Eighteen private well users in North Carolina were recruited to test the performance of under-sink, activated carbon block water filters to remove PFASs. Monthly sampling was conducted for eight months. Filters were certified for removal of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) under National Sanitation Foundation certification P473, but not for short-chain perfluoroalkyl acids (PFAAs) or perfluoroalkyl ether acids (PFEAs). Out of 47 targeted analytes, 17 PFASs were detected in filter influent samples (influent ∑PFAS 4.7-131 ng/L). Mixed-effects Tobit regression models showed that the filters effectively removed 97-99% of all influent PFASs, including short-chain PFEAs, for the entire manufacturer-recommended lifetime of the device. The prevalence of PFASs above the minimum reporting limits was reduced by 99.5% and the prevalence of any PFASs above the method detection limits was reduced by 92%. The results provide increased confidence in NSF P473-certified filters for private well water.
