Order Code RS20672
Updated January 17, 2007
Arsenic in Drinking Water:
Regulatory Developments and Issues
Mary Tiemann
Specialist in Environmental Policy
Resources, Science, and Industry Division
Summary
In January 2001, the Environmental Protection Agency (EPA) promulgated a new
regulation for arsenic in drinking water, as required by 1996 Safe Drinking Water Act
Amendments. The rule set the legal limit for arsenic in tap water at 10 parts per billion
(ppb), replacing a 50 ppb standard set in 1975, before arsenic was classified as a
carcinogen. The arsenic rule was to enter into effect on March 23, 2001, and public
water systems were given until January 23, 2006, to comply. When issuing the rule, the
EPA projected that compliance could be costly for some small systems, but many water
utilities and communities expressed concern that the EPA had underestimated the rule’s
costs. Subsequently, the EPA postponed the rule’s effective date to February 22, 2002,
to review the science and cost and benefit analyses supporting the rule. In October
2001, EPA affirmed the 10 ppb standard. The compliance date remained unchanged, and
the new standard became enforceable for water systems in January 2006.
Congress and the EPA have focused on how to help communities comply with the
new regulation. In the 109th Congress, various bills were offered to provide more
financial and technical assistance and compliance flexibility to small systems; however,
none of the bills was enacted.
Background
Sources of arsenic in water include natural sources, particularly rocks and soils, and
also releases from its use as a wood preservative, in semi-conductors and paints, and from
mining and agricultural operations. Elevated levels of arsenic are found more frequently
in ground water than in surface water. Because small communities typically rely on wells
for drinking water, while larger cities typically use surface-water sources, arsenic tends
to occur in higher concentrations more frequently in water used by small communities.
In the United States, the average arsenic 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 with the rest of the United States, Western
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states have more water systems with levels exceeding 10 ppb; levels in some locations in
the West exceed 50 ppb. Parts of the Midwest and New England also have some water
systems with arsenic levels exceeding 10 ppb, but most systems meet the new standard.
When issuing the rule, the EPA estimated that roughly 4,000 (5.5%) of the regulated
water systems, serving a total of 13 million people, were likely to exceed the 10 ppb
standard.
The previous 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 the 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. As a result of a
citizen suit, the EPA entered into a consent decree with a new deadline for the rule of
November 1995. The 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 the EPA to develop 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.
The EPA was required to conduct the study in consultation with the National Academy
of Sciences. In 1996, the 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 1999 and recommended that the standard be reduced,
but it did not recommend a particular level. The NRC affirmed that the 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 a Taiwan
study, deserved greater scrutiny. The NRC explained that the data in the study lacked the
level of detail needed for use in dose-response assessment. The Council also reported that
research suggested 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
were sufficient to add lung and bladder cancers to the types of 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
1 Food is a significant source of arsenic. The National Research Council estimates that, in the
United States, arsenic intake from food is comparable to drinking water containing 5 ppb arsenic.
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the United States.2 The NRC concluded that key studies for improving the scientific
validity of risk assessment were needed, and recommended specific studies to the EPA.
EPA’s 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. The 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), the EPA set the standard
at 10 ppb and applied it to non-transient, non-community water systems, as well as
community water systems. The Agency gave the water utilities five years to comply (the
maximum amount of time allowed under SDWA). The EPA estimated 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 standard.3
Standard-Setting Process. In developing standards under the Safe Drinking
Water Act, the 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. (The EPA sets the MCLG at zero for carcinogens [as it did for
arsenic], unless a level exists below which no adverse health effects occur.) The 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).4 EPA’s determination of whether a standard is feasible typically has been
based on costs to large water systems (serving more than 50,000 people). Less than 2%
of community water systems (roughly 750 of 54,000 systems) are this large, but they serve
roughly 56% of all people served by community systems.5
Variances and Exemptions. Congress has long recognized that the technical
and cost considerations associated with technologies selected for large cities often are not
applicable to small systems. In the 1996 amendments, Congress expanded SDWA
variance and exemption provisions to address small system compliance concerns.
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/arsenic/regulations.html].
4 For a more detailed discussion of these and other SDWA provisions, see CRS Report RL31243,
Safe Drinking Water Act: A Summary of the Act and Its Major Requirements.
5 SDWA does not discuss how the EPA should consider cost in determining feasibility; thus, the
EPA has relied on legislative history for guidance. The Senate report for the 1996 amendments
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, S.Rept. 104-169, Nov. 7, 1995, p. 14.) Systems serving 10,000
or more people serve about 80% of the population served by community water systems.
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The small system variance provisions require that for each rule establishing an MCL,
the EPA must list technologies that comply with the MCL and are affordable for three size
categories of small systems. If the EPA does not list affordable compliance technologies
for small systems, then it must list variance technologies. A variance technology need not
meet the MCL, but must be protective of public health. If the EPA lists a variance
technology, a state then may grant a variance to a small system, allowing the system to
use a variance technology to comply with a regulation. The EPA has not identified
variance technologies for arsenic or any other standards because, based on its current
affordability criteria, the EPA has determined that affordable compliance technologies are
available for all standards. Thus, small system variances are not available.
Congress took issue with EPA’s assessment that small system variance technologies
were not merited for the arsenic standard, and in 2002, directed the EPA to review the
criteria it uses to determine whether a compliance treatment technology is affordable for
small systems. In March 2006, EPA proposed three options for revising its affordability
criteria (71 FR 10671). Under the current affordability criteria, EPA considers a treatment
technology affordable unless the average compliance cost exceeds 2.5% of the area’s
median household income. Based on this measure, EPA determined that affordable
technologies are available for all SDWA standards. The proposed options under
consideration are well below the current level: 0.25%, 0.50%, and 0.75% of an area’s
median household income. The revised criteria, as proposed, are also expected to address
how to ensure that a variance technology would be protective of public health. According
to EPA, the final criteria would apply only to the new Stage 2 Disinfectants/Disinfection
Byproducts Rule and future rules, and not to the arsenic rule.
Exemptions potentially offer a source of compliance flexibility for small systems.
States may grant temporary exemptions from a standard if, for certain reasons (including
cost), a system cannot comply on time. The arsenic rule gives systems five years to
comply with the new standard; an exemption allows another three years for qualified
systems. Systems serving 3,300 or fewer persons may receive up to three additional 2-year
extensions, for a total exemption duration of 9 years (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 have noted that “unreasonable risk to
health” has never been defined, and that states must make a separate finding for each
system. Many states have indicated that they plan to grant few or no exemptions.
Balancing Costs and Benefits. When proposing a rule, the EPA must publish
a determination as to whether or not the benefits of the standard justify the costs. If the
EPA determines that costs are not justified, then it may set the standard at the level that
maximizes health risk reduction benefits at a cost that is justified by the benefits. The
EPA determined that the “feasible” arsenic level (for large systems) was 3 ppb, but that
the benefits of that level did not justify the costs. Thus, the EPA proposed a standard of
5 ppb. Also, the EPA 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.” The EPA applied the final rule to schools and similar non-community systems.
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Anticipated Benefits and Costs. In the proposed rule, the EPA noted the need
for more research to address the scientific uncertainty regarding the health risks of arsenic
ingestion; nonetheless, the EPA estimated that the rule would generate a range of health
benefits. In the final rule, the Agency estimated that reducing the standard to 10 ppb
could prevent roughly 19 to 31 bladder cancer cases and 5 to 8 bladder cancer deaths each
year. The EPA further estimated that the new standard could prevent 19 to 25 lung cancer
cases and 16 to 22 lung cancer deaths each year. The EPA estimated that the rule would
provide numerous other cancer and non-cancer health benefits that were not quantifiable.
Regarding the cost of meeting the 10 ppb standard, the EPA estimated that for
systems that serve fewer than 10,000 people, the average cost per household could range
from $38 to $327 per year. Roughly 97% of the systems that were expected to exceed the
standard are in this category, and most of these systems serve fewer than 500 people. For
larger systems, projects water cost increases range from $0.86 to $32 per household. The
EPA estimated the total national, annualized cost for the rule to be about $181 million.
EPA’s Science Advisory Board (SAB) raised concerns about the rule’s economic and
engineering assessment, and concluded that several cost assumptions were likely to be
unrealistic and other costs seemed to be excluded. The SAB also suggested that the EPA
give further thought to the concept of affordability as applied to this standard.6 Many
municipalities and water system representatives also disagreed with the Agency’s cost
estimates. The American Water Works Association (AWWA), while supporting a stricter
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 treatment residuals and the estimated number
of wells affected. The AWWA projected that the rule could cost individual households
in the Southwest, Midwest, and New England as much as $2,000 per year.7
Arsenic Rule Review. The EPA issued the final rule on January 22, 2001. In
March 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, 2001, the
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. The 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.”8 The NDWAC reported that the 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, the 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 comply.
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, Dec. 2000, p. 4.
7 AWWA, January 17, 2001. See [http://www.awwa.org/Advocacy/pressroom/pr/010111.cfm].
8 National Research Council, Arsenic in Drinking Water: 2001 Update, NAS, p. 14.
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Legislative Action
Since the arsenic standard was revised, Congress repeatedly has expressed concern
over the potential cost of the regulation, especially to small and rural communities. The
107th Congress directed EPA to review its affordability criteria and how the small system
variance and exemption programs should be implemented for arsenic (P.L. 107-73,
H.Rept. 107-272, p. 175). Congress directed EPA to report on its affordability criteria,
administrative actions, potential funding mechanisms for small system compliance, and
possible legislative actions. In 2002, EPA submitted its report to Congress, Small Systems
Arsenic Implementation Issues, on actions EPA was undertaking to address these
directives. Major activities included reviewing the small system affordability criteria and
variance process, and developing and implementing a small community assistance plan
to improve access to financial and technical assistance, improve compliance capacity, and
simplify the use of exemptions. To further help with compliance, EPA offered technical
assistance to small systems and sponsored research on low-cost arsenic treatment
technologies. EPA also issued Implementation Guidance for the Arsenic Rule, which
includes guidance to help states grant exemptions.
The 108th Congress also expressed concern over the financial impact that the new
standard could have in many communities. In the conference report for the omnibus
appropriations act for FY2005 (P.L. 108-447, H.Rept. 108-792), Congress provided $8.2
million for arsenic removal research. Conferees also expressed concern that many rural
communities would be unable to meet the new requirements which could pose a “huge
financial hardship.” The conferees directed the EPA to report on the extent to which
communities were being affected by the rule and to propose compliance alternatives and
make recommendations to minimize costs. This report is pending.
In the 109th Congress, legislative efforts focused on helping economically struggling
communities comply with the arsenic rule and other drinking water regulations. Various
bills were introduced to provide more regulatory flexibility, financial assistance, and
technical assistance, especially to small systems. The EPA’s uncompleted FY2007
funding bill, as reported by the Senate Committee on Appropriations (H.R. 5386, S.Rept.
109-275), would have required the EPA to make available at least $11 million for small
system compliance assistance. S. 41 and H.R. 1315 were introduced to require states to
grant small community water systems exemptions from regulations for naturally occurring
contaminants in certain cases. Companion bills, H.R. 2417 and S. 689, would have
required the EPA to establish a grant program to help qualified communities comply with
standards, delay enforcement of the arsenic rule until states implement the grant program,
and prevent EPA from enforcing a standard during the grant application process. H.R.
4495 proposed to give small systems two more years to comply with the arsenic rule. S.
1400 (S.Rept. 109-186), the Water Infrastructure Financing Act, would have increased
funding authority for the drinking water state revolving fund (DWSRF) program and
established a grant program for priority projects, including projects to help small systems
comply with standards. S. 2161 would have prevented enforcement of regulations for
small systems unless the EPA had identified a variance technology and sufficient DWSRF
funds were made available. S. 2161 also proposed to require EPA to develop new
affordability criteria related to small system variances. None of the bills was enacted,
and, consequently, interest in this issue may continue in the 110th Congress.