Stability of Antibiotics and Their Metabolites in Sewers: Implications for Wastewater-Based Epidemiology and Antibiotic Sustainability

Antibiotics and their metabolites are widely used as biomarkers in wastewater-based epidemiology (WBE) to estimate population-level antibiotic consumption. However, the stability of these markers in sewer systems, a crucial factor for reliable WBE, is not well understood. Furthermore, the persistence of these compounds in sewer networks may cause long-term pressure for antimicrobial resistance (AMR) selection, thereby undermining antibiotic sustainability. This study aims to evaluate the in-sewer stability of 98 antibiotic substances, including 72 parent compounds and 26 metabolites, using a lab-scale sewer reactor with high biological activities. In-sewer transformation was assessed for each compound, establishing stability criteria based on transformation half-lives and equilibrium states. Over 12 h, 33 stable, 35 moderately stable, and 30 unstable biomarkers were identified, informing their suitability for WBE. Based on half-life and equilibrium assessments, 51 antibiotics were identified as having high or moderate potential to exert long-term selective pressure for AMR in sewers. This evaluation offers insights into their suitability as WBE biomarkers and antibiotic sustainability by persistently exerting selective pressure on AMR selection within sewage systems and receiving environments.