Review on the Bioaccumulation, Trophic Magnification, and Aquatic Toxicology of PFAS: Perspectives from Molecular Structure.

Per- and polyfluoroalkyl substances (PFAS) are widely detected in aquatic environments, and their bioaccumulation, trophic magnification, and ecotoxicity have raised increasing concern. However, critical knowledge gaps remain regarding how differences in their molecular structures influence these processes and the mechanisms underlying such effects. This review synthesizes the current knowledge of the physicochemical properties, bioaccumulation, trophic magnification, and toxicity of PFAS in aquatic environments, with particular emphasis on the effects of the carbon-chain length, functional-group type, and acid or salt form. The current evidence generally indicates that long-chain PFAS exhibit higher bioaccumulation, trophic magnification, and toxicity than short-chain PFAS, largely because of their enhanced hydrophobicity, stronger protein-binding affinity, and slower elimination rates. As two major PFAS subclasses, perfluoroalkyl sulfonates (PFSAs) generally show higher bioaccumulation and toxicity than perfluoroalkyl carboxylates (PFCAs). For example, the bioaccumulation factor of perfluorooctane sulfonate (PFOS) is approximately two- to three fold higher than that of perfluorooctanoic acid (PFOA). Some ether-containing PFAS, developed as safer alternatives, also exhibit concerning ecological hazards, particularly a high potential for trophic magnification. In addition, acid form PFAS generally accumulate more readily and induce more severe toxic effects than their corresponding salt forms. These findings highlight the need to further improve structure-based frameworks for PFAS ecological risk assessment.