Ecological criteria for antibiotics in aquatic environments based on species sensitivity distribution

Due to the substantial production and use of antibiotics, they inevitably remain in aquatic environments, posing a serious threat to aquatic ecosystems. However, there are currently no criteria of antibiotics for ecological risk in the water environment. In the present study, three types of antibiotics (tetracyclines, sulfonamides and quinolones) that are often detected in water environments were investigated. Toxicity data regarding bacteria, algae, plants, invertebrates and vertebrates were selected, and the species sensitivity distribution was used to obtain the ecological risk criteria of antibiotics to aquatic organisms. Animals are the least sensitive to antibiotics. The overall toxicity of antibiotics is most sensitive to bacteria and cyanobacteria, followed by green algae and plants. The recommended ecological criteria for tetracyclines, quinolones, and sulfonamides are 22, 17, and 94 μg/L, respectively. Ofloxacin needs to be used with caution because it has a small acute predicted no-effect concentration (PNEC) of 0.6 μg/L. The ecological risk criterion for chronic toxicity of total antibiotics was determined to be 1.4 μg/L. The PNECs measured for the quinolone, tetracycline, and sulfonamide antibiotics were 0.5, 2.2, and 2.4 μg/L, respectively. Norfloxacin had the highest chronic toxicity zone of 353, indicating that chronic poisoning is most likely to occur. Moreover, there was an exponential correlation between acute PNEC and chronic PNEC. In addition, a quantitative structure-activity relationship model was constructed for acute ecological risk criteria of antibiotics to aquatic organisms. These findings can expand the ecological risk threshold data on the effects of antibiotics on aquatic organisms, and provide a theoretical basis for the environmental risk assessment of antibiotics.