What it is
PFAS — per- and polyfluoroalkyl substances — are a family of thousands of man-made chemicals used in consumer, commercial and industrial products since the 1940s.[1, 2] They're prized for resisting heat, grease and water. The same durability is the problem: EPA describes PFAS as long-lasting chemicals whose components break down very slowly over time, and many are found in the blood of people and animals all over the world.[1] That persistence is why they're called "forever chemicals."[3]
How it gets into water
USGS scientists point to firefighting foams used for training and emergencies at airports and military installations as a major source, along with many additional sources in consumer products, industrial processes and wastewater. Once PFAS reach groundwater, they can remain for decades.[4]
Water is one of several ways PFAS reach people. EPA lists drinking water contaminated with PFAS alongside certain foods, including fish, and products made with PFAS or packaged in materials that contain them.[5] Because tap water is something you drink every day, it's one exposure you can measure and do something about.
In 2023, USGS published the first national study of PFAS in tap water drawn straight from kitchen sinks — samples from 716 locations collected between 2016 and 2021 and tested for 32 PFAS. It estimated that at least 45% of the nation's tap water has one or more PFAS. USGS also estimated the probability of PFAS not being observed in tap water at about 75% in rural areas and around 25% in urban areas.[3, 6]
Health impacts
In 2022, the National Academies of Sciences, Engineering, and Medicine reviewed the research and found sufficient evidence of an association between PFAS exposure and four outcomes: decreased antibody response in adults and children, abnormal cholesterol levels (dyslipidemia) in adults and children, decreased infant and fetal growth, and increased risk of kidney cancer in adults.[7]
EPA's summary of current research lists additional potential effects linked to certain PFAS, including developmental effects in children such as low birth weight, increased risk of some cancers (including prostate, kidney and testicular), reduced immune response including to vaccines, interference with the body's hormones, and increased cholesterol.[5] Exposure can also come from food and products, not only water.[5] If you have concerns about your own exposure, talk to your doctor.
What the law says vs. what health science says
In April 2024, EPA finalized the first national drinking water standards for PFAS. For PFOA and PFOS, the health goal is zero and the enforceable limit is 4.0 parts per trillion each. The rule also set limits for several other PFAS.[8]
Since then, the rules have been in motion. In May 2025, EPA announced it would keep the PFOA and PFOS limits, propose extending the compliance deadline to 2031, and reconsider the limits for four other PFAS.[9] In May 2026, EPA published two proposals: one would let water systems request two more years — to 2031 — to meet the PFOA and PFOS limits, and another would rescind the limits for PFHxS, PFNA, HFPO-DA ("GenX") and a mixture of PFAS. Neither proposal is final.[10, 11]
The AquaGap™ here is stark: a health goal of zero, and a legal limit that is still being argued over. That's exactly why it helps to see both numbers for your own water.
What you can do
- Know your numbers. Check your AquaScore™ to see what's been found near you and how it compares to the legal limit and the health goal.
- Consider a home filter. EPA lists granular activated carbon, reverse osmosis and ion exchange as options, and suggests looking for filters certified to NSF/ANSI Standard 53 or 58. Filters only work if they're maintained according to the manufacturer's instructions.[12]
- Read the fine print. EPA notes that current certifications don't yet show whether a filter removes PFAS down to the levels in the new drinking water standard.[12]
- Remember boiling won't help. Boiling water that contains harmful chemicals will not make it safe.[13]
In the news
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Sources
- U.S. EPA. PFAS Explained.
- ATSDR / CDC. About PFAS.
- U.S. Geological Survey. Tap water study detects PFAS 'forever chemicals' across the US (July 5, 2023).
- U.S. Geological Survey. PFAS Integrated Science Team.
- U.S. EPA. Our Current Understanding of the Human Health and Environmental Risks of PFAS.
- Environment International. Smalling et al., Per- and polyfluoroalkyl substances (PFAS) in United States tapwater, Environment International 178 (2023).
- National Academies of Sciences, Engineering, and Medicine. Guidance on PFAS Exposure, Testing, and Clinical Follow-Up (2022), ch. Potential Health Effects of PFAS.
- U.S. EPA. Per- and Polyfluoroalkyl Substances (PFAS): Final PFAS National Primary Drinking Water Regulation.
- U.S. EPA. EPA Announces It Will Keep Maximum Contaminant Levels for PFOA, PFOS (May 14, 2025).
- U.S. EPA. Proposed PFOA and PFOS Compliance Extension Rule.
- U.S. EPA. Proposed PFAS Rescission Rule.
- U.S. EPA. Reducing PFAS in Your Drinking Water with a Home Filter.
- CDC. Drinking Water Advisories: An Overview.