PFAS Drinking Water Standards: State-by-state Regulations

Summary

The regulation of per- and polyfluoroalkyl substances ("PFAS") in drinking water remains one of the primary focuses for legislatures and agencies at both the state and federal levels. In May 2025, the United States Environmental Protection Agency ("EPA") affirmed Maximum Contaminant Levels ("MCLs") of 4 parts per trillion ("ppt") for two PFAS substances, perfluorooctanoic acid ("PFOA") and perfluorooctane sulfonic acid ("PFOS"). Many states have already regulated PFAS compounds in drinking water but have done so in a variety of different ways and at different levels.

The result is a patchwork of regulations and standards which presents significant operational and compliance challenges to impacted drinking water systems. This client alert surveys MCLs, as well as guidance and notification levels, for PFAS compounds in drinking water across the United States.