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Stakeholder Meeting
on Development of Regulation for Radon in Public
Drinking Water
October 19-20, 1998
On October 19 and 20, 1998, the U.S. Environmental Protection Agency
(EPA) held the fourth in a series of stakeholder meetings on the development
of a regulation for radon in public drinking watery systems. Issues discussed
at the meeting include:
- Updates on key technical inputs to developing the regulation, including
radon occurrence in public drinking water systems, analytical methods
to detect radon in drinking water, and treatment technologies to remove
radon from water;
- Findings of the National Academy of Sciences (NAS) Report: Risk
Assessment of Radon in Drinking Water and its implications for
the development of the radon rule; and
- Current concepts under consideration in the development of guidelines
for multimedia mitigation (MMM) programs.
Participants included representatives of public water utilities, state
drinking water and indoor air programs, public health and environmental
groups, academia, and industries related to radon testing and mitigation,
as well as US EPA and other federal agencies.
Overview
The 1996 Safe Drinking Water Act (SDWA Section 1412(b)) includes specific
requirements for developing a regulation for radon in drinking water,
including the NAS risk assessment, publication of a Health Risk Reduction
and Cost Analysis (HRRCA) for public comment by February 1999 (Federal
Register, 2/26/99, Vol. 64, No. 38), proposed rule by August 1999,
and final rule by August 2000. The SDWA also includes a provision for
development of an alternative Maximum Contaminant Level (AMCL) and a multimedia
mitigation program to reduce radon in indoor air.
In setting the Maximum Contaminant Level (MCL), EPA's primary focus will
be on public health protection, as required by SDWA. The MCL is required
to be set as close as feasible to the Maximum Contaminant Level Goal (MCLG),
taking costs into account. EPA will conduct a cost-benefit analysis, and
the SDWA requires the EPA Administrator to make a determination that the
benefits of an MCL justify the costs. The NAS risk assessment will be
one of many elements considered by EPA. Setting the MCL will ultimately
be a "risk management" decision that considers a variety of information
and analyses, including human health risk, nationwide occurrence of radon
in drinking water, performance of treatment technologies, costs of treatment,
and capabilities of analytical methods.
Technical Updates
Occurrence
EPA is updating its estimates of the national occurrence of radon in
public drinking water systems, using additional data provided by states
and information from the National Inorganics and Radionuclides Survey
(NIRS). EPA is addressing several issues raised in comments on the 1991
proposed regulation:
- Collecting additional data, primarily through states, to develop a
better estimate of influent radon levels;
- Disaggregating the occurrence data for small systems to look more
closely at potential impacts on the smallest system sizes (those serving
populations of 25 to 100 and 101 to 500);
- Evaluating the major sources of radon variability including analytical
variability, sampling variability, temporal (time) variability, and
intra-system variability (differences among radon levels in different
wells in the same system), and the effect of variability on predicting
the number of systems exceeding various radon levels.
Results of the new analysis show generally higher radon levels across
all system sizes than found in the 1991 analysis; no significant difference
in occurrence between the two smallest system sizes; and decreasing variability
with decreasing average radon levels. The results of the analysis investigating
the relative contributions of different sources of in radon variability
indicated that overall in a typical data set covering a wide range of
systems, sampling and analytical variability account for approximately
0.6 percent of the total variance, temporal variability accounts for between
13 to18 percent of the variance, variability in radon levels among different
wells contributes between 12 and 15 percent of the total variance, and
variation among systems accounts for the rest of the variance (approximately
69 percent). The relative contributions from these sources would vary
in different types of systems. For example, intra-system variability makes
a small contribution to total system variance in very very small systems
which tend to have a small number of wells (often only one).
In general, the highest radon in drinking water levels were found in
New England and the mid-Atlantic regions, followed by the Rocky Mountain
and Appalachian states and California. The states of the northwest, Great
Lakes, plains and Gulf coast regions generally had the lowest levels.
The HRRCA will use the occurrence analysis and the NAS risk assessment
to estimate annual deaths from exposure to radon in drinking water, and
to estimate the impact of radon in drinking water at various exposure
levels.
Analytical Methods
EPA is also assessing analytical methods to detect radon in drinking
water, building on the technical evaluation conducted for the 1991 proposal,
looking at performance, availability, and costs. In 1991, EPA proposed
liquid scintillation and de-emanation because of reliability, lack of
interference, availability of equipment, speed, and reasonable cost (currently
estimated at $40-70 per sample for lab analysis). To date, only Standard
Method 7500-Rn (liquid scintillation counting) and the Lucas Cell methods
have adequate inter-laboratory data for evaluation, and are likely to
be the methods proposed in 1999. Lab capacity is expected to be adequate;
however, as with any newly regulated drinking water contaminant, there
may be a short-term lag in certification, while a sufficient number of
laboratories become certified to analyze radon in water.
Treatment Technologies
EPA is evaluating treatment technologies for several reasons: to determine
feasible, "Best Available Technologies" (BAT) based on large municipal
systems; to identify affordable and technically feasible compliance strategies
and variance technologies for small systems (serving less than 10,000
people), and to estimate unit cost in order to complete the cost estimates
in the HRRCA. The primary treatment technologies under consideration are
aeration and granular activated carbon (GAC). There are a variety of aeration
technologies on the market appropriate for the various sizes of public
water systems. For example, of the packed tower aeration (PTA) options,
fully engineered installations are most feasible for large systems, whereas
package plant installations, which usually require less intensive on-site
engineering, may be best for small systems. Lower cost, simpler aeration
technologies also exist. While radon off-gas from aeration treatment is
not currently regulated, local restrictions may require permitting in
some areas. However, due to rapid dilution, radon from treatment off-gas
is usually not found above background levels at a utility's property line.
For cost estimates, EPA will assume that disinfection is either already
in place or would be added to systems where it is not. Although GAC will
likely not be listed as BAT, it may be available as a small systems compliance
technology under certain conditions. GAC as a point-of-entry treatment
technology is also a possible small systems compliance technology. In
general, there may be upper limits to the feasible radon influent level
that can be treated without requiring expensive frequent carbon replacement
schedules.
National Academy of Sciences Report: Risk Assessment of Radon
in Drinking Water
Under SDWA, EPA was required to arrange for the NAS to conduct a risk
assessment of radon in drinking water and an assessment of the health
risk reduction benefits associated with various measures to reduce radon
in indoor air. The NAS Committee's analysis, released on September 15,
1998, resulted in a modest reduction of the estimated overall risk associated
with radon in drinking water compared to previous EPA studies. The NAS
analysis indicates that most (87%) of the cancer risk from radon in drinking
water comes from the transfer of radon into indoor air and the subsequent
inhalation of radon decay products, and that 13% comes from ingestion
of water. The Committee also found that the biological basis for the risk
estimation is consistent with a linear, no-threshold relationship between
exposure and cancer risk. The Committee found insufficient scientific
information to permit development of risk estimates to potentially susceptible
populations (such as infants, children, pregnant women, smokers, and elderly
and seriously il persons), except for the increased lung cancer risk to
smokers.
With respect to the factors identified in SDWA as determinative of the
Alternative Maximum Contaminant Level (AMCL), the Committee determined
that the national average outdoor radon level is between 0.38 and 0.43
pCi/L, and that radon transfers from drinking water into indoor air based
on a factor of 10,000 pCi/L in water to 1 pCi/L in indoor air. Based on
these two factors, the Committee estimated that the AMCL would be about
4000 pCi/L.
Multimedia Mitigation Programs
The NAS report examined potential scenarios for multimedia mitigation
(MMM) programs, implemented at the community level by public water systems.
Based on input from stakeholders, EPA's interest is at the state level
and in developing guidelines to encourage adoption of MMM programs by
the states. EPA's goal is to develop guidance to enable the design and
implementation of do-able MMM programs that will be effective in reducing
risk from exposure to indoor radon. EPA will make every effort to develop
guidance that is simple and provides sufficient flexibility to accommodate
the variety of needs of different states, and to encourage innovation.
EPA is encouraging states and other stakeholders to provide input during
the development stage to help shape the guidelines. EPA will propose the
key elements of the guidelines for comment along with the proposed rule
in August, 1999.
EPA's specific goals for MMM programs are to:
- Reduce public's health risk from radon in indoor air
- Maintain results and infrastructure of ongoing state voluntary radon
programs
- Achieve long-term, continued increase in awareness, testing, mitigation
of existing homes, and new homes built radon-resistant, both nationally
and by state
- Encourage states to develop and implement MMM programs, and in doing
so, minimize the need for individual PWSs to submit MMM plans to EPA
EPA solicited input on several conceptual framework options for developing
the MMM program:
- Set specific numerical targets for states to meet
- Set a level of effort that states must demonstrate will be achieved
through the MMM plans
- Set minimum core program elements required for all MMM plans
Discussion focused on the need for broad EPA MMM guidelines, rather than
prescribed core elements or targets, to allow sufficient flexibility to
address particular state priorities and to use public input in MMM program
design. It was suggested that at a minimum, state MMM plans should:
- Include public participation
- Have a definable endpoint or goal,
- Logically show these endpoints can be attained through proposed MMM
measures, and
- Describe how results will be measured.
There was also discussion of possible funding options for state MMM programs.
EPA has decided to allow Program Assistance Grant funds and Program Management
Set-Aside funds from the Drinking Water State Revolving Fund (DWARF) to
be used by states in setting up and administering MMM programs. EPA is
also exploring the possible use of the DWARF for indoor air mitigation.
It will be up to states to decide whether to use any of these funds for
MMM purposes.
The next stakeholders meeting, to focus on the HRRCA and MMM programs,
will be held in Washington, DC on March 16, 1999.
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