On Jan. 2, the U.S. Environmental Protection Agency (EPA) signed a proposed National Primary Drinking Water Regulation (NPDWR) and Maximum Contaminant Level Goal (MCLG) for perchlorate.
The proposal stems from a history of attempted regulatory action on perchlorate and specifically came as a result of the D.C. Circuit Court’s May 2023 decision in the case, NRDC v. Regan.
The EPA is now proposing a health-based Maximum Contaminant Level Goal (MCLG) of 0.02 mg/L (20 µg/L). The EPA is co-proposing enforceable Maximum Contaminant Levels (MCLs) for perchlorate of 20 µg/L, 40 µg/L, or 80 µg/L.
The EPA has been evaluating perchlorate for decades. According to the agency, perchlorate is commonly used in solid rocket propellants, munitions, fireworks, airbag initiators for vehicles, matches and signal flares. It 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 in nitrate salts used to produce nitrate fertilizers, explosives and other products.
Background
In 2009, EPA made an initial determination to regulate perchlorate. In 2020, the agency under then-administrator Michael Regan withdrew that determination, claiming new data showed it didn’t meet the criteria to implement regulatory rules. But the Natural Resources Defense Council challenged that decision, and in 2023, the court ruled the EPA lacked the authority to withdraw a determination to regulate and must proceed with the rulemaking process for perchlorate under the Safe Drinking Water Act.
On the new proposal, EPA said it will accept comments to the public docket identified by Docket ID No. EPA-HQ-OW-2024-0592 at regulations.gov by March 9, 2026. The agency is also holding a public hearing on Feb. 19, 2026 at 1-4 p.m. ET, at which time the public will be invited to provide the EPA with verbal comments. Information and registration for the public hearing is available here.
In terms of impact to water utilities and their customers from a water quality standpoint, both EPA and industry groups indicated that few regulated water systems in the United States are likely to find perchlorate in drinking water above either the proposed enforceable limits or MCLG.
Both the Association of Metropolitan Water Agencies and the American Water Works Association, representing drinking water systems and professionals, said they welcome the opportunity to provide feedback on the proposal but stressed the importance of an affordable and efficient approach.
Reaction
Tom Dobbins, CEO of the Association of Metropolitan Water Agencies (AMWA), representing large U.S. drinking water systems, released the following statement:
“AMWA has routinely engaged with EPA in its years-long evaluation of perchlorate, encouraging the agency to use the most up-to-date science on health effects and occurrence in its determination of whether a national standard was warranted, and if so at what level. The association has consistently said that any new drinking water regulations must be practical, achievable, and protective of public health.
“Now that EPA has put forward several options for a perchlorate standard, AMWA looks forward to thoroughly reviewing the proposal to ensure it meets these parameters, while avoiding monitoring and public notice requirements that would impose unnecessary, expensive mandates on water systems and their ratepayers.
“AMWA and its member drinking water systems across the country share EPA’s commitment to the integrity of the Safe Drinking Water Act’s science-based evaluation and rulemaking process, and welcome the opportunity to provide constructive feedback and recommendations to EPA to collaboratively formulate an implementable rule that is protective of public health.”
American Water Works Association CEO David LaFrance added:
“AWWA will thoroughly review EPA’s new proposed rule and submit comments to encourage a rule that protects water consumers and is affordable and efficient to implement. On first read, it seems clear EPA thought carefully about how to manage the monitoring and administrative challenges regulation of perchlorate presents for public water systems and states.
“EPA notes that very few regulated water systems are likely to find perchlorate in drinking water above either the proposed enforceable limits or the maximum contaminant level goal (MCLG). This is consistent with AWWA’s analyses to date.”
Resources
EPA has made the following resources available with about perchlorate and the proposed National Primary Drinking Water Regulation.
- Notice of Proposed Perchlorate National Primary Drinking Water Regulation.
- Fact Sheet: Questions & Answers: Proposed National Primary Drinking Water Regulation for Perchlorate (pdf) (131.28 KB, December 2025, EPA 815-F-25-011).
- Fact Sheet: The EPA’s Proposed National Primary Drinking Water Regulation for Perchlorate: Fact Sheet for Public Water Systems (pdf) (508.04 KB, December 2025, EPA 815-F-25-010)
- Additional supporting information is available in Docket ID No. EPA-HQ-OW-2024-0592.
Source/s: U.S. EPA, AMWA, AWWA
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