Order Code RS20672
Updated April 29, 2002
CRS Report for Congress
Received through the CRS Web
Arsenic in Drinking Water:
Recent 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 propose
a new standard for arsenic in drinking water by January 1, 2000, and to issue a final
standard by January 1, 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 set the standard
at 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 June 22, 2000, EPA proposed a revised standard of 5
ppb and projected that compliance could be costly for small communities. A question of
ongoing scientific debate concerned whether significant adverse health effects occur from
ingesting arsenic at very low levels. Because EPA proposed the rule nearly 6 months late,
Congress extended the deadline to June 22, 2001, to give EPA time to evaluate public
comments and complete analyses before issuing a final rule.
On January 22, the final rule, which set the standard at 10 ppb, was published in the
Federal Register with an effective date of March 23, 2001; public water systems were
given until 2006 to meet the new standard. On May 22, EPA extended a previous 60-day
delay of the rule’s effective date to February 22, 2002 in order to review risk, benefit,
and cost issues associated with the rule. The 2006 compliance date for water systems
remained unchanged. In October, EPA announced that the standard would be 10 ppb.
In November, Congress approved EPA’s FY2002 appropriations bill which included
language prohibiting EPA from using the funds to delay the rule. The arsenic rule became
effective on February 22, 2002. This report reviews EPA efforts to develop a new arsenic
rule and summarizes key provisions and subsequent events.
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
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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,
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, and 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, still in effect, 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.
In 1989, after reviewing EPA’s 1988 risk assessment for arsenic, the EPA Science
Advisory Board (SAB) reported that: 1) studies suggesting that arsenic may be an essential
nutrient were not definitive; 2) data from Taiwan demonstrated that high doses of arsenic
could cause skin cancer; 3) the Taiwan data were inconclusive to determine cancer risk at
levels ingested in the United States; and 4) some low levels of arsenic may be detoxified
by the body. The SAB recommended that EPA set the standard “using a non-linear dose-
response (at some low dose, arsenic would not be toxic),” and that EPA revise its risk
assessment.2 In 1992, the Advisory Board expressed uncertainty as to whether EPA could
obtain enough data to regulate arsenic using a non-linear model.
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
1 Food is a significant source of arsenic. The NRC estimates that, in the United States, inorganic
arsenic intake from food is comparable to drinking water containing 5 ppb arsenic.
2 U.S. Environmental Protection Agency. Arsenic in Drinking Water: Regulatory History. See
Internet website: [http://www.epa.gov/safewater/ars/ars1.html].

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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 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.3 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 3 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
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, the available research was
inadequate to rule out linearity (i.e., any dose might have an adverse effect).4 The NRC
added that studies of critical importance for improving the scientific validity of arsenic risk
assessment are still needed, and recommended research studies to EPA.
EPA’s Proposed and Final Arsenic Rule
On June 22, 2000, EPA published its proposal to revise the arsenic standard from the
current level of 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 also 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 (such as schools and offices)
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 the rule to non-transient, non-community water systems
as well as to community systems. The rule’s general effective date was 60 days after
publication; however, public water systems were given until 2006 to comply. On May 22,
EPA delayed the rule’s effective date to February 22, 2002 (66 FR 28342), but did not
change the compliance date for systems (see below).
Standard-setting process. In developing standards, EPA is required to set a
nonenforceable 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
3 National Research Council. Arsenic in Drinking Water. National Academy Press. Washington,
D.C. 1999. p. 22.
4 National Research Council. p. 7.

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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.5
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 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. For the
arsenic rule, EPA did not identify variance technologies because the Agency determined
that affordable compliance technologies are available for small systems. Thus, small
system variances
are not available for the arsenic regulation.
States or EPA may grant temporary exemptions from the standard if, due to certain
compelling factors (including cost), a system cannot comply on time. All systems are
required to comply with the new standard in 5 years; an exemption allows an additional
3 years for qualified systems. Systems serving 3,300 persons or fewer may have up to 3
additional 2-year extensions, for a total exemption duration of 9 years (for a total of up
to 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).

Balancing costs and benefits. Another 1996 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,
EPA may set the standard at the level that maximizes health risk reduction benefits at a
cost that is justified by the benefits. For arsenic, EPA determined that the “feasible” level
(for systems serving more than 50,000 people) is 3 ppb, but that the benefits of this level
would not justify the costs. Consequently, 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.”
5 SDWA does not discuss how EPA should consider cost in determining feasibility; thus, EPA has
relied on legislative history for guidance. Congress most recently expressed its view in this matter
in the Senate report accompanying 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. p. 14.
Nov. 7, 1995.) EPA estimates that roughly 80% of the population is served by systems serving
10,000 or more people.

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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 various health benefits. In the proposal, EPA estimated that lowering the
standard to 5 ppb would prevent about 5 bladder cancer deaths nationwide annually, while
a 10 ppb standard would prevent 3 bladder cancer deaths annually. EPA projected that
arsenic-related lung cancers and cardiovascular diseases also would be reduced. In the
final rule, EPA estimated that, with a 10 ppb standard, the annual number of bladder and
lung cancer deaths avoided ranges from 21 to 30. EPA also stated that the rule would
provide numerous other cancer and non-cancer health benefits that were not quantifiable.
Regarding the cost of meeting the 10ppb standard, EPA estimated that, for small
systems (serving fewer than 10,000 people), the average annual cost per household ranges
from $38 to $327. 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 proposed rule, 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 that 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.6 Many municipalities and water system representatives also disagreed with
EPA’s 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 projects that the rule could cost individual households
in the Southwest, Midwest and New England as much as $2,000 per year.7
EPA statistical estimates indicate 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
would need to take measures to meet the new standard. Most of these systems serve fewer
than 500 people. (See [http://www.epa.gov/safewater/ars/ars_rule_techfactsheet.html].)
Legislative and EPA Actions

In response to EPA’s delay in proposing the arsenic rule, Congress extended the
deadline for the final rule from January 1, to June 22, 2001, in EPA’s FY2001
appropriations. On January 22, 2001, EPA issued a final rule. On March 23, the EPA
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
public water systems (66 FR 28342). At EPA’s request, the NAS 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 EPA’s
6 Science Advisory Board. Arsenic Proposed Drinking Water Regulation: A Science Advisory
Board Review of Certain Elements of the Proposal. EPA-SAB-DWC-01-001 December 2000. p.
4. Report available at [http://www.epa.gov/sab/dwc0101.pdf].
7 AWWA. January 17, 2001. Available at: [http://www.awwa.org/pressroom/pr/010111.htm].

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Science Advisory Board reviewed its benefits. On July 19, EPA issued a proposal
requesting comment on whether the data and technical analyses for the January rule
support setting the standard at 3, 5, 10, or 20 ppb (66 FR. 37617). The risk, cost, and
benefits reviews were completed in late summer. The NRC, in its review, 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" ppb. The NDWAC
reported that EPA produced a credible cost estimate, given constraints and uncertainties,
and offered recommendations to improve estimates. The SAB made recommendations to
improve the benefits analysis. EPA studied the reviews, and on October 31 announced that
the arsenic standard will be 10 ppb. EPA plans to provide $20 million over the next 2
years for research and development of more cost-effective technologies to help small
systems. EPA also will work with small communities to maximize loans and grants from
SDWA and Rural Utilities Service (U.S. Department of Agriculture) programs.
Various bills were introduced in response to this rule and its delay. The House and
Senate added arsenic amendments to their FY2002 appropriations bill for EPA (H.R.
2620). The House version prohibited EPA from using funds to delay the January rule or
to issue a rule that sets the standard above10 ppb. The Senate bill directed EPA to put into
effect immediately a standard that protects sensitive subpopulations and that lifts the
suspension of the January rule's effective date for new community reporting requirements
(the rule requires certain systems to provide additional risk information starting in 2002).
On November 8, the House and Senate approved the conference report to H.R. 2620 (H.
Rept. 107-272) which: (1) prohibits EPA from using funds to delay the January rule; (2)
requires EPA to review its affordability criteria and how small system variance and
exemption programs should be implemented for arsenic; (3) urges EPA to recommend
procedures to grant more time for small communities in cases where compliance by 2006
poses an undue economic hardship. The bill also required EPA to report to Congress by
March 2002, on a review of its affordability criteria, administrative actions, potential
funding mechanisms for small community compliance, and possible legislative actions.
(See EPA’s Report to Congress: Small Systems Arsenic Implementation Issues. March
2002, at: [http://www.epa.gov/safewater/arsenic.html].) Among other bills, H.R. 1252
would reduce the standard to 3 ppb by 2006, and authorize grants for small systems; H.R.
1413 would codify the January rule and increase funding for the SDWA state revolving
fund program. H.R.2112 would specify the use of federal grant programs for arsenic
treatment. S. 223 would void the new rule; S. 632 and S. 635 would reinstate the rule,
with S. 632 requiring funds to be allotted to states based on arsenic treatment needs. S.
1299 would create a grant program to help small systems comply with SDWA standards.
Conclusion
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 violations are expected. This rule also induced a range of policy responses and
illustrated some of the challenges and uncertainties associated with risk, cost, and benefit
analyses. Nonetheless, the NRC 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 has retained the
standard of 10 ppb, and Congress has affirmed that standard, and the January rule in
general. The rule became effective on February 22, 2002. EPA and Congress are now
focusing on how to help communities achieve compliance with the new standard by 2006.