50 Most PFAS-Contaminated Water Systems in America
The EPA's 5th Unregulated Contaminant Monitoring Rule (UCMR5) tested over 7,000 public water systems for 29 PFAS “forever chemicals” between 2023 and 2025. The results revealed widespread contamination — with some systems delivering water at levels more than 100 times the EPA's own limits. These are the worst 50, ranked by maximum detected concentration.
Parts per trillion (ppt) is an almost incomprehensibly small unit — but PFAS compounds are dangerous at these trace levels because they accumulate in the body over decades and never break down. The EPA set the MCL for PFOA and PFOS at 4 ppt in 2024, reflecting the scientific consensus that there is no truly safe level of exposure. Systems showing 100+ ppt are delivering water at 25 times the legal limit.
If your water system is on this list with active MCL violations, the EPA requires the utility to notify customers and take remediation steps. In the meantime, a certified reverse osmosis filter is the only technology independently proven to remove PFAS to safe levels at the tap. Standard Brita-style pitchers do not remove PFAS effectively.
The EPA currently has enforceable MCLs for only 6 PFAS compounds: PFOA, PFOS, PFNA, PFHxS, HFPO-DA (GenX), and a hazard index for certain combinations. Many other PFAS — like PFBA, PFPeA, and 6:2 FTS — are detected at high levels but are not yet subject to MCLs. This does not mean they are safe; it means the regulatory process has not caught up with the science.
Enter your ZIP code on WaterCheckup to see the full EPA report for your local water utility, including PFAS detections, violation history, and filter recommendations matched to your actual contaminant profile.
Enter your ZIP code to see the full EPA PFAS report, violation history, and certified filter recommendations for your specific water system.
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