Deriving predicted no-effect concentrations for PFASs to protect threatened and endangered fish: A comparison of...

Water pollution is an important driver of extinction for threatened and endangered (T&E) fish species. Accurate predicted no-effect concentrations (PNECs) are essential for developing effective environmental standards and risk management strategies. However, pollutant bioaccumulation can substantially compromise the reliability of water-based PNECs for protecting T&E species. To derive PNECs accurately for bioaccumulative pollutants, this study systematically compared water- and tissue-residue-based toxicity data of 27 per- and polyfluoroalkyl substances (PFASs) across 97 T&E fish species in the Yangtze River Basin. Based on water-borne toxicity, perfluorobutane sulfonic acid (0.103 mg/L), 8:2 chlorinated polyfluoroalkyl ether sulfonate (0.118 mg/L), and perfluoro-2,5-dimethyl-3,6-dioxanonanoic acid (0.176 mg/L) were identified as the most toxic PFASs, with Acipenser sinensis being the most sensitive species. In contrast, tissue-residue-based toxicity indicated that perfluoro-8-chloro-1-octanesulfonic acid (0.154 mg/kg), perfluoropentane sulfonic acid (0.360 mg/kg), and perfluorooctane sulfonic acid (0.402 mg/kg) were the most toxic, with Luciobrama macrocephalus, Chimarrichthys davidi, and Schizothorax parvus exhibiting the highest sensitivity. Notably, for species below the 5th percentile of sensitivity distribution curves, PFAS toxicity rankings differed significantly from those observed for less sensitive species. To quantify the influence of bioaccumulation, PNECs derived from water- and tissue-residue-based toxicity data were compared, and their ratios were used to represent errors associated with water-based assessments. Consequently, these errors increased with bioaccumulation potential: when the log K_ow of PFASs exceeded 4.5 or the bioaccumulation factor (BAF) surpassed 1000 L/kg ww, deviations between water-based and tissue-residue-based PNECs exceeded 50-fold. This study underscores the importance of bioaccumulation in ecological risk assessment and provides a scientific foundation for developing water quality criteria aimed at protecting T&E fish species.