Occurrence, spatiotemporal distribution, and potential toxicity analysis of pharmaceutically active compounds in the...

The occurrence, spatiotemporal distribution of 22 pharmaceutically active compounds (PhACs) was comprehensively investigated in the Pearl River Basin. Caffeine, cimetidine, and acetaminophen were the most ubiquitous compounds in the studied region. The total concentrations of all detected PhACs ranged from 9.89 to 42.07 ng∙L^-1 during the wet season, and from 18.33 to 202.85 ng∙L^-1 during the dry season. Hierarchical clustering indicated that the compositional associations among PhACs differed between the wet and dry seasons, while the principal coordinate analysis further demonstrated a distinct differentiation between seasonal periods. This study explores the application of USEtox in the Pearl River Basin as a complementary approach for evaluating and prioritizing PhACs. Characterization factors of PhACs were calculated using the USEtox model, with ecotoxicity characterization factors ranging from 10¹ to 10⁴ CTU_e∙kg^-1 and human toxicity characterization factors ranging from 0 to 10^-4 CTU_h∙kg^-1. Caffeine, gemfibrozil and 2-(4-Chloro-2-methylphenoxy) propanoic acid are the compounds with the highest potential toxicity impact scores. Notably, some PhACs (fenofibrate and paroxetine) exhibited comparatively low environmental concentrations but achieved relatively high potential ecotoxicity impact scores. This study explored a multidimensional risk assessment approach for PhACs in subtropical river basins, providing scientific basis for identifying priority control substances.