U.S. EPA PFAS National Primary Drinking Water Regulation (NPDWR)
ENFORCEMENT TIMELINE
Effective 2024; MCL compliance by 2029 (extension to 2031 proposed)
Overview
The National Primary Drinking Water Regulation (NPDWR) finalized by the U.S. Environmental Protection Agency (EPA) in April 2024 under the Safe Drinking Water Act (SDWA) set nationwide, legally enforceable Maximum Contaminant Levels (MCLs) for specific PFAS in drinking water: PFOA, PFOS, PFHxS, PFNA, HFPO-DA (GenX), and certain mixtures. The MCLs for PFOA and PFOS are 4.0 parts per trillion (ppt) each. In May 2026, however, EPA proposed a rule that would keep the PFOA and PFOS MCLs while allowing water systems that apply to extend their compliance deadline from 2029 to 2031, and a separate rule that would rescind the regulations for PFHxS, PFNA, HFPO-DA, and Hazard Index mixtures. Public comment on both proposals closed on July 20, 2026. As of September 27, 2026, neither has been finalized, and the current rule remains legally in effect.
Enforcement Timeline
April 10, 2024: EPA announces the final PFAS NPDWR (published in the Federal Register on April 26, 2024; effective June 25, 2024)
May 18, 2026: EPA proposes a rule to extend the PFOA/PFOS compliance deadline (2029 → 2031, upon water system application) (published May 20)
May 18, 2026: EPA proposes a separate rule to rescind the regulations for PFHxS, PFNA, HFPO-DA, and Hazard Index mixtures (published May 20)
July 7, 2026: Public hearings held on both proposed rules
July 20, 2026: Public comment period closes
2026 (EPA target): Final action on the rescission rule (not yet published as of September 27, 2026)
Timing not yet determined: Final action on the compliance-extension rule
April 26, 2027: Deadline to complete initial monitoring (under the 2024 rule; unchanged even if the extension rule is finalized)
April 26, 2029: MCL compliance deadline (April 26, 2031 for systems granted an extension, if the extension rule is finalized)
Business Impact
The current rule remains legally in effect, but its future is uncertain. Because the rule directly regulates water systems, the impact on manufacturers is indirect. Regulation of PFOA and PFOS themselves appears likely to be maintained, while regulations covering PFHxS, PFNA, and HFPO-DA may be rescinded. Companies should monitor developments separately for each substance.
Under the proposed extension rule, water systems granted an extension whose PFOA or PFOS results are at or above 12 ppt would be required to take short-term mitigation actions during the extension period. The initial monitoring requirement (deadline April 26, 2027) does not change, regardless of any extension.