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Water: Arsenic

Arsenic Rule

On January 22, 2001 EPA adopted a new standard for arsenic in drinking water at 10 parts per billion (ppb), replacing the old standard of 50 ppb.  The rule became effective on February 22, 2002.  The date by which systems must comply with the new 10 ppb standard is January 23, 2006.

The Arsenic and Clarifications to Compliance and New Source Contaminants Monitoring Final Rule was published in the Federal Register (66 FR 6976) on January 22, 2001.

  • Drinking Water Standard for Arsenic Fact Sheet provides information on the potential health effects of exposure to arsenic, an overview of the Final Rule, and background information on the natural occurrence of arsenic. EPA 815-F-00-015

  • Technical Fact Sheet provides technical information about the Final Arsenic Rule including its requirements and compliance dates, the health effects associated with exposure to arsenic, the costs, benefits, and number of systems affected by the rule, and where to find additional information. EPA 815-F-00-016

Rule-Making History

EPA proposed arsenic regulations to revise the existing NPDWR on June 22, 2000 (65 FR 38888), which proposed a Maximum Contaminant Level (MCL) of 0.005 mg/L (5 μg/L). The October 2000 appropriations bill for EPA amended the SDWA, directing EPA to promulgate a final arsenic standard no later than June 22, 2001. The Final Rule, published on January 22, 2001, established the MCL at 0.01 mg/L (10 μg/L) (40 CFR 141.62(b)(16)). The Rule was to become effective on March 23, 2001, 60 days after publication. The Rule established that the 0.01 mg/L (10 μg/L) MCL becomes enforceable on January 23, 2006, and that the clarifications to compliance and new source contaminants monitoring regulations become enforceable on January 22, 2004 (40 CFR 141.6(j) & (k)).

Because of the importance of the Arsenic Rule and the national debate surrounding it related to science and costs, EPA's Administrator publicly announced on March 20, 2001, that the Agency  would take additional steps to reassess the scientific and cost issues associated with this Rule. EPA requested that the National Academy of Sciences (NAS) convene a panel of scientific experts to review the Agency's interpretation and application of arsenic research, worked with its National Drinking Water Advisory Council (NDWAC) to review the assumptions and methodologies underlying the Agency's estimate of arsenic compliance costs, and asked its Science Advisory Board (SAB) to look at the benefits associated with the Rule. On October 31, 2001, the EPA Administrator announced that the 10 ppb (0.010 mg/L) standard for arsenic would remain stating that, "the 10 ppb protects public health based on the best available science and ensures that the cost of the standard is achievable."

See the Rule-making History page of this Web site for additional information and documents related to the history of the Arsenic Rule.

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