PFAS in Drinking Water: The Rules, the Science, the Filters

PFAS - per- and polyfluoroalkyl substances, the 'forever chemicals' - are a family of thousands of compounds used in nonstick coatings, stain repellents and firefighting foam. Two of them, PFOA and PFOS, are the most studied and the first to be federally limited in drinking water.

The rules, current as of this page

In April 2024 the EPA issued the first enforceable national PFAS drinking-water regulation, setting maximum contaminant levels of 4.0 parts per trillion for PFOA and for PFOS (with health goals of zero), plus limits for PFHxS, PFNA, GenX and a mixture hazard index. In May 2025 the EPA announced it would keep the PFOA and PFOS limits, extend their compliance deadline to 2031, and rescind the other four - a proposal that was moving through rulemaking at our last check. City systems must monitor and, where needed, treat; private wells are unregulated, as ever.

What actually removes PFAS

Three technologies carry real credentials: reverse osmosis (certified under NSF/ANSI 58 on some systems), specially rated activated carbon (certified under NSF/ANSI 53 for PFAS on specific models), and ion exchange at municipal scale. The catch is the per-model part: certification belongs to a specific product for a specific claim, not to a technology in general - a carbon filter certified for chlorine is not thereby certified for PFAS.

Our shortlist separates certified systems from tested-only ones: best filters for PFAS. The current certified tier includes the AquaTru Classic (IAPMO, P473 list), Aquasana's Claryum countertop (WQA, 53 including P473) and - at whole-house scale - Aquasana's HealthShield (WQA, 53, 99.9% to below 4 ppt).

Should you test first?

If you're on city water, your utility's PFAS monitoring results are public or available on request. On a well, a state-certified lab PFAS panel runs a few hundred dollars - worth it before spending the same again on treatment aimed at a problem you may not have. Start with how to test your water.