Global distribution and hydrological determinants of antibiotics in river systems

Antibiotics in freshwater systems pose ecological risks and contribute to antimicrobial resistance, yet their basin-scale controls within river networks remain poorly constrained. Here, we compiled a global dataset of 20,562 concentration records from 844 publications and synthesized spatial patterns of antibiotics across inland waters, with predictive analyses focused on rivers. Concentrations show strong spatial heterogeneity, with hotspots occurring in regions where intense anthropogenic inputs coincide with limited hydrological dilution, as reflected by discharge and related river-network attributes. Explainable machine-learning models further indicate that antibiotic levels are jointly governed by human pressures and hydroclimatic-hydrological controls, including river discharge, climatic forcing, and nutrient-related water quality conditions. These results strengthen a hydrological perspective on antibiotic transport and retention in river systems and provide a basis for basin-informed monitoring and management. • Global antibiotic concentrations in inland waters span 0-15,410,000 ng/L, with a median of 69 ng/L. • Hotspots are concentrated in South and East Asia, sub-Saharan Africa, South America, and parts of Europe. • Antibiotic levels exhibit an HDI-based pattern: Low > Medium ≈ High > Very High development groups. • Riverine antibiotic contamination is jointly controlled by anthropogenic loading and hydroclimatic-hydrological processes governing transport and dilution. • Explainable machine learning reveals nonlinear population-pollution relationships modulated by basin-scale hydrology.