RS20672: Arsenic in Drinking Water:
Recent Regulatory Developments and Issues

Mary Tiemann

Specialist in Environmental Policy
Resources, Science, and Industry Division

Updated August 23, 2001

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 issued the current 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 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, some stakeholders expressed concern that the Agency would not have time to evaluate public comments and complete analyses before issuing a final rule. In EPA’s FY2001 appropriations, Congress extended the deadline for the rule to June 22, 2001. On January 22, the final rule, which set the standard at 10 ppb, was published in the Federal Register with a general 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 reassess risk and cost issues associated with the new rule. The 2006 compliance date for water systems remains unchanged. In response to EPA’s action, the House and Senate each approved arsenic amendments to their FY2002 appropriations bills for EPA (H.R. 2620). This report reviews EPA’s efforts to develop a new arsenic rule and summarizes key provisions and subsequent events. 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 (ug/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 intake 1 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 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 (65 FR 38888). EPA stated that the proposal relied primarily on the NRC analysis, augmented with some more 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. (This and other SDWA standards also apply to cleanup of Superfund sites.) The rule’s general effective date was 60 days after publication; however, public water systems are 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 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

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).

Standards review and revision. EPA must review, and revise as needed, each drinking water standard at least every 6 years. A revision must maintain or increase public health protection. At issue here was that some of the research being done to support a new standard would not be available before the rule was due; also, the NRC had identified several factors that affected the reliability of EPA’s risk assessment. Some Members and stakeholders expressed concern that if EPA set the arsenic standard at a very low level while considerable health effects uncertainty remained, the Agency would likely be unable to relax the standard if the data showed that it was overly stringent; consequently, many households could be required to incur significant costs without gaining meaningful health benefits. If, however, the new data showed that a stricter standard was needed, EPA then could further tighten the standard. In setting the standard at 10 ppb in the final rule, EPA stated that, as part of the 6-year review process, it would evaluate new data to determine if the newly promulgated standard should be revised further (66 FR 7027).

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."

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 delayed proposal, 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 the rule. On March 23, the EPA Administrator delayed the rule for 60 days, citing concerns about the science behind the rule and its 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 is performing an expedited review of EPA’s arsenic risk analysis and latest research, the National Drinking Water Advisory Council is reassessing the rule’s cost, and EPA’s Science Advisory Board is reviewing 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). Comments are due by October 31, 2001. EPA also plans to request comment on the ongoing reviews this fall. (For more information, see [ http://www.epa.gov/safewater/arsenic.html ].)

Various legislative proposals have emerged in response to this rule or its delay. Both the House and Senate approved arsenic amendments to the FY2002 appropriations bills for EPA (H.R. 2620). The House bill states that EPA may not use funds to delay the January rule or to issue a rule that sets the standard above10 ppb. The Senate bill directs EPA to put into effect immediately an arsenic standard that protects sensitive subpopulations and that lifts the suspension of the rule’s effective date for systems with arsenic below 50 ppb to provide information to consumers about possible health risks of arsenic exposure at low levels (because systems were not required to meet the new standard until 2006, the rule required certain systems to provide additional risk information starting this year). Additionally, P.L. 107-16, the Economic Growth and Tax Relief Reconciliation Act of 2001, provides tax-exempt bond authority for arsenic treatment projects. A range of other bills have been introduced. H.R. 1252 would reduce the standard to 10 ppb by 2003, and to 3 ppb by 2006, and authorize grants for small systems; H.R. 1413 would codify the January rule and increase funding for the drinking water state revolving fund program. H.R.2112 would authorize use of federal funding 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.796 would reinstate the requirement in the January rule that systems with certain arsenic levels below 50 ppb include information on arsenic starting with this year’s report to consumers. S. 751 called for a new rule to be issued by June 22, 2001. S.J.Res. 14 expresses congressional disapproval of the delay and provides that the rule delaying the January rule shall have no force or effect.

Conclusion

The effort to revise the arsenic standard has been very controversial, and debate continues as to what level best reduces health risks at a cost that is justified, particularly for small systems where most violations are expected. The NRC concluded that studies essential for improving the accuracy of arsenic risk assessment are still needed, but that the standard should be reduced expeditiously. The majority of EPA’s Science Advisory Board Panel concluded that, in light of the continuing uncertainties in the risk estimates, technology, and significant implementation costs, EPA could consider a phased approach to the rule, addressing the most serious exposures first while leaving future flexibility to respond to results from both experience and research. 8 In contrast, many stakeholders object to further delay, noting that the World Health Organization has reduced its arsenic guideline to 10 ppb and that the European Union will do so at the end of 2003. This rule and its delay have generated a range of policy responses. Whatever the outcome, water suppliers and communities are urging Congress to provide more funding to help them comply with the arsenic standard and other SDWA mandates.

Footnotes

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 ].

3 National Research Council. Arsenic in Drinking Water. National Academy Press. Washington, D.C. 1999. p. 22.

4 National Research Council. p. 7.

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.

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].

8 Science Advisory Board. p. 4.