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Water: Arsenic

Rule-Making History

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Minor Clarification of National Primary Drinking Water Regulation for Arsenic - Final Rule

On March 25, 2003 EPA affirmed that the public health standard for arsenic in drinking water established in January 2001 is 10 parts per billion (ppb). The action made clear that when a monitoring result is expressed in milligrams per liter (mg/L) rather than ppb, that any monitoring result greater than 0.010 mg/l is a violation of the January 2001 arsenic standard. To assure that this clarification extends to the regulatory text for arsenic and to remove any implementation uncertainty relating to this issue, EPA has amended the arsenic Maximum Contaminant Level (MCL) to express it as 0.010 mg/l.

Report to Congress

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The Agency's report to Congress, "Small System Arsenic Implementation Issues", may be viewed or downloaded at this link along with a synopsis of the report. This March 2002 report describes three major activities that address an Agency review of national-level affordability criteria for drinking water rules and small systems implementation issues related to the new arsenic in drinking water standard.

Review of the 10ppb Standard

After publishing the final arsenic rule on January 22, 2001, EPA postponed the effective date of the rule until February 22, 2002, requested public comment on the standard, and began reviewing the new standard, the science, costs and benefits analyses that supported the regulation. “[A]s announced by the Administrator on October 31, 2001, EPA will not further postpone the January 2001, Arsenic and Clarifications to Compliance and New Source Contaminants Monitoring rule, and EPA also does not expect to take any other additional action relative to the July 2001 proposal in the interim (April 17, 2002 Federal Register notice, 67 FR 19030, footnote 3 of Table III-2 at 19037).” The Agency will continue to evaluate the three expert panel reports discussed below, public comments on the standard and the reports, and other relevant information as they become available. EPA expects to make a final decision on whether to revise the January 2001 rule as part of the next six-year review of drinking water standards, which is due in August 2008.

Three Expert Panel Reviews

Reports and recommendations on the science, cost of compliance, and benefits analyses in support of the 10 ppb final arsenic in drinking water rule were made available for review and public comment until October 31, 2001. These reports were prepared by independent, expert panels convened by the National Academy of Sciences, the National Drinking Water Advisory Council, and the EPA Science Advisory Board.

  1. The National Academy of Sciences: "Arsenic in Drinking Water: 2001 Update" Exit EPA Disclaimer (September 12, 2001)
  2. The National Drinking Water Advisory Council: Cost review report (48 pp, 329K)
  3. EPA's Science Advisory Board: Review of the Arsenic Rule Benefits Analysis (68 pp, 170K) ( August 30, 2001)
Request for comment on the new Arsenic standard

On July 19, 2001 (66 FR 37617), EPA issued a proposal to request comment on whether the data and technical analyses associated with the January 2001 arsenic rule support setting the arsenic standard at 3 ppb, 5 ppb, 10 ppb, or 20 ppb. On August 16, 2001, EPA provided a separate docket electronic mail (e-mail) address, ow-arsenic-docket@epa.gov, to help the Agency process comments on the July 19th proposed rule. The comment period closed October 31, 2001.

Health effects and risk review

The National Academy of Sciences’ (NAS) National Research Council’s subcommittee on arsenic held meetings on May 21, June 20, and July 18, 2001.

Process for the Cost Review

EPA requested nominations for the National Drinking Water Advisory Council workgroup. Arsenic cost workgroup membership and meetings summaries are available. A final workgroup meeting was held August 2-3 in Washington, DC. The entire NDWAC conferred on August 22 to discuss the report and what to transmit to EPA.

Process for the Benefits review

EPA’s Science Advisory Board (SAB) requested nominations for the SAB Arsenic Benefits Review Panel July 8, 2001.

Second Extension of the Effective Date
First Extension of Effective Date

In accordance with the January 20, 2001 memorandum from Andrew Card, Assistant to the President and Chief of Staff, entitled "Regulatory Review Plan," EPA temporarily delayed the effective date for this rule for 60 days, from March 23, 2001 until May 22, 2001. The delay of effective date was published in the Federal Register on March 23, 2001.

EPA Adopts a Stricter Standard for Arsenic

On January 22, 2001 EPA adopted a new standard for arsenic in drinking water at 10 ppb.

Proposed Arsenic Rule
On June 22, 2000 EPA proposed a 5 ppb standard for arsenic. EPA requested comment on 3 ppb, 10 ppb and 20 ppb.


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