Geospatial Trends of Per- and Polyfluoroalkyl Substances (PFAS) Incidence in Private Drinking Water in Virginia

Per- and polyfluoroalkyl substances (PFAS) are a class of synthetic organic compounds that are hydrophobic, thermally stable, and resistant to environmental degradation. Widespread industrial and household use has resulted in frequent environmental and drinking water detection, raising concerns about adverse human health effects associated with PFAS exposure. In response, the United States Environmental Protection Agency (USEPA) has established mandatory monitoring campaigns and future maximum contaminant levels (MCLs) for two PFAS compounds (PFOA and PFOS) in public water systems under the Safe Drinking Water Act. However, the 20-40 million Americans who rely on private drinking water supplies remain unregulated and comparatively understudied. This study investigates the incidence of PFAS in private drinking water under 'baseline' conditions and assesses the impacts of contributing land cover types, point sources, household characteristics, and traditional water quality parameters on PFAS incidence across Virginia. Point-of-use samples (n=382) were collected from private wells across 10 counties and analyzed for 30 PFAS compounds using USEPA Methods 533 and 537.1. Geospatial variables, household characteristics, and traditional water quality parameters (e.g., lead and bacteria) were analyzed using GIS and RStudio. At least one PFAS compound was detectable in all samples, with 90% exceeding method reporting limits, although median total sum PFAS concentrations were low (1.50 ppt). Short-chain PFAS compounds were more prevalent than long-chain legacy compounds in both total concentration and unique compound detection rates. The USEPA MCL of 4 ppt was exceeded in 2.4% and 5.2% of samples for PFOA and PFOS, respectively. While most samples had generally low total sum PFAS concentrations, 10% of samples exceeded 10.03 ppt with a maximum total sum PFAS concentration of 303 ppt. High PFAS sampled homes were associated with increased urban land cover, closer proximity to point sources, higher frequency of nearby point sources, older well age, elevated lead, and indicators of corrosive water chemistry, including low pH, and higher conductivity/total dissolved solids. These findings suggest PFAS concentrations in private drinking water are associated with more anthropogenic activity as well as potential mobilization of PFAS from in-home sources such as plumbing networks. Traditional water quality concerns remain prevalent, with exceedance of public water standards observed for lead (5.01% > 0.01 mg/L health-action-limit), E. coli (4.19% > absence), and total coliform bacteria (34.8% > absence). While 70% of homes employed some form of treatment, only 22% of homes used health based treatment types (e.g., reverse osmosis and activated carbon) which are capable of removing heavy metals, bacteria, or PFAS. These findings highlight the continued vulnerability of private drinking water users to both emerging and established contaminants and underscore the need for improved monitoring, targeted treatment adoption, and enhanced support for private drinking water supply stewardship.