Antiepileptic drugs in aquatic environments: Occurrence, toxicity, transformation mechanisms and fate

The increasing consumption of antiepileptic drugs (AEDs) has led to their widespread presence in aquatic environments, which poses a serious threat to human health and aquatic organisms. However, there is currently lack of a review to provide basic data and research directions for future scholars. This article was carried out to summarize toxicity, analytical methods, concentrations, transformation mechanisms and fate of AEDs and their metabolites/transformation products in aquatic environments according to existing literature. AEDs and their metabolites/transformation products were widely found in surface water, groundwater and drinking water with concentrations from ng L⁻¹-μg L⁻¹. AEDs at environmentally relevant concentrations have affected aquatic ecosystem, and partial AEDs could commonly cause the damage of antioxidant capacity for some aquatic organisms. The transformation of AEDs was always in the direction of oxidation, and hydroxylated and ketonizated products were conductive objectives in three pathways including human body, microorganisms and water treatment processes as the difference of transformation pathways was also observed. AEDs were supposed to dominate the concentration distribution in water phase than in sediment phase due to their chemical properties. Furthermore, photolysis was a main process for AEDs in the photic zone of receiving waters. Meanwhile, the current deficiencies of AEDs research are also pointed out. It is mainly reflected in the insufficient toxicity data and incomplete transformation pathways of AEDs and their metabolites/transformation products, which will underestimate their environmental hazards. Finally, the article also pointed out that more attention should be paid to identifying transformation products combining mechanisms analysis with nontarget analysis.