Study suggests EPA may miss more than half of PFAS in U.S. drinking water

Using computer models on the EPA’s Fifth Unregulated Contaminant Monitoring Rule data, a team from Texas Christian University estimated concentrations for 25 poly-fluoroalkyl substances across 9,991 community water systems. Their analysis shows that treating below-limit results as zero captures only 44% of the average combined PFAS concentration, implying actual levels could be roughly twice the reported figures. Lead author Gehendra Kharel notes that “below the reporting limit does not mean zero,” a point echoed by University of Southern California’s Jesse Goodrich, who links low-level water exposure to widespread blood detections.

Alissa Cordner of Northeastern University argues the EPA’s conservative zero-assumption understates risk and suggests alternative estimation methods. The researchers released an open-source tool, PFAS-CAST, to help agencies incorporate such estimates alongside traditional reporting. The findings arrive amid recent EPA proposals to relax drinking-water limits for four cancer-linked PFAS, raising concerns among scientists about cumulative health impacts.