Environmental Risk Assessment of PFAS in a Swedish Stream - A Case Study of Perstorpsbäcken Integrating Measured Concentrations and Species Sensitivity Distributions

Sammanfattning

Freshwater ecosystems are increasingly threatened by persistent chemical pollutants, including per- and polyfluoroalkyl substances (PFAS), which pose long-term risks to both ecosystems and human health. Small streams downstream of urban and industrial areas are often underrepresented in monitoring programmes, despite their potential vulnerability to PFAS contamination. Furthermore, environmental risk assessments (ERAs) of PFAS in small freshwater systems remain limited, particularly site-specific assessment based measured environmental concentrations (MECs). This study aimed to assess the occurrence and environmental risk of PFAS in Perstorpsbäcken, a Swedish stream receiving effluents from industrial areas and a wastewater treatment plant. Surface water concentrations of 24 PFAS compounds were measured at four locations along the stream. Using available chronic ecotoxicity data for locally relevant species, predicted no effect concentrations (PNECs) were derived from species sensitivity distribution (SSD) modelling for the two dominant PFAS compounds in Perstorpsbäcken. Environmental risk was assessed by comparing MECs with the derived PNECs. The results identified PFOS and PFHxS as the dominant compounds at most sampling sites, and a clear spatial contamination gradient was observed, with concentrations peaking shortly down stream of the wastewater treatment plant. A very low environmental risk was identified at the furthest upstream site, while the remaining locations were classified as having moderate risks. Comparison with previous monitoring data indicated that PFAS-related risks in Perstorpsbäcken may vary over time, suggesting that the stream may periodically be exposed to higher risks under different hydrological conditions. The findings highlight the importance of site-specific assessments and expanded monitoring and assessment strategies to support ecologically relevant assessments and appropriate water management.