Risk assessment of chlortetracycline, oxytetracycline, sulfamethazine, sulfathiazole, and erythromycin in aquatic environment: are the current environmental concentrations safe?

To understand potential risks of major pharmaceutical residues in waters, we evaluated ecotoxicities of five major veterinary pharmaceuticals, i.e., chlortetracycline, oxytetracycline, sulfamethazine, sulfathiazole, and erythromycin, which have been frequently detected in freshwater environment worldwide. We conducted acute and chronic toxicity tests using two freshwater invertebrates (Daphnia magna and Moina macrocopa) and a fish (Oryzias latipes). In general, D. magna exhibited greater sensitivity than M. macrocopa, and chronic reproduction was the most sensitive endpoints for both organisms. The population growth rate was adversely influenced by exposure to chlortetracycline, sulfamethazine, or sulfathiazole in water fleas, but reduction in population size was not expected. In O. latipes, the tested pharmaceuticals affected several reproduction related endpoints including time to hatch and growth. Based on the toxicity values from the present study and literature, algae appeared to be the most sensitive organism, followed by Daphnia and fish. Hazard quotients derived from measured environmental concentrations (MECs) and predicted no effect concentrations (PNECs) for erythromycin and oxytetracycline exceeded unity, suggesting that potential ecological effects at highly contaminated sites cannot be ruled out. Long-term consequences of veterinary pharmaceutical contamination in the environment deserve further investigation.