Executive Summary
National Academy of Sciences Meeting on Radon in Drinking Water
July 14-15
Washington, D.C.
The initial meeting of the National Academy of Sciences (NAS) Committee
on Risk Assessment of Exposure to Radon in Drinking Water was held in
Washington, DC on July 14-15, 1997. The purpose of the meeting was to
review the Committee charge and to receive briefings from the Environmental
Protection Agency (EPA) and others. As directed by the 1996 amendments
to the Safe Drinking Water Act (SDWA), EPA has arranged for the NAS to
conduct an independent evaluation of risks associated with exposure to
radon in drinking water. The Committee will review existing assessments,
and may undertake new analyses if viewed as necessary.
The full Committee has adequate funds to meet 5-7 times, and will try
to complete their report by April 1998, to allow for NAS' peer review
process and final report by July 31, 1998. The next full Committee meeting
is likely to be in October, after the release of the NAS report on BEIR
VI (soil gas radon risks). With the exception of executive sessions, these
meetings are expected to be open to the public.
Participants
All 12 Committee members attended, as well as representatives of the
American Water Works Association, and representatives of specific California
and Nebraska public water systems.
Key Issues Discussed
Committee members raised concerns about several issues (both within and
outside the scope of the charge to the Committee), including the number
of systems impacted by a radon in drinking water rule ( regarding EPA
occurrence data); ingestion exposure and risk and the model used, including
limitations of data used by EPA and uncertainties in radon distribution
to the target organs, especially stomach. Committee members also expressed
interest in hearing from other water utility organizations and other stakeholders.
AWWA (Dr. Richard Toohey, Oak Ridge Institute for Science & Education,
on behalf of AWWA) raised several issues, including the existence of a
threshold for radon risk, cost, treatment side effects, and need for better
occurrence data.
Dr. McLellan, Chair, Chafee-Lautenberg Study Review Committee (1994 Report
to Congress on Radon in Drinking Water) of the Science Advisory Committee
made a presentation and raised several issues, including the need for
new data on occurrence and cost, uncertainty of ingestion risks, and as
broad a perspective as possible taking into account risk from soil gas.
Charge to Committee
Risk Assessment: Initially the Committee will focus on producing
a unit (per pCi/L) risk estimate, may also decide to address population
risk. The Committee also discussed addressing transfer factor, ambient
radon level (important factors in EPA's determination of the alternative
maximum contaminant level). The Committee will also address overall uncertainty
as well as uncertainties of specific parameters used.
Health Risk Reduction Benefits of Reducing Radon in Indoor Air:
For reducing radon in indoor air (from soil gas), the Committee will assess
information provided by EPA on reducing radon levels in existing homes,
building homes radon resistant, and other health risk reduction measures
(if any). The NAS assessment will be used by EPA in developing guidelines
for multimedia mitigation programs. EPA will need to provide guidelines
on how to address risk reduction benefits on a state/local scale. The
Committee also expressed some interest in water mitigation; however, EPA
stated that this was not the primary need.
Uncertainties will be incorporated in each section, as well as addressed
in a separate section independently.
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