EPA proposes national drinking water rule for perchlorate

The U.S. Environmental Protection Agency has proposed a National Primary Drinking Water Regulation (NPDWR) for perchlorate, outlining potential new monitoring and compliance requirements for public water systems nationwide. The proposal follows a D.C. Circuit Court decision directing EPA to take regulatory action under the Safe Drinking Water Act, despite the agency’s current assessment that perchlorate is not present in drinking water at levels posing a public health concern.

Under the proposed rule, EPA would establish a health-based maximum contaminant level goal (MCLG) of 0.02 milligrams per liter (mg/L). The agency is seeking public comment on three potential enforceable maximum contaminant levels (MCLs): 0.02 mg/L, 0.04 mg/L, or 0.08 mg/L. In addition to setting an MCL, the rule would require public water systems to conduct monitoring for perchlorate and include results in public notifications and Consumer Confidence Reports.

Perchlorate is a naturally occurring and man-made chemical used in products such as rocket fuel, fireworks and explosives. It can interfere with iodine uptake in the thyroid, which is particularly concerning for infants, pregnant women and people with thyroid conditions. EPA previously determined in 2020 that regulating perchlorate was not warranted, citing low occurrence and high compliance costs, but the court ruling requires the agency to revisit that decision through rulemaking.

EPA stated that its analysis continues to show that perchlorate generally does not occur in public water systems at levels of public health concern and that the quantified benefits of regulation may not justify the costs. However, the agency emphasized that it is proceeding with the proposal to meet its legal obligations and to gather updated input from states, utilities, and other stakeholders.

Public comments on the proposed rule are due by March 9, 2026. EPA will also hold a virtual public hearing on Feb. 19, 2026, to solicit additional feedback from water sector stakeholders and the public.

Previously published EPA treatment options for perchlorate in drinking water systems can be viewed here.