Antibiotics are emerging contaminants (ECs) that have hazardous effects on various receptors through possible exposure pathways in water environment. Currently, many studies have been carried out in freshwater ecosystems with a focus on the downstream of rivers; while less attention was paid to marine environments, especially the East China Sea lacks the antibiotic data. As most of ECs are synthesized and consumed within human society, coastal region, where land and ocean connected, becomes the sink of anthropogenic contaminants. Under the perspective of One-Health, the specific hazard of antibiotics – antimicrobial resistance (AMR) on coastal region shall be included in the risk assessment.
To address above issues, first of all, we have conducted sampling campaign in East China Sea since 2017. Totally 43 antibiotics of 5 classes were detected in the seawater samples using UPLC-MS/MS, among which 83% of individual antibiotics were lower than 5 ng/L and CLIN (1508 ng/L) was the highest one. We then incorporated our data with other 41 datasets from 1605 publications (2000-2021) from Web of Science and ScienceDirect, and generated the spatial distribution of antibiotics in four China Seas. Totally 74 antibiotics were reported, of which TCs and QNs were the prevalent classes.  Secondly, we creatively added resistance (R) risk with persistence (P), bioaccumulation (B), and toxicity (T) to establish a more comprehensive PBTR framework for antibiotic-specific risk assessment. Using the new PBTR framework, we identified the priority antibiotics, i.e. the antibiotics with at least one risk, in China Seas. R risk was the top risk among the four risks. Each sea had its unique priority antibiotics, e.g. CLIN occurred in the China East Sea only; while there were 8 priority antibiotics existed widely in 4 seas, including ATM, CFX, ERFX, etc.  Thirdly, we came back to land and tracked antibiotic flows from two-stage wastewater treatment plants (WWTPs, i.e. pharmaceutical WWTP and integrated WWTP) to the final effluent receiving area in Hangzhou Bay. Although 86% of antibiotics were degraded by two WWTPs, there were 126 g/d of antibiotics (mainly QNs) were discharged into Hangzhou Bay, contributing 48% of antibiotic contamination in the coastal environment. Therefore, point-sources (i.e. WWTPs, especially industrial ones) are one of the main sources of antibiotic contamination of China Seas.

Antibiotics; risk assessment; antimicrobial resistance; wastewater treatment plant (WWTP); China Seas