12.9 3.6 0.6 0.8
2000........................................... 4.7 4.4 0.8 0.0 0.1
4000........................................... 1.1 1.1 0.1 0.0 0.0
----------------------------------------------------------------------------------------------------------------
Table 3-3 presents the total exposed population above each radon
level by system size category. Approximately 20% of the total
population for all system sizes are above the radon level of 300 pCi/l
and 63% are above a radon level of 100 pCi/l.
Table 3-3.--Population Exposed Above Various Radon Levels By System Size
[Thousands]
--------------------------------------------------------------------------------------------------------------------------------------------------------
Very very Very very
Radon level (pCi/l) small small Very small Small Medium Large Total
--------------------------------------------------------------------------------------------------------------------------------------------------------
25-100 101-500 501-3,300 3,301-10K 10K-100K >100K ............
--------------------------------------------------------------------------------------------------------------------------------------------------------
4,000................................................... 9.4 46 20 0.2 0.9 0.4 77.2
2,000................................................... 41 183 119 5.7 21.7 11.0 381
1,000................................................... 128 541 513 85.5 289 147 1,695
700..................................................... 202 848 962 267 859 436 3,558
500..................................................... 290 1,210 1,620 672 2,070 1,050 6,893
300..................................................... 445 1,880 3,140 2,080 6,060 3,070 16,641
100..................................................... 733 3,290 8,080 8,760 23,400 11,900 56,054
--------------------------------------------------------------------------------------------------------------------------------------------------------
Radon exposures also arise from NTNCWSs. The Agency estimates that
approximately 5.2 million people use water from NTNCWSs (US EPA 1998G).
An analysis of SDWIS data in 1998 shows there are approximately 19,500
active NTNCWSs in the United States. Over 96 percent of these systems
serve fewer than 1,000 people. EPA recently identified useful data on
radon levels in NTNCWSs from six States. A preliminary analysis of data
from these States suggested that geometric mean radon levels are
approximately 60 percent higher in NTNCWSs than in CWSs in the same
size category.
There are currently no data which enable the agency to determine
the extent to which the populations exposed to radon from CWSs and
NTNCWSs overlap. Some portion of individuals exposed through a CWS at
home may be exposed to radon from a NTNCWS at school or at work.
[[Page 9571]]
Similarly, the same populations may be exposed to radon from two
different community systems in the course of their normal daily
activities. Further, in the case of NTNCWSs, it is possible that the
same individual could be exposed sequentially throughout their life to
radon from a series of different systems; at school, then at work, etc.
3.1.2 Exposure Pathways
People are exposed to radon in drinking water in three ways: from
ingesting radon dissolved in water; from inhaling radon gas released
from water during household use; and from inhaling radon progeny
derived from radon gas released from water.
Typically, indoor air contamination arising from soil gas accounts
for the bulk of total individual risk due to radon exposure (NAS
1998B). Nationally, levels of radon in household air average
approximately 1.25 pCi/l (US EPA 1992A). Usually, the bulk of the radon
enters indoor air by diffusion from soils through basement walls or
foundation cracks or openings. Radon in domestic water generally
contributes a small proportion of the total radon in indoor air. The
NAS recommends that EPA use the central estimate of a transfer factor
of 1.0 pCi/l for radon in domestic water contributing 1x10-4
pCi/l to indoor air. As an example, for a typical ground water CWS with
a radon level of 250 pCi/l, the increment in indoor air activity would
be 0.025 pCi/l. This is about 2 percent of the average indoor level,
which is derived mostly from soils.
As noted, the bulk of radiation exposure through inhalation comes
from radon progeny, which tend to bind to airborne particulates. When
the particles are inhaled, they become deposited in the respiratory
tract, and further radioactive decay results in a radiation dose to the
respiratory epithelium. In contrast, when radon gas is inhaled, it is
absorbed through the lung, and much of this fraction remains in the
body only a short time before being exhaled.
Direct ingestion of radon gas in water is the other important
exposure pathway associated with domestic water use. If water is not
agitated or heated prior to consumption, the bulk (80 to 100 percent)
of the radon remains in the water and is consequently ingested with it
(US EPA 1995). Heating, agitation (for example, by a faucet aerator),
and prolonged standing cause radon to be released and the proportion
consumed to be reduced. After a person ingests radon in water, the
radon passes from the gastrointestinal tract into the blood. The blood
then circulates the radon to all organs of the body before it is
eventually exhaled from the lungs. When radon and its progeny decay in
the body, the surrounding tissues are irradiated by alpha particles.
However, the dose of radiation resulting from exposure to radon gas by
ingestion varies from organ to organ. Stomach, followed by the tissues
of colon, liver, kidney, red marrow, and lung appear to receive the
greatest doses.
Exposure patterns to radon vary with different exposure settings.
Depending on the relative radon levels in water and air, water use
patterns, and exposure frequency and duration, the relative
contribution of ingestion and inhalation exposure to total risks will
vary. In the case of domestic water use, inhalation of radon progeny
accounts for most of the total individual risk resulting from radon
exposure (Section 3.2). Inhalation exposure to radon from NTNCWSs is
expected to be less than for CWSs, however, because buildings served by
these systems tend to be larger, and ventilation rates higher, than the
corresponding values for domestic exposures. In addition, exposure at
these facilities tend to be less frequent and of shorter duration than
exposure from CWSs. Therefore, overall exposures at NTNCWSs will likely
be lower.
3.2 Nature of Health Impacts
Exposure to radon and its progeny is believed to be associated with
increased risks of several kinds of cancer. When radon or its progeny
are inhaled, lung cancer accounts for most of the total incremental
cancer risk (NAS 1998A). Ingestion of radon in water is suspected of
being associated with increased risk of tumors of several internal
organs, primarily the stomach (NAS 1998B). As discussed previously, NAS
recently estimated the lifetime unit fatal cancer risks associated with
exposure to radon from domestic water use for ingestion and inhalation
pathways. EPA subsequently calculated the unit risk of inhalation of
radon gas to 0.06 percent of the total risk from radon in drinking
water, using radiation dosimetry data and risk coefficients provided by
the NAS (NAS 1998B). The lifetime unit fatal cancer risk is defined as
the lifetime risk associated with exposures to a unit concentration (1
pCi/l) of radon in drinking water. The findings are summarized in Table
3-4.
Table 3-4.--Estimated Radon Unit Lifetime Fatal Cancer Risks in
Community Water Systems
------------------------------------------------------------------------
Cancer unit risk Proportion of
Exposure pathway per pCi/l in total risk
water (percent)
------------------------------------------------------------------------
Inhalation of radon progeny1...... 5.55 x 10-7 89
Ingestion of radon1............... 7.00 x 10-8 11
Inhalation of radon gas2.......... 3.50 x 10-10 0.06
-------------------------------------
Total............................. 6.25 x 10-7 100
------------------------------------------------------------------------
\1\ Source: NAS 1998B.
\2\ Source: Calculated by EPA from radiation dosimetry data and risk
coefficients provided by NAS (NAS 1998B).
These updated risk estimates indicate that inhalation of radon
progeny accounts for most (approximately 89 percent) of the individual
risk associated with domestic water use, with almost all of the
remainder (11 percent) resulting from ingestion of radon gas.
Inhalation of radon progeny is associated primarily with increased risk
of lung cancer, while ingestion exposure is associated primarily with
elevated risk of stomach cancer. Ingestion of radon also results in
slightly increased risk cancer of the colon, liver, and other tissues.
Inhalation of radon gas is estimated to account for approximately 0.06
percent of the total risk from household radon exposures, and the major
target organ is again believed to be the lung. In the following
sections, methods and parameter values developed by the NAS are applied
to the estimation of baseline population risks and the levels of risk
reduction associated with the different radon levels.
Radon, a noble gas, exhibits no other known toxic effects besides
carcinogenesis. The 1998 NAS report indicates that there is no
scientific
[[Page 9572]]
evidence to show that exposure to radon is associated with reproductive
or genetic toxicity. Therefore, the endpoints characterized in the risk
assessment for radon exposure are primarily increased risk of lung and
stomach cancers.
For the purposes of this Health Risk Reduction and Cost Analysis,
EPA is using the best estimates of radon inhalation and ingestion risks
provided by the NAS Report. In order to finalize the Agency's estimate
of lung cancer deaths arising from indoor air exposure, EPA's Office of
Radiation and Indoor Air is currently assessing various factors
integral to the approach for estimating the lung cancer risks of
inhaling radon progeny in indoor air provided in the NAS 1998 report
``The Health Effects of Exposure to Radon-BEIR VI'' (BEIR VI Report).
This assessment will be reviewed by the Agency's SAB and may result in
some adjustment to the estimated unit risk, and its associated
uncertainty, for inhalation of radon progeny used in this HRRCA
3.3 Impacts on Sensitive Subpopulations
Populations that might experience disproportional risk as a result
of radon exposure fall into two general classes: those who might
receive higher exposures per unit radon in water supplies and those who
are more sensitive to the exposures they receive. The former group
includes persons whose domestic water supplies have high radon levels,
and whose physiological characteristics or behaviors (high metabolic
rate, high water consumption, large amounts of time spent indoors)
result in high exposures per unit of exposure concentration. As noted
above, a portion of the population could be exposed to radon from more
than one source. For example, a student or worker might be exposed to
radon from the CWS in the household setting and also from a NTNCWS (or
from the same or different CWS) at school or work.
Different age and gender groups may also experience exposure
dosimetric differences. These differences in radiation dose per unit
exposure have been taken into account in the BEIR VI Report addressing
radon in indoor air (NAS 1998A), the NAS Report addressing radon in
drinking water (NAS 1998B), and the EPA Federal Guidance Report 13 (US
EPA 1998F).
The NAS Report concluded that there is insufficient scientific
information to permit separate cancer risk estimates for subpopulations
such as pregnant women, the elderly, children, and seriously ill
persons. The report did note, however, that according to the NAS risk
model for the cancer risk from ingested radon, which accounts for 11%
of the total lifetime fatal cancer risk from radon in drinking water,
approximately 30% of this fatal lifetime cancer risk is attributed to
exposure between ages 0 to 10.
The NAS did identify smokers as the only group that is more
susceptible to inhalation exposure to radon progeny. Inhalation to
cigarette smoke and radon progeny result in a greater increased risk
than if the two exposures act independently to induce lung cancer.
3.4 Risk Reduction Model for Radon in Drinking Water
Risk and risk reduction were estimated using a Monte Carlo model
that simulated the initial and post-regulatory distributions of radon
activity levels and population cancer risks. Each iteration of the
model selected a size stratum of community water systems. The system
sizes were stratified according to the following populations served:
<100; 101-500;="" 501-3,300;="" 3,301-10,000;="" and=""> 10,000 served. For each
size category, a lognormal distribution of uncontrolled radon levels
had been defined based on the updated occurrence analysis (USEPA
1998L). The model sampled randomly from the radon distribution for the
selected CWS size category to determine if the radon level was above
the selected maximum exposure level. The proportion of iterations
choosing each size stratum were determined by the relative national
populations served by each size stratum of systems. Thus, over a large
number of iterations (generally, benefit calculations were carried out
using 20,000 to 50,000 iterations), the model produced a population-
weighted distribution of radon levels.
In each iteration of the model, the simulated influent radon
activity level was compared to the maximum radon levels under
consideration (100, 300, 500, 700, 1000, 2000, and 4000 pCi/l). When
the simulated influent radon level was less than the target level, the
simulated level was passed directly to the risk calculation equations.
The equations calculated population fatal cancer risks from ingestion
of radon gas, inhalation of radon gas, and inhalation of radon progeny
using standard exposure factors and unit risk values derived by the
NAS.
When the simulated influent radon level in a given iteration
exceeded a target radon level, the model reduced the value by a
proportion equivalent to the performance of selected mitigation
technologies. The degrees of reduction are presented in Table 3-5:
Table 3-5.--Radon Treatment Assumptions to Calculate Residual Fatal
Cancer Risks
------------------------------------------------------------------------
If the radon level is Then the treated level is
------------------------------------------------------------------------
Less than the target level................ None; Influent = Effluent.
Above but less than two times the target Influent = 0.5 x Effluent.
level.
Above two times but less than five times Influent = 0.2 x Effluent.
the target level.
Greater than five times the target level.. Influent = 0.01 Effluent.
------------------------------------------------------------------------
Using this approach implies that a greater level of control is
achieved than if all the systems were simply assumed to reduce
exposures to the maximum exposure level. For example, a system with an
initial uncontrolled concentration of 400 pCi/l would need to employ a
mitigation technology with a 50 percent removal efficiency to comply
with a maximum exposure limit of 300 pCi/l, resulting in a final radon
level of 200 pCi/l. Limited sensitivity analysis suggests that this
approach does not provide very much in the way of extra risk reduction.
The preponderance of population risk reduction is achieved by reducing
radon levels in the relatively few systems that have initial
uncontrolled values far above the maximum exposure limits, not by the
relatively small incremental reductions below the target radon levels.
3.5 Risks From Existing Radon Exposures
In support of the regulatory development process for the revised
radon rule, EPA has updated its risk assessment for radon exposures in
drinking water. Previously, EPA developed estimates of risk from total
population exposure to radon in drinking water in support of the
proposed rule for radon in 1991 (US EPA 1991). In response to comments
from the SAB, EPA updated the risk assessment to include an analysis of
uncertainty in 1993 (US EPA 1993B). The assessment was further revised
to include revisions to risk factors and other variable values. The
latest uncertainty analysis was completed in 1995 (US EPA 1995).
EPA's revised risk analysis in support of this HRRCA takes into
account new data on radon distributions and exposed populations
developed in the updated occurrence analysis, as well as new
information on dose-response relationships developed by the NAS (NAS
1998B). For the HRRCA,
[[Page 9573]]
population risks are estimated using single-value ``nominal'' estimates
of the various exposure factors which determine individual risk, and
Monte Carlo simulation techniques are used to estimate risks associated
with the distributions of radon exposures from the various size
categories of CWSs. The risk equations and parameter values used in the
revised risk assessment are summarized in Appendix A. EPA is currently
conducting a comprehensive uncertainty analysis of radon risks using
two-dimensional Monte Carlo methods to better judge the level of
uncertainty associated with the radon risk estimates.
Table 3-6 summarizes the results of EPA's revised baseline risk
assessment. Because the NAS and EPA-derived dose-response and exposure
parameters factors discussed above were used in the risk assessment,
the proportions of risk associated with the various pathways were the
same as shown in Table 3-4. The total estimated population risks
associated with the current distribution of radon in CWSs was 160 fatal
cancers per year, 142 of which were associated with progeny inhalation.
Approximately 18 fatal cancers per year were associated with ingestion
of radon. These totals are similar to, but somewhat lower than, EPA's
1991 and 1993 baseline risk estimates (US EPA 1994C). In comparison,
there are an estimated 15,400 to 21,800 fatal lung cancers per year due
to inhalation of indoor air contaminated with radon emanating from soil
and bedrock (NAS 1998A).
The risks summarized in Table 3-5 do not include any contribution
from NTNCWSs, Thus, the potential baseline risks and benefits of a
radon rule may be somewhat underestimated. The limited available data
concerning radon levels in NTNCWSs suggest that levels may be
considerably higher (perhaps by 60 percent, on average) than those in
CWSs of similar size (US EPA 1998L). However, it appears that the
average exposure per unit activity in NTNCWSs is likely to be lower
than that for CWSs. Because of the expected lower inhalation exposures,
water ingestion rates, and frequencies and durations of exposure, the
individual fatal cancer risk associated with a NTNCWS is expected to be
lower compared to a CWS with similar radon levels. EPA is currently
conducting additional analyses of NTNCWS exposures from radon in an
attempt to refine the current approximate risk estimates.
Table 3-6.--Annual Fatal Cancer Risks for Exposures to Radon From Community Water Systems
----------------------------------------------------------------------------------------------------------------
Annual unit
risk (fatal Annual
cancers per population Proportion of
Pathway person per risk (fatal total annual
year per pCi/l cancers per risk (percent)
in water)1 year) 2
----------------------------------------------------------------------------------------------------------------
Inhalation of progeny........................................... 7.44 x 10-9 142 89
Ingestion of radon gas.......................................... 9.30 x 10-10 17.8 11
Inhalation of radon gas......................................... 4.7 x 10-12 0.1 0.06
Total..................................................... 8.37 x 10-9 160 100
----------------------------------------------------------------------------------------------------------------
\1\ Derived using NAS lifetime unit fatal cancer risks.
\2\ Estimated through simulation analysis described in Section 3.4; the risk equations and parameter values used
in the simulation analysis are summarized in Appendix A.
3.6 Potential for Risk Reductions Associated With Removal of Co-
Occurring Contaminants
Because radon is a naturally occurring ground water contaminant,
its occurrence patterns are not highly correlated with those of
industrial pollutants. Similarly, the Agency's re-evaluation of radon
occurrence has revealed that the geographic patterns of radon
occurrence are not significantly correlated with naturally occurring
inorganic contaminants that may pose health risks. Thus, it is not
likely that a relationship exists between the need to install radon
treatment technologies and treatments to remove other contaminants.
On the other hand, technologies used to reduce radon levels in
drinking water have the potential to reduce concentrations of other
pollutants as well. All of the aeration technologies discussed remove
volatile organic contaminants, as well as radon, from contaminated
ground water. Similarly, GAC treatment for radon removal effectively
reduces the concentrations of organic (both volatile and nonvolatile)
chemicals and some inorganic contaminants. Aeration also tends to
oxidize dissolved arsenic (a known carcinogen) to a less soluble form
that is more easily removed from water. The frequency with which radon
treatment would also reduce risks from other contaminants, and the
extent of risk reduction that would be achieved, has not been evaluated
quantitatively in the HRRCA.
3.7 Potential for Risk Increases From Other Contaminants Associated
With Radon Removal
As discussed in Section 5.1, the need to install radon treatment
technologies may require some systems that currently do not disinfect
to do so. While case studies (US EPA 1998D) of twenty-nine small to
medium water systems that installed treatment (24 aeration, 5 GAC) to
remove radon from drinking water revealed only two systems that
reported adding disinfection (both aeration) with radon treatment (the
systems either had disinfection already in place or did not add it), in
practice the tendency to add disinfection may be much more significant
than these case studies indicate. EPA also realizes that the addition
of chlorination for disinfection may result in risk-risk tradeoffs,
since, for example, the disinfection technology reduces potential for
infectious disease risk, but at the same time can result in increased
exposures to disinfection by-products (DBPs). This risk-risk trade-off
is addressed by the recently promulgated Disinfectants and Disinfection
By-Products NPDWR (US EPA 1998I). This rule identified MCLs for the
major DBPs, with which all CWSs and NTNCWSs will have to comply. These
MCLs set a risk ceiling from DBPs that water systems adding
disinfection in conjunction with treatment for radon removal could
face. The formation of DBPs is proportional to the concentration of
organic precursor contaminants, which tend to be much lower in ground
water than in surface water.
The NAS Report addressed several important potential risk-risk
tradeoffs associated with reducing radon levels in drinking water,
including the trade-off between risk reduction from radon treatment
that includes post-disinfection with the increased potential for DBP
formation (NAS 1998B). The
[[Page 9574]]
report concluded that, based upon median and average total
trihalomethane (THM) levels from EPA's 1981 Community Water System
Survey, a typical ground water CWS will face an incremental individual
lifetime cancer risk due to chlorination byproducts of
5x10-5. It should be emphasized that this risk is based on
average and median THM occurrence information that does not segregate
systems that disinfect from those that do. Further, the NAS Report
points out that this average DBP risk is smaller than the average
individual lifetime fatal cancer risk associated with baseline radon
exposures from ground water (untreated for radon), which is estimated
at 1.2 x 10-4 using a mean radon concentration of 213 pCi/l.
A more meaningful comparison is to look at the trade-off between
risk reduction from radon treatment in cases where disinfection is
added with the added risks from DBP formation. This trade-off will
affect only a minority of systems since a majority of ground water
systems already have disinfection in place. For the smallest systems
size category, approximately half of all CWSs already have disinfection
in place. The proportions of systems having disinfection in place
increases as the size categories increase, up to >95% for large systems
(Table 5-2). In addition, although EPA is using the conservative
costing assumption that all systems adding aeration or GAC would
disinfect, not all systems adding aeration or GAC would have to add
post-disinfection or, if disinfecting, may use a disinfection
technology that does not forms DBPs. For those ground water systems
adding treatment with disinfection, this trade-off tends to be
favorable since the combined risk reduction from radon removal and
microbial risk reduction outweigh the added risk from DBP formation.
An estimate of the risk reduction due to treatment of radon in
water for various removal percentages and finished water concentrations
is provided in Table 3.7. As noted by the NAS Report, these risk
reductions outweigh the increased risk from DBP exposure for those
systems that chlorinate as a result of adding radon treatment.
Table 3-7.--Radon Risk Reductions Across Various Effluent Levels and Percent Removals
----------------------------------------------------------------------------------------------------------------
Risk reduction Risk reduction Risk reduction Risk reduction
% Removal \1\ @ 50 pCi/L @ 100 pCi/L @ 200 pCi/L @ 300 pCi/L
----------------------------------------------------------------------------------------------------------------
60.............................................. \2\ NA NA 1.9E-04 2.8E-04
80.............................................. NA 2.5E-04 5.0E-04 7.6E-04
90.............................................. 2.8E-04 5.7E-04 1.1E-03 1.7E-03
99.............................................. 3.1E-03 6.2E-03 1.2E-02 1.9E-02
----------------------------------------------------------------------------------------------------------------
\1\ Influent levels used in risk reduction calculations are determined by the relationship, Effluent Level =
Influent Level*(1--%Removal/100).
\2\ NA = Not applicable since associated influent level would be outside the range of realistic values.
Comparing the risk reductions in Table 3.7 to the risks from THMs
at their MCL values (the maximum risk allowable under the DBP rule),
the ratios between risk reduction from radon removal and the
conservative assumption that DBPs are present at their MCL values are
shown in Table 3.8.
Table 3-8.--Radon Risk Reduction from Treatment Compared to DBP Risks
----------------------------------------------------------------------------------------------------------------
Estimated risk ratios (risk reduction from radon removal/risk
from THMs at 0.080 mg/L)
% Removal \1\ ---------------------------------------------------------------
Ratio @ 50 pCi/ Ratio @ 100 Ratio @ 200 Ratio @ 300
L pCi/L pCi/L pCi/L
----------------------------------------------------------------------------------------------------------------
60.............................................. \2\ NA NA 1.6 2.4
80.............................................. NA 2.1 4.2 6.3
90.............................................. 2.4 4.7 9.5 14.2
99.............................................. 26.0 52.0 104.0 155.9
----------------------------------------------------------------------------------------------------------------
Notes: \1\ Influent levels used in risk reduction calculations are determined by the relationship, Effluent
Level = Influent Level*(1--%Removal/100).
\2\ NA = Not applicable since associated influent level would be outside the range of realistic values.
As can be seen in Table 3.8, the risk ratios are favorable for
treatment with disinfection, ignoring microbial risk reduction, even
assuming the worst case scenario that ground water systems have THM
levels at the MCL. There is the possibility that accounting
quantitatively for the increased risk from DBP exposure for systems
adding chlorination in conjunction with treatment for radon may
somewhat decrease the monetized benefits estimates.
3.8 Risk for Ever-Smokers and Never-Smokers
As noted previously, cancer risks from inhalation of radon progeny
are believed to be greater for current and former smokers than for
``never smokers''. The NAS defines a ``never smoker'' as someone who
has smoked less than 100 cigarettes in their lifetime. Therefore,
``ever smokers'' include current and former smokers. EPA and NAS have
developed estimates of unit risk values (estimates of cancer risks per
unit of exposure) for radon progeny for ``ever-smokers'' and ``never-
smokers'' as shown in Table 3-9 (US EPA 1999A). The estimated unit risk
values for inhalation of radon progeny for ever-smokers (and therefore
the individual and population risk) is approximately 5.5 times greater
than that for never smokers.
Because of estimated higher individual risks for smokers, this
group accounts for a large proportion of the overall population risk
associated with radon progeny inhalation. The last two columns of the
table show that, given the current assumptions about smoking prevalence
and the relative impact of radon progeny on ever smokers and never
smokers, about 85 percent of the cancer cases from water exposures to
[[Page 9575]]
progeny will occur in the ever-smoker population.
Table 3-9.--Annual Lung Cancer Death Risk Estimates From Radon Progeny for Ever-Smokers, Never-Smokers, and the
General Population
----------------------------------------------------------------------------------------------------------------
Annual unit
risk (fatal Average annual Annual Proportion of
cancer cases individual population total annual
Smoking status per year per risk per year risk (fatal population
pCi/l in of exposure cancers per risk
water) year)
----------------------------------------------------------------------------------------------------------------
Ever............................................ 1.31X10-8 2.8X10-6 120 85
Never........................................... 2.44X10-9 5.1X10-7 22 15
Combined........................................ 7.44X10-9 1.6X10-6 142 100
----------------------------------------------------------------------------------------------------------------
Source: EPA analyses derived from NAS (1998) estimates.
Note: Ever-smoking prevalence was assumed to be 58 percent in males and 42 percent in females, and these rates
were assumed to be age independent.
4. Benefits of Reduced Radon Exposures
4.1 Nature of Regulatory Benefits
4.1.1 Quantifiable Benefits
The benefits of controlling exposures to radon in drinking water
take the form of avoided cancers resulting from reduced exposures.
Cancer risks (both fatal and non-fatal cancers per year) are calculated
using the risk model described in Section 3 for the baseline case
(current conditions) and each of the radon levels. The health benefits
of controls are estimated as the baseline risks minus the residual
risks associated with each radon level. The more stringent the radon
level, the lower the residual risks, and the higher the benefits.
The primary measures of regulatory benefits that are used in this
analysis are the annual numbers of fatal and non-fatal cancers
prevented by reduced exposures. Due to a lack of knowledge about how to
account for the latency period for radon-induced cancers, it has been
assumed that risk reduction begins to accrue immediately after the
reduction of exposures.
Exposures to radon and its progeny are associated with increases in
lung cancer risks. Ingestion of radon in drinking water is suspected of
being associated primarily with increased risks of tumors of the
stomach, and with lesser risks to the colon, lung, and other organs.
The first column of Table 4-1 summarizes the estimates of the
distribution of cancers by organ system for inhalation and ingestion
exposures given. For purposes of the risk assessment, inhalation of
progeny and radon gas are assumed to be associated exclusively with
lung cancer risk. In the case of radon ingestion, stomach cancer
accounts for the bulk (approximately 87 percent) of the total risk by
this pathway. Cancers of several other organ systems account for far
smaller proportions of the cancer risk from radon ingestion, and are
not included in this analysis.
Table 4-1.--Proportion of Fatal Cancers by Exposure Pathway and Estimated Mortality
----------------------------------------------------------------------------------------------------------------
Proportion of
fatal cancers
by organ and Mortality
Exposure pathway Organ affected exposure (percent) \2\
pathway
(percent) \1\
----------------------------------------------------------------------------------------------------------------
Inhalation of progeny, radon gas........... Lung............................... 89 95
Ingestion of radon gas..................... Stomach............................ 9.5 90
Colon.............................. 0.4 550
Liver.............................. 0.3 95
Lung............................... 0.2 95
General Tissue..................... 0.5 --
----------------------------------------------------------------------------------------------------------------
\1\ Source: US EPA analysis of dosimetry data and organ-specific risk coefficients (NAS 1998).
\2\ Source: US EPA analysis of National Cancer Institute mortality data.
The last column of Table 4-1 provides estimates of the mortality
rate associated with the various types of radon-associated cancers.
These values are used in this analysis to estimate the proportion of
fatal and non-fatal cancers by organ system and exposure pathway. Both
of the cancers that account for the bulk of the risk from radon and
progeny exposures (lung and stomach) have high mortality rates.
4.1.2 Non-Quantifiable Benefits
Reductions in radon exposures might also be associated with non-
quantifiable benefits. EPA has identified several potential non-
quantifiable benefits associated with regulating radon in drinking
water. These include any peace of mind benefits specific to reduction
of radon exposure that may not be adequately captured in the VSL
estimate. In addition, treating radon in drinking water with aeration
oxidizes arsenic into a less soluble form that is easier to remove with
conventional arsenic removal technologies. In terms of reducing radon
exposures in indoor air, it has also been suggested that provision of
information to households on the risks of radon in indoor air and
available options to reduce exposure is a non-quantifiable benefit that
can be attributed to some components of a MMM program. Providing such
information might allow households to make informed choices about the
appropriate level of risk reduction given their specific circumstances
and concerns. These potential benefits are
[[Page 9576]]
difficult to quantify due to the uncertainty surrounding their
estimation. However, they are likely to be somewhat less in magnitude
relative to the monetized benefits estimates.
4.2 Monetization of Benefits
4.2.1 Estimation of Fatal and Non-Fatal Cancer Risk Reduction
The ``direct'' health benefits of the regulation, as discussed
above, are the reduced streams of cancer cases associated with reduced
radon exposures. In this analysis, the data in Table 3-6 were used to
estimate the numbers of fatal cancers of each organ system associated
with inhalation and ingestion pathway from the risk model described in
Section 3.1. (These proportions, by the nature of the risk model that
is used, stay constant for all radon levels.) Subsequently, the total
number of cancers of each organ system was estimated. This is necessary
because the output of the risk model is fatal cancers, and the cost of
illness and willingness to pay for non-fatal cancers are only applied
to individuals who survive the disease. The total number of cancers per
year of exposure, and the number of non-fatal cancers were estimated
from the fatal cancer numbers using the mortality data in Table 4-1.
Thus, for example, a benefit of 100 cases of fatal lung cancer avoided
implies approximately 105 total lung cancers avoided, five of which are
non-fatal. This calculation omits rounding error, and the total number
of cases is equal to the fatal cases divided by the mortality rate.
Fatal and non-fatal population cancer risks under baseline
conditions were estimated first. Then, the residual cancer risks were
estimated for each of the radon levels. Consistent with the assumptions
made in the cost analysis, residual water radon levels were calculated
using a similar range of technology efficiencies. Radon levels were
assumed to be reduced below baseline levels by either 50, 80, or 99
percent, using the least stringent reduction which could comply with
the radon level under evaluation. Benefits took the form of the
reductions in the numbers of fatal and non-fatal cancers associated
with each final level compared to the baseline risks.
4.2.2 Value of Statistical Life for Fatal Cancers Avoided
As one measure of potential benefits, this analysis assigns the
monetary value of a statistical life saved to each fatal cancer
avoided. The estimation of the value of a statistical life involves
inferring individuals' implicit tradeoffs between small changes in
mortality risk and monetary compensation (US EPA 1998E). A central
tendency value of $5.8 million (1997$) is used in the monetary benefits
calculations, with low- and high-end values of $700,000 (1997$) and
$16.3 million (1997$), respectively, used for the purposes of
sensitivity analysis. These figures span the range of value of
statistical life (VSL) estimates from 26 studies reviewed in EPA's
recent guidance on benefits assessment (US EPA 1998E) which is
currently being reviewed by EPA's SAB and the Office of Management and
Budget (OMB). It is important to recognize the limitations of existing
VSL estimates and to consider whether factors such as differences in
the demographic characteristics of the populations and differences in
the nature of the risks being valued have a significant impact on the
value of mortality risk reduction benefits. As noted above, no separate
medical care or lost-time costs are included in the benefits estimate
for fatal cancers because it is assumed that these costs are captured
in the VSL for fatal cancers.
4.2.3 Costs of Illness and Lost Time for Non-Fatal Cancers
Two important elements in the estimation of the economic impacts of
reduced cancer risks for non-fatal cancers are the reductions in
medical care costs and the costs of lost time. The costs of medical
care represent a net loss of resources to society (not considering the
economic hardship on the cancer patient and family). The cost of lost
time represents the value of activities that the individual must
abandon (e.g., productive employment or leisure) as a result of radon-
induced cancer. Together, these two elements are often referred to as
the costs of illness (COI).
Medical care and lost-time costs have been estimated for lung and
stomach cancers, which are the two most common types of tumors
associated with radon exposures, and which account for 99 percent of
the total radon-associated cancers. Table 4-2 summarizes the Agency's
latest medical care and lost-time cost estimates for lung cancer (US
EPA 1998B, 1998C). Medical care costs have been estimated from survey
data for ten years after initial diagnosis. The medical costs in the
first year correspond to the costs of initial treatment, while medical
costs in subsequent years correspond to the average medical costs
associated with monitoring and treatment of recurrences among
individuals who survive to that year. These out-year costs are weighted
by the proportion of patients surviving to the given year.
The lost time due to the radon-induced tumors is assumed to be
concentrated in the first year after diagnosis. This is why the out-
year estimates for the costs of lost time in Table 2-8 are all zero.
The dollar costs of lost time given in the table are derived by
assigning values lost productive (work) and leisure (non-productive)
hours. The costs given in the top row of Table 4-2 correspond to 776
lost productive hours and 1,493 lost leisure hours per patient. The
estimates of lost hours are relatively low for lung cancer primarily
because the average age at diagnosis is advanced (fewer than 34 percent
of lung cancer patients are diagnosed before age 65).
Using a discount rate of seven percent, the estimated discounted
present value in 1997 dollars of combined medical care and lost-time
costs for a cancer survivor is approximately $108,000. The estimated
value varies with different discount rates. Using a discount rate of
three percent, combined costs are $121,600; at ten percent, combined
costs are approximately $100,200.
Table 4-3 summarizes the estimation of medical and lost-time costs
for survivors of stomach cancer. The combined discounted costs for
stomach cancer are similar to those for lung cancer, but slightly
higher. At a seven percent discount rate, combined discounted costs for
stomach cancer are approximately $114,000 (1997$). At three percent,
they are about $126,300 (1997$). Discounted at ten percent, the average
combined cost is $106,400 (1997$).
Table 4-2.--Estimated Medical Care and Lost-Time Costs Per Case for Survivors of Lung Cancer
----------------------------------------------------------------------------------------------------------------
Medical care Cost of lost Cost of lost
costs leisure productive time
Year after diagnosis (undiscounted (undiscounted (undiscounted
1997 dollars) \1\ 1997 dollars) \2\ 1997 dollars) \2\
----------------------------------------------------------------------------------------------------------------
1...................................................... $34,677 $9,886 $14,393
[[Page 9577]]
2...................................................... 9,936 0 0
3...................................................... 9,383 0 0
4...................................................... 8,969 0 0
5...................................................... 8,604 0 0
6...................................................... 8,262 0 0
7...................................................... 7,934 0 0
8...................................................... 7,609 0 0
9...................................................... 7,287 0 0
10..................................................... 6,974 0 0
Discounted Present Value at 7 Percent.................. 85,225 9,390 13,671
Total Discounted Value (1997 dollars).................. 108,287
----------------------------------------------------------------------------------------------------------------
\1\ Medical care cost estimates derived from US EPA 1998B.
\2\ Lost productive and leisure hours estimates from US EPA 1998B; value of productive time estimated at $12.47/
hr, value of leisure hour estimated at $9.64/hour (from US EPA 1998J).
Table 4-3.--Estimated Medical Care and Lost-Time Costs Per Case for Survivors of Stomach Cancer
----------------------------------------------------------------------------------------------------------------
Cost of lost Cost of lost
Medical care costs leisure productive time
Year after diagnosis (Undiscounted 1997 (undiscounted 1997 (undiscounted
dollars) \1\ dollars) \2\ 1997 dollars) \2\
----------------------------------------------------------------------------------------------------------------
1.................................................... $37,507.28 $19,337.84 13,288
2.................................................... 9,328.23 0 0
3.................................................... 8,749.24 0 0
4.................................................... 8,265.39 0 0
5.................................................... 7,829.62 0 0
6.................................................... 7,423.51 0 0
7.................................................... 7,035.81 0 0
8.................................................... 6,663.46 0 0
9.................................................... 6,300.32 0 0
10................................................... 5,946.38 0 0
Discounted Present Value at 7 Percent................ 82,997.35 18,368 12,621
Total Discounted Value (1997 dollars)................ 113,987
----------------------------------------------------------------------------------------------------------------
\1\ Medical care cost estimates derived from US EPA 1998C.
\2\ Lost productive and leisure hours estimates from US EPA 1998C; value of productive time estimated at $12.47/
hr, value of leisure hour estimated at $9.64/hour (from US EPA 1998J).
4.2.4 Willingness to Pay to Avoid Non-Fatal Cancers
As was the case for fatal cancers, willingness to pay (WTP)
measures of the values of avoiding serious non-fatal illness have also
been developed. These WTP measures were developed because the cost of
illness estimates may be seen as understating total willingness to pay
to avoid non-fatal cancers. The main reason that the cost of illness
understates total WTP is the failure to account for many effects of
disease--it ignores pain and suffering, defensive expenditures, lost
leisure time, and any potential altruistic benefits (US EPA 1998E).
Recently, EPA applied one such study to evaluate the benefits of
avoiding non-fatal cancers in the Regulatory Impact Analysis for the
Stage I Disinfection By-Products Rule (US EPA 1998M). That study
estimated a range of WTP to avoid chronic bronchitis ranging from
168,600 to 1,050,000 with a central tendency (mean) estimate of 536,000
(Viscusi et al. 1991). In the benefits assessment, EPA uses the central
tendency measure as a surrogate for the cost of avoiding non-fatal
cancers and an alternative to the cost of illness measures discussed
above. The high and low ends of the range are used in sensitivity
analysis of the monetized benefit estimates.
4.3 Treatment of Monetized Benefits Over Time
The primary measures of regulatory benefits that are used in this
analysis are the annual numbers of expected fatal and non-fatal cancers
prevented by reduced exposures to radon in drinking water. The monetary
valuation of fatal cancer risks used is a result of a benefits transfer
exercise from the risk of immediate accidental death to the risk of
fatal cancer. No adjustments to the benefits calculations have been
made to reflect the time between the reduction in exposure and the
diagnosis and illness or possible death from cancer. Also, no
adjustments have been made for any other factors which might affect the
valuation. Cancer valuations could be adjusted for how they differ from
accidental death valuations with respect to timing (latency) and with
respect to other factors that may affect individuals' willingness-to-
pay for cancer risk reduction, including dread, pain and suffering, the
degree to which the risk is voluntary or involuntary, and the amount by
which life spans are shortened. Such adjustments have been under debate
in the academic literature. In the absence of quantitative evidence on
the relative impact of each factor, EPA has not adjusted the benefits
estimates in this HRRCA to account for the factors discussed here. The
Agency is currently reviewing the various issues raised; at this time
no Agency policy regarding any such adjustments is in place.
[[Page 9578]]
5. Costs of Radon Treatment Measures
This section describes how the costs and economic impacts of
reductions in radon exposures were estimated. The most commonly used
and cost-effective technologies for mitigating radon are described,
along with the degree of radon removal that can be achieved. Costs of
achieving specified radon removal levels for specific flow rates are
discussed, along with the need for pre-and post-treatment technologies.
The methods used to estimate treatment costs for single systems and
aggregate national costs are explained, and the approach for
translating the costs into economic impacts on affected entities is
also described.
5.1 Drinking Water Treatment Technologies and Costs
The two most commonly employed methods for removing radon from
water supplies are aeration and granular activated carbon (GAC)
absorption. These treatment approaches can be technically feasible and
cost-effective over a wide range of removal efficiencies and flow
rates. In addition to the radon treatment technologies themselves,
specific pre-or post-treatment technologies may also be required. When
influent iron and manganese levels are above certain levels, pre-
treatment may be required to remove or sequester these metals and avoid
fouling the radon removal equipment. Also, aeration and GAC absorption
may introduce possible infectious particulates into the treated water.
Thus, disinfection is generally required as a post-treatment when radon
reduction technologies are installed.
When only low removal efficiency is required, and sufficient
capacity is available, simple storage may in some cases be sufficient
to reduce radon levels in water below specified radon levels. Radon
levels rapidly decrease through natural radioactive decay, and if
storage is in contact with air, through volatilization. Therefore,
storage has also been included in the cost analysis.
In some cases, water systems will choose to seek other sources of
water rather than employ expensive treatment technologies. Systems may
choose a number of strategies, such as shutting down sources with high
radon levels and pumping more from sources with low levels, or
converting from ground water to surface water. In the cost analysis,
however, it has been assumed that such options will not be available to
most systems, and they will need to obtain water from other systems.
This option is referred to as ``regionalization'' in the following
discussions.
These general families of technologies, along with the specific
variants used in the cost analysis, are described.
5.1.1 Aeration
Because of radon's volatility, when water containing radon comes
into contact with air, the radon rapidly diffuses into the gas phase.
Several aeration technologies are available. As will be discussed in
more detail below, the specific technology adopted in response to the
rule will depend on the system's influent radon level, size, and the
degree of radon removal that is required. The following common aeration
technologies have been included in this analysis. Other aeration
technologies are available (spray aeration, tray aeration, etc.) that
can potentially be used by water systems to remove radon. These
technologies have not been included in the analysis either because they
have technical characteristics that limit their use in public water
systems, or because their removal efficiencies are lower, and/or their
unit costs are higher than the three aeration technologies included in
the analysis.
Packed Tower Aeration (PTA). During PTA treatment, the water flows
downward by gravity and air is forced upward through a packing material
that is designed to promote intimate air-water contact. The untreated
water is usually distributed on the top of the packing with sprays or
distribution trays and the air is blown up a column by forced or
induced draft. This design results in continuous and thorough contact
of the liquid with , air (US EPA 1998O). In terms of radon removal, PTA
is the most effective aeration technology. Radon removal efficiencies
of up to 99.9 percent are technically feasible and not prohibitively
expensive for most applications. In this analysis, two different PTA
treatments are used to estimate radon removal cost. The costs are
dependant on the degree of reduction required to achieve compliance
with the allowable radon level. The first design is capable of reducing
radon levels by 80 percent; the second and more costly version reduces
radon in drinking water by 99 percent.
Diffused Bubble Aeration (DA). Aeration is accomplished in the
diffused-air type equipment by injecting bubbles of air into the water
by means of submerged diffusers or porous plates. The untreated water
enters the top of the basin and exits from the bottom [having been]
treated, while the fresh air is blown from the bottom and is exhausted
from the top (US EPA 1998O). Diffused bubble aeration can achieve radon
removal efficiencies greater than 90 percent. In this analysis, a DA
system with a removal efficiency of 80 percent is used as the basis for
estimating compliance costs.
Multiple Stage Bubble Aeration (MSBA). MSBA is a variant of DA
developed for small to medium water supply systems (US EPA 1998O). MSBA
units consist of shallow, partitioned trays. Water passes through
multiple stages of bubble aeration of relatively shallow depth. In this
analysis, an MSBA radon removal efficiency of 80 percent is assumed.
All of the aeration technologies discussed above are assumed to be
``central'' treatments in the cost analysis. That is, a single large
installation is used to treat water from a given source, prior to the
water entering the distribution system to serve many users. It is also
technically feasible to apply some of these technologies at the point
of entry (e.g. just before water from the distribution system enters
the household where it is to be used). However, most aeration
technologies are only cost-effective at minimum flows far above that
corresponding to the water usage rate of a typical household, and thus
would not likely be selected as the treatment of choice.
Also, in all of the aeration systems just discussed, the radon
removed from water is released to ambient (outdoor) air. In this
analysis, it has been assumed that the air released from aeration
systems will not itself require treatment, result in appreciable risks
to public health, or result in increased permitting costs for water
systems. For the 1991 proposed rule, EPA conducted analyses on radon
emissions and potential risks associated with radon and its progeny as
they disperse from a water treatment facility (US EPA 1988, 1989). In
summary, these analyses concluded that the annual risk of fatal cancer
from radon and its progeny in off-gas emissions was 2,700 times smaller
(108 cases/0.04 cases) than the annual risk of fatal cancer from radon
and its progeny from tap water after all ground water systems were at
or below the 1991 target level of 300 pCi/L. Using the occurrence
estimates at that time, the off-gas risk was estimated to be 4800 times
smaller (192 cases/0.04 cases) than the radon in tap water risk if no
water mitigation was done (US EPA 1994C). The EPA's SAB reviewed the
Agency's report and concluded that: (1) while the uncertainty analysis
could be upgraded to lend greater scientific credibility, the results
of modeling would not likely change, i.e., the risk posed by release of
radon through treatment would be less
[[Page 9579]]
than that posed by drinking untreated water; and (2) it is likely that
the conservative assumptions adopted by EPA in its air emissions
modeling resulted in overestimates of risk (US EPA 1994C).
5.1.2 Granular Activated Carbon (GAC)
The second major category of radon removal technology is treatment
with granular activated carbon. GAC adsorption removes contaminants
from water by the attraction and accumulation of the contaminant on the
surface of carbon. The magnitude of the available surface area for
adsorption to occur is of primary importance, while other chemical and
electrochemical forces are of secondary significance. Therefore, high
surface area is an important factor in the adsorption process (US EPA
1998O). GAC systems are commonly used in water supply systems to remove
pesticides or other low-volatility organic chemicals that cannot be
removed by aeration. Radon can also be captured by GAC filtration, but
the amounts of carbon and the contact times needed to produce a high
degree of radon removal are generally much greater than those required
to remove common organic contaminants. For most system sizes and design
configurations evaluated in this study, aeration can achieve the same
degree of radon reduction at lower cost than GAC. However, in the cost
analysis for the radon rule, it has been assumed that a small minority
of systems will nonetheless choose GAC technology over aeration
alternatives, due to system-specific needs (e.g., land availability).
Also, POE GAC (see below) may be cost-effective for systems serving
only a few households. Depending on the specific design and operating
characteristics, GAC can remove up to 99.9 percent of influent radon,
but high removal efficiencies require large amounts of carbon and long
contact times.
Two types of GAC systems have been evaluated: Central GAC and Point
of Entry GAC (POE GAC). Central GAC refers to a design configuration in
which the activated carbon treatment takes place at a central treatment
facility, prior to entry into the distribution system. GAC may be
combined with other treatments and may be used to remove contaminants
other than radon in large, centralized facilities. In this analysis,
costs are estimated for central GAC systems with removal rates of 50,
80, and 99 percent. POE GAC generally refers to small- to medium-sized
carbon filtration units placed in the water distribution system just
before use occurs (e.g., before water enters a residence from the
distribution system.) System maintenance involves periodic replacement
of the filter units. As noted previously, POE GAC may be the most cost-
effective treatment for very small systems serving few households.
Costs are estimated for POE GAC with removal rates of 99%.
5.1.3 Storage
Another technology that may be practical when only a relatively
slight reductions in radon levels are needed is the storage of water
for a period of time necessary for radioactive decay and volatilization
to reduce radon to acceptable levels. Depending on the configuration of
the vessel, storage for 24 to 48 hours may be sufficient to reduce
radon levels by 50 percent or more. The mode of removal is a
combination of radon decay and transfer of the radon from the water to
the storage tank headspace, which is refreshed through ventilation (US
EPA, 1998D). It has been assumed that a proportion of the smallest CWSs
(serving 500 people or fewer) with relatively low influent radon levels
and sufficient storage capacity may choose storage as the preferred
radon treatment technology. In estimating costs for the storage option,
it is assumed that the entire capital and O&M costs of the storage
system is attributable to the need to reduce radon levels. In fact, the
majority of CWSs choosing storage are likely to already have at least
some storage capacity available (ten percent of small systems have
atmospheric storage in place (US EPA 1997A)). These systems may be able
to add ventilation and/or other mechanisms to increase air/water
contact with a small capital investment, which supports the conclusion
that the present assumption of no storage in place is a conservative
assumption.
5.1.4 Regionalization
The last technology whose costs are included in the HRRCA is
regionalization. In this analysis, regionalization is defined as the
construction of new mains to the nearest system with water below the
required radon level. This cost is estimated to be $280,000 per system
(1997$). The cost of actually purchasing water is not included in
regionalization costs, for several reasons. In the first case,
regionalization may involve the actual consolidation of water systems,
and thus there may be no charge to the system which is
``regionalized''. In addition, the system which supplies the water to
the regionalized system will still incur the same (or nearly the same)
costs for radon treatment as before regionalization and could be
expected to pass them on to the regionalized system. This assumes that
the water production cost ($/kgal) for the CWS before it regionalizes
is equal to the unit price ($/kgal) it will pay to the water system
from which it purchases water. In reality, this will over-estimate
costs in some cases and under-estimate in others. Including a water
purchase price in the cost estimate for regionalization without
correcting it for the removal of water production costs would lead to
an over-estimate in the costs of regionalization.
5.1.5 Radon Removal Efficiencies
The amount of radon that the various technologies can remove from
water varies according to their specific design and operating
characteristics. At the most costly extreme, both aeration and GAC
technologies can remove 99 percent or more of the radon in water. Less
costly alternative designs remove less radon. In this analysis, one or
more cost estimates have been developed for the technologies discussed
above, corresponding to one or more radon removal levels. Approximate
cost ranges for achieving specified radon reduction efficiencies using
the various technologies are shown in Table 5-1. These costs are
estimated based on flow rates for a single installation, which may
treat water for an entire system or from a single source. For the
aeration and GAC technologies, costs have also been derived for
combined radon removal and post-treatment technologies, as discussed
below. The basis for the derivation of these cost estimates is
described in more detail in Section 5.4.
The procedures used to decide what proportion of CWSs will adopt
the various radon removal technologies is described in more detail in
Section 5.5. In general, however, the large majority of the systems are
assumed to select the least-cost technology required to achieve a
target radon level. Other systems, for reasons of technical
feasibility, may need to choose more costly treatment technologies.
5.1.6 Pre-Treatment to Reduce Iron and Manganese Levels
Pre-treatment technologies may also need to be part of radon
reduction systems. Aeration and GAC technologies can be fouled by high
concentrations of iron and manganese (Fe/Mn). EPA believes that Fe/Mn
concentrations greater than 0.3 mg/l would generally require
pretreatment to protect aeration/GAC systems from fouling. However,
since this level is near to the secondary MCL, it is believed that
essentially all systems with iron and manganese levels
[[Page 9580]]
above 0.3 are likely to already be treating to remove or sequester
these metals. Therefore, costs of adding Fe/Mn treatment to radon
removal systems are not included in the HRRCA. Preliminary EPA
estimates suggest that inclusion of Fe/Mn treatment costs will not
significantly effect overall cost estimates for radon removal. More
detailed analysis will be presented when the proposed NPDWR is
published.
BILLING CODE 6560-50-P
[[Page 9581]]
[GRAPHIC] [TIFF OMITTED] TN26FE99.000
BILLING CODE 6560-50-C
[[Page 9582]]
5.1.7 Post-Treatment--Disinfection
In addition to pre-treatment requirements, the installation of some
radon reduction technology may also require post-treatment, primarily
to reduce microbial contamination. Both aeration and GAC treatment may
introduce potentially infectious particulate contamination, which must
be addressed before the water can enter the distribution system. The
treatment of water for other contaminants may also introduce microbial
contamination. This is one reason why the majority of systems already
use disinfection technologies. As will be discussed in more detail
below, a substantial proportion of ground water systems (ranging from
50 percent in the smallest size category, to about 68 percent of the
largest systems) already disinfect. Costs of disinfection are only
attributed to the radon rule only for that proportion of systems not
already having disinfection systems in place. For systems that do not
already disinfect, chlorination is assumed to be the treatment of
choice. Alternative technologies are available, for example UV
disinfection, but chlorination is widely used in all size classes of
water supply systems, and the chlorination is considered to provide a
reasonable basis for estimating disinfection costs.
5.2 Monitoring Costs
While not strictly speaking a water treatment technology, ground
water monitoring will play an important role in any strategy to reduce
radon exposures. Therefore, monitoring costs have been included as a
cost element in the cost analysis. Although EPA has not yet defined a
monitoring strategy for the proposed NPDWR, it is clear that systems
will, first, have to sample influent water to determine the need for
treatment, and second, continue to monitor after treatment (or after a
decision is made not to mitigate). For the purpose of developing
national cost estimates, it has been assumed that all systems will have
to conduct initial quarterly monitoring of all sources, and continue to
conduct radon monitoring and analysis indefinitely after the rule is
implemented. This is a conservative assumption (likely to overstate
monitoring costs) because in reality a large proportion of systems with
radon levels below the MCL will probably be allowed to monitor less
frequently after the initial monitoring period.
Monitoring costs are simply the unit costs of radon analyses times
the number of samples analyzed. The number of intake sites per system
is estimated from SDWIS data, as discussed in Section 5.7. The cost of
analyzing each sample is estimated to be between $40 and $75, with an
representative cost of $50 per sample used for the national cost
estimate (US EPA 1998K).
5.3 Water Treatment Technologies Currently In Use
EPA has conducted an extensive analysis of water treatment
technologies currently in use by ground water supply systems (Table 5-
2). This table shows the proportions of ground water systems with
specific technologies already in place broken down by system size
(population served). Many ground water systems currently employ
disinfection, aeration, or Fe/Mn removal technologies. This
distribution of pre-existing technologies serves as the baseline
against which water treatment costs are measured. For example, costs of
disinfection are attributed to the radon rule only for the estimated
proportion of systems that would have to install disinfection as a
post-treatment because they do not already disinfect.
Within current EPA cost models, the estimate of the number of sites
(entry points into the distribution system) is ideally broken down into
three parts: estimates of the average national occurrence of the
contaminant in drinking water systems, the intra-system variability of
the contaminant concentration, and the typical number of sites within
system size categories. In prior RIAs, EPA modeled all drinking water
systems requiring treatment as installing centralized treatment, which
assumes that there is one point of treatment within a system. A more
accurate estimate of treatment would be to calculate costs according to
treatment installed at each well site that is predicted to be above the
target radon level within a water system. This intra-system variability
analysis accounts for the fact that, in reality, multi-site water
systems do not necessarily have the same radon level at each site.
However, because the analysis of intra-system variability for radon
occurrence is not yet complete, it is not possible to use this approach
to calculate treatment costs. For future rules, including the proposed
rule for radon, EPA will calculate national cost estimates based on the
number of sites rather than by the system as a whole. These estimates
will more accurately reflect the percentage of the population receiving
drinking water that has been treated in some way and will result in
more accurate national compliance cost estimates.
The cost analysis assumes that any system affected by the rule will
continue to employ pre-existing radon treatment technology and pre-and
post-treatments in their efforts to comply with the rule. Where pre-or
post-treatments are already in place, but radon treatment is currently
not taking place, it is assumed that compliance with the radon rule
will not require any upgrade or change in the pre-or post-treatments.
Therefore, no incremental cost is attributed to pre-or post-treatment
technologies. This may underestimate costs if pre-or post-treatments
need to be changed (e.g., a need for additional chlorination after the
installation of packed tower aeration). The potential magnitude of this
cost underestimation is not known, but is likely to be a very small
fraction of total treatment costs.
Table 5-2.--Estimated Proportions of Ground Water Systems With Water Treatment Technologies Already in Place
(Percent) \1\
----------------------------------------------------------------------------------------------------------------
System size (population served)
Water treatment technologies in -------------------------------------------------------------------------------
place 25-100 101-500 501-1K 1K-3.3K 3.3K-10K 10K-50K 50K-100K 100K-1M
----------------------------------------------------------------------------------------------------------------
Fe/Mn Removal & Aeration & 0.4 0.2 1.2 0.6 2.9 2.2 3.1 2.0
Disinfection...................
Fe/Mn Removal & Aeration........ 0.0 0.1 0.2 0.1 0.4 0.1 0.4 0.1
Fe/Mn Removal & Disinfection.... 2.1 5.1 8.3 3.0 7.8 7.4 9.7 6.8
Fe/Mn Removal................... 1.9 1.5 1.5 1.0 1.1 0.4 1.1 0.2
Aeration & Disinfection Only.... 0.9 3.2 9.8 13.7 20.9 19.7 18.6 19.9
Aeration Only................... 0.8 1.0 1.8 2.9 2.9 1.0 2.1 0.6
Disinfection Only............... 49.6 68.2 65.0 65.0 56.3 66.0 58.3 68.3
[[Page 9583]]
None............................ 44.3 20.7 12.2 13.7 7.7 3.2 6.7 2.1
----------------------------------------------------------------------------------------------------------------
\1\ Source: EPA analysis of data from the Community Water System Survey (CWSS), 1997, and Safe Drinking Water
Information System (SDWIS), 1998.
5.4 Cost of Technologies as a Function of Flow Rates and Radon Removal
Efficiency
EPA has developed a set of cost curves that describe the
relationships between the capital and operating and maintenance costs
of the various treatment technologies, flow rates, and the degree of
radon removal that is required (US EPA 1998A, 1998O). Cost curves were
developed using the most recent available data and standard cost
estimation methodologies. Separate functions for capital and operation
and maintenance (O&M) costs have been developed for each technology and
radon removal rate. For all of the technologies except regionalization,
both the capital and O&M cost curves are functions of flow rates.
Capital costs are estimated as a function of the design flow (DF) of
the technology. The DF for a technology is equal to a technology's
maximum flow capacity, or the largest amount of water that can be
processed per unit time. The DF is typically two to three times greater
than the average amount of water treated by a given system. O&M costs
are functions of the average flow (AF) through the system. Labor,
treatment chemicals and materials, periodic structure maintenance, and
water stewardship expenses are estimated based on daily average flows.
The cost curves developed by OGWDW for the various radon removal
technologies are provided in Appendix B.
5.5 Choice of Treatment Responses
The Agency has developed a set of assumptions regarding the choices
that CWSs will make in deciding how to mitigate water radon levels to
meet specific exposure reduction requirements. These assumptions have
been developed taking into account the expected influent radon levels,
the degree of radon removal needed to reach specified levels, the types
of technologies that would be technically feasible and cost-effective
for systems of a given size, and the distribution of pre-existing
technologies shown in Table 5-2. Generally, it is assumed that a system
will choose the least-cost alternative technology to achieve a given
radon level. For example, to achieve a radon level of 100 pCi/l, all
systems with average influent levels below 100 would not need to
mitigate, systems with influent radon levels between 100 and 200 pCi/l
would need to employ technologies that achieve 50 percent reduction,
systems with influent levels between 200 and 500 pCi/l would employ
technologies capable of 80 percent radon removal, and systems with
influent radon above 500 pCi would employ technologies with removal
efficiencies of 99 percent. In actuality, removal efficiencies would be
more variable; e.g., a removal efficiency of 90 percent, rather than 99
percent, could be employed for radon levels between 500 and 1,000 pCi/
l. However, this cost analysis has been limited to three removal
efficiencies to simplify the analysis. EPA does not believe that this
has introduced any significant bias into the assessment.
Table 5-3 presents the estimated proportions of systems of given
sizes that are expected to choose specified radon reduction
technologies for given degrees of radon removal. Most systems in most
size classes are assumed to choose aeration as the preferred radon
reduction technology with or without disinfection, depending on the
proportion of systems in that size stratum already disinfecting. This
is because some form of aeration is generally the most cost-effective
option for a given degree of radon reduction. For small systems and low
required removal efficiencies, multistage fixed-bed (MSBA) and diffused
bubble aeration (DA) tend to be the most cost-effective. For large
systems and high removal efficiencies, packed tower aeration (PTA) is
the only feasible aeration technology.
Small proportions of the smallest system size categories (less than
5 percent in all cases) are assumed to choose central GAC with or
without disinfection. A few percent of the smallest systems are also
assumed to choose POE GAC. Storage is assumed to be a viable option for
two percent of small systems where radon reduction of 50 percent or
less is required, and regionalization is assumed to be feasible for one
percent of the smallest systems. EPA has assumed in this HRRCA that no
systems would choose spray aeration or alternative source technologies.
It is believed that these technologies would be chosen only rarely, and
their omission has not biased the compliance cost estimates. This issue
will be addressed in more detail in the proposed NPDWR.
Table 5-3.--Decision Matrix for Selection of Treatment Technology Options: Up to 50 Percent Removal
--------------------------------------------------------------------------------------------------------------------------------------------------------
Percent of system size category (population served) choosing treatment technology
Treatment technology option -----------------------------------------------------------------------------------------------
<100 101-500="" 501-1000="" 1001-3.3k="" 3301-10k="" 10-50k="" 50-100k="" 100-1000k="" --------------------------------------------------------------------------------------------------------------------------------------------------------="" pta="" (80)................................................="" 2.6="" 7.8="" 16.8="" 31.9="" 60.8="" 86.9="" 86.3="" 96.4="" pta="" (80)="" +="" disinfection.................................="" 2.4="" 2.2="" 3.2="" 8.1="" 9.2="" 3.2="" 13.7="" 3.6="" msba/sta="" (80)...........................................="" 13.2="" 21.8="" 22.7="" 15.9="" 8.7="" 0.0="" 0.0="" 0.0="" msba/sta="" (80)="" +="" disinfection............................="" 11.8="" 6.2="" 4.3="" 4.1="" 1.3="" 0.0="" 0.0="" 0.0="" da="" (80).................................................="" 31.7="" 43.4="" 42.7="" 31.9="" 17.4="" 9.7="" 0.0="" 0.0="" da="" (80)="" +="" disinfection..................................="" 28.3="" 12.6="" 8.3="" 8.1="" 2.6="" 0.4="" 0.0="" 0.0="" retrofit="" spray..........................................="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" gac="" (50)................................................="" 2.6="" 2.3="" 0.8="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" [[page="" 9584]]="" gac="" (50)="" +="" disinfection.................................="" 2.4="" 0.7="" 0.2="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" poe="" gac="" (99)............................................="" 2.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" storage="" (50)............................................="" 2.0="" 2.0="" 1.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" regionalization="" (99)....................................="" 1.0="" 1.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" alternate="" source="" (99)...................................="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" all="" systems.............................................="" 100="" 100="" 100="" 100="" 100="" 100="" 100="" 100="" pta="" (80)................................................="" 4.2="" 10.9="" 20.2="" 31.9="" 60.8="" 96.5="" 86.3="" 96.4="" pta="" (80)="" +="" disinfection.................................="" 3.8="" 3.1="" 3.8="" 8.1="" 9.2="" 3.5="" 13.7="" 3.6="" msba/sta="" (80)...........................................="" 14.8="" 21.0="" 21.0="" 15.9="" 8.7="" 0.0="" 0.0="" 0.0="" msba/sta="" (80)="" +="" disinfection............................="" 13.2="" 6.0="" 4.0="" 4.1="" 1.3="" 0.0="" 0.0="" 0.0="" da="" (80).................................................="" 29.6="" 42.8="" 42.0="" 31.9="" 17.4="" 0.0="" 0.0="" 0.0="" da="" (80)="" +="" disinfection..................................="" 26.4="" 12.2="" 8.0="" 8.1="" 2.6="" 0.0="" 0.0="" 0.0="" retrofit="" spray..........................................="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" gac="" (80)................................................="" 2.6="" 2.3="" 0.8="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" gac="" (80)="" +="" disinfection.................................="" 2.4="" 0.7="" 0.2="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" poe="" gac="" (99)............................................="" 2.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" regionalization="" (99)....................................="" 1.0="" 1.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" alternate="" source="" (99)...................................="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" all="" systems.............................................="" 100="" 100="" 100="" 100="" 100="" 100="" 100="" 100="" pta="" (99)................................................="" 15.3="" 26.5="" 35.3="" 47.8="" 69.4="" 96.5="" 86.3="" 96.4="" pta="" (99)="" +="" disinfection.................................="" 13.7="" 7.5="" 6.7="" 12.2="" 10.6="" 3.5="" 13.7="" 3.6="" msba/sta="" (99)...........................................="" 34.3="" 49.1="" 48.7="" 31.9="" 17.4="" 0.0="" 0.0="" 0.0="" msba/sta="" (99)="" +="" disinfection............................="" 30.7="" 13.9="" 9.3="" 8.1="" 2.6="" 0.0="" 0.0="" 0.0="" gac="" (99)................................................="" 1.6="" 1.6="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" gac="" (99)="" +="" disinfection.................................="" 1.4="" 0.4="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" poe="" gac="" (99)............................................="" 2.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" regionalization="" (99)....................................="" 1.0="" 1.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" alternate="" source="" (99)...................................="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" 0.0="" totals............................................="" 100="" 100="" 100="" 100="" 100="" 100="" 100="" 100="" --------------------------------------------------------------------------------------------------------------------------------------------------------="" notes:="" 1.="" technology="" abbreviations:="" pta="packed" tower="" aeration,="" msba/sta="multi-stage" bubble="" aeration,="" gac="granular" activated="" carbon,="" poe="" gac="point" of="" entry="" granular="" activated="" carbon.="" numbers="" in="" parentheses="" indicate="" removal="" efficiencies.="" 2.="" capital="" costs="" for="" small="" systems="" include="" land="" costs.="" for="" large="" systems,="" it="" is="" assumed="" that="" additional="" land="" is="" not="" required.="" 3.="" sequestration="" costs="" are="" included="" in="" pta="" and="" msba/sta="" capital="" costs.="" 4.="" additional="" housing="" costs="" are="" included="" in="" pta,="" msba/sta,="" and="" gac="" capital="" costs="" and="" are="" weighted="" under="" the="" assumption="" that="" 50%="" of="" small="" systems="" will="" require="" additional="" housing,="" 100%="" of="" large="" systems="" will="" require="" additional="" housing.="" 5.="" permitting="" costs="" are="" included="" and="" are="" assumed="" to="" be="" 3%="" of="" capital="" costs,="" with="" a="" minimum="" of="" $2500.="" 6.="" pump="" and="" blower="" redundancies="" are="" included="" in="" capital="" costs.="" 5.6="" cost="" estimation="" 5.6.1="" site="" and="" system="" costs="" the="" costs="" of="" reducing="" radon="" in="" ground="" water="" to="" specific="" radon="" levels="" was="" calculated="" using="" the="" cost="" curves="" discussed="" in="" section="" 5.4="" and="" the="" matrix="" of="" treatment="" options="" presented="" in="" section="" 5.5.="" for="" each="" radon="" level="" and="" system="" size="" stratum,="" the="" number="" of="" systems="" required="" to="" reduce="" radon="" levels="" by="" up="" to="" 50="" percent,="" 80="" percent="" and="" 99="" percent="" were="" calculated.="" then,="" the="" cost="" curves="" for="" the="" distributions="" of="" technologies="" dictated="" by="" the="" treatment="" matrix="" were="" applied="" to="" the="" appropriate="" proportions="" of="" the="" systems.="" capital="" and="" o&m="" costs="" were="" then="" calculated="" for="" each="" system,="" based="" on="" typical="" estimated="" design="" and="" average="" flow="" rates.="" these="" flow="" rates="" were="" calculated="" on="" spreadsheets="" using="" equations="" from="" epa's="" safe="" drinking="" water="" suite="" model="" (us="" epa="" 1998n).="" the="" equations="" and="" parameter="" values="" relating="" system="" size="" to="" flow="" rates="" are="" presented="" in="" appendix="" c.="" the="" distributions="" of="" influent="" radon="" levels="" in="" the="" various="" system="" size="" categories="" were="" calculated="" using="" the="" results="" of="" epa's="" updated="" radon="" occurrence="" analysis="" (exceedance="" proportions="" calculated="" from="" data="" in="" us="" epa="" 1998l).="" capital="" and="" o&m="" costs="" were="" estimated="" separately="" for="" each="" ``site''="" (a="" separate="" water="" source,="" usually="" a="" well)="" within="" systems.="" where="" systems="" obtained="" water="" from="" only="" one="" site,="" costs="" are="" calculated="" by="" applying="" the="" entire="" system="" flow="" rate="" to="" the="" appropriate="" cost="" curves.="" where="" systems="" consisted="" of="" more="" than="" one="" site,="" the="" total="" system="" flow="" rate="" was="" divided="" by="" the="" number="" of="" sites,="" capital="" and="" o&m="" costs="" were="" then="" calculated="" for="" the="" resulting="" flow="" rate,="" and="" the="" total="" system="" cost="" was="" obtained="" by="" multiplying="" this="" result="" by="" the="" number="" of="" sites="" in="" the="" system.="" this="" approach="" provides="" conservative="" cost="" estimates,="" because="" it="" assumes="" that="" separate="" treatment="" systems="" would="" be="" built="" at="" each="" site.="" this="" approach="" also="" obscures="" some="" of="" the="" effects="" of="" variability="" in="" system="" sizes="" on="" costs,="" because="" each="" system="" in="" a="" given="" size="" category="" is="" assumed="" to="" have="" the="" same="" flow="" rate.="" table="" 5-4="" summarizes="" the="" numbers="" of="" sites="" per="" system="" for="" the="" various="" size="" categories="" of="" combined="" public="" and="" private="" community="" ground="" water="" systems.="" the="" average="" ranges="" from="" 1.1="" site="" per="" system="" serving="" less="" than="" 100="" people="" to="" almost="" nine="" sites="" per="" system="" serving="" greater="" than="" 100,000="" people.="" the="" distributions="" of="" the="" numbers="" of="" sites="" per="" systems="" are="" very="" skewed,="" with="" ninetieth-percentile="" values="" ranging="" from="" 2="" to="" 20="" sites="" per="" system="" for="" the="" smallest="" and="" largest="" size="" categories,="" respectively.="" a="" large="" proportion="" of="" the="" systems="" serving="" 10,000="" people="" or="" less="" obtain="" water="" from="" only="" one="" site.="" public="" and="" private="" water="" systems="" differ="" with="" regard="" to="" system="" design="" and="" average="" flows.="" for="" [[page="" 9585]]="" this="" reason,="" separate="" cost="" estimates="" have="" been="" developed="" for="" the="" public="" and="" private="" community="" ground="" water="" systems.="" table="" 5-4.--numbers="" of="" sites="" per="" ground="" water="" system="" by="" system="" size="" ------------------------------------------------------------------------="" 90th="" average="" percentile="" system="" size="" (population="" served)="" sites="" per="" sites="" per="" system="" system="" ------------------------------------------------------------------------="" 25-100........................................="" 1.1="" 2="" 101-500.......................................="" 1.2="" 2="" 501-1,000.....................................="" 1.4="" 3="" 1,001-3,300...................................="" 1.7="" 4="" 3,301-10,000..................................="" 2.3="" 4="" 10,001-50,000.................................="" 3.9="" 10="" 50,000-100,000................................="" 8.7="" 20="">100,000...................................... 8.8 20
------------------------------------------------------------------------
Source: EPA analysis of CWSS data, 1998.
In addition to the costs of radon treatment and disinfection,
monitoring costs were also calculated for each system. As noted
previously, the average cost of monitoring was estimated to be $50 per
sample, and it was assumed that each site in a system would need to be
monitored quarterly. Monitoring costs were added as an ongoing cost
stream to the O&M costs.
5.6.2 Aggregated National Costs
The estimated costs of reducing radon levels to meet different
radon levels were estimated by summing the costs for the individual
sites and systems in each size category and influent range. Separate
totals were compiled for capital and O&M costs. Capital costs were
annualized (over 20 years at a seven per cent discount rate) and added
to the annual O&M costs to provide single aggregate estimates of
national costs for each radon level. This approach implicitly assumes
that treatment devices have useful lives that are identical to the
period of financing. In reality, the useful life and period of
financing are not necessarily the same. The aggregate cost estimates
are presented in Section 6. As will be discussed in more detail below,
separate cost estimates were developed for implementation options
involving MMM programs and are presented in Section 7. Summary outputs
of the spreadsheet models used to estimate costs are provided in
Appendix D.
5.6.3 Costs to Community Water Supply Systems
As noted above, costs were estimated separately for public and
private ground water systems. Costs per system were calculated by
dividing total costs for a given size category of public or private
system by the total number of systems needing to mitigate radon. The
results of these assessments are presented in Section 6.
5.6.4 Costs to Consumers/Households
Costs to households have also been calculated for public and
private ground water systems. Costs are calculated by multiplying the
average annual treatment costs per thousand gallons by the estimated
average household consumption (83,000 gal/year). This approach assumes
that all water systems pass incremental costs attributable to the radon
rule on to system's residential customers and that the residential
customers will pay the same proportion of costs as other users. Average
household costs are calculated separately for public and private
community water systems across various system-size categories. Per
household costs are then compared to median household income data (US
EPA 1998H) for the same system-size categories. These impacts are
discussed in Section 6.
5.6.5 Costs of Radon Treatment by Non-Transient Non-Community Systems
Very little data are available that will support the development of
detailed estimates of radon treatment costs for the NTNCWS that could
be affected by a radon NPDWR. EPA is currently conducting a more
detailed evaluation of the characteristics of NTNCWSs that will be
completed in time for the proposed rule.
5.7 Application of Radon Related Costs to Other Rules
The baseline for the radon rule compliance cost estimates presented
in this draft HRRCA consists of the pre-existing treatment technology
distribution shown in Table 5-2. As the radon rule is implemented,
however, other rules may also require additional systems to install new
technologies (e.g., disinfection). Thus, attributing all costs of
increased use of disinfection at systems with high radon levels to the
radon rule would overstate its cost. At the present time, EPA has not
quantified the potential degree to which the costs of the radon rule
may be overstated.
6. Results: Costs and Benefits of Reducing Radon in Drinking Water
This section presents benefit, cost, and impact estimates for the
various radon levels. Section 6.1 provides an overview of the
analytical approach. Sections 6.2 and 6.3 present the monetized benefit
and cost estimates for the various radon levels evaluated. Section 6.3
summarizes the economic impacts on the various affected entities.
Section 6.5 compares the costs and benefits of the radon levels
evaluated. Section 6.6 presents a brief summary of the major
uncertainties in the cost, benefit, and impact estimates.
The presentation of costs and benefits in this Section is based on
analysis of radon levels of 100, 300, 500, 700, 1,000, 2,000, and 4,000
pCi/l in CWSs served by ground water.
6.1 Overview of Analytical Approach
The analysis of benefits quantifies the reduction in health risks/
impacts to the general population and considers the risks to
potentially sensitive subpopulations (qualitatively). The evaluated
health benefits of the rule consist of reduced fatal and non-fatal
cancer risks, and the monetary surrogates for these benefits have been
estimated, as described in Section 4.0. The national cost estimates
developed include the capital and O&M costs to reduce radon, along with
pre- and post-treatment costs where appropriate, as well as monitoring
costs. Record keeping and reporting costs and implementation costs to
States and government entities will be addressed in the RIA prepared
for the proposed rule.
The costs and benefits of a radon NPDWR will result in economic
impacts on affected individuals, corporate entities, and government
entities. In this analysis, the impacts on water systems and households
have been evaluated. These include: (1) the cost to systems of
different sizes and ownership types, and (2) changes in water costs to
households as a proportion of income. Public systems include those
owned by government entities. Private systems consist of investor-owned
entities that provide drinking water as their primary line of business.
Ancillary systems include drinking water systems that are operated
incidentally to another business. The vast majority of ancillary
systems are mobile home parks, but some are schools, hospitals, and
other entities. The economic impacts of the MMM programs on systems or
households have not been calculated, because there is no information at
present as to how these programs would be funded or upon whom the costs
would fall.
6.2 Health Risk Reduction and Monetized Health Benefits
The probabilistic risk model was used to calculate the cancer risk
reduction benefits of the various levels. Risk reduction benefits were
calculated by subtracting the estimated population risk (number of
fatal cancers per year at a particular radon level) from the
[[Page 9586]]
baseline (pre-regulation) population cancer risk due to radon exposure.
Estimates of the number of non-fatal cancers avoided were developed as
described in Section 4.2.1. The results of this analysis are summarized
in Table 6-1. Under the baseline scenario, the estimated number of
fatal cancers per year caused by radon exposures in domestic water
supplies is 160, and the number of non-fatal cancers is 9.2. As radon
levels decrease, residual risks decrease, and the risk reduction
benefits increase. Since very few people are exposed at levels above
2,000 pCi/l, the benefit of controls in this range is relatively small
(fewer than 7 cancers prevented per year). The health risk reduction
benefits then increase rapidly as radon levels decrease because
progressively larger populations are affected as more and more systems
are required to mitigate exposures.
Table 6-1.--Residual Cancer Risk and Risk Reduction From Reducing Radon in Drinking Water
----------------------------------------------------------------------------------------------------------------
Residual fatal Residual non- Risk reduction Risk reduction
cancer risk fatal cancer (fatal cancers (non-fatal
Radon level (pCi/l in water) (cases per risk (cases avoided per cancers avoided
year) per year) year) \1\ per year) \1\
----------------------------------------------------------------------------------------------------------------
(Baseline)................................... 160 9.2 0 0
4,000 \2\.................................... 158 9.1 2.2 0.1
2,000........................................ 153 8.8 6.5 0.4
1,000........................................ 143 8.2 16 0.9
700.......................................... 135 7.8 25 1.4
500.......................................... 124 7.1 36 2.1
300.......................................... 101 5.8 58 3.4
100.......................................... 44.8 2.6 115 6.6
----------------------------------------------------------------------------------------------------------------
\1\ Risk reductions and residual risk estimates are slightly inconsistent due to rounding.
\2\ 4000 pCi/l is equivalent to the AMCL estimated by the NAS based on SDWA provisions of Section 1412(b)(13).
At the lowest level (100 pCi/l) analyzed, the residual cancer risk
(the cancer risk occurring after controls are installed) is
approximately 45 fatal cancers per year. The risk reduction from this
radon level is 115 fatalities per year, a reduction of approximately 72
percent from the baseline of 160 per year. A similar proportional
reduction in non-fatal cancers is seen with decreasing radon levels.
The monetary valuation methods discussed in Section 4 were applied
to these risk reductions, as shown in Table 6-2. The central tendency
benefits estimates are based on a VSL of $5.8 million (1997$) and a WTP
to avoid fatal cancers of $536,00 (1997$). The ranges of benefits
estimated using the upper and lower bound estimates of the VSL and WTP
to avoid non-fatal cancers are also provided in the table.
Table 6-2.--Estimated Monetized Health Benefits From Reducing Radon in
Drinking Water
------------------------------------------------------------------------
Monetized
health Range of
benefits, monetized
central health
Radon Level (pCi/l) tendency benefits
(annualized, (annualized,
$millions, $millions,
1997) \1\ 1997) \2\
------------------------------------------------------------------------
4,000 \3\................................... 13 2-35
2,000....................................... 38 5-106
1,000....................................... 96 12-268
700......................................... 145 18-403
500......................................... 212 26-591
300......................................... 343 43-955
100......................................... 673 84-1875
------------------------------------------------------------------------
\1\ Includes contributions from fatal and non-fatal cancers, estimated
using central tendency estimates of the VSL of $5.8 million (1997$),
and a WTP to avoid non-fatal cancers of $536,000 (1997$).
\2\ Estimates the range of VSL between $0.7 and $16.3 million (1997$),
and a range of WTP to avoid non-fatal cancers between $169,000 (1997$)
and $1.05 million (1997$).
\3\ 4,000 pCi/l is equivalent to the AMCL estimated by the NAS based on
SDWA provisions of Section 1412(b)(13).
Using central tendency estimates for each of the monetary
equivalents, the baseline health costs of fatal and non-fatal cancers
associated with household radon exposures from CWSs are estimated to be
$933 million per year. Central tendency estimates of monetized benefits
range from $13 million per year for a level of 4,000 pCi/l up to $673
million for the most stringent level of 100 pCi/l. When different
values for the VSL are used, the benefits estimates change
significantly. Using a lower bound VSL of $0.7 million, the benefits
estimates are reduced approximately 9-fold compared to the central
tendency estimates. Using an upper bound VSL of 16.3 million increases
the benefits estimates by approximately 3-fold relative to the central
tendency estimate. Variations in the estimated WTP to avoid non-fatal
cancers affect benefit total estimates only slightly (i.e., less than 1
percent), since non-fatal cancers represent a very small proportion of
estimated radon cancer cases.
A more detailed breakout of the risk reduction, monetized benefits
estimates, and the total cost per fatal cancer case avoided for ever-
smokers and never-smokers is provided in Tables 6-3 and 6-4.
Table 6-3.--Risk Reduction and Monetized Benefits Estimates for Ever-Smokers1
----------------------------------------------------------------------------------------------------------------
Radon level, pCi/l
---------------------------------------------------------------------
40003 2000 1000 700 500 300 100
----------------------------------------------------------------------------------------------------------------
Fatal Cancers Avoided Per Year............ 1.7 5.2 13.2 19.9 29.2 47.1 92.5
Non-Fatal Cancers Avoided Per Year........ 0.1 0.3 0.8 1.1 1.7 2.7 5.2
Annual Monetized Health Benefits 10.2 30.6 77.1 115.8 170.0 274.7 539.3
($Millions, 1997)--Central Tendency......
[[Page 9587]]
Annual Incremental Health Benefits 10.2 20.4 46.5 38.7 54.2 104.7 264.6
($Millions/year)--Central Tendency.......
Annual Cost Per Fatal Cancer Avoided 7.0 4.4 3.7 3.7 3.7 4.0 4.3
($Millions, 1997) 2......................
----------------------------------------------------------------------------------------------------------------
\1\ Risk reductions for ever- and never-smokers were estimated using the NAS unit risk estimates summarized in
Table 3-4, an ever-smoking prevalence of 58% males and 42% females, a central VSL estimate of $5.8 million
(1997$), and central WTP estimate to avoid non-fatal cancer of $536,000 (1997$).
\2\ Total cost estimates come from Table 6-5. The cost per fatal cancer case avoided is calculated by dividing
the estimates of fatal cancers avoided per year by the annualized mitigation costs for each population. For
purposes of this analysis, it was assumed that the mitigation costs (for both water and MMM programs) would be
allocated equally to smoking and non-smoking populations.
\3\ 4000 pCi/l is equivalent to the AMCL estimated by the NAS based on the SDWA provisions of Section
1412(b)(13).
Table 6-4.--Risk Reduction and Monetized Benefits Estimates for Never-Smokers
----------------------------------------------------------------------------------------------------------------
Radon Level, pCi/l
----------------------------------------------------------------------------
4000 * 2000 1000 700 500 300 100
----------------------------------------------------------------------------------------------------------------
Fatal Cancers Avoided Per Year..... 0.4 1.3 3.2 4.8 7.0 11.4 22.3
Non-Fatal Cancers Avoided Per Year. 0.03 0.09 0.22 0.33 0.48 0.78 1.54
Annual Monetized Health Benefits 2.4 7.4 18.6 27.9 41.0 66.3 130.2
($Millions, 1997)--Central
Tendency..........................
Annual Incremental Health Benefits 2.4 5 11.2 9.3 13.1 25.3 63.9
($Millions/year)--Central Tendency
Annual Cost Per Fatal Cancer 29.2 18.3 15.3 15.4 15.5 16.4 17.8
Avoided ($Millions, 1997).........
----------------------------------------------------------------------------------------------------------------
*4000 pCi/l is equivalent to the AMCL estimated by the NAS based on SDWA requirements of Section 1412(b)(13).
6.3 Costs of Radon Mitigation
This section describes the incremental costs associated with each
of the radon levels. Discussion of the cost results includes: the total
nationally aggregated cost to all water systems that must comply with
the target radon levels. These include capital and O&M costs; the
average annualized cost per system exceeding the applicable radon
level; the average annualized costs per system and incremental costs
per household, broken out by public and private water system; and costs
and impacts to households under each radon level. All costs are
incremental costs stated in 1997 dollars. Capital costs were annualized
using a seven percent discount rate and a 20-year amortization period.
6.3.1 Aggregate Costs of Water Treatment
The total annual nationally aggregated cost varies significantly by
the specific radon level. Total national cost estimates for CWSs are
presented in Table 6-5. As demonstrated by the exhibit, water
mitigation costs increase substantially from the highest radon level
analyzed ($24 million at 4000 pCi/l) to the lowest level analyzed ($795
million at 100 pCi/l).
Table 6-5.--Estimated Annualized National Costs of Reducing Radon Exposures
[$Million, 1997]
----------------------------------------------------------------------------------------------------------------
Central
tendency Range of Cost per fatal
Radon level (pCi/l) estimate of annualized cancer case
annualized costs (+/-50%) avoided
costs
----------------------------------------------------------------------------------------------------------------
4000*........................................................... 24 12-36 11.3
2000............................................................ 46 23-70 7.1
1000............................................................ 98 49-146 5.9
700............................................................. 148 75-223 6.0
500............................................................. 218 109-327 6.0
300............................................................. 373 187-560 6.4
100............................................................. 795 398-1193 6.9
----------------------------------------------------------------------------------------------------------------
*4000 pCi/l is equivalent to the AMCL estimated by the NAS based on SDWA requirements of Section 1412(b)(13).
The costs borne by water systems are made up of annualized capital,
O&M, and monitoring costs. The contributions of these cost elements are
broken out in Table 6-6. As the radon level increases (i.e., is made
less stringent), the proportion of costs due to monitoring increases
relative to capital and O&M costs.
[[Page 9588]]
Table 6-6.--Capital and O&M Costs of Mitigating Radon in Drinking Water
[$Million, 1997]
----------------------------------------------------------------------------------------------------------------
Annual
Radon levels (pCi/l) Annual capital Annual O&M cost monitoring Total costs
cost costs
----------------------------------------------------------------------------------------------------------------
4000 *........................................ 8.0 5.2 11.4 25
2000.......................................... 19.8 15.3 11.4 46
1000.......................................... 48.9 37.4 11.4 98
700........................................... 77.9 58.5 11.4 148
500........................................... 119 87.7 11.4 218
300........................................... 210 124 11.4 373
100........................................... 460. 324 11.4 795
----------------------------------------------------------------------------------------------------------------
* 4000 pCi/l is equivalent to the AMCL estimated by the NAS based on SDWA requirements of Section 1412(b)(13).
6.4 Incremental Costs and Benefits of Radon Removal
Table 6-7 summarizes the central tendency and the upper and lower
bound estimates of the incremental costs and benefits of radon exposure
reduction. Both the annual incremental costs and benefits increase as
the radon level is incrementally decreased from 2000 pCi/l down to 100
pCi/l. The exhibit also illustrates the wide ranges of potential
incremental costs and benefits due to the uncertainty inherent in the
estimates. Incremental costs and benefits are within 10 percent of each
other at radon levels of 1000, 700, and 500 pCi/l. There is substantial
overlap between the incremental costs and benefits at each radon level.
Table 6-7.--Estimates of the Annual Incremental Costs and Benefits of Reducing Radon in Drinking Water
[$Millions, 1997]
--------------------------------------------------------------------------------------------------------------------------------------------------------
Radon Level, pCi/l
------------------------------------------------------------------------------------------
4000 * 2,000 1,000 700 500 300 100
--------------------------------------------------------------------------------------------------------------------------------------------------------
Annual Incremental Cost...................................... 24 46 52 50 70 156 422
Range of Annual Incremental Costs............................ 12-36 11-34 26-76 26-77 34-104 78-233 211-633
Annual Incremental Monetized Benefits........................ 13 25 58 48 67 130 329
Range of Incremental Monetized Benefits...................... 2-35 3-71 7-162 6-135 8-188 17-364 41-920
Incremental Cost Per Fatal Cancer Case Avoided............... 11.3 5.0 5.2 6.1 6.1 7.0 7.5
--------------------------------------------------------------------------------------------------------------------------------------------------------
* 4000 pCi/l is equivalent to the AMCL estimated by the NAS based on SDWA requirements of Section 1412(b)(13).
6.5 Costs to Community Water Systems
This section examines the regulatory costs that will be incurred by
individual CWSs at the various radon levels analyzed. Systems above the
target radon level will incur monitoring costs and treatment costs.
Systems below the target radon level will incur only monitoring costs.
The number of CWSs exceeding the applicable radon level increases
considerably with each decrease in the radon level analyzed as shown
Table 6-8. The table also shows that the vast majority (90 percent or
more) of affected systems, regardless of radon level, are very, very
small (serving 25-500 people) or very small (serving 501-3,300 people).
Table 6-8.--Number of Community Ground Water Systems Exceeding Various Radon Levels
----------------------------------------------------------------------------------------------------------------
VVSVS
Exposure level (pCi/l) -------------------- VS (501- S (3,301- M (10,000- L Total
(25-100) (101- 3,000) 10,000) 100,000) (>100K)
------------------------------------------500)------------------------------------------------------------------
4000 \1\.................... 364 759 60 5 1 0 1,190
2000........................ 949 1448 205 19 8 0 2,630
1000........................ 2149 2613 668 75 44 2 5,552
700......................... 3090 3459 1,153 151 94 5 7,951
500......................... 4201 4434 1,796 287 177 9 10,904
300......................... 6302 6233 3,059 657 387 19 16,657
100......................... 10,922 10,349 6,077 1,707 995 48 30,098
----------------------------------------------------------------------------------------------------------------
\1\ 4000 pCi/l is equivalent to the AMCL estimated by the NAS based on SDWA requirements of Section 1412(b)(13).
Source: (USEPA 19989L).
For CWSs that have radon in excess of a given level within each
size category, the average cost per system to reach the target level
varies little as the radon levels decrease. This is shown in Table 6-9,
which presents the average annualized cost per public and private CWS
by system size category. This pattern is due in large part to the
limited number of treatment options assumed to be available to systems
that may (in aggregate) be encountering a relatively wide range of
radon levels. In some cases (e.g., for very very small systems), the
average cost per system for a given
[[Page 9589]]
system size increases as the radon level decreases. In other cases, the
average cost per system remains virtually constant as the radon level
decreases. These inconsistent patterns are due to two competing
effects: (1) The average cost will tend to increase because some
systems must select a more costly treatment option; yet (2) the average
cost will also tend to decrease with the inclusion of previously
unaffected systems (those with lower radon levels) that are most likely
to use lower-cost treatments. The cases where average costs decrease
with decreasing radon levels are due to the latter effect.
These results show that changing the radon level affects the number
of CWSs that must treat for radon, but generally does not significantly
alter the cost per system for those systems above the target level.
Moreover, while large systems bear the greatest burden in terms of cost
per system, there are relatively few large systems with radon levels
above the exposure scenarios analyzed. The cost per system for CWSs
with a radon concentration below a target radon level will be the same
because monitoring costs are dependent on system size and not on
concentration. Monitoring costs range from less than $250 for the very
very small systems to almost $2,000 for large systems, again due to the
larger number of sites requiring monitoring.
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6.6 Costs and Impacts to Households
This section reports incremental household costs and impacts
associated with each radon level, assuming that costs incurred by
systems above the target radon levels are passed on to the systems'
customers (i.e., households). Costs per household reflects only
monitoring and treatment costs to CWSs above the target level. In
addition, households served by CWSs falling under the target radon
level also will incur monitoring costs, but no treatment costs. Costs
for these CWSs are relatively low, however, and are not evaluated at
the household level. As with per system costs, the results are
presented separately for public and for private CWSs. This is important
in considering impacts on households not only because the costs per
system are different for public versus private systems, but also
because the smallest private systems tend to serve fewer households
than do the smallest public systems. Therefore, the average household
served by a private system must bear a greater percentage of the CWS's
cost than does the average household served by a public CWS. This is
particularly important where capital costs make up a large portion of
total radon mitigation costs.
The annual cost per household is presented in Table 6-10 for
households served by public and private CWSs. As expected, costs per
household increase as system size decreases. Costs per household is
higher for households served by smaller systems than larger systems for
two reasons. First, smaller systems serve far fewer households than
larger systems and, consequently, each household must bear a greater
percentage share of the CWS's costs. Second, smaller systems tend to
have higher influent radon concentrations that, on a per-capita or per-
household basis, require more expensive treatment methods (e.g., one
that has an 85 percent removal efficiency rather than
[[Page 9590]]
50 percent) to achieve the target radon level.
Another significant finding regarding annual cost per household is
that, like the per-system costs, household costs (which are a function
of per system costs) are relatively constant across different radon
levels within each system size category. For example, there is less
than $1 dollar per year variation in cost per household, regardless of
the radon level being considered for households served by large public
or private systems (between $6 and $7 per year), by medium public or
private systems (between $10 and $11 per year, and by small public or
private systems (between $19 and $20 per year). Similarly, for very
small systems, the costs per household is consistently about $34 per
year for public systems and consistently about $40 per year for private
systems, varying little across radon level. Only for very very small
systems is there a modest variation in household costs. The range for
per household costs for public systems serving 25-500 people is $87 per
year (at 4000 pCi/l) to $135 per year (at 100 pCi/l). The corresponding
range for private systems is $139 to $238 per year. For households
served by the smallest public system (25-100 people), the range of cost
per household ranges from $292 per year at 4000 pCi/l to $398 per year
at 100 pCi/l. For private systems, the range is $364 to $489 per year,
respectively. Costs per household for very very small systems differ
more than do household costs for other system size categories because
very very small systems serve only between 25 and 500 people and,
consequently, serve fewer households. Therefore, even though per system
costs show little difference for any system size category, all system
size categories (other than for very very small systems) spread the
small difference out among many more households such that the
difference is indistinguishable.
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To further evaluate the impacts of these household costs on the
households that must bear them, the costs per household were compared
to median household income data for households in each system-size
category. The result of this calculation indicates a household's likely
share of incremental costs in terms of its household income. The
analysis considers only households served by CWSs with influent radon
levels that are above the target radon level. Households served by CWSs
with lower radon levels may incur incremental costs due to new
monitoring requirements, but these costs are not significant at the
household level.
Results are presented in Table 6-11 for public and private CWSs,
respectively. For all system sizes but one (very very small private
systems), household costs as a percentage of median household income
are less than one percent. Impacts exceed one percent only for
households served by very very small private systems, which are
expected to face impacts of just under 1.1 percent. Similar to the cost
per household results on which they are based, household impacts
exhibit little variability across radon levels.
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6.7 Summary of Costs and Benefits
Table 6-12 summarizes the central tendency estimates of annual
monetized benefits and annualized costs of the various regulatory
alternatives. The central tendency national cost estimates are greater
than the monetized benefits estimates for all radon levels evaluated,
although they are within 10 percent at levels of 1000, 700, 500, and
300 pCi/l. Mitigation costs increase more rapidly than the monetized
benefits as radon levels decrease. However, it is important to
recognize that due to the uncertainty in the costs and benefits
estimates, there is a very broad possible range of potential costs and
benefits that overlap across all of the radon levels evaluated.
Table 6-12.--Estimated National Annual Costs and Benefits of Reducing Radon Exposures--Central Tendency Estimate
[$Millions, 1997]
----------------------------------------------------------------------------------------------------------------
Annual
Radon level (pCi/l) Annualized Cost per fatal monetized
costs cancer avoided benefits
----------------------------------------------------------------------------------------------------------------
4000 \3\........................................................ 25 11.3 13
2000............................................................ 46 7.1 38
1000............................................................ 98 5.9 96
700............................................................. 148 6.0 145
500............................................................. 218 6.0 212
300............................................................. 373 6.4 343
100............................................................. 795 6.9 673
----------------------------------------------------------------------------------------------------------------
Notes: 1. Benefits are calculated for stomach and lung cancer assuming that risk reduction begins immediately.
Estimates assume a $5.8 million value of a statistical life and willingness to pay of $536,000 for non-fatal
cancers.
2. Costs are annualized over twenty years using a discount rate of seven percent.
3. 4000 pCi/l is equivalent to the AMCL estimated by the NAS based on SDWA requirements of Section 1412(b)(13).
The total annualized cost per fatal cancer case avoided is $11.3
million at a radon level of 4,000 pCi/l, drops to around $6.0 million
for radon levels in the range of 1,000 to 500 pCi/l, and increase again
back to $6.9 million per life saved at the lowest level of 100 pCi/l.
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6.8 Sensitivities and Uncertainties
6.8.1 Uncertainties in Risk Reduction and Health Benefits Calculations
The estimates of risk and risk reduction are derived based on
models which incorporate a number of parameters whose values are both
uncertain and highly variable. Thus, the estimates of health risks and
risk reduction are uncertain. In addition, to the extent that age-
specific smoking prevalence rates change, the risk from radon in
drinking water will change.
The cost of fatal cancers tend to dominate the monetized benefits
estimates. Approximately 94 percent of the cancers associated with
radon exposure and prevented by exposure reduction are fatal cancers of
the lung and stomach. In addition, the estimated value of statistical
life ($0.7 to 16.3 million dollars, with a central tendency estimate of
$5.8 million, 1997$) is much greater than the estimated willingness-to-
pay to avoid non-fatal cancers ($169,000 to $1.05 million, with a
central tendency estimate of $536,000, 1997$). If the COI measures are
used, non-fatal cancers account for an even smaller proportion of the
total monetized costs of cancers, since the medical care and lost-times
costs for lung and stomach cancer are on the order of $108,000 and
$114,000, respectively (1997$).
Unless the VSL is assumed to be near the lower end of its range,
the assumptions made regarding the monetary value of non-fatal cancers
are not a major source of uncertainty in the estimates of total
monetary benefits. For most reasonable combinations of values, the VSL
is the major contributor to the overall uncertainty in monetized values
of health benefits. As shown in Table
6-2, the upper and lower estimates of the monetary benefits for a given
radon level vary by a factor of approximately 23, corresponding to the
ratios of the lower- and upper-bound estimates of the VSL.
6.8.2 Uncertainty in Cost and Impact Calculations
The results of the cost and impact analysis are subject to a
variety of qualifications. As discussed in Section 5, the analysis is
subject to a variety of uncertainties in the models and assumptions
made in developing cost estimates. One important assumption is that for
all CWSs for which the estimated average radon level exceeds a given
level, treatment will be necessary at all sites. This is a very
important assumption, because if systems in reality have only a portion
of sites above the target level, then mitigation costs could be much
lower. EPA is currently evaluating intra-system variability in radon
levels, and will address this issue in more detail in the proposal.
In addition, CWSs are assumed to select from only a relatively
small number of treatment methods, and to do so in known, constant,
proportions. In actuality, systems could select technologies that best
fit their needs and optimize operating conditions to reduce costs. The
analysis also relies on various cost-related input data that are both
uncertain and variable. Some of these variables are entered as
constants, others as deterministic functions. For example: treatment
technology cost functions are based on EPA cost curves derived for
generic systems; households are assumed to use a uniform quantity of
83,000 gallons/year of drinking water, regardless of geographical
location, system size, or other factors; MMM program costs are assumed
to cost $700,000 per fatal cancer case avoided, regardless of the
specific types or efficiencies of activities undertaken by the
mitigation programs. One factor that may contribute significantly to
the overall uncertainty in cost estimates is the set of the nonlinear
equations (Appendix C) used to convert population served data to
estimates of average and design flow rates for ground water systems.
Relatively small errors in the specification of this model could result
in disproportionately large impacts on the cost estimates. Similarly,
the cost curves for some of the technologies are highly nonlinear
function of flow, adding another level of uncertainty to the cost
estimates.
Because of the complexity of the various cost models, EPA has not
conducted a detailed analysis of the uncertainty associated with the
various models and parameter values. Limited uncertainty analyses have
been performed, however, to estimate the impact of a few major
assumptions and models on the overall estimates of mitigation costs.
First, EPA has analyzed the impacts of errors of plus or minus 50
percent in the cost curves for the various radon treatment
technologies. The results of this analysis are shown in Figure 6-1.
Since water mitigation costs make up the bulk of the total costs of
meeting radon levels in the absence of MMM programs, the effect of
these changes is generally to increase or decrease the costs of
achieving the various levels by slightly less than 50 percent. It can
be seen from these results that the assumptions regarding costs can
affect the relationship between costs and monetized benefits. A
relatively small systematic change in water mitigation costs could
result in benefit estimates that either exceed, or are less than, a
wide range of radon levels.
In addition to assuming across-the board changes in radon
mitigation costs, EPA also examined the extreme situation in which none
of the water systems would adopt GAC treatment. Since the GAC
technologies are the most expensive treatments evaluated, the costs of
meeting the various radon levels are reduced if GAC is eliminated and
systems are assumed to employ aeration instead (Figure 6-1). Since,
however, so few systems are assumed to elect GAC in the first place
(five percent or less of the smallest systems) the cost decrease of
eliminating GAC is quite small.
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7. Implementation Scenarios--Multimedia Mitigation Programs Option
This Section presents a preliminary analysis of the likely costs
and benefits under two different implementation scenarios in which
States choose to develop and implement multimedia mitigation (MMM)
programs to comply with the radon NPDWR.
7.1 Multimedia Mitigation Programs
The SDWA, as amended, provides for development of an Alternative
Maximum Contaminant Level (AMCL), which public water systems may comply
with if their State has an EPA approved MMM program to reduce radon in
indoor air. The idea behind the AMCL and MMM option is to reduce radon
health risks by addressing the larger source of exposure (air levels in
homes) compared to drinking water. If a State chooses to employ a MMM
program to reduce radon risk, it would implement a State program to
reduce indoor air levels and require public water systems to control
water radon levels to the AMCL, which is anticipated to be set at 4000
pCi/l based on NAS's re-evaluation of the radon water to air transfer
factor. If a State does not choose a MMM program option, a public water
system may propose a MMM program for EPA approval.
The Agency is currently developing guidelines for MMM programs,
which will be published for public comment along with the proposed
NPDWR for radon in August 1999. For the purpose of this analysis, the
MMM implementation scenarios are assumed to generate the same degree of
risk reduction as achieved by mitigating water alone. For example, a
MMM scenario which includes the AMCL of 4,000 pCi/l and a target water
level of 100 pCi/l is assumed to generate the same degree of risk
reduction as the 100 pCi/l level alone. Thus, the HRRCA estimates the
health risk reduction benefits of MMM implementation options to be the
same as the benefit that would be achieved reducing radon in drinking
water supplies alone.
7.2 Implementation Scenarios Evaluated
EPA has evaluated the annual costs and benefits of two MMM
implementation assuming (1) all States (and all water systems) would
adopt MMM programs and comply with the AMCL, and (2) half of the States
(and half of the water systems) adopt the MMM/AMCL option. These
scenarios were analyzed in the absence of specific data on States'
intentions to develop MMM programs. The two scenarios, along with the
case where the MMM option is not selected by any States or water
systems (presented in Section 6), span the range of participation in
MMM programs that might occur when a radon NPDWR is implemented. At
this point, however, it is not possible to estimate the actual degree
of State participation. The economic impacts of the MMM programs at the
system or household level have not been calculated, because there is no
information at present as to how these programs would be funded or upon
who the costs would fall.
The presentation of costs and benefits is based on analysis of
radon levels of 100, 300, 500, 700, 1,000, 2,000, and 4,000 pCi/l in
public domestic water supplies, supplemented by States (50 or 100
percent participation) implementing MMM programs and complying with an
AMCL of 4,000 pCi/l.
For the scenario evaluated in which one-half of the States
(estimated to include 50 percent of all CWSs) were assumed to implement
a MMM program and comply with an AMCL of 4000 pCi/l option, while the
other half mitigated
[[Page 9596]]
radon in water to the target radon levels without MMM programs. In the
other scenario, all of the States (and 100 percent of the CWSs) were
assumed to adopt MMM programs and comply with the AMCL.
7.3 Multimedia Mitigation Cost and Benefit Assumptions
For the HRRCA, a simplified approach to estimating the costs of
mitigating indoor air radon risks was used. Based on analyses conducted
by EPA (US EPA 1992B, 1994C) a point estimate of the average cost per
life saved of the current national voluntary radon mitigation program
was used as the basis for the cost estimate of risk reduction for the
MMM option. In the previous analysis, the Agency estimated that the
average cost per fatal lung cancer avoided from testing all existing
homes in the United States and mitigating all those homes at or above
EPA's voluntary action level of 4 pCi/l is approximately $700,000 (US
EPA 1992B). This value was originally estimated by EPA in 1991. The
same nominal value is used in the HRRCA based on to anecdotal evidence
from EPA's Office of Radiation and Indoor Air that there has been an
equivalent offset between a decrease in testing and mitigation costs
since 1992 and the expected increase due to inflation in the years
1992-1997. This dollar amount reflects that real testing and mitigation
costs have decreased, while nominal costs have remained relatively
constant. The estimated cost per fatal cancer case avoided by building
new homes radon-resistant is far lower (Marcinowski 1993). For the
purposes of this analysis, only the cost per fatal cancer case avoided
from mitigation of existing homes is used.
To estimate the national cost of the MMM program's air mitigation
component, MMM costs were estimated by multiplying the cost per fatal
cancer case avoided by the number of fatal cases avoided in going from
a water radon level equal to the AMCL (4,000 pCi/l) to a water level
equal to various radon levels analyzed in the HRRCA. The number of
fatal cancer cases avoided was estimated using the risk reduction model
described in Section 3.
7.4 Annual Costs and Benefits of Multimedia Mitigation Program
Implementation
The total annual cost of the radon levels analyzed varies
significantly depending on assumptions regarding the number of States
implementing MMM programs. This variation can be seen in Tables 7-1 and
7-2. Under an assumption that 50 percent of States choose to implement
MMM programs, the cost of the rule varies from about $38 million per
year to achieve a radon level in water of 2,000 pCi/l to about $450
million per year to achieve an level of 100 pCi/l. Assuming that 100
percent of States implement MMM programs, the cost of the rule varies
from about $29 million per year to achieve an radon level of 2,000 pCi/
l to about $106 million per year to achieve an level of 100 pCi/l.
The monetized benefits of both MMM implementation scenarios exceed
the estimated mitigation costs across all radon levels. When the 50
percent MMM participation scenario is evaluated, the mitigation costs
at 2,000 pCi/l are just less than the estimated benefits ($38 million
versus $39.6 million, respectively). In the case of 100 percent
multimedia participation, mitigation costs begin at about 65 percent of
the benefits at a radon level of 2,000 pCi/l, and decrease rapidly so
that at 100 pCi/l the monetized benefits of radon reduction exceed the
mitigation costs by almost 7-fold.
Assuming 50 percent MMM participation, the total cost per fatal
cancer case avoided is $5.8 million at a radon level of 2,000 pCi/l,
dropping to around $3.7 million at a level of 500 pCi/l, and increasing
slightly to about $3.9 at 100, pCi/l (Table 7-1). As expected, the cost
per fatal cancer case avoided is lowest for the 100 percent MMM
participation option, ranging from from $4.5 at a radon level of 2,000
pCi/l to about $900,000 at a level of 100 pCi/l.
For the 50 percent MMM participation, the incremental cost per
fatal cancer case avoided decreases from 2000 pCi/l to 500 pCi/l ($8.7
million to $3.4 million, respectively), then increases to $4.1 million
at 100 pCi/l. In the case of the 100 percent MMM participation, the
incremental cost per life saved starts at about $4.3 million for the
maximum target levels of 2,000 pCi/l, and then drops sharply to about
700,000 per life saved for the other radon.
Table 7-1.--Central Tendency Estimates of Annualized Costs and Benefits of Reducing Radon Exposures With 50% of
States Selecting the MMM/AMCL Option
[$million, 1997]
----------------------------------------------------------------------------------------------------------------
Water mitigation component Multimedia mitigation component
-----------------------------------------------------------------------------------
Cost per Cost per
Radon level (pCi/l) Fatal fatal Fatal fatal
Annual Annual cancer cancer Annual Annual cancer cancer
costs benefits cases case costs benefits cases case
\2\ avoided avoided avoided avoided
----------------------------------------------------------------------------------------------------------------
Baseline.................... 0 0 0 ........ 0 0 0 0
4000........................ 25 13 2.2 11.3 0 0 0 0
2000........................ 35 25 4.3 8.2 2.3 13 2.2 1.1
1000........................ 61 54 9.0 6.6 5.8 42 7.1 0.81
700......................... 86 78 13 6.4 8.6 66 11 0.77
500......................... 121 112 19 6.3 12.7 99 17 0.74
300......................... 199 177 30 6.6 20 164 28 0.73
100......................... 410 341 58 7.0 40 328 56 0.71
----------------------------------------------------------------------------------------------------------------
\1\ Equivalent to the cost of complying with an AMCL of 4000 pCi/l.
[[Page 9597]]
Table 7-2.--Central Tendency Estimates of Annualized Costs and Benefits of Reducing Radon Exposures With 100% of States Selecting the MMM/AMCL Option
[$million, 1997]
--------------------------------------------------------------------------------------------------------------------------------------------------------
Water mitigation component Multimedia mitigation component
-------------------------------------------------------------------------------------
Cost per
Radon level (pCi/l) Fatal fatal Fatal Cost per
Annual Annual cancer cancer Annual Annual cancer fatal
costs\1\ benefits cases case costs benefits cases cancer case
avoided avoided avoided avoided
--------------------------------------------------------------------------------------------------------------------------------------------------------
Baseline.......................................................... 0 0 0.0 ........ 0.0 0.0 0.0 0.0
4000.............................................................. 25 13 2.2 11.3 0.0 0.0 0.0 0.0
2000.............................................................. 25 13 2.2 11.3 4.6 25 4.4 1.1
1000.............................................................. 25 13 2.2 11.3 12 83 14 0.81
700............................................................... 25 13 2.2 11.3 17 131 23 0.77
500............................................................... 25 13 2.2 11.3 25 198 34 0.74
300........................................................... 25 13 2.2 11.3 41 328 56 0.73
100............................................................... 25 13 2.2 11.3 80 654 112 0.71
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Equivalent to the cost of complying with an AMCL of 4000 pCi/l.
7.6 Sensitivities and Uncertainties
EPA conducted a sensitivity analysis associated with potential
uncertainty in the cost-effectiveness of MMM programs. Since the value
used is a point estimate ($700,000 per life saved), and since the
ability to employ MMM programs results in substantial decreases in
estimated costs, it might be expected that changes in the cost-
effectiveness value would affect the cost estimates for these options
substantially. Figure 7-1 summarizes the impact of different estimates
of the cost of MMM programs on the total cost of radon mitigation.
Costs are graphed for the 50 percent and 100 percent participation
options for radon level. Costs were estimated for a high-end case
(assuming a MMM cost 50 percent above the central tendency value), a
low-end case (50 percent below the central tendency), and for a central
tendency case that assumes the current $700,000 per life saved as the
MMM cost.
The relative impacts of changing MMM costs on the total costs of
reducing radon exposure can also be seen in Figure 7-1. The figure
illustrates that the central tendency estimate of monetized benefits is
e well above the estimated costs for all ranges except for the high-end
estimate of the 50 percent MMM participation scenario. This is due to
the greater impact of water mitigation costs relative to the MMM cost
component to total costs compared to the 100 MMM scenario, where the
MMM component contributes the largest share to total costs.
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[FR Doc. 99-4416 Filed 2-25-99; 3:08 pm]
BILLING CODE 6560-50-P
