Dissolved and particulate micropollutant mixtures in surface waters: in vitro and chemical assessment in Rio de Janeiro versus global trends

Many micropollutants occur in aquatic environments due to anthropogenic activities leading to environmental risks to ecosystems. However, their combined effects remain underexplored, particularly in developing countries. A panel of in vitro bioassays indicative of xenobiotic metabolism (AhR, PPARγ and PXR), estrogenic activity via estrogen receptor alpha (ERα) activation, glucocorticogenic activity (GR), developmental neurotoxicity (SH-SY5Y), oxidative stress response (AREc32), mitochondrial membrane potential inhibition and cytotoxicity was used to investigate water quality in the Guandu River basin, a major source water catchment area in Rio de Janeiro State, Southeastern Brazil. The contribution of dissolved and suspended particulate matter (SPM) phases was considered, and the environmental relevance of effects was assessed against effect-based trigger (EBT) values in dry and wet seasons. Increased ERα activity was the most concerning endpoint and primary risk driver. SPM contributed more to cytotoxicity than to specific effects. Seasonal influences such as changing climate and hydrological conditions only had a minor role in explaining variation in the main river. In total, 269 chemicals were detected with target analysis, mostly pharmaceuticals and pesticides, but they explained only up to 1% of measured effects in AhR, PPARγ, SH-SY5Y and AREc32 assays. 1,2-Benzisothiazolinone, Mebendazole, Diuron, Benzothiazole, Diclofenac and 2-Benzothiazolesulfonic acid were identified as relevant toxicity drivers for neurotoxicity, xenobiotic metabolism and oxidative stress response. Attention is drawn to the pollution level in the investigated waters from a tropical developing country, which has similar water pollution levels as observed worldwide.