At the state and federal level, regulations governing per- and polyfluoroalkyl substances (PFAS) continue to evolve rapidly. In May 2026, the U.S. Environmental Protection Agency (EPA) formally proposed significant changes to its April 2024 National Primary Drinking Water Regulations (NPDWR), including a proposal to rescind drinking water standards for certain PFAS compounds and to extend compliance deadlines for PFOA and PFOS.

At the same time, the Wisconsin Department of Natural Resources (WDNR) is continuing to move forward with revisions to Wisconsin Administrative Code chapter NR 809 to incorporate the currently effective federal PFAS drinking water standards into state law, while separately advancing groundwater quality standards for certain PFAS compounds under chapter NR 140. These changes will significantly lower allowable PFAS levels in public drinking water systems across the state and may trigger new monitoring, treatment, compliance and infrastructure obligations for municipalities, utilities and other regulated entities.

Given that the April 2024 NPDWR remains effective unless and until the EPA completes additional rulemaking, regulated entities should continue planning for compliance based on the currently enforceable federal standards. However, the EPA’s proposed revisions and Wisconsin’s ongoing rulemaking create regulatory uncertainty and may significantly affect future compliance obligations, remediation requirements, permitting considerations, capital planning and long-term infrastructure investments.

What does the federal drinking water rule currently require?

In April 2024, the EPA finalized the first federal drinking water standards for certain PFAS under the Safe Drinking Water Act. As shown in the following table, the EPA established enforceable Maximum Contaminant Levels (MCLs) for certain PFAS. The EPA also established health-based, non-enforceable Maximum Contaminant Level Goals (MCLGs), which reflect contaminant concentrations at which no known or anticipated adverse health effects are expected.

PFAS Compound	MCL (ppt)	MCLG (ppt)
PFOA	4	0.0
PFOS	4	0.0
PFHxS	10	10
PFNA	10	10
HFPO-DA (GenX)	10	10
Mixtures containing two or more PFHxS, PFNA, HFPO-DA, and PFBS	1 (unitless) Hazard Index*	---

Under the current rule, public drinking water systems are required to:

• Monitor for the regulated PFAS and complete initial monitoring within three years (by 2027), followed by ongoing compliance monitoring. Beginning in 2027, systems must provide the public with information regarding PFAS levels in their drinking water.
• Implement treatment or other corrective measures within five years (by 2029) if PFAS concentrations exceed the applicable MCLs and provide public notice regarding violations.

What changes has the EPA proposed to the PFAS drinking water standards?

In May 2026, the EPA formally proposed two rules related to PFAS in drinking water, following through on changes it first announced in May 2025. One proposed rule would rescind the regulatory determinations and remove the associated drinking water standards applicable to PFHxS, PFNA, HFPO-DA (GenX chemicals) and the Hazard Index mixture standard involving PFHxS, PFNA, HFPO-DA and PFBS, but retain the existing 4.0 ppt MCLs for PFOA and PFOS. Unless and until the EPA finalizes that proposed rescission rule, the April 2024 standards for those compounds remain enforceable. In addition, a separate proposed rule would extend certain compliance deadlines for PFOA and PFOS from 2029 to 2031, and establish a federal exemption framework for certain public water systems.

How is Wisconsin responding to the federal PFAS drinking water standards?

Wisconsin is moving forward with revisions to the state’s Safe Drinking Water Standards under NR 809 that align the state’s drinking water regulations with the current federal PFAS drinking water standards promulgated under President Biden. Importantly, this rulemaking was designed to incorporate the April 2024 NPDWR that existed when the state rulemaking began and does not reflect the potential federal changes signaled by the EPA.

The updated rule lowers Wisconsin’s prior enforceable standard of 70 ppt for PFOA and PFOS to 4 ppt, consistent with the current federal MCLs. The rule also incorporates standards for additional PFAS compounds consistent with the federal framework and includes related updates to lead and copper requirements.

Wisconsin’s administrative rulemaking process includes provisions requiring additional legislative review for certain rules with significant economic impacts (commonly referred to as the REINS Act provisions). Under those provisions, additional review requirements may be triggered if a proposed rule is expected to result in $10 million or more in implementation and compliance costs over any two-year period. In the draft Fiscal Estimate and Economic Impact Analysis accompanying the proposed NR 809 revisions, the Wisconsin Department of Natural Resources (WDNR) concluded that the rule would not impose any additional compliance costs beyond those already associated with the federal PFAS drinking water standards—the very requirements that the EPA now proposes to modify.

In practical terms, the WDNR’s position is that incorporating the federal standards into state regulations does not independently increase compliance obligations beyond the existing federal baseline, even though the underlying monitoring, treatment and infrastructure costs associated with PFAS compliance may be substantial for affected drinking water systems.

If the EPA ultimately repeals or modifies the 2024 NPDWR, Wisconsin is unlikely to decrease its stricter drinking water rules for PFAS to align with the federal framework. Under the Safe Drinking Water Act in 42 U.S.C. § 300g-2(a)(1), state drinking water programs must be at least as stringent as federal requirements, but states may adopt or retain more protective requirements. This rule groups Wisconsin with other states including Michigan, Massachusetts, Maine and Rhode Island, that have adopted state-specific enforceable PFAS drinking water standards more stringent than the EPA.

The public comment period on the draft economic impact analysis closed on May 7, 2026. Following completion of the remaining rulemaking steps, including finalization of the economic impact analysis, Natural Resources Board adoption, gubernatorial approval and legislative review, the final NR 809 rule is expected to be published on July 1, 2026.

How is Wisconsin addressing PFAS groundwater standards?

Separate from the NR 809 drinking water standards, the WDNR is also moving forward with groundwater quality standards for certain PFAS compounds under NR 140. In April 2026, the WDNR published a draft rule that would establish groundwater enforcement standards that are consistent with the individual federal MCLs for PFOA, PFOS, PFHxS, PFNA and HFPO-DA, and the Health-Based Water Concentration (HBWC) for PFBS.

PFAS Compound	Proposed Enforcement Standards (ppt)
PFOA	4
PFOS	4
PFHxS	10
PFNA	10
HFPO-DA (GenX)	10
PFBS	2,000

The current proposal follows updated groundwater standard recommendations issued by the Wisconsin Department of Health Services after the WDNR withdrew an earlier PFAS groundwater standards proposal. Unlike the draft Fiscal Estimate and Economic Impact Analysis for the NR 809 drinking water discussed above, WDNR estimated the highest two-year implementation and compliance cost of the proposed groundwater rule at $9,893,388, just short of the $10 million threshold under the REINS Act.

Given NR 140 groundwater standards are frequently used in remediation, permitting and other environmental regulatory programs, adoption of PFAS groundwater standards would have significant implications for stakeholders beyond public water systems. These standards affect contaminated site investigation and remediation obligations, redevelopment projects, solid and hazardous waste programs, wastewater permitting, and environmental due diligence in real estate and business transactions.

What should regulated entities consider?

Although the EPA has proposed revisions to the federal PFAS drinking water rule, the April 2024 NPDWR remains the currently enforceable federal standard unless and until the EPA completes the proposed rulemaking. In Wisconsin, public water systems should also plan for compliance with the state PFAS drinking water standards being incorporated into NR 809, which may remain more stringent than the federal framework if the EPA ultimately rescinds or narrows portions of the 2024 NPDWR. Regulated entities should continue evaluating compliance obligations based on the current federal requirements while closely monitoring proposed changes at the state and federal levels.

Public water systems, municipalities, industrial users, developers, property owners and potentially responsible parties should evaluate how evolving PFAS standards may affect:

• Drinking water monitoring and treatment obligations
• Capital infrastructure planning
• Permitting and operational requirements
• Site investigation and remediation activities
• Environmental due diligence and other transactional risks
• Redevelopment projects
• Potential contribution, cost recovery and other liability exposure

How can Godfrey & Kahn help?

Godfrey & Kahn continues to monitor state and federal PFAS regulatory developments. For more information regarding these updates or how these standards may affect your operations, please contact a member of our Environmental team.