Pan-continental assessment of socioeconomic and environmental predictors of PFAS occurrence in European rivers from a harmonised monitoring study

Per- and polyfluoroalkyl substances (PFAS) are persistent contaminants that are widely detected in surface waters and are of growing global concern. However, the factors associated with variations in PFAS contamination across space and time at a continental scale remain poorly understood. Here, we combine results from a harmonised pan-European river monitoring study with partial least squares path modelling (PLS-PM) to identify the key factors associated with PFAS contamination in European rivers. Seven high-priority PFAS were monitored at 280 sites across 93 rivers in 31 European countries, representing the PFAS footprint of approximately 309 million people. At least one PFAS was detected at 93% of monitoring locations. Highest concentrations were observed in parts of southern, southeastern and western Europe and were associated with landfills, wastewater discharges and industrial activity. Higher PFAS concentrations occurred in summer, potentially reflecting dilution-related effects associated with lower flow conditions. PLS-PM revealed that PFAS concentrations were associated with socioeconomic pressures and environmental conditions. The Human Footprint Index showed the strongest association among the socioeconomic variables examined, while electrical conductivity was the environmental variable most strongly associated with PFAS concentrations, possibly reflecting shared transport pathways with wastewater and industrial effluents. An indicative, screening-level assessment against existing regulatory threshold values suggested that PFAS concentrations at 61% of sites are of potential concern. These findings support the use of combined human pressure and hydrochemical indicators to inform more targeted, risk-based monitoring and regulatory prioritisation at large spatial scales.