Recently, we reported in <i>ES&T Letters</i> the initial discovery of neonicotinoid insecticides in finished drinking water. Neonicotinoids are part of a growing class of target-specific pesticides, wherein receptor binding specificity is conferred through a specific structural pharmacophore (in this case, an electronegative nitro-group).  In this follow-up work, we focused on two areas of study: (1) determining the relevance of neonicotinoid metabolites in source waters / drinking water; (2) discovering the transformation products of neonicotinoids following chlorination, as would occur during disinfection operations. We discovered that two known metabolites of the neonicotinoid imidacloprid were present in the finished drinking water at our field test site (Iowa City, IA) at lower levels than the parent compounds (ng/L). Nevertheless, the presence of these metabolites may be of greater human health concern because of the higher binding affinity to mammalian receptors compared to the parent compounds. Using batch chlorination experiments with high-resolution mass spectrometry fragment analysis, we elucidated and propose structures for novel chlorinated byproducts of neonicotinoids and their metabolites. Several of these new products are further chlorinated and / or have the insecticidal pharmacophore altered / removed, both characteristics that may broaden toxicity or binding to non-target organisms. Furthermore, the altered compound charge distribution of the metabolites lowers the removal propensity using activated carbon. This work demonstrates the importance of trace organic contaminants as potential disinfection byproduct precursors in impacted source waters as well as the importance of understanding how the structural transformation of target-specific pesticides can lead to unintended ecosystem impacts / human health exposure.<br/>

Discovery of neonicotinoid insecticides in finished drinking water and formation of novel products with altered pharmacophores during chlorination

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.