Multl-Media Risk Assessment for Radon Review of Uncertainty Analysis of Risks Associated With Exposure to Radon

Unfed State* Sciunc* Advitoiy EPA*SAB«A€
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
July 9, 1993
OFFICE OF THE ADMINISTRATOR
SCIENCE ADVISORY BOARD
EPA-SAB-RAC-93-014
Honorable Carol M. Browner
Administrator
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, DC 20460

Rt: Review of Uncertainty Analysis of Risks Associated with Exposure to
Radon--"Chafee-Lautenberg Multi-media Risk Study"

Dear Ms. Browner:

The Science Advisory Board (SAB) is working with the Agency to reply to the
so-called "Chafee-lautenberg amendment" which is a part of the Agency's FY93
appropriation act. The Act calls for Agency generation and SAB review of a Study
that addresses: (a) a multi-media risk assessment of radon gas; and (b) an
assessment of the costs of mitigating those risks. As described in our recent
commentary (EPA-SAB-EC-CQM-93-OQ3), the attached report is the first of three SAB
reports that you will receive in connection with the Chafee-Lautenberg Study. This
report addresses the risks posed by radon gas in various media (e.g., basements of
homes and drinking-water), with a focus on the Agency's quantitative uncertainty
analysis associated with these risk estimates.

Specifically, this report is based upon the Radiation Advisory Committee's
review of the EPA risk assessment study, Uncertainty Analysis of Risks Associated
with Exposure the Ration in Drinking Water (January 29, 1993), related documents
and public comment. The review was conducted at a public meeting February 17-19,
1993.

The Committee commends the EPA staff for having produced an excellent
document that responds to previous SAB comments on uncertainty analysis and the
exposure to radon gas at the point of use (e.g., showering). This response is ail the
more impressive given the constraint of tight deadlines imposed upon it by
Congressional and Court mandates. Its quantitative analysis of uncertainties in the
radon risk assessment represents a methodology that is essentially state-of-the-art
and significantly enhances the scientific credibility of the EPA's decision-making basis.
The Committee assumes that this reflects the EPA's recently stated commitment to a
more rigorous approach to evaluating uncertainties in its risk analyses of radiological
and other hazardous exposures in the future. However, the Committee continues to
have concerns about the exposures and risks that could be associated with certain
treatment options (e.g., granular activated carbon), once those options are selected,

Based on the current analysts, the risks associated with radon gas in homes
from underground sources is considerably greater than the risks associated with the
risks posed by radon gas in the drinking water supply. That smaller risk from radon
gas in drinking water is composed of nearly equal contributions of the inhalation and
ingestion pathways. The Committee notes, however, that the quantitative uncertainty
analysis for the drinking water case does not cover some of the more important
uncertainties. In particular, the Committee believes that the overall uncertainty
regarding the ingestion risk estimate is substantially greater than would be inferred
from the quantitative confidence interval.

Overall, the Committee finds that the EPA has adequately addressed most of
the issues raised by the Committee in its earlier reports, either by incorporating the
Committee's previously recommended changes into the new documents or by
providing additional background documentation supporting the EPA's position. In the
accompanying report the Committee makes a number of specific scientific comments
and recommendations for additional improvements to the document These deal with
important issues such as uncertainties associated with an unpublished study on xenon
that contributes significantly to the estimated internal doses from ingested radon-
containing drinking water, the influence of smoking on lung cancer risks from radon,
and, again, unsettled question of treatment technologies. These issues can generally
be addressed by including clarifying statements. Further, the changes in most cases
would not substantially change the document's estimates of central values for risks.

Policy Considerations

The comments below, to some extent, reach beyond the strictly technical issues
examined by the Committee. However, the Committee feels thai it was important that
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the Agency have the benefits of these thoughts, also, as the decision making process
continues.

The Radiation Advisory Committee has long encouraged the use of integrated
quantitative uncertainty analysis in a variety of EPA assessments. As noted above,
the Committee is extremely pleased to see that the EPA has done such an analysis in
this case. The Committee applauds EPA for its timely incorporation of a full
quantitative uncertainty analysis for each pathway in its assessment and hopes that
the use of quantitative uncertainty analysis will become a routine part of all EPA
assessments, not only those associated with radiation risks. This information should
be a valuable aid in guiding EPA in its consideration of possible regulatory strategies.

The Committee agrees with the Agency's Feb. 26, 1992 "risk characterization
memo" that articulates the EPA policy of explicitly disclosing uncertainty in quantitative
risk assessment. Screening risk assessments involve only point estimate calculations,
and assumptions used to derive these estimates are generally biased on the
conservative side and can be misleading in terms of indicating the need for regulatory
action. In contrast, regulatory action must be based on realistic estimates of risk and
these require a full disclosure of uncertainty. The disclosure of uncertainty enables
the scientific reviewer, as well as the decisionmaker, to evaluate the degree of
confidence that one should have in the risk assessment.

In its January 29, 1992, Commentary: Reducing Risks from Radon; Drinking
Water Criteria Documents (EPA-SAB-RAC-COM-92-003), the Committee noted that
the radon risk reduction situation reflects the fragmentation of environmental policy
identified in Reducing Risk (EPA-SAB-EC-90-Q21). Therefore, the Committee
suggested that the EPA focus its efforts on primary sources (e.g., radon in some
home basements), rather than on secondary sources of risk, such as radon in drinking
water, which is a very small contributor to radon risk, except in rare cases.

In summary, within the limitations of the data currently available, the EPA has
now successfully prepared a scientifically credible multi-media risk assessment for
regulatory decision-making on radon. The Committee's agreement with the principle
of radiation protection optimization and in the concepts articulated in Reducing Risk
lead it to note once again that radon in drinking water represents only a small fraction
of radon exposure and risk compared to radon in indoor air from non-water sources.
We acknowledge, however, that the relative emphasis given to various radon
exposure reduction methods—whether for radon from water or non-water sources—is a
policy choice for which scientific analysis is only one of many important inputs.

The Radiation Advisory Committee appreciates the opportunity to comment on
the EPA's uncertainty analysis of risks associated with exposure to radon. We look
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forward to receiving the EPA's response to the this report, particularly as it relates to
our explicit recommendations.

Sincerely,
)r. Raymond C, Loej
Chair, Executive Committee
Science Advisory Board
Dr. Genevieve4l Matanoski
Chair, Radiation Advisory Committee
Science Advisory Board
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NOTICE

This report has been written as a part of the activities of the Science Advisory
Board, a public advisory group providing extramural scientific Information and advice
to the Administrator andL other officials of the Environmental Protection Agency. The
Board is structured to provide balanced, expert assessment of scientific matters
related to problems facing the Agency. This report has not been reviewed for
approval by the Agency and, hence, the contents of this report do not necessarily
represent the views and policies of the Environmental Protection Agency, nor of other
agencies in the Executive Branch of the Federal government, nor does mention of
trade names or commercial products constitute a recommendation for use.
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ABSTRACT

The Radiation Advisory Committee has reviewed the EPA's, "Uncertainty
Analysis of Risks Associated with Exposure the Radon in Drinking Water" (January
29, 1993), related documents and public comment. The Committee reviewed the
adequacy of the EPA's revisions of the risk assessment for both the ingestion and
inhalation exposure pathways, and the adequacy of the associated uncertainty
analysis has been examined. The Committee also considered the EPA's estimates of
risks associated with radon exposures due to releases at drinking water treatment
facilities. The Committee was mindful of its previously expressed concerns regarding
the Agency's: (a) lack of quantitative uncertainty analyses; (b) failure to consider direct
exposure to radon and its progeny released by showers; (c) lack of an assessment of
risks associated with drinking water treatment; and (d) tack of consideration of
potential occupational exposures and risk.

Overall the Committee finds that EPA has adequately addressed most of the
issues raised in earlier reports from the Committee. The quantitative uncertainty
analysis developed by the EPA represents a methodology that is state-of-the-art and
significantly improves the scientific basis for the EPA's decision-making. The revised
estimates for ingestion and inhalation risks due to radon in drinking water are
scientifically acceptable. There is concern, however, that the uncertainties in the
estimate of ingestion risk are larger than suggested by the quantitative uncertainty
analysis. The Committee recommends that the EPA incorporate a qualitative
discussion of known, but not quantified, uncertainties in its analyses and given the
larger uncertainty bounds associated with the ingestion risk, that consideration be
given to keeping the ingtsiion and inhalation risks separate in the EPA's deliberations
on standards for radon in drinking water The Committee also reiterated its previously
stated concerns that the overall risks associated with radon in drinking water are small
compared with the average radon exposures due to indoor air and that the drinking
water risks be placed in context with other radon risks in the summary documents
developed by the EPA.

The Committee's report also provides comments and recommendations
regarding the adequacy of the analysis and the approaches taken. Among these was
the recommendation that the EPA look at a range of water treatment technologies and
include in the analyses risks due to occupational radiation exposures and potential
waste disposal issues. Finally, the Committee also recommends that particular
attention be given to the uncertainties associated with the variance and shape of the
probability density functions used by the EPA to represent variability of exposures
among individuals,

KEYWORDS: radon, drinking water, uncertainty, inhalation, ingestion
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U.S. ENVIRONMENTAL PROTECTION AGENCY
SCIENCE ADVISORY BOARD
RADIATION ADVISORY COMMITTEE

"• ROSTER

CHAIR

Dr. Genevleve M. Matanoski, The Johns Hopkins University, School of Hygiene and
Public Health, Department of Epidemiology, 624 North Broadway, Room 280,
Baltimore, Maryland 21205

MEMBERS

Dr. Stephen L. Brown, ENSR Consulting & Engineering, 1320 Harbor Bay Parkway
Alameda, California 94501

Dr. June Fabryka-Martin, Los Alamos National Laboratory, Mail Stop J-514, Los
Alamos, New Mexico 87545

Dr. Ricardo Gonzalez, U.P.R. School of Medicine, Post Office Box 365067, San
Juan, Puerto Rico 00§36

Dr. F. Owen Hoffman, SENES Oak Ridge, Inc., Center for Risk Analysis, 677 Emory
Valley Road, Oak Ridge, Tennessee 37830

*Dr. Arjun Makhijani, Institute for Energy and Environmental Research, 6935 Laurel
Avenue, Takoma Park, Maryland 20912

Dr. Oddvar F. Nygaard, Division of Radiation Biology, Case Western Reserve
University, 2199 Adalbert Road, Cleveland, Ohio 44106

Dr. Richard G. Scxtro, Indoor Environment Program, Lawrence Berkeley Laboratory
Building 90, Room 3058, Berkeley, California 94720

**Mr. Paul G. Voilteque, MJP Risk Assessment, Inc., Historic Federal Building, 591
Park Avenue, Idaho Falls, Idaho 83405-0430

Dr. James E. Watson, Jr., Department of Environmental Sciences and Engineering,
Campus Box 7400, University of North Carolina at Chapel Hill, Chapel Hill,
North Carolina 27599-7400
in
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SCIENCE ADVISORY BOARD STAFF

Mrs. Kathleen W. Conway, Designated Federal Official, Science Advisory Board
(A-101F), U,S, Environmental Protection Agency, 401 M Street, S.W.,
Washington, DC^2Q460

Mrs. Dorothy M. Clark, Staff Secretary, Science Advisory Board (A-101FJ, U.S.
Environmental Protection Agency, 401 M Street, S.W., Washington, DC 20460
* Although Dr. Makhijani attended the February 17-19 meeting, his participation
in this review was limited.

**Mr. Voilleque was unable to attend the February 17-19, 1993 meeting where
this review was conducted and has subsequently resigned from the Radiation
Advisory Committee.
IV
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TABLE OF CONTENTS
1. EXECUTIVE SUMMARY , 1
1.1 Background.^ , . . . , 1
1,2 Technical Considerations , . .' 2
1,3 Policy Considerations , . . . . 6

2, INTRODUCTION . . , 8
2.1 Relevant Prior SAB Reports 8
2.2 Procedural History of this Review .,......,,,, 8

3, FINDINGS AND DETAILED DISCUSSION , , , 11
3.1 Adequacy of Revisions to ingestion and Inhalation Risk Estimates ... 11
3,1.1 Are revisions of ingestion risk estimates for waterborne
radon and its progeny adequate? , , 11
3.1.2 Are revisions of inhalation risk estimates for waterborne
radon and its progeny adequate? 12
3.1,3 Discrepancies in Numerical Values: Are EPA's choices for
risk parameters and the uncertainties adequately defended? . 13
3.1.3.1 Estimates of risk due to inhalation of indoor air . 13
3.1.3.2 Estimates of risk associated with inhalation of
outdoor air , 13
3.1.3.3 Estimates of risks and uncertainties
associated with water ingestion , . . 14
3.2 Adequacy of Quantitative Uncertainty Analyses Regarding Risk
Assessment 14
3.2.1 Are the basic methods used to propagate uncertainty
acceptable? 14
3.2.2 Are tht probability density functions (PDFs) selected to
describe Type A and Type B uncertainty of each variable
reasonable? , 15
3.2.3 Are there any important terms or assumptions that have not
. ^ been adequately evaluated? , . 16
3,3 Adequacy of Characterization of Risks from Water Treatment
Facilities 17
3.3.1 Has the EPA adequately characterized the risks introduced
by radon that would be released by aeration from water
treatment facilities? 17
3.3.2 Has the EPA adequately characterized the risks introduced
by radon that would be released from other types of water
treatment facilities? 19
3.3.3 Occupational Exposures 19
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3.4. Other Scientific Issues 20
3.4,1 Recommended extensions of the risk and uncertainty
analysis and publication of results in peer-reviewed journals . 20
3.4.1.1 Individual risks 20
3A1.2 Population risks 21
3.4,2 Estimate of Lives Saved 22
3.4.3 Peer Review and Publication , 23

4. POLICY CONSIDERATIONS 24
4.1 The Importance of Quantitative Uncertainty Analysis 24
4.2 The Relative Risk of Radon in Drinking Water 25
4.3 Harmonizing ...',,... 25

5. REFERENCES 27
5,1 Documents Received by the Radiation Advisory Committee During
this Review 27
5.2 Science Advisory Board Reports of Potential Interest 35
5.3 Literature cited . , 36
APPENDIX A: Brief Chronology of Relevant SAB Reports
APPENDIX B: Congressional Record-Senate, S15103, September 25, 1992
VI
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1. EXECUTIVE SUMMARY

1.1 Background

In EPA's 1993 appropriation1, Congress required EPA to, "conduct a risk
assessment of radon considering: ... the risk of adverse human health effects
associated with exposure to various pathways of radon .... Such an evaluation shall
consider the risks posed by the treatment and disposal of any wastes produced by
water treatment." Congress also required that, "The Science Advisory Board shall
review the Agency's study and submit a recommendation to the Administrator on its
findings." This letter and the accompanying report set forth the Radiation Advisory
Committee's findings and recommendations based on its review of the EPA risk
assessment study, Uncertainty Analysis of Risks Associated with Exposure the Radon
in Drinking Water (January 29, 1993), related documents and public comment. The
EPA uncertainty analysis addressed four radon exposure pathways: inhalation indoors
of radon from non-water sources, inhalation of radon outdoors, ingestion of waterbome
radon, and inhalation of waterborne radon. The review was conducted at a public
meeting February 17-19,1993,

The Committee's charge was to review the adequacy of revisions of inhalation
and ingestion risk from radon progeny and the adequacy of uncertainty analysis
regarding risk assessment of water-borne radon, including health risk analysis and
exposure analysis. In considering adequacy in the review, the Committee was mindful
of concerns it had expressed in reports about earlier EPA documents on radon in
drinking water transmitted to the Administrator on January 9 and 29, 1992: (a) that
uncertainties associated with the selection of particular models, specific parameters
used in the models, and the final risk estimates were not adequately addressed in any
of the documents; (b) that high exposure to radon from water at the point of use (e.g,,
a shower) had not been adequately addressed; (c) that regulation of radon in drinking
water introduces risk from the disposal of treatment byproducts, tradeoffs which the
EPA should consider more explicitly in Its regulatory decision-making; and (d) that
regulation and removal of radon in drinking water may result in occupational
exposures.
Departments of Veterans Affaire and Housing and Urban Development, and Independent Agencies Appropriation Act, 1993,
PU8-1,102-398, Sedton 519,106 STAT1618 (1992)

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1,2 Technical Considerations

Regarding the Committee's charge and concerns (a) and (b) above, the
Committee commends the EPA staff for producing an excellent document all the more
impressive given the constraint of tight deadlines imposed upon it by Congressional
and Court mandates. Its quantitative analysis of uncertainties in the radon risk
assessment represents a methodology that is essentially state-of-the-art for a
regulatory agency and significantly enhances the scientific credibility of the EPA's
decision-making basis. The Committee assumes that this reflects the EPA's recently
stated commitment to a more rigorous approach to evaluating uncertainties in its risk
analyses of radiological and other hazardous exposures in the future. With respect to
concerns (c) and (d) above, the Committee recommends that EPA re-examine its
assumptions about which water treatment technologies will be used for radon removal.
When EPA has determined the likely treatment options, then EPA should perform an
uncertainty analysis for occupational exposure based on that distribution (including the
uncertainty about how frequently the various options will be used). If granular
activated carbon is among those treatment options, then EPA should broaden the
uncertainty analysis to include the disposal of granular activated carbon.

With respect to the EPA's analysis, the risk assessment of radon in drinking
water has been revised and an uncertainty analysis has been conducted using Monte
Carlo simulation methods. The uncertainty analysis incorporates quantifiable
uncertainties in exposure and toxicology, as well as true variation in exposure among
individuals, EPA's mean estimate for the lifetime individual inhalation risk of lung
cancer deaths per pCi/L of radon in drinking water is 3.6 x 10"f, with a stated 90%
confidence interval around the mean of 1,8 x 10"7to 7,0 x 1Q"7. The Agency's mean
estimate for the lifetime individual ingestion risk of fatal cancers per pCi/L of radon in
drinking water is 1.8 x 1Q"7 with a stated confidence interval around the mean of 6.9 x
10"8 to 6.4 x 1Q"V The Agency's nominal estimate for individual lifetime inhalation and
ingestion risk per pCi/L for radon in drinking water are 3,0 x 10'7 and 3.5 x 10"7,
respectively. Therefore, for drinking water risks, the contributions of the inhalation and
ingestion are almost equal.

The Committee notes, however, that the quantitative uncertainty analysis for the
drinking water case does not cover *some of the more important uncertainties. In
particular, the Radiation Advisory Committee believes that the stated uncertainty range
for the ingestion risk is too small in comparison with that for inhalation, because the
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ingestion risk estimate is based on two major factors: (a) an estimate of the
distribution of radon to organs in the gastrointestinal tract, based on an unpublished
study using xenon-133, and (b) the use of organ radiation risk factors that are based
on high dose and high'dose rate exposures to low-LET radiation extrapolated to low
dose and low-dose rates. These risk factors are then converted to high-LET radiation
risks for alpha particles associated with radon and its progeny. The Committee
recommends that EPA not only make this clear in its documents but also consider
keeping the estimates or risks from inhalation and ingestion separate in its discussion
of standards for radon in drinking water.

Overall, the Committee finds that the EPA has adequately addressed most of
the issues raised by the Committee in its earlier reports, either by incorporating the
Committee's previously recommended changes into the new documents or by
providing additional background documentation supporting the EPA's position. The
Committee makes the following scientific comments and recommendations for
additional improvements to the document, but notes that these issues can generally
be addressed by including clarifying statements and that the changes in most cases
would not substantially change the document's estimates of central values for risks.
(A more detailed discussion of each of the comments and recommendations can be
found in the report section identified in parentheses,)

a) Recommendation Organ-specific doses used in the document for
assessment of ingestion risks are based, in part, upon a single study of
kinetics of xenon in humans, work that has not been published in the
peer-reviewed literature. The cited study also did not include a mass
balance determination. Consequently, the Committee recommends that
the EPA carefully review this study to evaluate whether the uncertainties
attributed to the results are adequately described. (3.1.1)

b) Comment With regard to assessment of inhalation risks associated with
drinking water exposure (e.g., showering), the Committee believes that
the EPA's uncertainty analysis is satisfactory and that, given the nature
of the uncertainties, the transfer factor approach used in the document
adequately accounts for risks arising from episodic shower exposures.
(3,1.2)
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c) Recommendation The Committee noted some minor inconsistencies
between values In relevant documents and recommends that the EPA
review its selection of parameter values (including ranges and their
uncertainties) for each exposure pathway to ensure consistency with
original data sources. (3.1.3)

d) Comment The Committee believes that the basic methods used to
propagate uncertainty are acceptable. Proper consideration has been
given to the possibility of covariance, and the Monte Carlo simulation
' methods are state-of-the-art. (3.2.1)

e) Recommendation The Committee recommends that particular attention be
given to more completely addressing uncertainty about the variance and
shape of the probability density functions (PDFs) that have been
assumed by the EPA to represent variability in exposures among
individuals, (3.2.2)

f) Recommendation The Committee recommends that the EPA include in its
uncertainty analysis a qualitative discussion of known uncertainty
variables which were not quantified in the uncertainty analysis. These
include the issue of a linear dose rate response extending to low doses,
the influence of smoking on increasing lung-cancer risks from radon, and
the effect of population mobility on the distribution of risks. (3.2-3)

i) Recommendation In order to increase the scientific credibility of the results,
the Committee recommends that EPA consider upgrading the uncertainty
analysis for the risks associated with aeration for radon removal;
however, the proposed revisions to the analysis will not change the
conclusion that the risk for a maximally exposed individual attributable to
radon released from a water treatment facility will be less than or equal
to the average risk attributable to 300 pCi/L of radon in drinking water
used in the home. (3.3.1)

h) Recommendation If EPA determines that granular activated carbon will be
used for radon removal, the Committee urges EPA to thoroughly and
completely analyze any potential risk and/or disposal problems related to
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the use of granular activated carbon (GAG) for radon removal from
drinking water

i) Recommendation EPA did not provide an analysis of occupational exposures
as a result" of water treatment for radon. The potential for such
exposures appears to depend heavily upon the choice of water treatment
technology, and the Committee recommends that such a comparative
analysis be conducted for different technologies, such as aeration or
granular activated carbon filtration, especially in view of waste disposal
problems that may result from use of the latter technology. (3,3.3)

j) Recommendation The Committee recommends that the document include a
summary of the results of the uncertainty analysis regarding the
contribution of the various exposure pathways to the overall radon risk to
individuals and to the general population. This summary should also
highlight the major sources of uncertainty contributing to the total
uncertainty in the risk estimate for each pathway. Such a discussion
would provide the information necessary to factor uncertainties and
variabilities into the cost-benefit analysis for the proposed regulation and
to calculate a range for the estimates of cost/life saved, (3,4.1)

k) Recommendation The Committee recommends that the EPA extend its
population risk assessment and uncertainty analysis to obtain an
estimate of the lives that would be saved by the proposed maximum
contaminant level, using the same assumptions as were used to
calculate present-day risks but using for radon concentration a lognormal
probability density function truncated at the maximum contaminant level.
(3.4,2)

I) Recommendation The Committee urges the EPA to submit its risk analyses
for publication in appropriate journals which would provide peer-review
and recognition that the EPA's science is of high-quality and that it
becomes part of the mainstream of scientific criticism, revision, and
acceptance (or rejection). Publication will also assist in raising
awareness within the scientific community to the risk issues associated
with radon. (3.4,3)
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1.3 Policy Considerations

The comments below, to some extent, reach beyond the strictly technical issues
examined by the Committee, However, the Committee felt that it was important that
the Agency have the benefits of these thoughts, also, as the decisionmaking process
continues.

The Radiation Advisory Committee has long encouraged the use of integrated
quantitative uncertainty analysis in a variety of EPA assessments. The Committee is
extremely pleased to see that the EPA has done such analysis in this case. The
Committee applauds EPA for its timely incorporation of a full quantitative uncertainty
analysis for each pathway in its assessment and hopes that the use of quantitative
uncertainty analysis will become a routine part of all EPA assessments, not only those
associated with radiation risks. This information should be a valuable aid in guiding
EPA in its consideration of possible regulatory strategies.

The Committee believes strongly that the explicit disclosure of uncertainty in
quantitative risk assessment is necessary. Screening risk assessments involve only
point estimate calculations, and assumptions used to derive these estimates are
generally biased on the conservative side and can be misleading in terms of indicating
the need for regulatory action.

Regulatory action must be based on realistic estimates of risk and these require
a full disclosure of uncertainty. The disclosure of uncertainty enables the scientific
reviewer, as well as the decision-maker, to evaluate the degree of confidence that one
should have in the risk assessment, (deleted sentence redundant with end of
previous paragraph)
\
In its January 29, 1992, Commentary; Reducing Risks from Radon; Drinking
Water Criteria Documents (EPA-SAB-RAC-COM-92-003), the Committee noted that
the radon risk reduction situation reflects the fragmentation of environmental policy
identified in Reducing Risk (SAB-EC-iO-021). Because radon in drinking water is a
very small contributor to radon risk except in rare cases, the Committee suggested
that the EPA focus its efforts on primary rather than secondary sources of risk. Within
the limitations of the data currently available, the EPA has now successfully prepared
a scientifically credible multi-media risk assessment for regulatory decision-making on
radon. The Committee's agreement with the principle of radiation protection

6
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optimization and in the concepts articulated in Reducing Risk lead it to note once
again that radon in drinking water represents only a small fraction of radon exposure
and risk compared to radon in indoor air from non-water sources. The emphasis on
various radon exposure reduction methods-whether for radon from water or non-water
sources-is a policy choTce for which scientific analysis is only one of many important
inputs,

In its May 8, 1992 Commentary on Harmonizing Chemical and Radiation Risk
Reduction Strategies (EPA-SAB-RAC-CQM-92-007), the Committee brought to the
EPA's attention the need for a more coherent policy for making risk reduction
decisions with respect to radiation and chemical exposures. The control of radon in
drinking water presents a situation where a radiological contaminant being regulated
by a paradigm developed for chemicals, yet radon in drinking water represents only a
small fraction of radon exposure, The Committee appreciates the EPA's difficulty in
establishing a coherent risk reduction strategy under the variety of statutes governing
EPA and acknowledges that harmonization does not necessarily imply identical
treatment. However, the Committee urges the EPA to explain dearly why the risks
from radiation (in this case radon in indoor air) and chemicals (in this case radon in
drinking water) are treated differently under specified conditions and in specified
exposure settings. The Committee urges EPA, the Congress and the public to
carefully consider how chemical and radiation risks are being regulated in this case.
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2. INTRODUCTION

2.1 Relevant Prior SAB Reports

For many years the Radiation Advisory Committee and other SAB committees
have urged the incorporation of quantitative uncertainty analysis into EPA
assessments to explicitly disclose the extent of confidence that one should have in the
results of these assessments and to identify areas where the acquisition of additional
information could lead to substantial improvements in the estimation of risks and
uncertainties. In its recent multi-media radon risk assessment study entitled,
Uncertainty Analysis of Risks Associated with Exposure the Radon in Drinking Water
(January 29, 1993) the EPA has implemented most of the SAB's recommendations in
a scientifically credible manner. A brief chronology of relevant SAB reports can be
found in Appendix A.

2.2 Procedural History of this Review

This review resulted from the Chaffee-Lautenberg amendment. (A copy of the
complete language can be found in Appendix B.) More formally known as the
Departments of Veterans Affairs and Housing and Urban Development, and
Independent Agencies Appropriation Act 1993, PUB. L 102-398, Section 519, 106
STAT 1618 (1992), the amendment was also published in the U.S. Congressional
Record and appears as Attachment 1 to this report. Regarding this review, Congress
required EPA to,

conduct a risk assessment of radon considering: (A) the risk of adverse human
health effects associated with exposure to various pathways of radon; (B) the
costs of controlling or mitigating exposure to radon; and (C) the costs for radon
control or mitigation experienced by households and communities, including the
costs experienced by smalt communities as the result of such regulations.
Such an evaluation shall consider the risks posed by the treatment or disposal
of any wastes produced by water treatment The Science Advisory Board shall
review the Agency's study and submit a recommendation to the Administrator
on its findings.

This report by the SAB's Radiation Advisory Committee is a review of EPA's
work in response to (A). The SAB's Drinking Water Committee is reviewing the

8
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Agency's work in response to (B) and (C) and is generating a separate SAB report. In
addition, a subcommittee of the SAB Executive Committee will generate a third SAB
report that, reviews the Agency's "synthesis document" that is being generated by EPA
for submission to the Congress.

At publicly announced conference call meetings November 30, December 2,
December 3, and December 17, 1992, the Radiation Advisory Committee together
with members of the Drinking Water Committee, Environmental Engineering
Committee, and Indoor Air Quality Committee provided a consultation to the EPA staff.
The consultation was on EPA's outline for a multi-media radon risk assessment and
on the parameters and uncertainty analysis for the assessment. The SAB has
developed the consultation as a mechanism to advise the EPA on technical issues
that should be considered in the development of regulations, guidelines, or technical
guidance before the EPA has taken a position. Consultations differ from other SAB
activities in that no report is generated by the SAB and no response from the EPA is
required.

The review of "Uncertainty Analysis of Risks Associated with Exposure to
Radon in Drinking Water" (January 29, 1993), related documents and public comment
was conducted at a February 17-19, 1993 publicly announced meeting of the
Radiation Advisory Committee. The first draft of this report was made available to the
EPA and the public on February 19, Written comments were received from the EPA
and the public subsequent to the meeting. The Committee held non-public writing
sessions by conference call to revise the draft prior to its submittal to the Executive
Committee,

The Committee's charge was to review the adequacy of revisions of inhalation
and ingestion risk from radon progeny and the adequacy of uncertainty analysis
regarding risk assessment of water-borne radon, including health risk analysis and
exposure analysis. In considering adequacy in the review, the Committee was mindful
of concerns it had expressed in reports about earlier EPA documents on radon in
drinking water transmitted to the Administrator on January 9 and 29, 1992: (a) that
uncertainties associated with the selection of particular models, specific parameters
used in the models, and the final risk estimates were not adequately addressed in any
of the documents; (b) that high exposure to radon from water at the point of use (e.g.,
a shower) had not been adequately addressed; (c) that regulation of radon in drinking
water introduces risk from the disposal of treatment byproducts, tradeoffs which the
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EPA should consider more explicitly in its regulatory decision-making; and (d) that
regulation and removal of radon in drinking water may result in occupational
exposures.
10
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3. FINDINGS AND DETAILED DISCUSSION

3.1 Adequacy of Revisions to Ingestion and Inhalation Risk Estimates

3.1.1 Are revisions of ingestion risk estimates for waterborne radon and
its progeny adequate?

Recommendation Organ-specific doses used in the document for assessment
of ingestion risks are based, in part, upon a single study of kinetics of xenon in
humans, work that has not been published in the peer-reviewed literature. The cited
study also did not include a mass balance determination. Consequently, the
Committee recommends that the EPA carefully review this study to evaluate whether
the uncertainties attributed to the results are adequately described.

Discussion. Revisions of ingestion risk resulted from modifications of
gastrointestinal (Gl) and lung dosimetry and from the use of revised organ-specific risk
coefficients, particularly that for the stomach. The revised ingestion risk is greater
than the previous estimate (EPA, 1991) by a factor of 2,3. The Committee has
reviewed these revised risk coefficients. The Committee's primary concern is that
radon retention times in organs are based upon a single study of kinetics of xenon in
humans (Correia et al,, 1987), work that has not been published in the peer-reviewed
literature. The xenon study also did not include a mass balance determination.
Consequently, the Committee recommends that the EPA carefully review this study to
evaluate whether the uncertainties attributed to the results are adequately described.
Other factors in the EPA's biological model that are difficult to verify are the
assumptions that a diffusion gradient exists in the & tract and that lead-214 and
subsequent decay products are removed from the Gl tract before decaying and do not
contribute to dose^. The implications of these assumptions have been considered in
the uncertainty analysis, and in this case also the Committee recommends the EPA
carefully review these factors to evaluate whether the uncertainties are adequately
described. Many of these uncertainties are difficult to quantify because alternative
formulations and parameter values have not been proposed. EPA has adequately
captured the apparent quantifiable uncertainties in the ingestion risk estimates and has
propagated them properly, in the opinion of the Committee. However, the quantitative
uncertainty bounds may give rise to a false sense of the overall reliability of the
ingestion risk estimates. Qualitative uncertainties about the formulation of the
exposure models and the applicability of high-dose, high-dose-rate, low-LET risk

11
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coefficients to the low-dose, iow-dose-rate, high-LET exposure conditions present with
ingestion of radon in drinking water are substantial. An expanded discussion of the
implication of these qualitative uncertainties is important to EPA's consideration of
regulations for radon in drinking water.

3.1.2 Are revisions of inhalation risk estimates for waterborne radon and
its progeny adequate?

Qpjpjnenj With regard to assessment of Inhalation risks, the Committee
believes that the EPA's uncertainty analysis is satisfactory and that, given the nature
of the uncertainties, the transfer factor approach used in the document adequately
accounts for risks arising from episodic shower exposures,

Discussion. The analysis of inhalation risk from radon in water has two
components. The first considers exposures from radon released from general water
use within a house. The EPA applied a general transfer factor that describes radon
release from water indoors. The factor used had a value of 1 in 10,000 (i.e., 10,000
pCi/L in water yields an average indoor air concentration of 1 pCi/L), which is
consistent with values used and published by others. In order to investigate whether
exposures to radon from releases in showers represent a significant episodic peak
exposure not captured by an average transfer factor approach, the EPA used a
multicompartment model, based on one developed by McKone (1987). Because the
analysis of shower exposures required that radon progeny ingrowth and decay be
accounted for, the model specifically recognized the differences between radon and
radon progeny exposures. The multicompartment model yielded results that were
somewhat higher for radon but somewhat lower for radon progeny when compared
with the analysis based on use of an average transfer factor.

The Radiation Advisory Committee believes, first, that the EPA's analysis,
incorporating an uncertainty analysis, is satisfactory and, second, that given the nature
of the uncertainties, the EPA's conclusion that episodic shower exposures are
adequately accounted for by a transfer factor approach is also satisfactory.
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3.1.3 Discrepancies In Numerical Values: Are IPA's choices for risk
parameters and the uncertainties adequately defended?

Recommendation The Committee noted some minor inconsistencies between
values in relevant documents and recommends that the EPA review its selection of
parameter values (including ranges and their uncertainties) for each exposure pathway
to ensure consistency with original data sources.

Discussion. Some examples of discrepancies follow.

3.1.3.1 Estimates of risk due to inhalation of indoor air

In general, the estimated central value for the annual number of lung cancer
cases and the corresponding upper and lower bounds appear to be in the same range
in the present assessment as in the previous assessment. However, the lack of
consistency in the risk factor used is troubling. The summary information presented in
Table 6-2 of the EPA document (EPA, 1993) does not appear to be entirety consistent
with the parameter values used previously. The Committee recommends that the
previous values be used throughout or that clarification of the differences be made in
the document.

3.1.3.2 Estimates of risk associated with inhalation of outdoor air

Although the total risk associated with inhalation of radon and its progeny in
outdoor air is small compared with that attributable to inhalation of radon and its
progeny in indoor air, the estimated lung cancer risks due to outdoor radon/radon
progeny exposures are, in fact, larger than those estimated to arise from radon in
drinking water. Hence, it is important that the uncertainties in the risk assessment for
the outdoor pathway be assessed in a manner consistent with that used for the indoor
(drinking water) pathway. Examples of points of concern follow:

a) There are inconsistencies in the inhalation risk factors used and in their
uncertainties. For example, the text (at p. 6-2) states that one would
expect the unattached fraction to be lower outdoors than indoors, which
is consistent with the few measurements that have been made.
However, this reduction - which would reduce the dose conversion factor
» is not reflected in the geometric mean chosen for this value, nor is the

13
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geometric standard deviation (GSD) increased to capture this
uncertainty.

b) The average outdoor radon concentration used in the calculations
presented"(0.3 pCi/L) does not appear to be consistent with the
UNSCEAR (1988) observation that a population-weighted average value
is about 0,14 pCi/L In fact, the UNSCEAR value falls outside the stated
credibility interval of 0,19 to 4.6 pCi/L A GSD of 1.3 is clearly much too
small for a concentration as uncertain as this.

c) Similarly, relatively few measurements are available to assess the
average equilibrium factor for outdoor exposure settings. Although the
observed values fall in a small range, the GSO of 1.05 implies greater
accuracy in the value chosen {0.8} than is warranted,

d) Time spent outdoors is estimated to be 7.5%, on average. The
variability in this factor is much larger than a GSD of 1.1 would imply.

3.1.3.3 Estimates of risks and uncertainties associated with water
ingestion

The variability assumed for the amount of direct tap water consumed appears
to be biased high, at least as reflected in the analyses presented on pp. 5-26+.

3.2 Adequacy of Quantitative Uncertainty Analyses Regarding Risk
Assessment

Are quantitative uncertainty analyses regarding risk assessment of water-borne
radon, including health risk analysis and exposure analysts, adequate? At the
suggestion of the EPA staff, this question has been broken down into three subparts;

3.2.1 Are the basic methods used to propagate uncertainty acceptable?

Comment The Committee believes that the basic methods used to propagate
uncertainty are acceptable. Proper consideration has been given to the possibility of
covariance, and the Monte Carlo simulation methods are state-of-the-art.
14
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Discussion. In making this determination, the Committee considered the
following:

a) The EPA acknowledged uncertainty in each step of the calculation.
b) The EPA identified the sources of that uncertainty,
c) The EPA examined uncertainty about best estimate values and about
best estimate distributions whereby the distributions represent variability
in exposures and risk among individuals.
d) This latter approach whereby uncertainty is expressed about a best
estimate distribution of exposures is the current state-of-the -art in
uncertainty analyses.
e) The EPA distinguished between variability and uncertainty, which past
analyses have not always done.
f) Perhaps most important, the EPA has also shown what the most
dominant sources of uncertainty are in the calculation. In the case of the
multi-media exposures to radon, the dominant source of uncertainty is
associated with the uncertainty of translating an exposure to radon to an
estimate of health risk. This risk conversion factor will probably be the
parameter which is most difficult to estimate accurately.
g) Nevertheless, the uncertainty associated with the dose to risk conversion
for radon, although it is the dominant contributor to overall uncertainty, is
still much less than the uncertainty associated with other carcinogens
that EPA regulates.

3.2.2 Are the probability density functions (PDFs) selected to describe
Type A and Type B uncertainty of each variable reasonable?

Recommendation The Committee recommends that particular attention be
given to more completely addressing uncertainty about the variance and shape of the
probability density functions (PDFs) that have been assumed by the EPA to represent
variability in exposures among individuals.

Discussion. The Committee believes that the general treatment of the PDFs
used by the EPA in its uncertainty analysis is adequate, subject to the points made
below. The EPA analysis considers two types of uncertainty. First, It recognizes that
different individuals living in an area with the same level of radon in water will have
different exposures, and therefore risks, as a result of differences in household

15
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characteristics, water consumption rates, and other factors. The uncertainty due to
stochastic variability in the lifetime exposure per individual in the U.S. population (Type
A uncertainty) differs from uncertainty attributable to limitations in our knowledge about
the quantities (mean, variance and shape) that describe the true distribution of
individual lifetime exposures (Type B uncertainty). This latter uncertainty also reflects
limitations that influence the average risk per individual.

While the Committee notes that the EPA analysis has not completely
recognized these distinctions, it believes that the EPA has captured the most
important features of quantitative uncertainty analysis and has adequately documented
its choice of PDFs used in its analysis for describing uncertainty about the true vaiue
of risk for the average individual.

3.2.3 Are there any Important terms or assumptions that have not been
adequately evaluated?

Recommendation The Committee recommends that the EPA include in its
uncertainty analysis a qualitative discussion of known uncertainty variables which were
not quantified in the uncertainty analysis. These include the issue of a linear dose
rate response extending to low doses, the influence of smoking on increasing lung-
cancer risks from radon, and the effect of population mobility on the distribution of
risks.

Discussion. The EPA is weil aware that other model and parameter
uncertainties may be important but are difficult to quantify given current state of
knowledge. Many of these are mentioned in its draft documents, such as the issue of
a linear dose response extending to low doses. Another issue that the Committee
would like to see discussed qualitatively in the document is the influence of smoking
on increasing lung-cancer risks from radon. The risk coefficient for airborne radon is
an average value that underestimates the risk to smokers and overestimates it for
nonsmokers. The average risk value thus depends implicitly upon assumptions about
the nature of the relationship between lung cancer risk factors of smoking and radon
exposure, and on the fraction of smokers in the population.

The EPA assessment of radon in water is designed to apply to people whose
water supplies have the same radon content for their entire 70-year lifetimes. The
Committee recognizes that this design assumption is consistent with EPA policy to

16
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promulgate an MCL for radon that is protective for those people who might live out
their lives in a water service area with radon at the maximum contaminant level. The
Committee notes, however, that the mobility of the population implies that not every
person currently living in an area with especially high or especially low radon levels in
water will remain there.~The distribution of radon exposures and risks therefore will
not be the same as if every person remained in the same area for a lifetime. In
general, fewer people will have very high or very low exposures and risks and more
will have intermediate levels of risk than under the no-mobility assumption. The effect
of mobility on overall population risk (cancers per year in the United States arising
from radon in drinking water), in contrast, will likely be negligible because most people
moving from a high radon area to a low one will be replaced by people moving in the
other direction, except for any effect of net population migration within the country.

3.3 Adequacy of Characterization of Risks from Water Treatment Facilities

3.3.1 Has the EPA adequately characterized the risks introduced by radon
that would be released by aeration from water treatment facilities?

Recommendation In order to increase the scientific credibility of the results, the
Committee recommends that EPA consider upgrading the uncertainty analysis for the
risks associated with aeration for radon removal; however, the proposed revisions to
the analysis will not change the conclusion that the risk for a maximally exposed
individual attributable to radon released from a water treatment facility wilt be no more
than the average risk attributable to 300pCi/L of radon in drinking water used in the
home.

Discussion. The EPA has proposed air-stripping as Best Available Technology
(BAT) for achieving the proposed radon standard for drinking water where current
levels exceed the proposed standard. Recognizing that this technique would
discharge much of the waterborne radon to the atmosphere, the EPA analyzed the
risks of such discharges in terms of the risks to a maximally exposed individual (ME!)
living near the treatment facilities. The EPA also projected the population risk or
annual cancer incidence assuming that each water supplier exceeding the proposed
standard were to use air-stripping at a single location in order to bring itself into
compliance with the proposed standard (EPA, 1988; 1989).
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The EPA reasoned that if the individual and population risks from the treatment
facilities were small relative to the risks avoided by applying the proposed standard,
thtn a comparative risk tradeoff would favor implementation of the standard. To
ensure that this comparison would not favor the proposed standard solely through
differences in assessment methods, the EPA estimated the risks attributable to water
treatment by using two radiation risk models, AJRDOSE and MINEDOSE. Although
the Committee has reservations about the degree of validation of these models, the
MINEDOSE model is thought to provide conservative risk estimates. In the
assessment of risk from water treatment, the EPA also made assumptions that were
the same as or more conservative than those used for assessing the risks of radon in
water used in the home. Specifically, the individual risks were calculated for an MEI
who was defined as exposed to the highest concentrations for the longest possible
time from discharges under worst-case meteorological conditions. The Committee
concurs that the set of assumptions chosen was generally quite conservative.

The MEI risks presented to the Committee ranged up to 8 x 1C"4, or about 4
times the nominal value for the risk of 300 pCi/L radon in drinking water. However,
this was a single value derived from largely unrealistic assumptions, and more typical
MEI risks appear to be much lower, generally falling at or below the risk due to
exposure to radon in drinking water at 300 pCi/L.

The EPA also projected population risk using AIRDOSE and estimated total
cancer death rate of approximately 0.1/yr, a value that is considerably less than the
reduction of 80 cancer deaths/yr estimated to be achieved by implementing the
proposed standard.

The EPA conducted a semiquantitative uncertainty analysis of the MEI risk
calculation and concluded that upper bound risks would remain in the vicinity of 1 x
10*4, given the conservative nature of the nominal values. The uncertainty analysis
was less rigorous and more subjective than that for the risks of radon in drinking
water. Although more rigor is unlikely to change the conclusion, improvement of the
uncertainty analysis would improve the scientific credibility of the results.
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3.3.2 Has the EPA adequately characterized the risks introduced by radon
that would be released from other types of water treatment
facilities?
'-^
Recommendation' If EPA determines that granular actived carbon will be used
for radon removal, the Committee urges EPA to thoroughly and completely analyze
any potential risk and/or disposal problems related to the use of granular activated
carbon (GAC) for radon removal from drinking water

Discussion Another technology for radon removal from drinking water is
Granular-Activated-Charcoal (GAC). Although GAC has not been designated a best
available treatment (BAT) for radon removal, in a draft technical memorandum from
the Office of Water (dated January 1993 and circulated to the RAC on February 18,
1993), EPA discussed various issues related to the use of this technology which
mentioned radioactivity accumulation in the GAC (mostly Iead-210). However, while
the memorandum mentioned the Issue of GAC building up levels of radioactivity such
that the residuals would require disposal at a low-level-radioactive-waste (or naturally
occurring radioactive material waste) repository, the memorandum was without
sufficient data or analysis for the Committee to evaluate this possibility and the
implications of this problem.

The Committee urges EPA to thoroughly and completely analyze any potential
risk and/or disposal problems related to the use of GAC for radon removal from
drinking water.

3.3,3 Occupational Exposures

Recommendation EPA did not provide an analysis of occupational exposures
as a result of water treatment for radon. The potential for such exposures appears to
depend heavily upon the choice of water treatment technology, and the Committee
recommends that such a comparative analysis be conducted for different technologies,
such as aeration or granular activated carbon filtration, especially in view of waste
disposal problems that may result from use of the latter technology.

Discussion. The EPA did not provide an analysis of potential radiation
exposures to workers in water treatment or.ancillary facilities. The RAC notes that in
the case of aeration techniques, proper ventilation of the water treatment facility

19
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should result in little increase in radon concentrations and exposures to personnel.
There should be no other significant sources of radiation due to such treatment.
However, the EPA has not ruled out treatment by other means, including granular
activated carbon filtration (GAG), in which case build-up of radon progeny in the bed
can result in an increased radiation field near the beds. Furthermore, the handling
and disposal of GAC beds containing radionudides has not been analyzed nor, in fact,
have provisions been made for such disposal in the event it is necessary. In order to
provide a complete risk analysis, the Committee believes that the EPA needs to
consider the possibility of worker exposures either to radiation or to chemicals (such
as those used as biocides in aeration facilities) resulting from some water treatment
technologies.

3,4 Other Scientific Issues

3.4.1 Recommended extensions of the risk and uncertainty analysis and
publication of results in peer-reviewed journals

Recommendation The Committee recommends that the document include a
summary of the results of the uncertainty analysis regarding the contribution of the
various exposure pathways to the overall radon risk to individuals and to the general
population. This summary should also highlight the major sources of uncertainty
contributing to the total uncertainty in the risk estimate for each pathway. Such a
discussion would provide the information necessary to factor uncertainties and
variabilities into the cost-benefit analysis for the proposed regulation and to calculate a
range for the estimates of cost/life saved. (3,4.1)

Discussion. One aspect that was lacking in the reviewed document was a
summary and interpretation of the uncertainty analysis for radon in drinking water.
The Committee has studied the results presented by the EPA and offers the following
interpretation.

3.4.1.1 Individual risks

The following table lists the unit risks attributable to drinking water by inhalation
and ingestion pathways, including the 9u% confidence interval around the median, the
upper-bound 95th percentile, and the lower-bound 5th percentile for risk.
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Table 1, Unit Risk Boundaries for Exposure to Radon In Drinking Water
(Fatal cancers/person/year per pCi/L)

Inhalation
Ingaslion
Sth
pwewtito
Lowtr Bound ^
1.6x10-"
1.2K10-"1
Sth p«fwntlle
Mudian

1.1 X Iff'
3.7 x 10"™
Median

2.7 X 10''
1.7X101*
95th (MMCMtU*
Median

6,3 x 10-"
6-5 x 10''
95th
PMemtil*
Upper Bound
42 X 104
2,0 X 10-"
The nominal unit risk in the proposed rule is 9.4 x 10"* fatal caneers/person/year
per pCi/L. This nominal risk can be compared to the median inhalation and ingestion
risks from radon in drinking water shown in Table 1. The nominal risk is larger than
the median inhalation risk by a factor of 3.5 and is larger than the ingtstion median
risk by a factor of 5.5. Therefore, the combined unit risk from inhalation and ingestion
exposure will be <3.5, and well within the range encompassed by the 90% confidence
interval of risk about the median. The same comment applies to the nominal unit risk
presented in Chapter 3 of the reviewed document.
3.4.1.2
Population risks
The estimates of cancer fatalities due to exposure of radon in drinking water
are based upon 81 million people being exposed. This number was presented to the
Committee during a briefing on 2/17/93, and comes from a preliminary contractor
report on occurrence of radon in drinking water (Wade Miller, 1992). That report is
being reviewed by the EEC of the SAB, Any changes in that estimate will affect the
results presented below,

Table 2. Cancer Fatalities per Year due to Exposure to Radon
Exposur* Pathway
Inhalatiott du* to Water
Treatment
Inhalation from Drinking
Water
ingtMiion from Drinking
Water
Inhalation fn»m Outdoor Mr
Inhalation from Indoor Air
Slh Percentikt
Median
_
48
19
280
8,790
Median
—
105
S3
657
14,410
Median
—
233
in
1,500
30,950
Bound
* 1
—
—
—
—
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The estimated lung cancer deaths attributable to inhalation exposure to radon in
drinking water range from 48 to 233 per year. The estimated fatal cancer cases
attributable to ingestion exposure to radon in drinking water range from 19 to 166 per
year. Therefore, estimated total fatal cancer cases attributable to waterbome radon
will be about a quarter of the risks associated with exposure to radon in outdoor air,
and about one percent of the risks associated with exposure to radon in indoor air and
of the total risks attributable to exposure to radon by all pathways. These calculations
also indicate that population risks from exposure to radon in drinking water are similar
to or higher than those normally addressed by regulation of chemical pollutants in
drinking water. Although the risk attributable to inhalation and ingestion of radon in
drinking water were apportioned equal weight in the calculation of the nominal value in
Chapter 3, the weight obtained as a result of the uncertainty analysis is approximately
two-thirds for inhalation and one-third for ingestion. This last set of values is similar to
those presented in the Proposed Rule (EPA, 1991).

3.4.2 Estimate of Lives Saved

Recommendation The Committee recommends that the EPA extend its
population risk assessment and uncertainty analysis to obtain an estimate of the lives
that would be saved by the proposed maximum contaminant level, using for radon
concentration the same assumptions as were used to calculate present-day risks but
using a lognomnal probability density function truncated at the maximum contaminant
level.

Discussion. The Committee could not carry out an analysis of the estimated
number of lives that would be saved by the Proposed MCL of 300 pCi/L because no
uncertainty analysis was done on the number of cancer fatalities projected for the rule
in place. The Committee recommends that a population risk assessment and
uncertainty analysis be carried out, using the same assumptions as were used to
calculate present-day risks but using for radon concentration a lognomnal PDF
truncated at the proposed MCL, An uncertainty for the tolerance in the measurement
of radon as described in the section regarding monitoring of the Proposed Rule should
also be factored into this uncertainty analysis. From these calculations, one would
obtain a 90% confidence interval for the cancer fatalities that would remain with
enforcement of the proposed MCL, and the difference between the values in Table 2
and those calculated with the truncated PDF would yield a range of lives saved. This
analysis would then allow the persons conducting the cost-benefit analysis to factor

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these uncertainties and variabilities into their calculations, leading to a rangs of costs
per life saved. The Committee believes that this extension to the EPA's uncertainty
analysis would enhance the usefulness of the document reviewed.

3.4.3 Peer Review and Publication

Recommendation The Committee urges the EPA to submit its risk analyses for
publication in appropriate journals which would provide peer-review and recognition
that the EPA's science is of high-quality and that it becomes part of the mainstream of
scientific criticism, revision, and acceptance (or rejection). Publication will also assist
in raising awareness within the scientific community to the risk issues associated with
radon.

Discussion. The Committee believes that overall, the use of the peer-reviewed
literature as both a source of data and information and also as a method of
disseminating the EPA's own scientific work is an important means by which the EPA
and the public can be assured that the best science is being used or produced. In
this particular case, the estimate of the ingestion risk due to radon in drinking water
rests heavily upon data and analyses that have not been published and therefore have
not been broadly circulated within the scientific community. Reliance upon such
results should be done with considerable caution.

Although publication in peer-reviewed journals does not, by Itself, assure
infallibility, It is the only generally recognized means by which scientific work gets
accepted by members of the scientific community. In seeking to improve the quality
and the scientific acceptability of its science, the EPA should encourage its scientists
to submit their work for peer-reviewed publication. The work and methodologies
presented here mark an important advance in the risk and uncertainty analyses
undertaken by the' EPA and are certainly worthy of such publication.
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4. POLICY CONSIDERATIONS

4.1 The Importance of Quantitative Uncertainty Analysis
-*»
The Radiation Advisory Committee has long encouraged the use of integrated
quantitative uncertainty analysis in a variety of EPA assessments. The Committee is
extremely pleased to see that the EPA has done such analysis in this case . The
Committee applauds EPA for its timely incorporation of a full quantitative uncertainty
analysis for each pathway in its assessment and hopes that the use of quantitative
uncertainty analysis will become a routine part of all EPA assessments, not only those
associated with radiation risks. This information should be a valuable aid in guiding
EPA in its consideration of possible regulatory strategies.

The Committee believes strongly that the explicit disclosure of uncertainty in
quantitative risk assessment is necessary any time the assessment is taken beyond a
screening calculation. Screening risk assessments typically involve only point
estimate calculations. The assumptions used to derive these point estimates are
generally biased on the conservative side to ensure that the true risk to individuals will
not be underestimated. Screening calculations are thus useful for identifying situations
that are clearly below regulatory risk levels of concern. They can be grossly
misleading in terms of indicating the need for regulatory action.

The need for regulatory action must be based on more realistic estimates of
risk. Realistic risk estimating, however, requires a full disclosure of uncertainty. The
disclosure of uncertainty enables the scientific reviewer, as well as the decision-maker,
to evaluate the degree of confidence that one should have in the risk assessment
The confidence in the risk assessment should be a major factor in determining
strategies for regulatory action,
\

Large uncertainty in the risk estimate, although undesirable, may not be critical
if the confidence intervals about the risk estimate indicate that risks are dearly below
regulatory levels of concern. On the other hand, when these confidence intervals
overlap the regulatory levels of concern, consideration should be given to acquiring
additional information to reduce the uncertainty in the risk estimate by focusing
research on the factors that dominate the uncertainty, The dominant factors
controlling the overall uncertainty are readily identified through a sensitivity analysis
conducted as an integral part of quantitative uncertainty analysis. Acquiring additional

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data to reduce the uncertainty in the risk estimate is especially important when the
cost of regulation is high. Ultimately, the explicit disclosure in the risk estimate should
be factored into analyses of the cost-effectiveness of risk reduction as well as in
setting priorities for the allocation of regulatory resources for reducing risk.

4.2 The Relative Risk of Radon in Drinking Water

In its January 29, 1992, Commentary: Reducing Risks from Radon; Drinking
Water Criteria Documents (EPA-SAB-RAC-CQM-92-QQ3), the Committee noted that
the radon risk reduction situation reflects the fragmentation of environmental policy
identified in Reducing Risk (SAB-EC-iO-021). Because radon in drinking water is a
very small contributor to radon risk except in rare cases, the Committee suggested
that the EPA focus its efforts on primary rather than secondary sources of risk. Within
the limitations of the data currently available, the EPA has now successfully prepared
a scientifically credible multi-media risk assessment for regulatory decision-making on
radon. The Committee's agreement with the principle of radiation protection
optimization and in the concepts articulated in Reducing Risk lead It to note once
again that radon in drinking water represents only a small fraction of radon exposure
and risk compared to radon in indoor air from non-water sources. The emphasis on
various radon exposure reduction methods—whether for radon from water or non-water
sources—is a policy choice for which scientific analysis is only one of many important
inputs.

4.3 Harmonizing

In its May 8, 1992 Commentary on Harmonizing Chemical and Radiation Risk
Reduction Strategies {EPA-SAB-RAC-CQM-92-QQ7), the Committee brought to the
EPA's attention the need for a more coherent policy for making risk reduction
decisions with respect to radiation and chemical exposures. The control of radon in
drinking water presents a situation where a radiological contaminant being regulated
by a paradigm developed for chemicals yet radon in drinking water represents only a
small fraction of radon exposure. The Committee appreciates the EPA's difficulty in
establishing a coherent risk reduction strategy under the variety of statutes governing
EPA and acknowledges that harmonization does not necessarily imply identical
treatment. However, the Committee urges the EPA to explain clearly why the risks
from radiation (in this case radon in indoor air) and chemicals (in this case radon in
drinking water) are treated differently under specified conditions and in specified

25
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exposure settings. The Committee urges EPA, the Congress and the public to
carefully consider how chemical and radiation risks are being treated in this case.
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5. REFERENCES

5.1 Documents Received by the Radiation Advisory Committee During this
Review

A. DOCUMENTS RECEIVED BEFORE THE FEBRUARY 17-19 PUBLIC
MEETING

Documents Provided by EPA

1. Departments of Veterans Affairs and Housing and Urban Development, and
Independent Agencies Appropriation Act, 1993, PUB. L 102-398, Section 519,
106STAT1618(1992)

2. Draft 2 "Uncertainty Analysis of Risk Associated with Exposure to Radon in
Drinking Water" prepared by U.S. EPA Office of Science and Technology,
Office of Radiation and Indoor Air, Office of Groynd Water and Drinking Water,
and Office of Policy Planning and Evaluation, January 29, 1993

3, Proposed Revisions in EPA Estimates of Radon Risks and Associated
Uncertainties

4. An Analysis of the Uncertainties in Estimates of Radon-Induced Lung Caner by
Jerome S. Puskin in Risk Analysis Volume 12, Number 2. 1992

5. Response to SAB Radon Comments

6, Preliminary % Risk Assessment for Radon Emissions from Drinking Water
Treatment Facilities, a memorandum from Warren D. Peters and Christopher B,
Nelson to Stephen W. Clark, June 28, 1988

7, An Analysis of Potential Radon Emissions from Water Treatment Plants Using
the MINEDOSE Code, a memorandum from Pare. J. Parrotta to Greg Helms,
November 22, 1989

8. Proposed Methodology for Estimating Radiogenic Cancer Risks (no author or
date given)

27
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i. Cancer Fatalities from Witerborne Radon (Rn-222) by Douglas J, Crawford-
Brown in Risk Analysis, Volume 11, Number 1, 1991

Public Comment

10. Letter re: National Primary Drinking Water Regulations: Radionydides (Radon)
[WH-FRL 3956-4] from John H. Sullivan of the American Water Works
Association to Honorable Carol Browner, Administrator of the Environmental
Protection Agency, January 26, 1993. There were 27 Appendices to this letter.

1. EPA Technical Support Document for the 1992 Citizen's Guide
to Radon, EPA 400-R-i2-011 (May 1992)
2. "Harmonizing Chemical and Radiation Risk-Reduction Strategies -
A Science Advisory Board Commentary,"(May 18,1992)
3. Letter from SAB Chairman Raymond Loehr to EPA
Administrator William Reilly Re: "Radionudides in
Drinking Water" (EPA-SAB-RAC-91-XXX) (September 1991)
4. "An SAB Report: Radionudides in Drinking Water"
(EPA-SAB-RAC-91-Q09) (December 1991)
5. Letter from SAB Chairman Raymond Loehr to EPA
Administrator William Reilly Re: "Reducing Risks
from Radon; Drinking Water Criteria Documents,"
(EPA-SAB-RAC-COM-92^003) (January 29, 1992)
6. Letter from SAB Chairman Raymond Loehr to EPA
Administrator William Reilly Re; "Status of EPA
Radionudides Model" (EPA-SAB-RAC-COM-92-001)
(January 9, 1992)
7. SAB, "Review of the office of Drinking Water's
Assessment of Radionudides in Drinking Water and
Four Draft Criteria Documents" (July 1987)
8. Letter from SAB Chairman Raymond Loehr to EPA
Administrator William Reilly Re: "Review of Draft
Criteria Documents for Radionudides in Drinking
Water (EPA-SAB-RAC-92-QQ09) (January 9, 1992)
9. Letter from SAB Chairman Raymond Loehr to EPA
Administrator William Reilly Re: "Revised Radon
Risk Estimates and Assodated Uncertainties" (EPA-

28
-------
SAB-RAC-LTR-92-OG3) (January 9, 1992)
10. Puskin, Jerome, "An Analysis of the Uncertainties in
Estimates of Radon-Induced Lung Cancer," Risk
Analysis, Vol. 12, No. 2» p, 277 (1992)
11. SEIZES Consultants Limited Memorandum Re: "Exposure
and Risk from Radon Released in Showers" (December 3, 1992)
12, Fensterheim, Robert, Stolwijk, Jan, "Critique of
Hess and Bernhardt Radon Shower Exposure Study,"(
13. Testimony of Jonathan M. Samet before the
Subcommittee on Transportation and Hazardous
Materials, House Energy and Commerce Committee
(June 3, 1992)
14. Neuberger, John S., "Residential Radon Exposure and
Lung Cancer: An Overview of Published Studies,"
Cancer Detection and Prevention, Vol.15, Issue 6,
(1991)435-443
15, Neuberger, John S., et at, "Residential Radon
Exposure and Lung Cancer; Evidence of an Inverse
Association in Washington State," Journal of
Environmental Health, Nov/Dec. 1992, 23-25
29
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16. "Proposed Guideline for Radon-222 in Drinking
Water," prepared by SENES Consultants Limited for
Health Protection Branch, Health and Welfare Canada
(March 1992)
17. Draft of SAB Radiation Advisory Committee Comments
on EPA's "Suggested Guidelines for the Disposal of
Drinking Water Treatment Wastes Containing
Naturally-Occurring Radionudides" (July 6, 1992)
18. Testimony of Dr. Jill Lipoti on HR 3258, the "Radon
Awareness and Disclosure Act of 199111 before the
House Subcommittee on Transportation and Hazardous
Materials (June 3, 1992)
19. Factor Analysis for Differences Between EPA and RCG
Compliance Cost Estimates
20, Table Comparing Compliance Costs for A Radon MCL of
300 pci/l; Letter to Editor and Response in American
Water Works Association Journal
21. Comments of the State of Idaho Department of Water
Resources (May 18, 1992)
22. Letter from Dr. Alvin Young, Chairman of Committee
on Interagency Radiation Research and Policy
coordination, to Dr. Donald Henderson, Office of
Science and Technology Policy (May 21, 1992)
23. Testimony of Dr. Jan Stolwijk before the House
Subcommittee on Transportation and Hazardous
Materials (June 3, 1992)
24. Valentine, Richard, "Radon and Radium From
Distribution System and Filter Media Deposits/" AWWA
Water Quality Technology conference, Toronto (1992). 24
25. Comments of the State of New York Department Health
to EPA (February 12, 1992)
26. "Evaluation of the Impact of a Radon-222 MCL on
Small Water Systems," by John E. Reanier, Alabama
Rural Water Association (May 10, 1992)
27. Comments of the Association of State Drinking Water
Administrators (November 19, 1991)
30
-------
11. Letter to Administrator Browner and three SAB Chairs from Bill Mills, Steve
Hall, and Tom Levy of the Alliance for Radon Reduction, February 2, 1993
31
-------
B. DOCUMENTS RECEIVED AT THE FEBRUARY 17-19 PUBLIC MEETING

Documents Provided by EPA

1. Draft Summary (no date or author given, appears to be a draft summary for the
"Uncertainty Analysis of Risk Associated with Exposure to Radon In Drinking
Water41

2. Overheads: Briefing for SAB on Multimedia Risk Assessment of Human
Exposure to Radon, Office of Science and Technology, Office of Radiation and
Indoor Air, Office of Policy, Planning, and Evaluation, Office of Ground Water
and Drinking Water.

3. Overheads: Risk Assessment for Radon Emissions from Drinking Water
Treatment Facilities, EPA Office of Radiation and Indoor Air, February 17, 1993

4. Overheads: Cancer Risks Associated with Radon in Drinking Water-
Uncertainty and Variability Analysis

5. "Review of Risk Assessments of Radon Emissions from Drinking Water
Treatment Facilities" from Christopher Nelson ORIA to Mark Parrotta ODW

6. Radon Documents for SAB Review, a memorandum from Nancy Chiu of
OST/OW to William F, Raub, Science Advisor

7. Draft Technical Memorandum: Problems with the Use of GAG for Radon
Removal, printed date is January 19i3 (handwritten date is 2/11)

Public Comment

8. Review of Technical Justification of Assumptions and Methods Used by the
Environmental Protection Agency for Estimating Risks Avoided by Implementing
MCLs for Radionuclides by S.C, Morris, M,D. Rosw, S. Holtzman, and A,F.
Meinhoid and Brookhaven National Laboratory, November, 1992

9. Letter from Edward J, Schmidt to Comments Clerk-Radionuelides, Subject
Comments on National Primary Drinking Water Regulations: Radionuclides

32
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Proposed Rule, 40CFR Parts 141 & 142, Thursday, July 18, 1991, September
30, 1991

10. Letter to James R, Elder from Raymond F. Peiletier, Office of
Environmental Guidance, U.S. Department of Energy, January 27, 1993

C. DOCUMENTS RECEIVED SUBSEQUENT TO THE FEBRUARY 17-19
PUBLIC MEETING

Documents Provided by EPA

1. One-page note to Kathleen Conway from Jan Auerbach, February 23, 1993

2. Note to Kathleen Conway, RAG DFO from Nancy Chui OGWDW, faxed to the
Radiation Advisory Committee, March 10, 1993

Public Comment

3, Letter to the SAB Radiation Advisory Committee from Frederick W. Pontius of
the American Water Works Association, February 24. This letter had seven
enclosures:
a. Lognormal Distributions for Water Intake by Children and Adults,
by Ann M, Roseberry and David. E. Burmaster in Risk Analysis,
Volume 12, Number 1, 1992
b. Distribution and Expected Time of R e sidence for U.S.
Households by Milton Israeli and Christopher B. Nelson in Risk
Analysis, Volume 12, Number 1, 1992
c. Review of Risk Estimates for Inhalation of Radon Progeny by
Miners: Presentation by the Atomic Energy Control Board of
Canada (ACB) before the ICRP Main Commission, printed date is
November 1992, there is also a stamped date of February 12,
1993
d, A Cohort Study in Southern China of Tin Miners Exposed to
Radon and Radon Decay Products by Xuan Xiang-Zhen, Jay, H.
Lubin, and others in Health Physics, Volume 62, Number 10,
pages 120-131, February 1993
33
-------
. e. Contribution of Waterbome Radon to Home Air Quality, prepared
by Arun K. Deb of Roy F., Eston, Inc. for the AWWA Research
Foundation, undated
f. Final Report: Risk and Uncertainty Analysis for Radon in Drinking
Water prepared by Douglas J. Crawford Brown for the American
Water Works Association.
g. Proposed Guideline for Radon-222 in Drinking Water prepared by
SENES Consultants Limited for the Health Protection Branch of
Health and Welfare Canada, March 1992

4, Letter to the Radiation Advisory Committee from Douglas Crawford-Brown of
the University of North Carolina, March 2,1993

5- Letter to Dr. Genevieve Matanoski from Bill Mills, Steve Hal! and Tom Levy of
the Alliance for Radon Reduction, March 11, 1993

6. Letter to Dr. Genevieve Matanoski from Robert J. Fensterheim, consultant to
the Alliance for Radon Reduction, March 16, 1993

7, Fax from Robert J, Fensterheim referencing Brown-Senate Letter and Naomi
Harley Study, March 16, 1993. This fax included both a March 11, 1i93 letter
from nine senators to Administrator Carol M, Browner and A Biokinetic Model
for the Distribution of Rn-22 Gas in the Body Following Ingestion by Naomi H.
Harley and Edith S, Robbing, March 12, 1993

8. Letter to Dr. Vern Ray, Chairman of the Radon Engineering Cost Subcommittee
from Stephen Hall of the Association of California Water Agencies, March 22,
1993
34
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5.2 Science Advisory Board Reports of Potential Interest

1. Report of the Scientific Basis of EPA's Proposed National Emission Standards
for Hazardous Air Pollutants for Radionuclides: A report of the Subcommittee
on Risk Assessment for Radionuclides, August 1984 (There is no report
number because this report was produced before the SAB developed a report
numbering system.)

2, Radionuclides in Drinking Water (SAB-RAC-87-035)
3. Effective Dose Equivalent Concept (SAB-RAC-88-Q26)
4, Radon Risk Estimates (SAB-RAC-88-042)
5. Radionuclides NESHAP (SAB-RAC-89-Q03)
6. EEC Mathematical Models Resolution (SAB-EEG-8i-01)
7. Radionuclides NESHAP (SAB-RAC-89-024)
8, Radon Risks (SAB-RAC-91-LTR-001)
9. Status of EPA Radionuclide Models (EPA-SAB-RAOCOM-92-00)
10. Revised Radon Risk Estimates and Associated Uncertainties
(EPA-SAB-RAC-LTR-92-003)
11. Criteria Documents for Radionudides in Drinking Water
(EPA-SAB-RAC-92-009)
12. Reducing Risks from Radon/Drinking Water Criteria Documents
(EPA-SAB-RAC-COM-003)
13. Harmonizing Chemical and Radiation Risks (EPA-SAB-RAC-CQM-92-00?)
14. Drinking Water Treatment Wastes Containing NORM (EPA-SAB-RAC-LTR-92-
018)
15. Radon in Water: Consultation (EPA-SAB-RAC-CON-92-002)
35
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5.3 Literature cited

Correia JA, Weise SB, Caliahan RJ» Strauss HW, 1987. The kinetics of ingested Rn-
222 in humans determined from measurements with Xe-133. Massachusetts
General Hospital, Boston MA, unpublished report Prepared for Health Effects
Research Laboratory, U.S. EPA, Report No. EPA/600/1-87/013.

Crawford-Brown DJ, 1991 Cancer fatalities from waterborne radon (Rn-222). Risk
Anal. 11:135-143.

EPA, 1988. "Preliminary Risk Assessment for Radon Emissions from Drinking Water
Facilities," memorandum from Warren Peters and Christopher Nelson to Stephen
Clark, June 28, 1988,

EPA, 1989. "An Analysis of Potential radon Emissions from Water Treatment Plants
using the MINEDOSE Code," memorandum from Marc Parrotta to Greg Helms,
November 22, 1989,

EPA, 1991. "Notice of Proposed Rulemaking for Radionuclides in Drinking Water

EPA, 1989. "Draft 2 "Uncertainty Analysis of Risk Associated with Exposure to
Radon in Drinking Water" prepared by U.S. EPA Office of Science and
Technology, Office of Radiation and Indoor Air, Office of Ground Water and
Drinking Water, and Office of Policy Planning and Evaluation, January 29, 1993

McKone, TE, 1987. Human exposure to volatile organic compounds in household tap
water: the indoor inhalation pathway. Environ. Sci. Technol, 21:1194-1201

UNSCEAR, Sources, Effects and Risks of Ionizing Radiation, United Nations Scientific
Committee on the Effects of Atomic Radiation, United Nations: New York, 1988,
p.64.

Wade Miller Associates, 1992, Draft addendum to the occurence and exposure
assessments for radon, radium-226, radium-228, uranium, and gross alpha particle
activity in public drinking water supples, EPA contract No. 68-CQ-QQ69 September
30, 1992.
36
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APPENDIX A: Brief Chronology of Relevant SAB Reports

In 1984 a specialized ad hoc Subcommittee of the Science Advisory
Board reviewed the scientific basis for EPA's proposed national emissions
standards for hazardous air pollutants for radionuclides. That report led to the
formation of the Radiation Advisory Committee to "review risk assessments for
radiation standards", The report also stated,"A scientifically defensible risk
assessment for radionuciides should address at least five major elements, These
include 1} identification of the significant. ,„ sources; 2) a description of the
movement. . from a source ... to people; 3) calculation of doses; 4} estimation of
. . . health effects, and 5) incorporation of estimates of uncertainty into elements
1-4. . . ." The routine incorporation of uncertainty analysis into risk assessments
has been a recurring theme in Radiation Advisory Committee reports.

In the summer of 1986, the Drinking Water Subcommittee of the
Radiation Advisory Committee reviewed the Office of Drinking Water's
Assessment of Radionuclides in Drinking Water and Four Draft Criteria
Documents, (SAB-RAC-87-Q35), This Subcommittee did not explicitly address
uncertainty analysis. While recommending some improvements in science and
presentation, the Subcommittee concluded, "that the Office of Drinking Water has
developed scientifically comprehensive assessment documents." This report was
transmitted to the Administrator July 27, 1987.

In 1988 and 1989 reviews of revisions to the scientific basis for the
radionuclides NESHAP, the Radiation Advisory Committee again raised concerns
about quantitative uncertainty analysis. The cover letter of the November 10,
1988 report (SAB-RAC-89-QG3) highlighted three findings for serious attention by
the EPA, including, "To date, EPA's treatment of modeling uncertainties has been
qualitative rather than quantitative although state-of-the-art methods for estimating
uncertainty are available." The June 30, 1989 report (SAB-RAC-89-024) noted in
the cover letter (p.2),"... the Radiation Advisory Committee and the Science
Advisory Board has repeatedly urged the use of best estimates and ranges in the
specifications of risk, and a detailed explanation of the uncertainties in the
estimates themselves,"

On January 13, 1989, the SAB transmitted to the Administrator the
Environmental Engineering Committee's Resolution on the Use of Mathematical

A-1
-------
Models by EPA for Regulatory Assessment and Decision-Making (EPA-SAB-EEC-
89-012). The Committee (p.1) had reviewed "a number of integrated
environmental modeling studies" and "noted a number of problems" including, "a
lack of studies quantifying the uncertainties associated with model predictions, and
concurrently, the potential misuse of particular uncertainty analysis techniques,"
The resolution's fourth recommendation (p.3) was, "Sensitivity and uncertainty
analysis of environmental models and their predictions should be performed to
provide decision-makers with an understanding of the level of confidence in model
results, and to identify key areas for future study."

In the summer of 1990, the Radionuclides in Drinking Water
Subcommittee of the Radiation Advisory Committee reviewed draft criteria
documents for radionuclides in drinking water, including those for uranium, radium,
radon, and a combined document on beta particles and gamma emitters.
The Subcommittee found that, "The overall quality of the four draft criteria
documents was not good. . . . recommendations from a 1987 Science Advisory
Board report on its review of the standards for radionuclides in drinking water
(SAB-RAC-87-035) had not been addressed. Nor did the new criteria documents
address recommendations from other available SAB reports that are directly
relevant (such as SAB-RAC-88-026 and SAB-EEC-89-012). .. . Uncertainties
associated with the selection of particular models, specific parameters used in the
models, and the final risk estimates are not adequately addressed in any of the
documents." Although the review was conducted in 1990 and draft reports
circulated at that time, this SAB report was not transmitted to the Administrator
until January 9, 1992, (EPA-SAB-RAC-92-009)

In the summer and fall of 1991, the Radiation Advisory Committee
received revised criteria documents and declined to review them. It did, however,
produce a commentary which noted (pA) that, "Although each criteria document
now includes a chapter discussing uncertainty, the content of the chapters is very
qualitative and is not the rigorous technical analysis envisioned by the
Committee." In its section on policy considerations, the Committee also noted
(p.3) that, "radon in drinking water is a very small contributor to radon risk except
in rare cases and the Committee suggests the EPA focus its efforts on primary
rather than secondary sources of risk." This commentary was transmitted to the
Administrator January 29, 1992 (EPA-SAB-RAC-COM-92-003)
A-2
-------
The January 9 and 29, 1992 reports also contained other advice
relevant to the scientific assessment of the risk of radon in drinking water.
Additionally, the January 29, 1992 report provided policy-related comments on
radon in light of the SAB report, Reducing Risk, A May 8» 1992 Radiation
Advisory Committeericommentary, "Harmonizing Chemical and Radiation Risk
Reduction Strategies," described chemical and radiation risk reductions
paradigms, discussed the difficulties of applying a paradigm developed for one
type of contaminant to the other, and recommended harmonization.

In the winter and spring of 1992, the Committee conducted a review
of the EPA's, "Suggested Guidelines for the Disposal of Drinking Water Treatment
wastes Containing Naturally-Occurring Radionuclides" dated July 1990. The
Committee found that such guidelines were needed because of the potential
radiation closes to treatment plant workers and the public. However, the 1990
guidelines did not fully assess the magnitude of risk from exposure to treatment
wastes, nor did the document specify whether the radiation exposures to workers
should be considered as occupational exposures or viewed against dose limits for
the general public, a decision which wilt have considerable bearing on any final
guidelines. This letter report was transmitted to the Administrator September 30,
1992 (EPA-SAB-RAC-LTR-92-018),
A-3
-------
APPENDIX B: Chaffee-lautenberg Language from the Congressional Record
B-1
-------
Jptsmber 25, 1&32
CONGRESSIONAL RECORD—SEHA11
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fcra«m« Jteef t>* Me /'reriiKnl to tAt Coiwrcn, to
the entire Kuwait u dowwittrf &v Oupreu of
Sit emttfencg re«wtrtMien{ puf*ucUti tfl MCdOfl
of Me flairoeart 5ud«et and
Deftcit Control Act of IMS, a*
*andf2l«M«in(rM«)na«ertMder the
"CHaausr ntxttanae direct ioa* pro-
STO« q«o /v«d*. 0» KJD.OOOJXO to

r/ui: not lo crcwi t^!.000,006 ft aiutiaele /or di-
rect loan oWuxuxnu provided to efipW
: or to 5tdta Bwl«r ttcfloa J/S o/ tAe
T. Stafford Daamer Aastet&iKt and
ReUef As. a* a**ende4: Provided farther,
Th&t not td A2Ctfild J300,£^M)$0 ^ OtiajM$$Je /^r
Onmunliy dua»«f toanj to local flOr»} of the Bolanctxt Budget
Emergency Defctl Control Act o/ /AB, as
rf. Tint th« HOBM r««de from Its
ill&n«T«f mwt to the amandjiwuit of the S»n-
ace Qiuno«rgd >T to the afonnid blU.
coacur tacrtto w]t&. ao airiftndment a* fol-
lows:
In lien of the soa-propoied by said tmend-
$tSO,WSj909: /VMided further, That up to
11.000.000 sf Hie fwat apjrvprtnttd under tftit
tuaatne may be tra*4/ferrcd to awl nursed irttft
mm* approjuloted /or "Office cf fnxpe&if G#n-
ernl"
Resotovt, TT»t tke Hone* r*e#r«
r«$ulr««Aii and priorai«. Die rerteui JftaC fn.
ait anasmenf o/ me Nattmal Fnswred-
Otr*cttrraSe unit et(u*L** potential alter*
to meet Mat rftnciorafe'i prtndjxij t*-
ii«CT«nrint4oca
the r»»uttKirti«tloo of the S*f*
,Wk(MT Act. Sflch report ihaU nJdrMi—
(1} tbe advune
witti c0a«*ittlfiut« la drlnldw w«tet *ad th*
public luwJtt uid otner benefits tbAt m*7 te
iflaUiad fiy Miuorlnf nch wnttaatawittK
(3) t&* proems for idefitUytBf conuml-
D*BC« tfl Ortnklnf water «4 9«l*ctlaj OOD-
tunlnanC* for control;
(3) wdwdttiM (or th» deTBlopm*nt ot r*fu-
litiona KI tha »fi»«uM bill, uid
Cd&c&r tbwrwtn with u mrtndmnot •£ fol-
lowi; " -."
IB U«a oC tfae rt*ttor propowd br slid
Me /iwsMdal ami tBftcinE fOfoaty of
Staiet to tntpienKQf *A* dffnUiw imutr ifrogwam,
i>icfwitxg epetau /or (neraoKitf /uaiinp o/
State praptturu; and
(7> (>inH»ti«e and aiierrmHix; ntetludt tc *G-
craat the flnxnaesi and te^tiricnJ Gap&ntr of
to
the putc«r *trtck*B by
amendment, tmonded bo r**d U foUowjr
(4) the fluacli! ud wsMlc*! cap*city of
drinking wstftf a,Tat«ma to Intplement mon-
Itortue n«{n#Bte •saociatod wlti) n^o-
!at*d mid ncrt.ruiat*d contai&laiusts «nd op-
tions to fcclllute UnplimooUUon of snch
(b) M&uTOJtrux 4PD RSKHT air
MtKUOES Oi DlttMtlttC W+7Wt,~- txtemUon of tke dmdZiit«' su^wiwii
decree /or JTTD*
o/ tAe raddm mnuSam to a dole ma
later Man OC«6*r 1, 1SS3.
(c) SmoX System Moniioriiif Ctai KedtoC-
*0Bl«iit Olid Me Saznct
/or
. pesticides, PCBt-'ar
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trntor or a jrrtmaty State may "uxtify tank rt-
to pnMde tAat a«ir cfrlnAinc uaar
Mratfw a peputaOuA o/ lew Man 330S
penon* $Jkal2 not M required to conduce addi-
tional qu&rlttlv won<»rlxtf /CT C Jf«c»fr-
*ecflon and prior io Oetater 7, JSS3 /PT any iucA
to detect Urc
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The PRESIDING OFFICER The
clark will report tha ajnendment.
The leglfllativ* clerk read a* follows:
Aexived, thit the House »c«de from Its
disagreenest te th* un«mlm«Dt of the &ea-
»M nwnterwl !»12 to tho •lortsa.id bid. *nd
coDewr therein, with an ama&dsuat M (al-
low*:
IB lieu of th« mauer proposri by said
•iBaadme&t. i&a*rt H: Prwtoixt, That th*
CooBctl OB EonroiurwDtjtl Quality and Offlc*
of EnvtroonwKittl QnaJtty S2l»ll ralrcbiir**
oth*r ac«Bcl«s for not low dua we-half of
th« jpofiOBBel coropdnsaUon coed of LmU¥ld-
ttala dMudl«d to it-".
Mr. METZSNBAUM, M;
rise on behalf of Senator W»TH to ad-
dreBB myself to this amendaieat. which
I very atraagrly $iipi»rt. Senator WIRTH
is unable to bs with UB at this lat«
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Distribution List
Administrator
Deputy Administrator
Assistant Administrators
Regional Administrators
Office of Policy, Planning and Evaluation
Office of Radiation Programs
Office of Water
DOE
NWTRB
NRG
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