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Perchlorate in Drinking Water

 

Perchlorate Molecule

On March 31, 2022, EPA announced multiple integrated actions to ensure that public health is protected from perchlorate in drinking water.  Read EPA's Plan to Address Perchlorate Contamination.

The Agency has completed its review of a July 2020 determination to not regulate perchlorate in drinking water. The agency concluded that the 2020 decision is supported by the best available peer reviewed science. While EPA is not pursuing a drinking water regulation at this time, the agency will continue to consider new information on the health effects and occurrence of perchlorate. EPA’s decision does not impact any state standards for perchlorate. EPA will continue to consider if perchlorate should be added to future Contaminant Candidate Lists for possible regulation under the Safe Drinking Water Act.

Final Action

On July 21, 2020 the U.S. Environmental Protection Agency (EPA) published a final action regarding the regulation of perchlorate under the Safe Drinking Water Act (SDWA). Considering the best available science and the proactive steps that EPA, states and public water systems have taken to reduce perchlorate levels, the agency has determined that perchlorate does not meet the criteria for regulation as a drinking water contaminant under the SDWA. Therefore, the agency is withdrawing the 2011 regulatory determination and is making a final determination to not issue a national regulation for perchlorate at this time. 

EPA also performed a new health impact analysis based on recommendations from the Science Advisory Board. The new analysis shows that the concentrations at which perchlorate may present a public health concern are higher than the concentrations considered in the 2011 regulatory determination.

The updated occurrence information and the new health impact analysis are the best available information. Based on this updated data and analysis, EPA is making a final determination that perchlorate is not found in drinking water with a frequency and at levels of public health concern to support a meaningful opportunity for health risk reduction through a national perchlorate drinking water regulation.

Proposed Rule

The Environmental Protection Agency (EPA) published a notice of proposed rulemaking in the Federal Register on June 26, 2019 seeking public input on a range of options regarding the regulation of perchlorate in public drinking water systems. The agency requested comment by August 26, 2019 on a proposed National Primary Drinking Water Regulation (NPDWR) for perchlorate to establish a Maximum Contaminant Level (MCL) and a health-based Maximum Contaminant Level Goal (MCLG) at 56 micrograms per liter. 

In addition, the agency requested comment on three alternative regulatory options:

  • An MCL and MCLG for perchlorate set at 18 micrograms per liter.
  • An MCL and MCLG for perchlorate set at 90 micrograms per liter.
  • Withdrawal of the agency’s 2011 determination to regulate perchlorate in drinking water.

The agency also requested comment on all relevant aspects of the proposed rule including, but not limited to perchlorate monitoring and reporting requirements for public water systems, a list of treatment technologies that would enable water systems to comply with the MCL, and affordable compliance technologies for small systems serving 10,000 persons or less. EPA also requested comment on its methodology for deriving the MCLG, the underlying assumptions and analysis of its cost and benefit estimates, and other specific items listed in the proposed rule.

Perchlorate is commonly used in solid rocket propellants, munitions, fireworks, airbag initiators for vehicles, matches, and signal flares. Perchlorate may occur naturally, particularly in arid regions such as the southwestern United States and is found as an impurity in hypochlorite solutions used for drinking water treatment and nitrate salts used to produce nitrate fertilizers, explosives, and other products. 

Background

On February 11, 2011, EPA determined that perchlorate meets the Safe Drinking Water Act criteria for regulation as a contaminant. The Agency found that perchlorate may have an adverse effect on the health of persons and is known to occur in public drinking water systems with a frequency and at levels that present a public health concern. Since that time, EPA has been reviewing the best available scientific data on a range of issues related to perchlorate in drinking water including its health effects, occurrence, treatment technologies, analytical methods, and the costs and benefits of potential standards.

Perchlorate Peer Reviews

 As part of EPA’s commitment to ensuring the safety of America’s drinking water, the Agency conducted two independent, expert peer reviews to determine the appropriate scientific approach for understanding the adverse health impacts of perchlorate in drinking water.

EPA collaborated with Food and Drug Administration scientists to implement the 2013 Science Advisory Board (SAB) recommendations to develop a Physiologically Based Pharmacokinetic/Pharmacodynamic (PBPK/PD) or Biologically Based Dose Response (BBDR) model that integrated available health related information in a robust and transparent analysis of the effects of perchlorate on thyroid hormone production. A peer review was conducted on the draft model and model report in January 2017. After considering the findings of this review, EPA revised the Perchlorate BBDR Model to focus on increasing the scientific rigor of the model and modeling results. In addition, EPA developed a two-stage approach linking the revised BBDR model results with quantitative information on neurodevelopmental outcomes from epidemiological studies. EPA also developed an alternative population-based approach that uses the revised Perchlorate BBDR Model to evaluate a shift in the population of pregnant women who could be hypothyroxinemic.

Final Peer Review Reports

The final reports for both peer reviews are available through Docket ID No. EPA-HQ-OW-2016-0439. 

Supplemental Information

Technical Fact Sheet

A technical fact sheet has been developed for perchlorate that includes: physical and chemical properties; environmental health impacts; existing federal and state guidelines; and detection and treatment methods.

Perchlorate Reference Dose

EPA has established a reference dose (RfD) for perchlorate, which is consistent with the reference dose recommended by the National Research Council’s 2005 report.

Interim Health Advisory

In January 2009, EPA issued an Interim Health Advisory for perchlorate to assist state and local officials in addressing local contamination of perchlorate in drinking water while the Agency conducted its evaluation of the opportunity to reduce risks through a national primary drinking water regulation.

Federal Register Notices

Public Meeting Notices

Final Regulatory Determination Notice for Perchlorate 

EPA decided to regulate perchlorate under the Safe Drinking Water Act (SDWA). The science that lead to this decision has been peer reviewed by independent scientists and public health experts including the National Academy of Sciences.

Supplemental Request for Comments on Preliminary Regulatory Determination

On August 19, 2009, EPA published the Perchlorate Supplemental Request for Comments requesting comment on additional approaches to analyzing data related to EPA’s perchlorate preliminary regulatory determination. 

Preliminary Regulatory Determination Notice for Perchlorate

On October 10, 2008, EPA published a preliminary regulatory determination for perchlorate. This notice requested public comment on its determination that perchlorate did not occur with a frequency and at levels of public health concern and that development of a regulation did not present a meaningful opportunity for health risk reduction for persons served by public water systems.
Additional information including support documents for the regulatory determination may be found in:
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Last updated on April 1, 2022