A year of research into the occurrence and ecotoxicological risk assessment of cocaine and benzoylecgonine in a marine tropical bay (Santos, São Paulo, Brazil).

Monitoring of illicit drug contamination in coastal marine ecosystems is critical, particularly in regions such as Brazil, where inadequate wastewater treatment infrastructure coincides with high rates of drug consumption. In this context, this study aimed to investigate the temporal variability and ecotoxicological risks associated with the presence of cocaine (COC) and its main metabolite, benzoylecgonine (BEN), in the recreational coastal waters of Santos Bay, in southeastern Brazil. Four sampling campaigns were conducted between July 2023 and April 2024. COC and BEN were consistently detected across all samples, with concentrations ranging from 14.0 to 110.1 ng/L and 29.1 to 154.0 ng/L, respectively, indicating their widespread presence and environmental relevance as contaminants of emerging concern. Ecotoxicological risk assessment based on acute toxicity data revealed that both compounds pose significant risks across all tested trophic levels (algae, invertebrates and fish). Specifically, COC presented moderate risk to algae and fish, and high risk to crustaceans, while BEN showed moderate risk to algae and high risk to fish. In contrast, chronic toxicity assessments indicated low ecological risk for algae, with negligible risk for other organisms, for both compounds. Additionally, mixture toxicity evaluation of COC and BEN suggested a high acute risk, but a low chronic risk associated with their combined presence. The scarcity of ecotoxicological data for marine species, especially tropical organisms, remains a major limitation for comprehensive risk characterization. Therefore, this study highlights the urgent need for further toxicological research to support regulatory frameworks and environmental protection in marine tropical ecosystems.