Short-chain PFASs dominance and their environmental transport dynamics in urban water systems: Insights from multimedia transport analysis and human exposure risk

The increasing prevalence of short-chain per- and polyfluoroalkyl substances (PFASs) poses significant challenges for urban water systems (UWS) due to their persistence, high mobility, and widespread occurrence. This study provides a comprehensive assessment of the occurrence, environmental transport, influencing factors, removal efficiency, and human health risks of PFASs across UWS impacted by industrial activities. Regulatory restrictions on long-chain PFASs have led to their replacement with short-chain analogues, resulting in their dominance in effluents from manufacturing plant parks (MPPs), with concentrations ranging from 30.28 to 3738.51 ng/L (mean: 557.68 ± 1072.03 ng/L). Wastewater treatment plant (WWTP) serve as both sources and sinks of PFASs, with a negative average removal efficiency (-47.4 %) and an estimated annual discharge of 12.29 kg of PFASs into the environment. Downstream of WWTP, PFASs concentrations in rivers decrease exponentially due to dilution and sediment partitioning; however, short-chain PFASs persist over long distances due to their high aqueous mobility. While the detected PFAS levels in rivers pose low health risks to humans, they present low to medium ecological risks to aquatic organisms, particularly algae, invertebrates, and fish. Advanced statistical analyses using piecewise structural equation modeling (piecewiseSEM) and co-occurrence network analysis (CNA) identified key environmental drivers of PFASs behavior, including heavy metals (effect size: 0.70), nutrient levels (0.36), and physicochemical parameters (-0.52). Furthermore, drinking water treatment plants (DWTPs) demonstrated limited removal efficiency, with tap water concentrations ranging from 27.95 to 84.72 ng/L, exceeding the regulatory limits set by the US EPA (2022) (PFOA: 0.004 ng/L, PFOS: 0.02 ng/L) and Health Canada (Σ₂₅PFAS: 30 ng/L). These findings underscore the urgent need for enhanced regulations, the development of sustainable alternatives, and the implementation of advanced treatment technologies to mitigate the environmental and public health risks associated with short-chain PFASs.