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PFAS in Drinking Water: A Scientist's Guide For Your Home
March 6, 2025
Eric Roy, PhD | Chief Scientist
I spent the early part of my career studying water chemistry in a lab, but I learned quickly that the most important questions come from people in crisis. Families in Flint who found lead leaching from their pipes. Communities discovering PFAS in their water. Almost everyone asks the same question: Is my water safe to drink?
With PFAS, the honest answer is that safe and legal are two different things. Your utility has to meet a legal limit, which is a number negotiated against the cost of treatment. Whether the water is safe to drink is a separate question, and I'll stick to the science.
PFAS (per- and polyfluoroalkyl substances, ie "forever chemicals") are synthetic compounds that were used for decades to make products resist heat, oil, grease, and water. They show up in nonstick pans, food packaging, firefighting foam, and a great deal of industrial waste, and they get into drinking water before it ever reaches the treatment plant.
Two things make PFAS worth acting on. They are linked to serious health problems, including kidney and testicular cancer, thyroid disruption, and weaker immune response in children. And they are persistent and don't readily break down (in nature or in your body). That means that when your water is contaminated with PFAS, the chemicals build up in your body faster than they clear.
Please bear with me, as this is confusing, frustrating, and changing in real-time.
In April 2024, the EPA set the first federal drinking-water limits for 6 PFAS compounds and set up a framework to assess toxicity of mixtures. In May 2026, it reversed course, proposing to strike the limits for four of them, including GenX, on procedural grounds, while keeping the limits for PFOA and PFOS and pushing their compliance deadlines back. (I walk through that reversal in a separate piece on the GenX case.)
Even at their strongest, federal rules move very slowly, so most of the regulations protecting drinking water have come from state governments. Maine, Michigan, New Jersey, and Vermont run some of the strictest PFAS programs in the country. The result is a patchwork, where whether anyone is required to test or fix your water depends largely on where you live.
Perhaps even more confusing, if you are on a private well, none of it applies. Your water is unregulated, meaning that government agencies are not responsible for testing your water for harmful contaminants, or fixing problems that are discovered during testing.
Fortunately, filtration is simpler than the regulations when you know what to look for.
Water filtration products can carry third party certifications for contaminant claims. Those certifications come from NSF, WQA, or IAPMO, and they require testing across the filter's entire rated life, not just the first few gallons that some brands build marketing claims from. What you want is PFAS reduction certified under NSF/ANSI Standard 53 or Standard 58, either for PFOA and PFOS (the older standard) or for "Total PFAS" (the newer one).
Be skeptical of the language on the box and in marketing materials. "Filters contaminants" and "third-party laboratory tested" sound rigorous and mean almost nothing, because they let a company test on its own terms. If a product does not carry an NSF/ANSI 53 or 58 certification for PFAS, you're trusting the manufacturer's marketing department.
Can I boil PFAS out of my water? No. Boiling drives the water off as vapor and leaves the PFAS behind, slightly more concentrated.
Do refrigerator or pitcher filters handle PFAS? Usually not. Most use loose carbon built for taste and odor, without the contact time PFAS need. Look for the certification before you trust one.
Does PFAS ever leave your body? Slowly. The half-lives run to years, but once you switch to filtered water, the level in your blood starts to fall.
Should I worry about showering in it? Swallowing is the main exposure. Skin absorption is low, so a drinking-water filter is where your effort belongs.