Global Aquatic Hazard Assessment of Ciprofloxacin: Exceedances of Antibiotic Resistance Development and Ecotoxicological Thresholds.

Rapid urbanization represents a global megatrend that is resulting in an increasingly urban water cycle frequently contaminated by human medicines and other chemicals. Concentration of chemical consumption is occurring faster than implementation of environmental health systems and interventions, particularly in megacities of developing countries, while 80% of global sewage production remains untreated. In these urban areas, antibiotics in the environment influence development of antibiotic resistance (ABR) by pathogens. Here, we examined the occurrence of ciprofloxacin, designated a critically important antibiotic by the World Health Organization, in fresh surface water, groundwater, saltwater, treated municipal effluent, raw municipal sewage, treated hospital effluent, and raw hospital sewage around the world. We examined 260 articles reporting ciprofloxacin in these water matrices, including 111 studies from Europe, 105 from Asia, and 32 from North America. Only five and seven studies were identified from South America and Africa, respectively. Probabilistic hazard assessments were then performed to identify probabilities of exceedances of reported ABR and ecotoxicological predicted no effect concentrations (PNEC) for ciprofloxacin in water. Remarkably, across all geographic regions, 58% of municipal effluents exceeded the ABR PNEC (100ng/L) for ciprofloxacin, whereas ecotoxicity PNEC (1200ng/L) was exceeded 16% of the time. In surface water, 25% reported concentrations exceeded the ABR PNEC with 31% and 29% in Europe and North America, respectively, compared to 67% exceedance identified for Africa. Such observations highlight the importance of global scanning assessments to identify matrices and regions, including areas strategically advancing water reuse, for additional study and to prioritize locations for interventions aimed at reducing ABR development.