Structure-driven bioaccumulation of legacy and emerging PFAS across freshwater biota and tissues: Implications for dietary exposure and age-specific risks.
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Understanding how molecular structure, species, and tissue govern bioaccumulation of per- and polyfluoroalkyl substances (PFAS) is critical for evaluating dietary exposure and health risks from both legacy and emerging compounds. We analyzed 19 PFAS in crucian carp, freshwater snails, and freshwater mussels from a freshwater ecosystem, assessing occurrence, tissue distribution, bioaccumulation, dietary exposure, and health risk. Freshwater snails had the highest PFAS burdens, followed by crucian carp and freshwater mussels. Legacy PFAS (L-PFAS) dominated in crucian carp, while short-chain PFAS (S-PFAS) were more prevalent in freshwater snails and freshwater mussels. L-PFAS, hexafluoropropylene oxide dimer acid, and 6:2 chlorinated polyfluoroalkyl ether sulfonate accumulated preferentially in metabolically active, protein-rich tissues, whereas S-PFAS were enriched in muscle. Bioaccumulation factors showed initially increasing and then gradually decreasing with perfluorinated carbon chain length and were higher for sulfonates. Several emerging PFAS exhibited comparable or greater bioaccumulation than L-PFAS. Mechanistically, bioaccumulation patterns were influenced by habitat, feeding habits, circulatory physiology, protein content and types, and PFAS molecular structure. Dietary exposure assessment revealed pronounced age-specific exposure patterns, with children experiencing the highest non-carcinogenic risks, primarily driven by PFAS intake from freshwater snails and crucian carp. While carcinogenic risks from perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) were negligible, non-carcinogenic risks from PFOA, PFOS, and perfluorohexane sulfonate (PFHxS) exceeded safety thresholds. These findings suggest that PFAS bioaccumulation and dietary risks in freshwater systems are governed by molecular structure, species- and tissue-specific processes, underscoring the need to explicitly account for age-specific vulnerability alongside compound-specific behavior in dietary exposure assessment and regulatory decision-making.