Per- and polyfluoroalkyl substances (PFAS) are a family of more than 12,000 synthetic chemicals manufactured since the 1940s. They're used in non-stick cookware, water-repellent clothing, food packaging, firefighting foam (AFFF), and hundreds of industrial processes. They're called "forever chemicals" because the carbon-fluorine bond (one of the strongest in organic chemistry) doesn't break down naturally in the environment or in the human body.
How Widespread Is the Contamination?
According to EPA's Fifth Unregulated Contaminant Monitoring Rule (UCMR 5), which tested approximately 10,290 public water systems as of January 2026:
- 34.4% of public water systems detected at least one PFAS compound
- 8.0% of systems had one or more PFAS averages above the new EPA MCL
- The Environmental Working Group's broader data estimates 9,728 PFAS-contaminated sites nationwide
Track current contamination data for every state on SafeWater's PFAS Tracker →
The New EPA MCLs (April 2024)
In April 2024, the EPA finalized the first-ever legally enforceable limits for PFAS in drinking water:
- PFOA: 4 ppt (parts per trillion)
- PFOS: 4 ppt
- PFHxS, PFNA, HFPO-DA (GenX): 10 ppt each
- Mixtures of PFBS/PFHxS/PFNA/HFPO-DA: Hazard Index of 1.0
Water utilities must comply by 2029. The 4 ppt limit for PFOA and PFOS is the lowest measurable level, a signal that EPA considers no amount truly safe.
Health Effects
PFAS accumulate in the blood and organs over time. Peer-reviewed research has linked chronic exposure to:
- Kidney and testicular cancer (PFOA, PFOS)
- Thyroid disease and hormone disruption
- Immune system suppression, including reduced vaccine effectiveness in children
- High cholesterol and cardiovascular disease
- Pregnancy-induced hypertension and low birth weight
Where Does It Come From?
The largest sources of PFAS in drinking water are military bases and civilian airports that used AFFF firefighting foam, industrial manufacturing sites (especially in the Southeast and Midwest), landfills leaching into groundwater, and agricultural application of PFAS-containing biosolids ("sludge").
What Can You Do?
Reverse osmosis systems and activated carbon block filters certified under NSF/ANSI 58 can remove a significant portion of PFAS. Learn more in our guide: Do Water Filters Remove PFAS? What Actually Works →