First Multi-Facility Antimicrobial Surveillance in Japanese Hospital Wastewater Reveals Spatiotemporal Trends and Source-Specific Environmental Loads.

Background: Hospitals are recognized as point sources of antimicrobials in urban wastewater systems; however, comprehensive evaluations of their discharge profiles have not yet been conducted. Methods: This study presents a multi-site investigation of residual antimicrobial concentrations in effluents from five general hospitals and a commercial facility in the metropolitan area of Japan. Over a 12-week period (December 2023-March 2024), extensive sampling was conducted. Fifteen antimicrobials from multiple classes were quantified using high-throughput analysis. Results: The results revealed consistently higher concentrations in hospital effluents, particularly for levofloxacin, vancomycin, and ampicillin, than in non-clinical sites. Distinct facility-specific and temporal patterns suggest strong links between local prescribing practices and the effluent composition. Some compounds, such as clarithromycin and minocycline, showed dual contributions from both hospital and commercial sources. Conclusions: These findings highlight the need for source-targeted monitoring and antimicrobial pollution control strategies and provide a foundation for expanding surveillance efforts and informing environmental policies related to antimicrobial resistance (AMR).