pfasmcldrinking-watercerclaregulatory-update

PFAS Drinking Water Standards - Where Things Stand in 2026

Updated June 26, 2026

The Short Version

If you need to know which PFAS numbers to use right now, here’s the current status as of June 2026:

PFOA and PFOS - The federal MCLs of 4 parts per trillion (ppt) each are staying. EPA has proposed to keep these standards. On May 18, 2026, EPA proposed a rule that would let public water systems request a two-year extension of the compliance deadline, moving it from 2029 to 2031 for systems that apply. PFOA and PFOS are also designated hazardous substances under CERCLA (Superfund), effective July 2024. The current administration has confirmed it will retain and defend that designation.

PFHxS, PFNA, HFPO-DA (GenX), and the Hazard Index mixture - On May 18, 2026, EPA proposed rescinding the individual MCLs (10 ppt for PFHxS, PFNA, and GenX) and the Hazard Index mixture standard that were finalized in April 2024. The proposal was published in the Federal Register on May 20, 2026 (Docket EPA-HQ-OW-2025-0654), with a comment period closing July 20, 2026. The rescission is not final. Until EPA takes final action - which it intends to do in 2026 - those four MCLs technically remain in effect.

What Happened

In April 2024, the Biden administration finalized the first-ever National Primary Drinking Water Regulation (NPDWR) for PFAS (Per- and Polyfluoroalkyl Substances). The rule set MCLs for six PFAS compounds and gave public water systems until 2027 to complete initial monitoring and until 2029 to comply with the MCLs.

The rule was immediately challenged in court by water utilities and industry groups who argued EPA underestimated compliance costs and used an untested Hazard Index approach for regulating PFAS mixtures.

In May 2025, the Trump EPA announced it would keep the PFOA and PFOS MCLs but pull back on the other four PFAS. Specifically:

Kept: PFOA MCL at 4 ppt, PFOS MCL at 4 ppt. A two-year compliance extension to 2031 proposed for systems that request it.

Proposed for rescission: Individual MCLs for PFHxS (10 ppt), PFNA (10 ppt), and HFPO-DA/GenX (10 ppt), plus the Hazard Index MCL for mixtures of PFHxS, PFNA, GenX, and PFBS.

EPA acted on that intent on May 18, 2026, issuing two proposed rules: one to extend the PFOA/PFOS compliance deadline, and one to rescind the four-compound determinations. EPA’s stated reasoning for the rescission is that the regulatory determinations for those four compounds were not promulgated in accordance with the Safe Drinking Water Act (SDWA) and need to be corrected. Both proposals carry a comment period closing July 20, 2026, with a public hearing on July 7, 2026.

CERCLA Hazardous Substance Status

Separately from the drinking water standards, EPA designated PFOA and PFOS as hazardous substances under CERCLA in April 2024 (effective July 2024). This designation triggers Superfund cleanup authority, release reporting requirements (reportable quantity of one pound in 24 hours), and cost recovery provisions.

In September 2025, the administration confirmed it will retain and defend the CERCLA designation for PFOA and PFOS. The U.S. Chamber of Commerce’s legal challenge to the designation is being litigated in the D.C. Circuit. Oral argument was held January 20, 2026, with a decision possible later this year.

EPA is also planning a framework rule to guide future CERCLA hazardous substance designations, which could eventually cover additional PFAS compounds.

On the RCRA (Resource Conservation and Recovery Act) side, EPA has worked toward a rule that would add nine PFAS compounds to the list of hazardous constituents, which would require corrective action for releases at permitted hazardous waste facilities. Check the current rule status before relying on it in scope-of-work language.

What This Means for Consultants

For drinking water compliance: PFOA and PFOS at 4 ppt are the numbers. Public water systems need to be monitoring and planning for compliance, with an extension to 2031 proposed for systems that request it. The status of the other four PFAS MCLs is unsettled - they remain in effect but are under a proposed rescission - so if you’re advising a water system, monitor the rulemaking closely.

For site assessment and cleanup: PFOA and PFOS are CERCLA hazardous substances. This means PFAS should be evaluated at sites where PFOA/PFOS may have been used, released, or disposed of. Phase I ESAs should consider PFAS as a potential concern even though they remain “non-scope” under ASTM E1527-21 (because the CERCLA designation postdates the standard). The practical advice: include PFAS in your scope of work at sites with industrial history, firefighting foam use, or wastewater/biosolids handling.

For state programs: Many states have their own PFAS standards or guidance values that may differ from the federal MCLs. Ohio, for example, revised its PFAS Action Plan (to “Action Plan 2.0”) to align its drinking water Action Levels with the 2024 federal MCLs - 4 ppt for PFOA and PFOS, and 10 ppt each for PFHxS, PFNA, and GenX (PFBS is set at 2,000 ppt based on EPA’s 2023 Health Based Water Reference Concentration). Ohio’s older 2019/2020 levels (70 ppt combined for PFOA/PFOS) have been superseded and should not be used for current screening. When both federal and state standards exist, the more restrictive typically applies for public water systems. For voluntary cleanup programs, check which standards your state program uses. See our Ohio PFAS Groundwater and Drinking Water Standards page for Ohio-specific details.

For property transactions: The CERCLA hazardous substance designation for PFOA and PFOS increases the importance of evaluating PFAS risk during due diligence. Properties with potential PFAS contamination carry Superfund liability implications that didn’t exist before July 2024.

What to Watch

Several developments expected in 2026 could change the landscape:

The D.C. Circuit’s decision on the CERCLA hazardous substance designation challenge could uphold, modify, or vacate the rule. A decision is expected sometime this year.

EPA’s proposed rule to rescind the PFHxS/PFNA/GenX/Hazard Index MCLs is open for comment through July 20, 2026, with EPA intending to take final action in 2026. The separate proposed rule extending the PFOA/PFOS compliance deadline to 2031 shares the same comment deadline.

EPA’s RCRA rulemaking to add nine PFAS to the hazardous constituents list - confirm its current status before relying on it.

Congressional action on “passive receiver” liability protections for water utilities and other entities that did not manufacture or intentionally use PFAS remains possible but uncertain.

We will update this post and our PFAS standards pages as these developments occur.