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EPA/OW RIN: 2040-AF28 Publication ID: Fall 2018 
Title: National Primary Drinking Water Regulations: Regulation of Perchlorate 

A consent decree entered by the U.S. District Court for the Southern District of New York states that EPA shall propose a national primary drinking water regulation (NPDWR) with a proposed Maximum Contaminant Level Goal (MCLG) for perchlorate in drinking water no later than 10/31/18 and finalize a MCLG and NPDWR for perchlorate in drinking water no later than 12/19/19. The EPA has begun the process for developing a NPDWR for perchlorate. The Safe Drinking Water Act describes the EPA's requirements for regulating contaminants. In accordance with these requirements, the EPA will consider the Science Advisory Board's guidance on how to best interpret perchlorate health information to derive a MCLG for perchlorate. The agency is also evaluating the feasibility and affordability of treatment technologies to remove perchlorate from drinking water and will examine the costs and benefits of a Maximum Contaminant Level (MCL) and alternative MCLs. The EPA is also seeking input through informal and formal processes from the National Drinking Water Advisory Council, the Department of Health and Human Services, State and Tribal drinking water programs, the regulated community (public water systems), public health organizations, academia, environmental and public interest groups, and other interested stakeholders on a number of issues relating to the regulation of perchlorate.

Agency: Environmental Protection Agency(EPA)  Priority: Other Significant 
RIN Status: Previously published in the Unified Agenda Agenda Stage of Rulemaking: Proposed Rule Stage 
Major: Undetermined  Unfunded Mandates: Undetermined 
EO 13771 Designation: Regulatory 
CFR Citation: 40 CFR 141    40 CFR 142   
Legal Authority: 42 U.S.C. 300f et seq., Safe Drinking Water Act   
Legal Deadline:
Action Source Description Date
Final  Judicial  Consent Decree, NRDC v. EPA (No. 16 Civ. 1251, S.D.N.Y., October 18, 2016)  12/19/2019 
NPRM  Judicial  Consent Decree, NRDC v. EPA (No. 16 Civ. 1251, S.D.N.Y., October 18, 2016)  10/31/2018 

Statement of Need:

The EPA issued a final determination to regulate perchlorate on February 11, 2011. The EPA's 2011 determination was based upon the three criteria for regulation under the Safe Drinking Water Act: 1) The EPA determined that perchlorate may have adverse effects on the health of persons based upon the National Research Council's study that found perchlorate inhibits the thyroid's ability to uptake iodide needed to produce hormones. 2) The EPA concluded that perchlorate occurs with frequency at levels of health concern in public water systems based upon data collected under the first Unregulated Contaminant Monitoring Rule (UCMR 1) from 2001 to 2005. Monitoring results reported to the EPA under UCMR 1 show that perchlorate was measured in over four percent of water systems. 3) The EPA concluded that there was a meaningful opportunity to protect public health through a drinking water regulation by reducing perchlorate exposure for the 5 to 17 million people who may be served perchlorate in their drinking water. In 2013, the Science Advisory Board (SAB) recommended that the EPA use models, rather than the traditional approach to establish the health-based maximum contaminant level goal for a perchlorate regulation. The EPA and FDA scientists worked collaboratively to develop biological models in accordance with SAB recommendations. The EPA completed peer review of this analysis in March 2018. The EPA will utilize the best available, peer-reviewed science to inform regulatory decisionmaking for perchlorate.

Summary of the Legal Basis:

On October 18, 2016, the U.S. District Court for the Southern District of New York entered a consent decree, which requires the EPA to sign, for publication in the Federal Register, a proposed MCLG and NPDWR for perchlorate by October 30, 2018 and issue a final MCLG and NPDWR by December 19, 2019. See NRDC v. EPA, No. 16 Civ. 1251 (S.D.N.Y.). The Safe Drinking Water Act (SDWA), section 1412(b)(1)(A), requires the EPA to make a determination whether to regulate at least five contaminants from its Contaminant Candidate List every 5 years. Once the EPA makes a determination to regulate a contaminant in drinking water, SDWA section 1412(b)(1)(E) requires the EPA to issue a proposed maximum contaminant level goal (MCLG) and national primary drinking water regulation (NPDWR) within 24 months and a final MCLG and NPDWR within 18 months of proposal (with an opportunity for one 9-month extension). The EPA made a determination to regulate perchlorate in drinking water on February 11, 2011.


The alternatives will be determined.

Anticipated Costs and Benefits:

The anticipated costs and benefits will be determined.


Perchlorate competes with iodide for transport into the thyroid gland, which is a necessary step in the production of thyroid hormones. Therefore, perchlorate may lead to decreases in levels of these hormones. Thyroid hormones are essential to the growth and development of fetuses, infants, and young children, as well as to metabolism and energy regulation throughout the life span. Primary pathways for human exposure to perchlorate are ingestion of contaminated food and drinking water.

Action Date FR Cite
NPRM  10/00/2018 
Final Rule  12/00/2019 
Additional Information: Docket #:EPA-HQ-OW-2009-0297
Regulatory Flexibility Analysis Required: Undetermined  Government Levels Affected: Undetermined 
Federalism: Undetermined 
Included in the Regulatory Plan: Yes 
RIN Information URL:  
Sectors Affected: 221310 Water Supply and Irrigation Systems; 924110 Administration of Air and Water Resource and Solid Waste Management Programs 
RIN Data Printed in the FR: No 
Agency Contact:
Samuel Hernandez
Environmental Protection Agency
Office of Water
1200 Pennsylvania Avenue NW, Mail Code 4607M,
Washington, DC 20460
Phone:202 564-1735

Lisa Christ
Environmental Protection Agency
Office of Water
1200 Pennsylvania Avenue NW,
Washington, DC 20460
Phone:202 564-8354