EPA Proposes Major Changes to PFAS Drinking Water Rule

The proposals mark a significant shift from the Biden administration’s April 2024 PFAS National Primary Drinking Water Regulation, which established nationwide enforceable standards for drinking water for six PFAS compounds.

2024 PFAS National Primary Drinking Water Regulation
In April 2024, EPA finalized a rule that established Maximum Contaminant Levels (MCLs) for six PFAS substances under the Safe Drinking Water Act (SDWA): perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorohexane sulfonic acid (PFHxS), perfluorobutane sulfonic acid (PFBS) and hexafluoropropylene oxide dimer acid (HFPO-DA, also known as GenX chemicals).

The rule established enforceable MCLs of 4 parts per trillion (ppt) for PFOA and PFOS and 10 ppt limits for PFHxS, PFNA and HFPO-DA. By regulating these chemicals on the scale of ppt, these MCLs were orders of magnitude lower and, therefore, more stringent than the standards promulgated for other chemicals regulated under the NPDWR, though it is worth noting that the ppt standard was itself a compromise, since EPA had initially proposed MCLs on the order of parts per quadrillion for PFOA and PFOS. The rule also established a Hazard Index of 1 for any mixture of at least two of PFHxS, PFBS, HFPO-DA and PFNA. Under the 2024 regulation, public water systems were mandated to finish initial monitoring by 2027 and obtain compliance by 2029.

EPA’s Proposed Amendments
EPA’s May 20, 2026, rulemakings proposed to extend compliance deadlines while preserving enforceable limits for PFOA and PFOS, and rescind the drinking water standards established in the 2024 rulemaking for four additional PFAS compounds and mixtures.

Extension of Compliance Deadlines for PFOA and PFOS
In Docket EPA-HQ-OW-2025-1742-0001, EPA proposed a rulemaking that would extend dates for compliance with the MCLs for PFOS and PFOS from April 26, 2029, until April 26, 2031. The regulation would maintain the current MCLs for PFOA and PFOS at 4 ppt; however, qualifying systems may submit an application for the compliance deadline extension. Eligible facilities will include public water systems (defined in 40 CFR 141.2) and state and tribal agencies responsible for drinking water regulation and enforcement.

Under the proposed rule, water systems seeking an extension must submit:

-Recent sampling results for PFOA and PFOS;

-Certifications that the system is not able to comply with the 2029 deadline, and that restructuring or managerial changes cannot reasonably be made to achieve compliance by 2029; and

-A certified statement and evidence that the system is taking all practicable compliance steps, and that the system either (1) cannot meet the standard without certain capital improvements that will not be completed prior to April 2029; (2) where financial assistance is needed for the improvements, the assistance is reasonably likely to be obtained within the exemption period; or (3) the system has a formal, enforceable agreement to join a regional public water system.

Systems with PFOA or PFOS concentrations at or above 12 ppt will also be required to implement at least two prescribed interim control measures (and make them available for all customers) during the period between April 26, 2029, and April 26, 2031, such as providing certified water filters, supplying alternative water sources, installing point-of-use treatment devices or conducting public education initiatives.

Rescission of Standards for Four Additional PFAS
In a separate proposed rulemaking (Docket EPA-HQ-OW-2025-0654-0001), EPA announced its intent to rescind the drinking water standards and regulatory determinations for PFHxS, HFPO-DA and PFNA, and the Hazard Index for mixtures of these PFAS with PFBS. EPA stated that it intends to reconsider whether regulation of those substances complies with SDWA procedural and substantive requirements.

EPA identified the rescission as a necessary action because EPA was not authorized to promulgate regulations for all of the relevant PFAS in tandem, in the manner done in the 2024 rulemaking.

Potential Legal Challenges
The proposed amendments are expected to generate substantial interest and litigation from both environmental organizations and industry stakeholders. For example, opponents of the rollback may invoke SDWA’s “anti-backsliding” provision in 42 U.S. Code § 300g-1(b)(9), which generally requires amendments to national drinking water regulations to maintain or enhance protection of the public. The extension proposal may also face challenges regarding EPA’s use of SDWA exemption authority under 42 U.S. Code § 300g-5 to create what critics may characterize as a de facto nationwide compliance delay rather than individualized exemptions.

At the same time, industry and utility groups continue to pursue pending litigation challenging the original 2024 PFAS rule as technologically infeasible and excessively costly.

Public Comments
EPA will accept public comments on the proposed rules until July 20, 2026, and also plans to hold a virtual public hearing on July 7, 2026. Commenters can submit their comments on Federal Register Dockets EPA-HQ-OW-2025-0654-0001 and EPA-HQ-OW-2025-1742-0001. EPA has not provided a timeline for when the new standards would be issued.