Enantioselective\nToxicity of Ibuprofen to Earthworms:\nUnraveling the Effect and Mechanism on Enhanced Toxicity of <i>S</i>‑Ibuprofen Over <i>R</i>‑Ibuprofen

With the global implementation of wastewater reuse, accurately\nassessing the soil ecological risk of chiral pollutants from wastewater\nnecessitates a comprehensive understanding of their enantioselective\ntoxicity to soil animals. Ibuprofen (IBU) is the most prevalent chiral\npharmaceutical in municipal wastewater. However, its enantioselective\ntoxicity toward soil animals and the underlying mechanism remain largely\nunknown. In this study, the toxicity of IBU enantiomers, <i>S</i>-IBU and <i>R</i>-IBU, to earthworms was evaluated at environmentally\nrelevant concentrations (10 and 100 μg/L), simulating wastewater\nreuse for irrigation. The results demonstrated that IBU adversely\naffects the growth, reproduction, regeneration, defense systems, and\nmetabolic processes of earthworms, with <i>S</i>-IBU exhibiting\nstronger toxic effects than <i>R</i>-IBU. The bioavailability\nassessment revealed that <i>S</i>-IBU was more readily absorbed\nby earthworms and converted to its enantiomer within earthworms than <i>R</i>-IBU. This is consistent with molecular docking results\nshowing that <i>S</i>-IBU had stronger affinities for functional\nproteins associated with xenobiotic transport and transformation.\nThe findings of this study highlight that <i>S</i>-IBU poses\na higher risk than <i>R</i>-IBU to soil organisms under\nwastewater reuse scenarios and that the chirality of chemical pollutants\nin wastewater deserves more attention when implementing wastewater\nreuse. In addition, our study underscores that the differences in\nbioavailability and bioactivity may account for the enantioselective\ntoxicity of chiral pollutants.