Map Reveals Locations of PFOA and PFOS Detections in U.S. Drinking Water
Federal data visualizes where two widely studied PFAS chemicals have been found in public drinking water systems across the United States.
Data from the EPA's Fifth Unregulated Contaminant Monitoring Rule has been compiled into a map that identifies public drinking-water systems with detections of the PFAS chemicals PFOA and PFOS at or above the federal limit of 4 parts per trillion. Over 1,700 systems logged at least one such result during the 2023-2025 monitoring period. The agency notes that an isolated reading at this level does not constitute a breach of the Maximum Contaminant Level, which is determined through ongoing compliance monitoring and averaged over time.
The International Agency for Research on Cancer classifies PFOA as carcinogenic and PFOS as possibly carcinogenic, with links to various health issues. Recent EPA website updates, prompted by a complaint from the Public Employees for Environmental Responsibility, now acknowledge that PFOA may still be produced or imported. Additionally, the EPA has proposed allowing certain systems up to two extra years to meet the existing limits, potentially shifting the deadline from 2029 to 2031, though the rule has not been finalized.
Why it matters
Understanding where PFAS appear in drinking water helps communities assess potential health risks and informs regulatory actions.
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