Geospatial and socioeconomic factors of PFAS contamination in private drinking water wells: Insights for monitoring and management

Due to limited regulation of private wells, individuals who rely on wells as a potable water supply frequently face significant challenges in ensuring safe drinking water. Widespread occurrences of per- and poly-fluoroalkyl substances (PFAS) in groundwater increase these challenges and pose additional threats to public health. Addressing these challenges requires an understanding of the geophysical factors influencing PFAS contamination and the socioeconomic conditions that shape access to resources for testing and mitigation. This study evaluates both within a more densely sampled region than previous studies to increase our understanding of PFAS contamination. Over a three-year period (2021–2023), a community-science campaign sampled 167 private wells across the Commonwealth of Pennsylvania, United States (120,000 km²) with 13 wells re-sampled in a subsequent year to assess variability of the PFAS concentrations between sampling periods. Overall, 65 % of the private wells were found to have detectable levels of PFAS, with perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) detected most frequently, in 52 % and 47 % of the wells, respectively. Eighteen percent of the wells exceeded at least one health-related maximum contaminant level. The percentage of developed land and the Socioeconomic Score correlated positively with PFAS concentration for individual wells and PFAS concentrations varied significantly between samplings. At the county level, developed land and total point sources were positively correlated with detection frequency but Socioeconomic Score was not. Results highlight the importance of both temporal and spatial sampling to understand PFAS drivers. Targeted outreach and sampling of socioeconomically marginalized communities should be prioritized in future private well monitoring efforts.