Occurrence of organic micropollutants in an urbanized sub-basin and ecological risk assessment.

The João Mendes River - an important contributor to the Piratininga/Itaipu lagoon system in Rio de Janeiro State, Brazil - receives untreated sewage from the population occupying the drainage basin with no proper sanitation infrastructure. The present study assessed the ecological risk resulting from the presence of five organic micropollutants (17α-ethynylestradiol, ibuprofen, trimethoprim, sulfamethoxazole, bisphenol A) based on four monitoring campaigns which included three sampling points and one reference area. Chronic ecotoxicity assays were conducted with the bioindicators R. subcapitata, C. dubia and O. niloticus. Estrogenicity was assessed with genetically modified S. cerevisiae based on YES protocol. The Ecological Risk Assessment was conducted based on the Chemical and the Ecotoxicological Lines of Evidence (LoE). In order to analyse the results from different sampling points, principal component analysis (PCA) was performed using a correlation matrix. Micropollutants below limit of detection or in very low concentrations were detected in the reference area; no significant differences were observed when samples from the reference area were compared to the negative controls for the ecotoxicity assays. A PCA including selected variables revealed the latent relationships among the three sampling points (not verified for the reference area), which confirmed the analytical results. An extreme ecological risk index was estimated for all sampling points in all campaigns. The extreme ecological risk index was mostly associated to the high concentrations of 17α-ethynylestradiol and the antibiotic sulfamethoxazole.