Which water filters actually remove PFAS

Reverse osmosis pushes water through a semi-permeable membrane and is the most effective widely available option for PFAS, typically installed under a sink to treat drinking and cooking water only. It wastes some water to drain and removes minerals along with contaminants.

Activated carbon adsorbs PFAS onto a large internal surface area. Granular activated carbon and carbon block filters can perform well, with two caveats: performance falls as the medium saturates, so cartridge replacement schedules are not optional, and short-chain PFAS are adsorbed less effectively than long-chain compounds such as PFOA and PFOS.

Anion exchange is the third technology with good evidence and is more common at utility scale than in homes.

Look for certification to NSF/ANSI 53 (carbon and similar, health effects) or NSF/ANSI 58 (reverse osmosis), with an explicit PFOA and PFOS reduction claim on the certification listing rather than in the marketing copy.

The distinction is real. A filter can be certified to NSF/ANSI 42 for taste and odour and remove nothing relevant. Certification is per-claim, so 'NSF certified' with no claim named tells you nothing about PFAS.

Certifier listings are searchable and free. Checking the model number against the listing takes a minute and is the single most useful thing a buyer can do.

• Water softeners: they exchange calcium and magnesium and are not designed for PFAS.
• Standard refrigerator and pitcher filters: most are taste-and-odour products. A few pitcher models do carry PFAS claims, which is exactly why the certification listing rather than the category is what to check.
• Boiling: it concentrates PFAS instead of removing them, because these compounds do not evaporate with water.
• UV treatment: it inactivates microorganisms and does nothing to PFAS.
• Sediment and whole-house particulate filters: they catch particles, not dissolved compounds.

Point of use, treating one tap, is where the evidence and the economics are best for PFAS. Drinking and cooking water is the dominant exposure route, and reverse osmosis at one sink costs a few hundred dollars.

Whole-house treatment costs $1,500 to $3,000 or more installed and treats every fixture, which matters more where there is a broader water quality problem than PFAS alone, such as iron, hardness or hydrogen sulphide on a well.

Whichever route, test after installation. A filter's certification describes the model under test conditions; a before-and-after pair of lab samples describes yours.