Characterization and prioritization of legacy and novel PFAS in Hangzhou Bay, China, to inform upstream source control

The ongoing transition from legacy per- and polyfluoroalkyl substances (PFAS) to novel alternatives calls for comprehensive monitoring in key regions to capture current emission patterns. Herein, we characterize and prioritize 78 legacy and novel PFAS in seawater and sediments from Hangzhou Bay in East China, a global hotspot for PFAS emissions that receives the two largest riverine mass discharges. In total, 68 PFAS spanning 13 classes were detected with a median seawater concentration of 152.6 ng/L, among the highest level and diversity reported for coastal environments, though the lack of trifluoroacetic acid (TFA) may underestimate total PFAS. Novel PFAS contributed comparably to legacy PFAS in seawater, whereas long-chain legacy compounds predominated in sediments; this contrast reflects differences in partitioning behavior. Health risk assessed by Monte Carlo simulations revealed substantial exposure via seafood consumption and emphasized additive risks from PFAS mixtures. An integrated risk prioritization combining exposure and hazard metrics indicated that most medium- to high-risk PFAS are novel species, with hexafluoropropylene oxide trimer acid (HFPO-TrA) and perfluorooctanoate (PFOA) exhibiting the highest risk in seawater. As emission signatures of fluoropolymer production, these compounds align with source apportionment results and underscore that substitution of legacy PFAS with alternatives does not necessarily reduce risk. These findings provide actionable guidance for controlling unregulated novel PFAS and mitigating emissions from upstream fluorochemical industries.