Cocaine and benzoylecgonine in urban rivers: Occurrence, developmental toxicity and oxidative stress in zebrafish embryos.

Cocaine (COC) and its primary metabolite, benzoylecgonine (BE), have been increasingly detected in surface waters and aquatic organisms. Herein, five urban rivers in Rio de Janeiro city, southeastern Brazil, were monitored monthly for COC and BE over 12 months. Furthermore, embryo zebrafish were exposed to environmentally relevant concentrations of both compounds (100, 750, 1250, 2500, 3500, and 5000 ng L⁻¹) for 96 h followed by assessments concerning morphological and teratogenic alterations, heart rate effects, antioxidant modulations (superoxide dismutase - SOD, catalase - CAT, glutathione-S-transferase - GST) and oxidative damage (protein carbonylation, lipid peroxidation). Both COC and BE were detected in most sampling campaigns (97 and 100%, respectively), ranging from <LOQ to 1.0208 × 103 ng L-1 (COC; average = 2.421 × 102 ng L-1) and from 4.36 × 101 to 1.8505 × 103 ng L-1 (BE; average = 7.512× 102 ng L-1). Detected concentrations often exceed those reported in other superficial waters worldwide and, in some cases, wastewater treatment plant (WWTP) and raw sewage influents. Exposure to both compounds caused morphological and teratogenic effects in zebrafish, particularly COC at 1250 ng L⁻¹ and BE at 100 ng L⁻¹, with yolk sac and pericardium edema/swelling as the most prominent COC and BE effects, respectively. Increased heart rates were noted following BE exposure only, at all concentrations. Exposure to both compounds resulted in oxidative stress, with BE eliciting more significant effects than COC for all biomarkers. These findings indicate a critical environmental scenario of COC and BE contamination in rivers in Rio de Janeiro city, serving as a warning regarding illicit drug-related risks in urban water bodies worldwide and stressful fish conditions in early life stages.