For the first time, per- and polyfluoroalkyl substances (PFAS) have been publicly identified in the drinking water of 34 US cities or counties. They include Atlanta; Boston; Charleston, South Carolina; Chicago; Columbus, Ohio; New Orleans; Philadelphia; Pittsburgh; and Washington, DC. The advocacy organization Environmental Working Group (EWG) conducted the investigation into single water samples taken in 45 locations, including 10 where the chemicals had been found previously. PFAS, a class of highly persistent compounds, are linked to a number of health problems. EWG scientists say they used a commercial lab that is accredited by the US Environmental Protection Agency to analyze the water against test standards for 30 different PFAS. At least one PFAS chemical was detected in every sample except the one from Meridian, Mississippi. The investigation found two areas with PFAS levels in water above 100 parts per trillion: Brunswick County, North Carolina, which draws its water downstream from a Chemours plant that has discharged PFAS for decades; and Davenport, Iowa. Many of the chemicals that the EWG looked for are among the PFAS the EPA has added to the Toxics Release Inventory.