Perchlorate in Drinking Water

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.

Read frequently asked questions about perchlorate in drinking water

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.

Read the 2013 recommendations of the Science Advisory Board

Public Meeting Announcement for Peer Review of BBDR Model and Report

EPA has announced the final peer reviewers and details regarding the peer review meeting scheduled for January 10 and 11, 2017, in Arlington, Virginia. EPA invites the public to register to attend the meeting as observers, either in-person or via teleconference. Time at the meeting will be set aside for brief oral statements from the public regarding the peer review materials. Persons wishing to make a brief statement must register as described in the Federal Register notice by January 3, 2017 and will be considered on a first-come, first served basis.

Federal Register Notice: Peer Review of EPA’s Biologically Based Dose-Response (BBDR) Model for Perchlorate in Drinking Water – Final List of Peer Reviewers, Notice of the Pubic Peer Review Meeting and Final Peer Review Charge Questions

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. Once the peer review of the BBDR report is complete, the Agency will seek peer review of a second report that evaluates methods to apply the BBDR model to develop a Maximum Contaminant Level Goal for perchlorate in drinking water.

The materials that were made available for review can be found at:

Read questions and answers about the perchlorate peer review

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

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.

Read the technical fact sheet

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.

Integrated Risk Information System (IRIS) reference dose for chronic oral exposure (RfD)

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.

Interim Drinking Water Health Advisory for Perchlorate, EPA 822-R-08-25, December 2008

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.

Federal Regster Notice - Drinking Water: Regulatory Determination on Perchlorate - February 11, 2011

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.

Federal Register Notice - Drinking Water: Perchlorate Supplemental Request for Comments - August 19, 2009

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.

Federal Register Notice - Drinking Water: Preliminary Regulatory Determination on Perchlorate - October 10, 2008

Additional information including support documents for the regulatory determination may be found in:

Regulatory Determination Fact Sheets

Read the fact sheets on several stages of regulatory determination

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