Risk of tap water exposure to toxic PFAS chemicals higher in Southern California

In what is considered to be the nation’s first large-scale analysis of PFAS in tap water from private wells and public water supplies, researchers estimated that at least 45% of drinking water across the nation could contain one or more of the chemicals. Study authors also concluded that drinking-water exposures may be more common in Southern and Central California, as well as the Great Plains, Great Lakes and Eastern Seaboard regions.

While study authors found an 8% probability that one or more of the chemicals would be detected in drinking water in rural areas, the detection probability skyrocketed to more than 70% in urban areas.

In Southern California, PFAS concentrations tend to come from downstream wastewater treatment plants that discharge to local rivers and recharge water back into groundwater, which eventually gets picked up and becomes drinking water, Polhemus said. PFAS-contaminated drinking water is particularly prevalent in disadvantaged communities, according to a 2021 study by the Natural Resources Defense Council.