Researchers detected at least one of the chemicals—known as PFAS, or per- and polyfluoroalkyl substances—in about 45% of U.S. drinking-water samples.
They took samples from private and public water supplies in 716 locations nationwide from 2016 to 2021, the agency said, testing for 32 of 12,000 PFAS compounds.
The study was the first to examine PFAS contamination in private wells, which aren’t regulated by the EPA. About 40 million U.S. residents receive their drinking water from private wells, according to the study.