Structure and QSAR analysis of photoinduced transformation products of neonicotinoids from EU watchlist for ecotoxicological assessment

Abstract

Current research is increasingly focusing on the ecotoxicity of anthropogenic micro-pollutants and their degradation and transformation products resulting from biological and chemical treatment processes. These products enter the aquatic environment through various routes and may endanger aquatic organisms and plants. In this study, five neonicotinoids from the EU watchlist and their degradation products induced by UVC irradiation were examined. All identified photoinduced degradation or transformation products were subsequently submitted to Quantitative Structure Activity (QSAR) analysis. Among the investigated structures, 15 substances already identified in previous studies and eleven new transformation products were analyzed. By using QSAR analysis, it became possible to predict ecotoxicity of individual substances with mere computational effort. Starting from the chemical structure, lower toxicity against green algae and invertebrates was predicted for the transformation products in general. For other aquatic target organisms, such as branchiopoda, actinopterygii and fathead minnow, the residual hazardous effect as compared to the initial compound depends on the presence of specific structural elements. For the neonicotinoids investigated, the cleavage or elimination of the nitrile or nitro group through the degradation process, was predicted to increase toxicity.