Influence of PFAS Physicochemical Characteristics on Detection Patterns and Exposure Risk in Private Wells

Per- and Polyfluoroalkyl substances (PFAS) are persistent environmental contaminants widely detected in groundwater. They are associated with immune dysregulation, developmental impacts, and increased risk of chronic disease. Many municipal water systems are regulated under the Safe Drinking Water Act; however, private well owners do not follow the same monitoring regulations. Therefore, private wells not regulated under this act lead to an exposure awareness and a health protection gap. In Wisconsin, where approximately 30% of residents depend on private wells as their main water source, undetected PFAS poses a significant public health concern. This research evaluated the presence and extent of PFAS across private wells in Dodge, Rock, and Price counties as a targeted community sampling initiative to determine spatial patterns and to contribute to the development of a toolkit to support local and tribal health agencies in their sampling and communication efforts. Private wells were recruited based on proximity to known contaminated hazard wells, and water samples were collected and analyzed utilizing the EPA Method 1633 for 40 PFAS analytes. All results were categorized based on Wisconsin PFAS health-based standards for exceedance levels and hazard index. The detection results for PFAS across all counties indicate widespread presence of these chemicals, with short-chain analytes with high aqueous mobility being more frequently detected than their long-chain counterparts. Analyte detection categories varied within and between counties. They were not solely dependent on distance from known contamination sources, suggesting that hydrogeologic conditions and well construction characteristics also influenced their presence. Application of the EPA hazard index criteria resulted in increased classification of wells as higher risk due to mixture effects involving PFHxS and PFBS. These findings highlight PFAS contamination in private wells, resulting in chronic exposure among residents without their knowledge. Given the established association between PFAS exposure and adverse health outcomes, PFAS contamination represents a significant public health concern. Understanding the characteristic behavior of PFAS analytes is critical for improving risk detection, sampling strategies, and mitigation efforts, which are considered critical for reducing exposure and protecting the health of residents who rely on private well water.