EPA Moves to Reshape PFAS Drinking Water Standards

The proposed rollback represents broad implications for municipal water systems and industry stakeholders, shaping compliance strategies, operational planning, and PFAS treatment decisions

On May 18, the U.S. Environmental Protection Agency announced a proposed rollback of portions of its 2024 National Primary Drinking Water Regulations for per- and polyfluoroalkyl substances (PFAS), signaling another shift in the federal approach to regulating these persistent chemicals in drinking water systems.

The proposal introduces targeted regulatory relief for certain PFAS while maintaining enforceable limits for others, creating a simpler federal compliance landscape for public water systems and adjacent industry stakeholders. For municipal drinking water providers, these changes impact compliance timelines and may affect treatment system design. 

While this proposal would remove some federal limits on certain PFAS in drinking water, state programs and expanding scrutiny of industrial and municipal discharges continue, suggesting that the compliance burden is shifting — not shrinking.

What's changing — and what's not

EPA has proposed rescinding enforceable maximum contaminant levels (MCLs) for several PFAS, specifically perfluorohexane sulfonic acid (PFHxS), perfluorononanoic acid (PFNA), and hexafluoropropylene oxide dimer acid (HFPO-DA, commonly known as GenX), along with the associated hazard index used to evaluate combined exposure from PFHxS, PFNA, GenX, and perfluorobutane sulfonic acid (PFBS). The proposal also removes the corresponding Maximum Contaminant Level Goals (MCLGs), eliminating both enforceable standards and health-based targets for this subset of PFAS.

At the same time, the agency has indicated it will retain the existing MCLs for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), which apply to public drinking water systems serving at least 25 people. These compounds remain the primary focus of federal regulation due to their broader occurrence and more established toxicological profiles.

This recalibration aligns with observed occurrence patterns in national monitoring data. Results from the Fifth Unregulated Contaminant Monitoring Rule (UCMR 5) data collected thus far indicate that exceedances for the originally proposed MCLs for PFHxS, PFNA, and GenX are significantly less frequent than for PFOA and PFOS. Among 9,238 monitored public water systems, only 64 (0.7%) reported exceedances for PFHxS, 9 (0.1%) for PFNA, and 3 (0.03%) for GenX, compared to 820 (9%) for PFOS and 735 (8%) PFOA. These differences in occurrence help explain EPA's emphasis on maintaining enforceable standards for the most prevalent PFAS while reassessing regulatory approaches for compounds detected far less frequently.

In parallel, EPA has initiated a rulemaking process that would allow certain drinking water providers to request up to a two-year extension beyond the current 2029 compliance deadline for PFOA and PFOS standards. The agency has also indicated that the rescinded PFAS may be re-evaluated through a revised regulatory process, leaving open the possibility of future standards for these compounds. The proposed opt-in extension for PFOA and PFOS compliance introduces additional time for water systems to evaluate approaches and implementation of treatment systems, which may influence how utilities phase-in treatment upgrades as technologies continue to evolve.

Implications of the proposed rollback

The proposed changes represent minor impacts to public drinking water systems subject to federal MCLs. Importantly, most exceedances for the rescinded PFAS MCLs co-occur in systems that already exceed the PFOA, or PFOS limits. This overlap makes the change largely inconsequential in terms of identifying and addressing public water systems with elevated PFAS. Furthermore, drinking water treatment options for PFNA and PFHxS are often similar to those used for PFOS and PFOA, such as granular activated carbon and ion exchange resins. 

The opt-in, two-year compliance implementation extension may have more consequential impacts for drinking water providers by providing critical breathing room to finance, design, construct, and implement treatment systems required for PFOS and PFOA. Because treatment technologies are rapidly evolving, this delay may also allow utilities to deploy more refined and cost-effective treatment systems in the near future. 

However, removing the legally enforceable limits for PFNA, PFHxS, and GenX may also impact adjacent environmental frameworks. Specifically, it may alter cleanup standards at active remediation sites and affect effluent discharge standards under the Clean Water Act. 

Given this federal step back, individual states may step in to fill the perceived regulatory void for these rescinded PFAS compounds. If so, that risks creating a patchwork of state-level drinking water regulations across the country.  

Next steps for municipal water systems and industry stakeholders

As PFAS regulations continue to evolve, organizations are navigating a combination of federal rulemaking, state-level activity, and ongoing technical developments related to detection and treatment. Considerations often differ depending on where stakeholders sit across municipal systems and industrial operations.

For public water systems:

• Evaluating how revised MCL scope affects the need for treatment or changes in treatment design
• Incorporating extended compliance timelines into capital planning and infrastructure upgrades
• Assessing treatment performance for PFOA and PFOS while monitoring potential future standards for additional PFAS

For manufacturers and other industry stakeholders:

• Tracking how federal and state requirements diverge across compounds, uses, and reporting thresholds
• Evaluating PFAS presence in materials, products, and waste streams in the context of evolving regulatory scrutiny
• Assessing potential exposure related to industrial discharges, site remediation, and downstream drinking water impacts

Across both groups, the regulatory landscape continues to develop across multiple programs rather than a single standard, requiring alignment between regulatory tracking, technical evaluation, and risk assessment activities as new requirements emerge.

EPA will accept public comments on the proposed regulatory changes through July 20, 2026 via the federal rulemaking docket (EPA-HQ-OW-2025-0654) at www.regulations.gov. Public water systems, manufacturers, and other stakeholders are encouraged to review the proposal and provide input on the rescission of certain PFAS standards, the structure of the compliance extension framework, and the agency's proposed approach to re-evaluating these compounds before finalizing revisions to the drinking water regulations. EPA will also hold a virtual public hearing on July 7, 2026, where stakeholders may provide additional input as part of the rulemaking process.