According to a new machine learning-assisted predictive model, as many as 95 million Americans may rely on groundwater containing PFAS for their drinking water supplies before any treatment, researchers report. This raises concerns about unmonitored contamination in domestic and public water supplies. Per- and polyfluoroalkyl substances (PFAS), often called "forever chemicals," are highly persistent environmental contaminants linked to adverse environmental and health effects. Used in many consumer products, these organic pollutants have become ubiquitous in the environment and are routinely found in groundwater and surface water. Although the U.S. Environmental Protection Agency (EPA) has introduced new monitoring requirements to address PFAS contamination in drinking water, these efforts do not cover small public water systems or private groundwater wells, which collectively supply drinking water to millions of Americans. To address these gaps, Andrea Tokranov and colleagues present a national predictive model using the machine learning approach XGBoost (IeXtreme Gradient Boosting), trained on PFAS contamination samples taken between 2019 and 2022 from three well networks within principal aquifers across the U.S. This allowed the authors to broadly estimate PFAS occurrence in groundwater based on environmental variables, well depth, and known sources of PFAS contamination. Model predictions they derived are for the source groundwater prior to any treatment.
Tokranov et al. found that 71 to 95 million people across the U.S. potentially rely on groundwater with detectable levels of PFAS before treatment, with small public water systems accounting for the majority. States like Florida, California, and Michigan had the highest populations affected, while Massachusetts and the District of Columbia reported the highest percentages of affected users. The authors note that although many public water suppliers now monitor and treat PFAS, treatment costs remain challenging, particularly for low-income communities, and domestic well users often lack testing or remediation, increasing their vulnerability. "The footprint of PFAS occurrence at the depth of public and domestic water supply may continue to expand as groundwater is recharged to aquifers and migrates downward over time, given the extensive PFAS contamination reported in air, rain, and soil, among many other sources," write Tokranov et al. "Awareness and regular monitoring of PFAS coupled with appropriate drinking water treatment will help reduce human exposure from drinking water sources."
