The EPA’s New Proposals to Modify PFAS Drinking Water Standards

On May 18, 2026, the U.S. Environmental Protection Agency (EPA) announced two proposed rules modifying regulations for treating per- and polyfluoroalkyl substances (PFAS) in drinking water under the Safe Drinking Water Act (SDWA).¹ The EPA proposals seek to extend compliance deadlines for two common PFAS compounds, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), and rescind four other forever chemicals.² The rules would change the scope of the EPA’s 2024 PFAS drinking water standards.

Extending the Compliance Deadline for the PFOA and PFOS Maximum Contaminant Levels
The first proposed rule targets the previously established limits of PFOA and PFOS under the 2024 National Primary Drinking Water Regulations (NPDWR). Under the original 2024 regulations, the EPA set Maximum Contaminant Levels (MCLs) at 4.0 nanograms per liter.³ This compliance standard required utilities and public water systems to implement highly technical treatment systems. The new proposal introduces a federal exemption that would allow eligible drinking water systems an additional two years to comply with these limits by pushing the final compliance deadline from April 2029 to April 2031.

The question remains, why is the EPA proposing to provide more time for systems to achieve compliance? The EPA explains that implementation challenges have posed a regulatory burden for small and disadvantaged communities. The EPA acknowledges that local water systems are grappling with a variety of issues, including the extensive time required to clear, fund, and construct capital improvement projects; a nationwide shortage of certified operators capable of running treatment facilities; and financial limitations. The extension of compliance deadlines will assist struggling utilities to secure technical and financial resources without being immediately non-compliant.⁴

The Proposal of Rescinding Regulatory Determinations and Removal of Related Provisions for Four PFAS Substances
While the first rule modifies the compliance timeline, the second proposal narrows the scope of federal oversight. The EPA proposed to rescind its final regulatory determinations and remove all associated regulatory provisions for four PFAS substances: perfluorohexane sulfonic acid (PFHxS), perfluorononanoic acid (PFNA), hexafluoropropylene oxide dimer acid (HFPO-DA, commonly known as GenX), and the multi-chemical Hazard Index mixtures of these three substances plus perfluorobutane sulfonic acid (PFBS).⁵

The rescission is not due to new scientific or health findings but rather to correct a procedural flaw in how the contaminants were added to the list of regulated contaminants. Under the SWDA, the EPA regulates drinking water contaminants through a specific two-step process. First, the EPA must issue a Contaminant Candidate List (CCL) every five years with contaminants that are not currently regulated but are expected to occur in public water systems. The EPA must invite public comment to weigh in on whether the contaminants should be regulated. The EPA then officially makes its determination on whether they will regulate the contaminants. The second step is setting the standard for the regulation by the following procedure: the EPA proposes regulation through specific numbers and limits; there is another round of public comments on the specific limits proposed; and the regulation becomes law.

For PFOA and PFOS, the agency followed this sequence perfectly. However, the EPA bypassed this process with the other four chemicals. On April 26, 2024, the EPA simultaneously issued the decision to regulate the chemicals and finalized the specific MCLs. Under the statutory process, the EPA does not have the authority to propose exact limits when there was not an official determination to regulate. This shortcut led to federal litigation from water utility companies, such as American Water Works Association. The proposal seeks to remove this illegal foundation on which the regulations were built.⁶

Looking Ahead
Because the PFOA and PFOS requirements were procedurally appropriate, the MCLs remain in effect for those chemicals. Thus, the water systems need to be updated to comply and filter out the PFOS and PFOA contaminants, which often leads to treating the water for PFHxS, PFNA, HFPO-DA as well, even without the federal mandate to do so.

The EPA proposals attempt to give the public water systems a better opportunity to comply with federal chemical limits through updated technology. However, states can fill that gap if they choose to because the SDWA sets a floor, not a ceiling, so states remain free to adopt or retain their own MCLs for PFHxS, PFNA, HFPO-DA, and PFBS regardless of the EPA’s recission. For instance, both Michigan and Vermont have set state standards for PFHxS and PFNA, and Michigan has also regulated HFPO-DA.⁷

Both proposals are open for public comment through July 20, 2026, giving water systems, states, and the public a final chance to weigh in before either rule is finalized, with public hearings scheduled for July 7, 2026.⁸

¹ Proposed PFOA and PFOS Compliance Extension Rule, U.S. Env't Prot. Agency, (last updated May 20, 2026).
² Proposed PFAS Rescission Rule, U.S. Env't Prot. Agency, (last updated June 23, 2026).
³ Conquering Forever Chemicals: U.S. EPA Regulates PFAS in Nation’s Drinking Water, Nat'l Sea Grant L. Ctr. (June 2024).
⁴ EPA, Proposed PFAS Rescission Rule, supra note 2.
⁵ Rescission of Regulatory Determinations and Removal of Related Provisions for Four PFAS Substances (PFHxS, PFNA, HFPO-DA (GenX), and the Mixture of These Three PFAS Plus PFBS), 91 Fed. Reg. 29,413 (proposed May 20, 2026) (to be codified at 40 C.F.R. pts. 141, 142).
⁶ Id.
⁷ Comparative Analysis of State Regulation of PFAS in the Great Lakes and Lake Champlain Regions, Nat'l Sea Grant L. Ctr. (2025).
⁸ EPA, Proposed PFOA and PFOS Compliance Extension Rule, supra note 1.