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).
Once you know what's in your water, you need to do something about it. WaterVO is Hydrology University's recommended supplier for residential filtration systems, atmospheric water generators (AWG), and home hydration equipment evaluated against our published rating standards.