The EPA's New 4 ppt PFAS Limit — And Why It Matters
For the first time, the EPA set enforceable limits on PFOA and PFOS at just 4 parts per trillion. Many public water systems still test above that line.
enforceable EPA limit for PFOA & PFOS
compliance deadline for public water systems
of U.S. tap water estimated to contain PFAS
The Story Behind the Number
PFAS — per- and polyfluoroalkyl substances — are a family of thousands of synthetic 'forever chemicals' used in nonstick coatings, firefighting foam, and water-resistant products. They do not break down naturally and accumulate in the human body over time.
In its national drinking-water standard, the EPA set the maximum contaminant level for PFOA and PFOS at 4 parts per trillion — among the strictest limits for any drinking-water contaminant. Public water systems have until 2031 to comply, which means many homes are still being served water above this level today.
What This Means for Your Home
- 4 parts per trillion is roughly four drops in an Olympic-sized swimming pool — the limit is this low because research links PFAS to serious health effects even at tiny concentrations.
- Because the compliance deadline runs to 2031, utilities are not required to hit the limit immediately, so the safest move is to verify and treat at your own tap.
- Reverse-osmosis and certified activated-carbon systems are the most effective home treatments for reducing PFAS in drinking water.
Filter PFAS at your tap
WaterVO, our sister company, supplies the PFAS-rated reverse-osmosis and advanced filtration systems we recommend after editorial review.
Sources: EPA National Primary Drinking Water Regulation for PFAS; USGS tap-water sampling study (2023).
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