Spatial occurrence of emerging contaminants in rivers and wastewater. Analysis of environmental and human risks

This study assesses the occurrence of emerging contaminants (ECs) from agricultural and livestock production activities along the Salado River (Santa Fe province, Argentina). Of the 23 ECs studied, 8 were detected and quantified in river and wastewater samples, including ciprofloxacin, enrofloxacin, chlorpyrifos-methyl, albendazole, fenbendazole, levamisole, diazepam, and thiamethoxam. In river samples, the highest concentrations corresponded to ciprofloxacin, chlorpyrifos-methyl, and enrofloxacin. In wastewater samples, albendazole, fenbendazole, ciprofloxacin, enrofloxacin, and thiamethoxam were found. The detection frequency ranged from 4.2% to 54.2% in river samples and from 11.1% to 22.2% in wastewater samples. The spatial distribution of contaminants showed different concentrations, with higher levels often found near urban and agricultural areas, suggesting anthropogenic sources. Ecological risk assessments for different organisms were conducted. Ciprofloxacin posed the highest risk, especially affecting bacteria, cyanobacteria, and algae. Diazepam also was found to pose significant risks to algae, crustaceans, and fishes. Chlorpyrifos-methyl was identified as highly hazardous to multiple living organisms, which is in agreement with the fish mortality that occurred at the sampling sites. The risk assessment in humans showed differences among children, adolescents, and adults, with infants (6 months to 1 year) being at a higher risk than adults. Children may be at a higher daily intake of contaminants than adults, raising concerns about the long-term effects of exposure. This work underscores the critical need for monitoring and regulating ECs in aquatic environments. Further studies are necessary to fully understand their impact and to develop effective strategies for mitigating their presence in water systems.