Perchlorate in Drinking Water

Perchlorate Molecule

Background

Perchlorate is a naturally occurring and manufactured chemical anion that consists of one chlorine atom bonded to four oxygen atoms (ClO4-). Perchlorate is commonly used as an oxidizer in rocket propellants, munitions, fireworks, airbag initiators for vehicles, matches and signal flares. It is naturally occuring in some fertilizers.

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 occurrence, treatment technologies, analytical methods and the costs and benefits of potential standards.

Perchlorate BBDR Model

EPA has 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 will integrate available health related information in a robust and transparent analysis of the effects of perchlorate on thyroid hormone production.

Perchlorate Model and model Report Peer Review

A peer review has been completed for the Perchlorate Biologically Based Dose Response (BBDR) model and model report. A panel meeting of the peer reviewers was held on January 10 and 11, 2017, in Arlington, Virginia. The Peer Review Summary Report is available in Docket ID No. EPA-HQ-OW-2016-0439. The Agency intends to conduct a future peer review of a subsequent report that will evaluate methods to develop a Maximum Contaminant Level Goal for perchlorate in drinking water.

Materials and Federal Register Notices Related to the Peer Review

On September 30, EPA announced the availability of perchlorate peer review materials for public comment including a draft list of external peer review candidates, draft charge questions, a draft biologically-based dose-response (BBDR) model and draft BBDR accompanying report. The materials that were made available for review can be found in the Docket folders below:

Read questions and answers about the perchlorate peer review

Read previously published Federal Register Notices pertaining to this peer review effort:

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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.

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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:

Regulatory Determination Fact Sheets

Read about perchlorate's regulatory stage in EPA's Regulatory Development and Retrospective Review Tracker

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