PFAS in tap water explained: what EPA's limits mean

What PFAS are

Per- and polyfluoroalkyl substances (PFAS) are a group of chemicals widely used in industrial and consumer products. EPA says they have been shown to cause health issues and that reducing PFAS levels in your water is an effective way to limit exposure. Individual compounds have different abbreviations: PFOA and PFOS are the best known; PFHxS, PFNA, HFPO-DA (known as GenX) and PFBS appear in EPA’s rule too.

What researchers say about health

The CDC says researchers continue to study how PFAS chemicals affect health, and that current evidence suggests high levels may lead to higher cholesterol levels, changes in liver enzymes, decreased vaccine response in children, a higher risk of high blood pressure or pre-eclampsia in pregnant women, small decreases in infant birth weights, and a higher risk of kidney or testicular cancer. These are findings about high levels of exposure; they do not tell you what your own tap water means for your health. Ask a clinician.

What EPA’s 2024 rule sets

EPA’s National Primary Drinking Water Regulation set limits for five individual PFAS (PFOA, PFOS, PFNA, PFHxS and HFPO-DA) and for a mixture of four (PFHxS, PFNA, HFPO-DA and PFBS). The limits for PFOA and PFOS are 4.0 parts per trillion each. A part per trillion is an extremely small amount, which is why PFAS testing needs specialized laboratory methods.

Regulatory status is changing. According to EPA, utilities have until 2029 to comply with the PFOA and PFOS limits, with a proposed extension to 2031, and EPA has proposed to rescind the limits for PFHxS, PFNA, GenX and the hazard-index mixture. Check EPA’s PFAS page for the current status. We label that on every page with PFAS data.

What the data shows

Between 2023 and 2025, EPA’s UCMR 5 program required testing for 29 PFAS (what UCMR 5 is). We summarize the results for every U.S. utility serving 3,300 or more people (state by state). A detection is not a violation: compliance is judged later, on a running annual average from regulatory monitoring.

What you can do

1. Look up your utility (find it).
2. Ask the utility how it plans to meet the 4 ppt limits and whether it publishes PFAS results.
3. Consider a certified filter for drinking and cooking water. EPA says carbon, ion exchange and reverse osmosis point-of-use systems can greatly reduce PFAS when maintained (choosing one).
4. Don’t count on boiling or a softener. The Minnesota Department of Health says boiling does not remove PFAS and that softeners and iron filters are not likely to remove them (details).
5. Private well: your well is not covered by UCMR 5; a lab test is the way to know (test options).

Questions about health effects belong with a clinician or your state health department.