On May 18, 2026, EPA proposed two significant changes to the federal drinking water regulations for PFAS (per- and polyfluoroalkyl substances), commonly known as “forever chemicals.” The first would rescind the Biden-era standards for four categories of PFAS. The second would extend the time for water systems to comply with existing standards for PFOA and PFOS by up to two years. Each of these proposed changes will have significant implications for regulated entities and other stakeholders. Both will likely face legal challenges, which could further shape the emerging PFAS regulatory landscape.

Background

In April 2024, EPA set enforceable limits for six PFAS compounds. The rule established legally enforceable maximum contaminant levels (MCLs) of 4.0 parts per trillion (ppt) for PFOA and PFOS, and 10 ppt for PFHxS, PFNA, and HFPO-DA. It also regulated certain mixtures of PFHxS, PFNA, HFPO-DA, and PFBS through a hazard-index approach that measured each compound’s concentration relative to its health-based threshold and summed the results, with compliance achieved if the combined score did not exceed 1.0. The rule required public water systems to comply with these MCLs by April 2029.

Then in May 2025, EPA announced its plan to scale back and extend compliance deadlines for federal PFAS drinking water regulations, stating that it intended to retain standards for PFOA and PFOS but would reconsider regulations for the other four compounds: PFHxS, PFNA, HFPO-DA, and PFBS.

First Proposed Change: Recission of Regulations for Four PFAS

The first proposed change would rescind the regulatory determinations and related drinking water requirements for PFHxS, PFNA, HFPO-DA, and hazard-index mixtures of those three PFAS plus PFBS, including the 10 ppt MCLs. EPA says this proposal is “solely” intended to correct what it calls “unlawful process” under the Safe Drinking Water Act (SDWA). Specifically, EPA claims that under the Biden administration, it erred by issuing rules for these PFAS “without first completing the regulatory determination as a necessary prerequisite to rulemaking.” EPA determined this process to be “unlawful” based upon “relevant issues raised in litigation” and the U.S. Supreme Court’s elimination of Chevron deference for federal agencies in Loper Bright Enterprises v. Raimondo, 603 U.S. 369 (2024) that occurred only months after this rule was published. EPA states that it may evaluate additional PFAS in drinking water for future regulation after a final action.

Second Proposed Change: PFOA and PFOS Compliance Extension

The second proposed change would keep the federal PFOA and PFOS MCLs of 4 ppt in place while creating an option for drinking water systems to seek two additional years to comply(until 2031). EPA describes the proposal as creating a “federal exemption framework” for systems in states, territories, and Tribes that have not obtained primary enforcement responsibility for public water systems for the PFOA and PFOS MCLs. EPA characterizes the extension as a practical measure meant to ease implementation of the MCLs and address challenges posed by long construction timelines for treatment facilities, workforce challenges, financial limitations, and availability of water-quality data to inform capital improvement decisions.

Under the proposed changes, the water systems that receive exemptions would still have to meet monitoring and reporting requirements on the timelines established in the 2024 rule, and those with PFOA or PFOS sample results at or above 12 ppt would be required to implement short-term mitigation actions to reduce exposure to their consumers during the exemption period.

Effects and Takeaways

For public water systems, the immediate takeaway is that the 4 ppt MCLs for PFOA and PFOS remain in place, even if qualifying systems may obtain more time to achieve compliance. For water systems already planning capital projects, treatment procurement, or source-water changes, the proposed extension may provide some flexibility; however, because monitoring, reporting, public notice, and potential interim mitigation obligations would continue, this is not a complete pause.

For many stakeholders, such as manufacturers, site owners, those engaged in remediation projects, and those conducting environmental due diligence, these proposed changes do not eliminate risk; they create more uncertainty. In Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA, also known as Superfund) cleanups, MCLs often become applicable or relevant and appropriate requirements (ARARs). Thus, these PFAS MCLsmay affect cleanup expectations for groundwater contamination. EPA’s proposal to allow two-year extensions for compliance with the PFOA and PFOS MCLs would provide no relief to CERCLA PRPs (potentially responsible parties). As the MCLs are staying and only the compliance timeline is moving, they would remain likely ARARs. Conversely, the rescission of the other four PFAS standards, if finalized, could eliminate them as a requirement for Superfund site cleanups.

Additionally, several states, including New York, Massachusetts, Illinois, and Californiahave now enacted their own PFAS drinking water standards, which adds to the complexity of the PFAS regulatory landscape. Thus, entities currently preparing for compliance with PFHxS, PFNA, HFPO-DA, and PFBS or facing remediation liability under state statutes should closely monitor the rulemaking for this rescission, as federal obligations for these PFAS may be eliminated, but state-level regulations could still apply and have significant impacts.

EPA will hold a virtual public hearing on July 7, 2026, to receive verbal comments on both of the proposed regulations. EPA will present information on the proposed rules and exemption schedules before opening the hearing for public comment. Registration is required to attend or provide comments, and the deadline to pre-register to speak is July 1, 2026. Interested parties can learn more about the public hearing and register here. EPA is also accepting written comments on the proposed rules until July 20, 2026.

For assistance with government relations or environmental matters, feel free to contact CMBG₃ Law and our environmental team. Our team is ready to provide guidance on regulatory issues, policy changes, and compliance concerns.