Characterizing PFAS Risk, Distribution, and Source Dynamics in an Urban Watershed: A Case from the Schuylkill River System

Abstract

This study investigates 16 locations sampled along a 50-mile stretch of the Schuylkill River, a major drinking water source, to examine the presence, spatial distribution, and risk assessment of PFAS. The most prevalent compounds were PFBA, 6:2 FTS, PFOA, and PFOS, which were detected in nearly 100% of the samples. The Risk Quotient (RQ) method, which was applied to conduct risk assessments according to the EPA’s 2016 guidelines, indicated that more than 61% of the samples showed a medium-risk profile. However, the 2024 EPA regulations resulted in a high-risk profile for all February samples for PFOA, with 67.7% and 87% of the May and July samples also categorized as high-risk. In the same vein, a high-risk profile for PFOS was observed in 61.5–81% of the samples. Furthermore, the Hazard Index (HI) was evaluated to assess the cumulative hazard of PFNA, GenX Chemicals, PFHxS, and PFBS; notably, 19% of July samples exceeded the HI threshold, indicating increased health risks. Potential PFAS contamination pathways were investigated. These results emphasize the critical importance of ongoing monitoring and mitigation strategies to protect public health and guarantee the safety of water resources.