Why It Matters

The U.S. Environmental Protection Agency's (EPA) May 2026 proposal to rescind drinking water standards for four PFAS compounds threatens to unwind one of the agency's most expensive environmental rules, even as Congress pushes new legislation on the chemicals.

A Congressional Research Service (CRS) report published June 23 examines the stakes, which include $14.4 billion in aggregate capital costs by 2029 that water systems have begun planning to absorb and a legal challenge that could reshape how the EPA can regulate contaminants under the Safe Drinking Water Act. The rescission would abandon standards for PFHxS, PFNA, PFBS, and GenX chemicals, compounds that persist indefinitely in the environment and human tissue, while leaving the more familiar PFOA and PFOS rules intact.

The Big Picture

In May 2026, the EPA proposed to rescind the regulatory determinations for PFHxS, PFNA, PFBS, and GenX chemicals, citing procedural grounds. The agency argues it erred in 2023 by simultaneously proposing both a regulatory determination and a regulation for those four compounds, a move it contends was unlawful. The EPA stated the rescission is not based on any change in its findings about health effects, occurrence, or health risk reduction opportunity.

The Safe Drinking Water Act explicitly allows EPA to propose a regulation concurrent with a determination to regulate. The statute also contains an anti-backsliding provision requiring that any revision to a drinking water regulation maintain or provide greater protection of public health.

Compliance costs weigh heavily on smaller utilities. The average per-system investment for PFAS compliance is approximately $2.8 million, alongside $1.2 billion per year in ongoing operations and maintenance costs. Yet 87% of water systems covered by the regulation serve fewer than 3,300 people, and smaller systems face greater affordability challenges per customer than larger ones.

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