EPA Proposes Two New Rulemakings Set to Shape Safe Drinking Water Act Regulation of PFAS

On May 18, the Environmental Protection Agency proposed the PFOA and PFOS Compliance Extension Rule and the PFAS Rescission Rule, extending the compliance period for federal drinking water standards for PFOA and PFOS while withdrawing standards for three other PFAS compounds and a controversial hazard index approach. The proposed rules, published in the Federal Register on May 20, respond to a 2024 Safe Drinking Water Act rulemaking by the Biden administration that has been the subject of litigation in the DC Circuit.

KEY TAKEAWAYS

• The Environmental Protection Agency (EPA) is maintaining the national primary drinking water standards for perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) of 4 ppt but is providing a pathway for utilities to seek more time to comply with the new limits.
• The agency is proposing a case-by-case exemption process that could extend compliance deadlines for eligible systems by up to two years (from 2029 to 2031).
• EPA is proposing to rescind the regulatory determinations and related standards for three other PFAS including perfluorohexanesulfonic acid (PFHxS), perfluorononanoic acid (PFNA), hexafluoropropylene oxide dimer acid (HFPO-DA), and the hazard index covering those three compounds and perfluorobutanesulfonic acid (PFBS).
• The rescission proposal is framed as a procedural correction under the Safe Drinking Water Act (SDWA), not a reassessment of the substantive scientific or health findings underlying the 2024 rule.
• Litigation challenging one or both proposed rules is a strong possibility, particularly of the proposed rescission under the anti-backsliding provisions of the SDWA.

BACKGROUND

In April 2024, EPA finalized the first federal National Primary Drinking Water Regulation for per- and polyfluoroalkyl substances (PFAS). The rule established enforceable maximum contaminant levels (MCLs) for PFOA and PFOS and regulated PFHxS, PFNA, HFPO-DA, and mixtures of those three PFAS together with PFBS through a hazard index approach.

The 2024 rule required public water system compliance by April 2029. Since then, municipalities, utilities, industry groups, and other stakeholders have raised implementation, cost, scientific, and procedural concerns, including through a rulemaking challenge in the DC Circuit.

CONTINUED FOCUS ON PFOA AND PFOS

EPA’s PFOA and PFOS Compliance Extension Rule maintains enforceable federal standards for PFOA and PFOS but creates a mechanism for eligible water systems to seek up to two additional years to comply, extending the deadline from 2029 to 2031.

The extension would not be automatic. Water systems would need to affirmatively apply and satisfy the criteria that EPA plans to establish in the final rule. Systems that do not seek or receive an extension would remain subject to the existing compliance deadline.

Systems with PFOA or PFOS sampling results above 12 ppt would be required to implement short-term mitigation measures to reduce potential exposures to PFOA and PFOS during the exemption period. Systems with PFOA and PFOS above the 4 ppt MCLs likewise would be required to conduct periodic monitoring and reporting.

PROPOSED RESCISSION OF DRINKING WATER STANDARDS FOR ADDITIONAL PFAS

EPA’s PFAS Rescission Rule would rescind the regulatory determinations and associated standards for PFHxS, PFNA, and HFPO-DA as well as the hazard index covering those three PFAS and PFBS.

EPA’s rationale for this proposed rescission is procedural. The agency states that the SDWA requires EPA to first make a preliminary regulatory determination, allow public comment, and finalize the determination to regulate, and only then propose a drinking water regulation. According to EPA, the 2024 rule proposing regulation of the three additional PFAS and hazard index failed to comply with these strict public notice and comment requirements under the statute.

Importantly, EPA is not proposing rescission based on a reassessment of health risks, occurrence data, toxicity, or compliance costs. Instead, the agency expressly limited the reversal to EPA’s updated interpretation of the procedural requirements under the SDWA.

That framing appears significant because the SDWA contains anti-backsliding provisions that can limit EPA’s ability to weaken drinking water protections once finalized. By characterizing the proposal as a procedural correction rather than a substantive reevaluation of the standards, EPA may be attempting to strengthen its position against anticipated legal challenges.

Notably, EPA also left open the possibility of future regulation of these PFAS through a new rulemaking process.

SCIENTIFIC AND OCCURRENCE ISSUES REMAIN RELEVANT

Although EPA is not reopening its substantive evaluation of these PFAS in the rescission proposal, occurrence data will likely remain central to any future drinking water regulation of additional PFAS.

Unregulated Contaminant Monitoring Rule (UCMR) 5 data, of which 95% has been reported by EPA, indicates that PFOA and PFOS continue to appear more frequently in public water systems than other PFAS compounds. By contrast, PFHxS, PFNA, HFPO-DA, and hazard index appear in a comparatively small percentage of sampled water systems.

Questions also remain regarding the hazard index approach itself, including whether the regulated PFAS frequently co-occur and whether there is scientific support for regulating them collectively. The hazard index methodology was a novel proposal under the SDWA and generated significant controversy.

LITIGATION OUTLOOK

These proposals will likely trigger additional litigation. For example, environmental and public interest groups may challenge the rescission as unlawful backsliding under the SDWA. The anti-backsliding provision prohibits EPA from weakening drinking water protections. Under Section 1412(b)(9) of the SDWA, revisions to water standards must “maintain” or provide greater protection to human health. EPA’s procedural framing appears designed to preempt the anti-backsliding argument, but the DC Circuit may ultimately still need to determine whether rescission based on alleged procedural defects complies with the statute.

The proposed compliance extension framework may also face scrutiny. Because the SDWA sets forth specific compliance timelines, challengers may argue that a broadly available exemption process effectively creates an impermissible extension beyond the statutory deadline.

Meanwhile, a key part of the pending industry litigation challenging the 2024 rule in the DC Circuit may become moot or narrowed if EPA finalizes rescission of the standards for the four additional PFAS and hazard index.

LOOKING AHEAD

The proposed rules will be subject to a 60-day public comment period following their May 20 publication in the Federal Register, or until July 20, 2026, and EPA has scheduled a public hearing for July 7, 2026.

The proposals appear to reflect a narrower and more pragmatic federal drinking water strategy focused primarily on PFOA and PFOS while maintaining flexibility for future regulation of additional PFAS. The final rules and related litigation along with EPA’s continued efforts involving source reduction and treatment technologies will shape the next phase of federal PFAS regulation and compliance planning.