Order Code RS20672
Updated February 7, 2005
CRS Report for Congress
Received through the CRS Web
Arsenic in Drinking Water:
Regulatory Developments and Issues
Mary Tiemann
Specialist in Environmental Policy
Resources, Science, and Industry Division
Summary
In 1996, Congress directed the Environmental Protection Agency (EPA) to issue
a new standard for arsenic in drinking water by January 2001. Congress also directed
EPA, with the National Academy of Sciences (NAS), to study arsenic’s health effects
to reduce the uncertainty in assessing health risks associated with exposure to low levels
of arsenic. EPA had adopted an interim standard of 50 parts per billion (ppb) in 1975.
In 1999, the NAS concluded that the standard did not achieve EPA’s goals for public
health protection and recommended that it be tightened as soon as possible.
On January 22, 2001, EPA issued a final rule and set the standard at 10 ppb, with
an effective date of March 23, 2001; water systems were given until January 23, 2006
to meet the standard. EPA projected that compliance could be costly for some small
systems, but water utilities and communities expressed concern that EPA had
understated the rule’s costs. Subsequently, EPA postponed the rule’s effective date to
February 22, 2002, in order to review the science, costs, and benefits analyses that
supported the rule. In October 2001, EPA announced that the standard will be 10 ppb.
The rule became effective on February 22, 2002, and the compliance date for water
systems remained unchanged. EPA and Congress are now focusing on how to help
communities comply with the new rule by January 23, 2006. This report reviews the
arsenic rule and subsequent EPA and congressional actions. It will be updated.
Regulatory Background
Arsenic is a widely distributed, naturally occurring element in the Earth’s crust and
is present in trace amounts in all living organisms. Higher levels of arsenic tend to be
found more frequently in ground water than in surface water. Because small water
systems typically rely on wells for drinking water, while the largest systems typically rely
on surface-water sources, arsenic tends to occur in higher levels more often in water used
by small communities. In the United States, the average level measured in ground-water
samples is less than or equal to 1 part per billion (ppb, or micrograms per liter (:g/L);
however, higher levels are not uncommon. Compared to the rest of the United States,
Congressional Research Service ˜ The Library of Congress

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Western states have more water systems with levels exceeding 10 ppb, and levels exceed
50 ppb in some locations. Parts of the Midwest and New England also have some water
systems with arsenic levels exceeding 10 ppb, but most systems have lower levels. EPA
projects that 5.5% of water systems, serving 11 million people, are likely to exceed the10
ppb level. Sources of arsenic in water include natural sources, releases from its use as a
wood preservative, in semi-conductors and paints, and from agriculture and mining.
The current federal drinking water standard for arsenic, 50 ppb, was set by the U.S.
Public Health Service in 1942. EPA adopted that level and issued an interim drinking
water regulation for arsenic in 1975. This standard was based on estimated total dietary
intake1 and non-cancer health effects. In 1986, Congress amended the Safe Drinking
Water Act (SDWA), converted all interim standards to National Primary Drinking Water
Regulations, and included arsenic on a list of 83 contaminants for which EPA was
required to issue new standards by 1989.
EPA’s extensive review of arsenic risk assessment issues had caused the Agency to
miss the 1989 deadline for issuing a new standard. As a result of a citizen suit, EPA
entered into a consent decree with a new deadline for the rule of November 1995. EPA
continued work on risk assessment, water treatment, analytical methods, implementation,
and occurrence issues but, in 1995, decided to delay the rule in order to better characterize
health effects and assess cost-effective removal technologies for small utilities.
Arsenic and the 1996 SDWA Amendments
In the 1996 SDWA Amendments (P.L. 104-182), Congress directed the EPA to
propose a new drinking water standard for arsenic by January 1, 2000, and to promulgate
a final standard by January 1, 2001. Congress also directed EPA to develop, by February
1997, a comprehensive research plan for arsenic to support the rulemaking effort and to
reduce the uncertainty in assessing health risks associated with low-level exposures to
arsenic. EPA was directed to conduct the study in consultation with the National
Academy of Sciences and others. Congress authorized appropriations of $2.5 million for
each of fiscal years 1997 through 2000 for arsenic studies. In 1996, EPA requested the
National Research Council (NRC) to review the available arsenic toxicity data base and
to evaluate the scientific validity of EPA’s risk assessments for arsenic.
The NRC issued its report in March 1999, and recommended that the standard be
reduced, but did not recommend a particular level. The NRC reported that available data
provided ample evidence for EPA’s classification of inorganic arsenic as a human
carcinogen, but that EPA’s dose-response assessment, which was based on the Taiwan
study, deserved closer scrutiny. The NRC explained that the data limitations of the study
for use in dose-response assessment were due to insufficient detail, as the study contained
only a summary of data. The Council also reported that research suggests that arsenic
intake in food is higher in Taiwan than in the United States, further complicating efforts
to use the data for arsenic risk assessment. Based on findings from three countries where
individuals were exposed to very high levels of arsenic (several hundreds of parts per
billion or more), the NRC concluded that the data are sufficient to add lung and bladder
1 Food is a significant source of arsenic. The NAS estimates that, in the United States, inorganic
arsenic intake from food is comparable to drinking water containing 5 ppb arsenic.

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cancers to the cancers caused by ingestion of inorganic arsenic; however, the NRC noted
that few data address the risk of ingested arsenic at lower concentrations, which would
be more representative of levels found in the United States. The Council concluded that
while a nonlinear dose-response curve is most probable for arsenic (i.e., at some low dose,
arsenic would not be toxic), the available research was inadequate to rule out linearity
(i.e., any dose might have an adverse effect).2 The NRC added that studies of critical
importance for improving the scientific validity of arsenic risk assessment were still
needed, and recommended research studies to EPA.
EPA’s Proposed and Final Arsenic Rule
In June 2000, EPA published its proposal to revise the arsenic standard from 50 ppb
to 5 ppb and requested comment on options of 3 ppb, 10 ppb, and 20 ppb. EPA stated
that the proposal relied primarily on the NRC analysis and some recently published
research, and that it would further assess arsenic’s cancer risks before issuing the final
rule. As proposed, the standard would have applied only to community water systems.
Non-transient, non-community water systems (e.g., schools with their own wells) would
have been required only to monitor and then report if arsenic levels exceeded the standard.
In the final rule, published on January 22, 2001 (66 FR 6976), EPA set the standard at 10
ppb and applied it to non-transient, non-community water systems as well as community
systems. Water systems have until January 23, 2006, to comply.3 EPA estimates that
3,000 (5.5%) of the 54,000 community water systems, and 1,100 (5.5%) of the 20,000
non-transient, non-community water systems will need to take measures to meet the
standard. Most of these systems serve fewer than 500 people.
Standard-Setting Process. In developing standards, EPA is required to set a
maximum contaminant level goal (MCLG) at a level at which no known or anticipated
adverse health effects occur and that allows an adequate margin of safety. (EPA sets the
MCLG at zero for carcinogens (as it did for arsenic), unless a level exists below which
no adverse health effects occur.) EPA must then set an enforceable standard, the MCL,
as close to the MCLG as is “feasible” using the best technology, treatment, or other means
available (taking costs into consideration). EPA’s determination of whether a standard is
“feasible” typically is based on costs to systems serving more than 50,000 people. Less
than 2 % of community water systems (753 of the 54,352 systems) are this large, but they
serve roughly 56% of all people served by community systems.4
2 National Research Council, Arsenic in Drinking Water, National Academy of Sciences,
National Academy Press, Washington, D.C., 1999, pp. 7, 22.
3 See EPA’s Technical Fact Sheet: Final Rule for Arsenic in Drinking Water, available online
at [http://www.epa.gov/safewater/ars/ars_rule_techfactsheet.html].
4 SDWA does not discuss how EPA should consider cost in determining feasibility; thus, EPA
has relied on legislative history for guidance. Congress most recently discussed this matter in the
Senate report for the 1996 Amendments. The report states that “[f]easible means the level that
can be reached by large regional drinking water systems applying best available treatment
technology. ... This approach to standard setting is used because 80% of the population receives
its drinking water from large systems and safe water can be provided to this portion of the
population at very affordable costs.”(U.S. Senate, Safe Drinking Water Amendments Act of 1995,
Report of the Committee on Environment and Public Works on S. 1316, S.Rept. 104-169, Nov.
7, 1995, p. 14.) About 80% of the population is served by systems serving 10,000 or more
(continued...)

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Variances and Exemptions. Congress recognized that the technical and cost
considerations associated with technologies selected for large cities often are not
applicable to small systems. The 1996 Amendments require that each rule establishing an
MCL must list technologies or other means that comply with the MCL and are affordable
for three size categories of small systems. The amendments also directed EPA to identify
variance technologies for small systems, if no affordable compliance technology is listed.
A variance technology need not meet the MCL, but must protect public health. EPA has
not identified variance technologies for this or any other rule, because the Agency has
determined that affordable compliance technologies are available for small systems. Thus,
small system variances are not available for the arsenic rule.
States may grant temporary exemptions from the standard if, for certain reasons
(including cost), a system cannot comply on time. The arsenic rule gives systems 5 years
to comply with the new standard; an exemption allows another 3 years for qualified
systems. Systems serving 3,300 or fewer persons may receive up to 3 additional 2-year
extensions, for a total exemption duration of 9 years (and a total of 14 years to achieve
compliance). In the final rule, EPA noted that exemptions will be an important tool to
help states address the number of systems needing financial assistance to comply with this
rule and other SDWA rules (66 FR 6988). However, to grant an exemption, the law
requires a state to hold a public hearing and make a finding that the extension will not
result in an “unreasonable risk to health.” Because the exemption process is complex,
states have seldom granted them. State officials note that “unreasonable risk to health”
has never been defined, and that states must make a separate finding for each system.
Thus, it is uncertain whether states will be able to, or choose to, grant many exemptions.

Balancing Costs and Benefits. Another 1996 SDWA provision requires that,
when proposing a rule, EPA must publish a determination as to whether or not the
benefits of the standard justify the costs. If EPA determines that the benefits do not justify
the costs, then EPA may set the standard at the level that maximizes health risk reduction
benefits at a cost that is justified by the benefits. EPA determined that the “feasible”
arsenic level (for systems serving more than 50,000 people) is 3 ppb, but that the benefits
of that level would not justify the costs. Thus, EPA proposed a standard of 5 ppb. Also,
EPA had proposed to require non-transient, non-community water systems (e.g., schools)
only to monitor and report (as opposed to treating), largely because of cost-benefit
considerations. In setting the standard at 10 ppb, EPA cited SDWA, stating that this level
“maximizes health risk reduction benefits at a cost that is justified by the benefits.” EPA
also applied the final rule to non-transient, non-community water systems.
Anticipated Benefits and Costs. In the proposed rule, EPA noted the need for
additional research to address the scientific uncertainty concerning the health effects and
risk associated with arsenic ingestion; nonetheless, EPA estimated that the rule would
generate a range of health benefits. In the final rule, EPA estimated that reducing the
standard to 10 ppb will prevent roughly 19 to 31 bladder cancer cases and 5 to 8 bladder
cancer deaths each year. EPA further estimated that the new standard could prevent 19
to 25 lung cancer cases and 16 to 22 lung cancer deaths each year. EPA estimated that
the rule would provide numerous other cancer and non-cancer health benefits that were
not quantifiable.
4 (...continued)
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Regarding the cost of meeting the 10 ppb standard, EPA estimated that, for small
systems (serving fewer than 10,000 people), the average cost per household ranges from
$38 to $327 per year. Roughly 97% of systems expected to exceed the standard are small
systems. For large systems, water cost increases range from $0.86 to $32 per household.
EPA estimated the total national, annualized cost for the rule to be about $181 million.
In its role of providing an expert assessment of the proposal, EPA’s Science Advisory
Board (SAB) raised a number of concerns about EPA’s economic and engineering
assessment and reported that several of EPA’s cost assumptions were likely to be
unrealistic and various costs seemed to be excluded. The SAB also suggested that EPA
should give further thought to the concept of affordability as applied to this standard.5
Many municipalities and water system representatives have disagreed with EPA’s
cost estimates. The American Water Works Association (AWWA), for example, while
supporting a reduced standard, estimated that the new rule will cost $600 million annually
and require $5 billion in capital outlays. The AWWA attributed differences in cost
estimates partly to the costs of handling arsenic-contaminated residuals and the estimated
number of wells affected. AWWA projected that the rule could cost individual households
in the Southwest, Midwest and New England as much as $2,000 per year.6
Arsenic Rule Review. On January 22, 2001, EPA issued a final rule. On March
23, 2001, the Administrator delayed the rule for 60 days, citing concerns about the science
supporting the rule and its estimated cost to communities. On May 22, EPA delayed the
rule’s effective date until February 22, 2002, but did not change the 2006 compliance date
for water systems (66 FR 28342). At EPA’s request, the NRC undertook an expedited
review of EPA’s arsenic risk analysis and recent health effects research, the National
Drinking Water Advisory Council (NDWAC) reassessed the rule’s cost, and the SAB
reviewed its benefits. EPA also requested public comment on whether the data and
analyses for the rule support setting the standard at 3, 5, 10, or 20 ppb (66 FR 37617).
The NRC concluded that “recent studies and analyses enhance the confidence in risk
estimates that suggest chronic arsenic exposure is associated with an increased incidence
of bladder and lung cancer at arsenic levels in drinking water below the current MCL of
50 :g/L.”7 The NDWAC reported that EPA produced a credible cost estimate, given
constraints and uncertainties, and suggested ways to improve estimates. The SAB offered
ways to improve the benefits analysis. In October 2001, EPA concluded that 10 ppb was
the appropriate standard, and announced plans to provide $20 million for research on
affordable arsenic removal technologies to help small systems. This research is ongoing.
Legislative and EPA Actions

Many bills were offered in the 107th Congress in response to the arsenic rule and its
delay. The conference report to EPA’s FY2002 appropriations act, P.L. 107-73 (H.Rept.
107-272) prohibited EPA from using funds to delay the rule; required EPA to review its
affordability criteria and how small system variance and exemption programs should be
implemented for the new arsenic rule; and urged EPA to recommend procedures to grant
5 Science Advisory Board, Arsenic Proposed Drinking Water Regulation: A Science Advisory
Board Review of Certain Elements of the Proposal
, EPA-SAB-DWC-01-001, Dec. 2000, p. 4.
6 AWWA, January 17, 2001. See [http://www.awwa.org/Advocacy/pressroom/pr/010111.cfm].
7 National Research Council, Arsenic in Drinking Water: 2001 Update, NAS, p. 14.

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more time for small communities in cases where compliance by 2006 poses an undue
economic hardship. Conferees directed EPA to report on its review, potential funding
mechanisms for small community compliance, and possible legislative actions that, if
taken by the Congress, “would best achieve appropriate extensions of time for small
communities while also guaranteeing maximum compliance” (H.Rept. 107-272, p. 175).

EPA’s March 2002 Report to Congress summarized agency activities that addressed
these directives. Major activities included (1) reviewing the small system affordability
criteria and variance process; (2) developing a small community assistance plan to
improve access to financial and technical assistance, improve compliance capacity, and
simplify the use of exemptions; and (3) implementing a $20 million research and
technical assistance strategy.8 EPA has completed a number of efforts to help states and
water systems meet the requirements of the arsenic rule. In August 2002, EPA issued
Implementation Guidance for the Arsenic Rule, which includes guidance to help states
grant exemptions. EPA has offered technical assistance and training to small systems, and
is sponsoring research on low-cost treatment technologies for removing arsenic from
drinking water. Also, EPA is working with small communities to maximize loans and/or
grants under SDWA and U.S. Department of Agriculture water infrastructure programs.
The 108th Congress evidenced concern over the financial impact that compliance
with this standard may present for communities. In the conference report for the omnibus
appropriations act for FY2005 (P.L. 108-447, H.Rept. 108-792), conferees expressed
concern that many rural communities will be unable to meet the new requirements which
could pose a “huge financial hardship.” The conferees directed EPA to report by August
2005 on the extent to which communities will be impacted by the arsenic rule, and to
propose compliance alternatives and make recommendations to minimize costs. The
conference report included $8.2 million for arsenic removal research. Other bills would
have created grant programs to help small systems comply with the arsenic rule and other
SDWA standards, increased funding for the Drinking Water State Revolving Fund
(DWSRF) program, and authorized research on affordable arsenic removal technologies.
In the 109th Congress, the Rural Community Arsenic Relief Act has been
reintroduced (S. 41) to require states to grant small nonprofit water systems exemptions
from regulations for naturally occurring contaminants, in certain circumstances.
EPA’s effort to revise the arsenic standard generated considerable debate as to what
standard best reduces health risks at a cost that is justified, particularly for small towns,
where most elevated arsenic levels occur. This rule also provoked a range of policy
responses and illustrated some of the challenges and uncertainties associated with risk,
cost, and benefit analyses. Nonetheless, the National Academy of Sciences concluded that
while studies for improving the accuracy of arsenic risk assessment are still needed, recent
analyses suggest that the risks for cancer incidence are greater than previously thought.
Consequently, EPA retained the standard of 10 ppb, and Congress affirmed that standard.
Now, as the January 23, 2006, deadline nears, Congress and EPA are focusing on helping
communities achieve compliance with the new standard. (See also CRS Issue Brief
IB10118, Safe Drinking Water Act: Implementation and Issues. For federal financial
assistance information, see CRS Report RL30478, Federally Supported Water Supply and
Wastewater Treatment Programs
.)
8 For details, see EPA’s Report to Congress: Small Systems Arsenic Implementation Issues,
March 2002, available at [http://www.epa.gov/safewater/arsenic.html].