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NRC/NAS Report
on Arsenic in Drinking Water
What is the NRC/NAS Report on Arsenic in Drinking Water?
- The Office of Water of the U.S. Environmental Protection Agency (EPA)
commissioned this report in 1996. EPA asked the National Research Council
(NRC) of the National Academy of Sciences (NAS) to review the current
state of the science for estimating risks associated with arsenic in
drinking water.
- This report is based on a more complete database and research findings
that have become available since the 1988 EPA risk assessment.
What does the report say?
- The report recommends lowering the current drinking water standard
of 50 micrograms per liter (ug/L; equivalent to parts per billion (ppb)).
(EPA initially set this standard in 1975 as an interim standard for
arsenic; the Safe Drinking Water Act, as amended in 1986, converted
it to a maximum contaminant level (MCL) in 1986.)
- This recommendation is based on NRC assessments of the risks of skin,
lung, and bladder cancer from drinking water containing inorganic arsenic.
The report also describes potential risks of cardiovascular effects.
What is EPA going to do?
- EPA expected the NRC to recommend lowering the MCL. The NRC report
provides the update to the science needed to support revising the risk
characterization to develop the health-based non-enforceable goal for
drinking water, known as the maximum contaminant level goal (MCLG).
- Under the Safe Drinking Water Act as amended in 1996, EPA has to propose
a new arsenic regulation by January 1, 2000 and finalize a new rule
by January 1, 2001. In addition, EPA must review the new regulation
by 2007, at the latest, and revise it, if appropriate, based on new
data and information.
- EPA has been preparing to propose an arsenic regulation (new MCL,
an MCLG and compliance treatment technologies) and will issue the proposed
and final regulations on schedule. In addition to using the results
of a revised risk characterization, the MCL takes into account factors
such as the availability of appropriate analytical methods; the efficiency
of treatment technologies for all sizes of public water systems; the
cost of treatment options; and the health benefits achieved by different
arsenic levels in drinking water.
- Also as required by the 1996 amendments, EPA submitted a research
plan to Congress in 1997 that would provide data for the next appraisal
of the arsenic standard.
- EPA will reexamine its criteria and existing policy for arsenic under
the Clean Water Act. The current ambient water quality arsenic criterion
is already much lower than the current drinking water MCL.
Who is at risk? Since the current MCL is at 50 ppb, is everyone exposed
to 50 ppb?
- Arsenic levels are already below the 50 ppb level in all community
water systems with surface water supplies and are infrequently exceeded
by community water systems with ground water supplies.
- In a 1992 study, EPA estimated that only 1% of all public water systems
would have arsenic levels greater than 20 ppb. The proposed rule will
be based on a new national occurrence estimate using more current monitoring
data.
The NRC/NAS Report is available online:
Full
Report 
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