Modeling human-use antibiotics pollution in Chinese Rivers: A multi-scale analysis of drivers, pathways, and hotspots

Emissions of human-use antibiotics in China pose a significant threat to aquatic ecosystems and accelerate the spread of antimicrobial resistance. Existing assessments lack the facility-level resolution required for effective policy-making and targeted mitigation. This study aims to enhance the understanding of the spatial distribution of human-use antibiotic emissions to water systems, pathways, risks, and associated mitigation strategies in China. We developed SEAAL-China to quantify emissions of 19 major antibiotics from sewered and unsewered populations across more than 10,000 wastewater treatment plants (WWTPs). The national analysis of the removal efficiencies showed significant differences among treatment technologies, ranging from approximately 30-90%. Additionally, over half (57%) of China's WWTPs employ moderately effective technologies (removal rate <60%). We modeled a total of 3741 t of human-use antibiotic emissions to water systems in 2020, with 41% of the unsewered population accounting for more than half of the total. This highlights the need to expand basic sanitation infrastructure in rural and peri-urban areas to address the sanitation deficit. The emission hotspots are distributed in Guangdong, Shandong, and Henan, primarily driven by factors such as regional GDP and the imbalance in healthcare infrastructure. These areas cover 12% of the country's area and account for more than half of the calculated antibiotic emissions, suggesting that management should prioritize upgrading treatment technologies in hotspot areas to close the efficacy gap. A further risk assessment of antibiotic resistance selection revealed that fluoroquinolones are the dominant class with co-occurring emission and risk hotspots (630 dual-hotspot counties, 21.8% of the national total). Collectively, the above findings may help to inform both region-specific and compound-specific management strategies for human-use antibiotic pollution.