Occurrence of Pharmaceutical and Pesticide Transformation Products in Freshwater: Update on Environmental Levels, Toxicological Information and Future Challenges

Pharmaceuticals and pesticides are recognized micropollutants in freshwater systems. Their ever-increasing frequency of detection, levels found and little information available about their effects on non-target organisms, make them emerging contaminants. However, parental compounds are not the only substances of concern. Their metabolites and degradation products, hereby referred to as transformation products, are increasingly detected in freshwater samples and wastewater effluents. In the past years, a wealth of publications provided concentration levels detected in freshwater and some toxicological data, which required critical systematization. This review identified concentrations for 190 transformation products (92 from pesticides and 98 from pharmaceuticals) in water bodies and wastewater effluents. A concentration heatmap was produced to easily spot the substances found at higher levels and plan future research. The very limited available toxicological data link exposure to transformation products to adverse outcomes in humans (genotoxicity and alteration in detoxification processes) and aquatic species (mostly related to apical endpoints). Overall, environmental levels of these transformation products may pose a severe threat to aquatic organisms and need to be further investigated in sound experimental designs, testing for the effects of the single substances as well as of their mixtures. Such toxicological information is highly needed to improve both water treatment technologies and monitoring programmes.

Automated summary

Pharmaceuticals and pesticides are recognized as micropollutants in freshwater systems, and their effects on non-target organisms are still poorly understood. Previous studies have summarized the concentration levels and toxicological data of transformation products, but further research is needed to understand their potential harm to aquatic organisms.