PFAS in drinking water: what it is and how to filter it out

What people ask us next.

What are PFAS, and why are they in drinking water?

PFAS, per- and polyfluoroalkyl substances, are a family of several thousand synthetic chemicals used since the 1940s in non-stick coatings, firefighting foam, food packaging, and stain and water repellents. They are called forever chemicals because the carbon-fluorine bond is among the strongest in chemistry, so they do not break down meaningfully in the environment or the body. They reach drinking water by leaching from industrial sites, landfills, and firefighting-foam training grounds into groundwater and rivers that feed public supplies. A US Geological Survey study published in 2023 in Environment International estimated that at least 45 percent of US tap water contains one or more PFAS.

How much PFAS is in my water, and is there a legal limit?

In the US there is now an enforceable limit. In April 2024 the EPA finalized the first national drinking water standard for PFAS, setting a maximum contaminant level of 4 parts per trillion for PFOA and PFOS individually, with limits for several other PFAS, and required public water systems to monitor and reduce levels by 2029. The EU set its own limit under the recast Drinking Water Directive: 0.1 microgram per liter for the sum of 20 PFAS, and 0.5 microgram per liter for total PFAS. Your local water utility publishes an annual report, and in the US the EPA's monitoring data is increasingly public. If you are on a private well, no one tests it but you, so certified lab testing is the only way to know.

Are PFAS in tap water actually harmful?

The evidence here is stronger than for many contaminants, which is why regulators acted. The US National Academies concluded in a 2022 report that PFAS exposure is associated with decreased antibody response, dyslipidemia (raised cholesterol), reduced infant birth weight, and kidney cancer. The EPA's health assessments link PFOA and PFOS to these and other effects, and classified PFOA as a likely human carcinogen. These are population-level associations at the exposure ranges studied, not a guarantee of harm to any individual, and we will not overstate them. But the weight of evidence is why the EPA set its limit near the lowest level reliably detectable.

Does a Brita or standard pitcher filter remove PFAS?

Most basic pitcher filters were not designed for it, so do not assume. The technologies proven to remove PFAS are activated carbon (especially granular activated carbon), reverse osmosis, and ion exchange resins. The EPA names these three as effective. Reverse osmosis is the most thorough, typically removing well over 90 percent. A quality activated-carbon filter also works if it is certified for PFAS specifically. The key is certification: look for NSF/ANSI 53 or the newer NSF/ANSI 58 (for reverse osmosis) listing PFOA and PFOS reduction. A filter that is merely certified for taste and chlorine under NSF 42 does not necessarily reduce PFAS. We compare certified options in our water-filter guide.

Reverse osmosis or activated carbon for PFAS?

Both can work; the choice is about thoroughness, cost, and waste. Reverse osmosis is the most complete, removing the broadest range of PFAS plus most other contaminants, but it installs under the sink, costs more, and wastes some water. A certified activated-carbon system, whether a high-end pitcher, faucet, or under-sink unit, removes PFAS at lower cost and with no wastewater, but carbon filters saturate and must be replaced on schedule or they stop working. For a household on a confirmed PFAS-affected supply, we lean toward reverse osmosis or a carbon system independently certified to NSF/ANSI 53 for PFOA and PFOS. Whichever you choose, replace the cartridge on time, because an exhausted filter quietly stops protecting you.

Should I be worried, or is this overblown?

Concern is warranted, panic is not, and the practical response is simple. PFAS are genuinely widespread and the health associations are better established than for many contaminants, so this is not a manufactured scare. At the same time, the fix is straightforward and one-time: find out your water's PFAS level from your utility report or a certified test, and if it is elevated, install a certified carbon or reverse-osmosis filter. That single step addresses the largest controllable exposure for most people. Boiling does not remove PFAS and can slightly concentrate them, so it is not a substitute. Treat this as a known problem with a known solution rather than an emergency.

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