Perchlorate in Drinking Water
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.
- Read the Federal Register Notice
- Additional supporting information is avalable in Docket ID No. EPA-HQ-OW-2018-0780
- Fact Sheet: Reductions of Perchlorate in Drinking Water (May 2020)
- Fact Sheet: Steps Water Systems Can Take to Address Perchlorate in Drinking Water (May 2020)
- Press Release: EPA Notes Successes in Reducing Perchlorate in Drinking Water (May 14, 2020)
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 occurring in some fertilizers.
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.
The final reports for both peer reviews are available through Docket ID No. EPA-HQ-OW-2016-0439.
Technical Fact Sheet
Perchlorate Reference Dose
Interim Health Advisory
Interim Drinking Water Health Advisory for Perchlorate, EPA 822-R-08-25, December 2008
Federal Register Notices
Public Meeting Notices
- Notice of a Public Meeting: Stakeholder Meeting Concerning EPA's Intent To Regulate Perchlorate Levels in Drinking Water - September 20, 2012
- Notification of a Public Meeting and Public Teleconference of the Science Advisory Board: Perchlorate Advisory Panel - July 18-19, 2012 and September 25, 2012
- Notice of a Public Meeting: Environmental Justice Considerations for Drinking Water Regulatory Efforts - March 3, 2011