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Stakeholder Meeting Summary
EXECUTIVE SUMMARY
Summary of Second Committee Meeting
October 9-10, 1997
Washington D.C.
I. Background
The 1996 amendments to the Safe Drinking Water Act (§1412(b)(13))
directed the Environmental Protection Agency (EPA) to arrange for the
National Academy of Sciences (NAS) to conduct a risk assessment for radon
in drinking water and an assessment of the health risk reduction benefits
associated with various mitigation methods of reducing radon in indoor
air. EPA issued a grant to NAS in February 1997, and the NAS selected
a committee of scientific experts to address the required assessments.
The Committee has scheduled a series of meetings, beginning in July 1997,
and is expected to provide its report to EPA by July 1998.
II. Summary of October, 1997 Meeting
The second meeting of the National Academy of Sciences/National
Research Council (NAS/NRC) Committee on Risk Assessment of Exposure to
Radon in Drinking Water was held in Washington, D.C. on October 9-10,
1997. The meeting was attended by the Committee Chair, NAS Study Director
and all Committee members, including one member who participated by video
conference. The Committee was briefed on progress of subcommittees, which
are addressing issues such as risk per unit dose of radon in drinking
water, transfer factor from radon in water to radon in residential indoor
air, ambient radon level, uncertainty, and mitigation. Subcommittees have
developed outlines for their sections of the NAS report and are reviewing
literature and available data.
Committee members heard presentations from EPA (Office of Ground
Water and Drinking Water and Office of Radiation and Indoor Air), including
an update on the schedule for the rulemaking process, and an overview
of issues raised at stakeholder meetings on radon risks, risk to smokers
and sensitive or vulnerable populations, multimedia mitigation, equity
impacts of implementing a multimedia mitigation program, analytical methods,
treatment technologies, risk communication and tribal issues.
The Committee also heard a lecture from Dr. Edith Robbins, Professor
of Cell Biology (NYU) on histology of the stomach and G.I. tract. The
key emphasis was the relative inaccessibility of stem cells along the
entire digestive tract, but particularly within the stomach. The information
Dr. Robbins' presented raised questions among some Committee members about
whether radon could cause stomach cancer by direct exposure, or only through
the circulatory system. The Committee will hear presentations from other
experts on ingestion risk before making a final determination on the risks
of ingesting radon in drinking water.
The Committee requested clarification on some elements of the charge,
particularly "estimates of cancer risks per unit of exposure" and asked
EPA to write a letter confirming mutual understanding that the exposure
refers to "per unit concentrations of radon in drinking water."
The Committee will rely on the Biological Effects of Ionizing Radiation
(BEIR) VI study (December 1997 release expected) for cancer risk estimates
for smokers, and will also identify risks to any other sensitive subpopulations.
III. Next Steps
Future committee meetings are planned on November 6-7 (Beckman Center,
Irvine, CA), December 2-3 (Washington, DC), and January 5-6 (Beckman Center,
Irvine, CA).
Subcommittees addressing transfer factors and national ambient radon
level are expected to provide more detailed progress reports at the November
meeting.
IV. For More Information
More detailed information about the NAS Committee meetings, including
the agenda for the next meeting, will be available via the Office of Ground
Water and Drinking Water home page at http://www.epa.gov/safewater/,
under the "Calendar" section, or at the National Academy of Sciences homepage
at http://www.nas.edu 
(follow the link at the bottom of the page for "More Events") or go directly
to http://www2.nas.edu/meeting/
.
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