Disinfection byproducts formed from oxidation of pesticide micropollutants in water: Precursor sources, reaction kinetics, formation, influencing factors, and toxicity

Widespread production and use of pesticides have brought pollution issues in drinking water sources. Organic pesticides may react with disinfectants during the disinfection process of drinking water, generating various undesired disinfection byproducts (DBPs) with great health risks. This article presents a comprehensive review of recent research on DBPs derived from pesticides, covering their sources, reaction kinetics, formation mechanisms, influencing factors, and toxicity. The presence of high pesticide concentrations in the influent of drinking water treatment plants is one of the primary causes for the formation of pesticide-derived DBPs. The oxidation reactions between organic pesticides and chlorine generally follow second-order kinetics, with first order in the free active chlorine concentration and first order in the pesticide concentration. The halogens can transfer from oxidants to DBPs through substitution reactions. The presence of bromine in pesticide molecules or surrounding environment can lead to the formation of a variety of brominated DBPs, such as bromoform, dibromochloromethane, and bromodichloromethane. The factors primarily investigated for their impact on the formation of pesticide-derived DBPs include the oxidation method, oxidant/pesticide ratio, pH level, coexisting ions, and natural organic matter. Toxicity research of pesticide-derived DBPs is one of the crucial steps in effectively controlling their health risks, yet its complexity makes the studies lack of systematicness and pertinence. Future research should prioritize source control measures for pesticide pollution, innovation in disinfection technology, investigation into the formation mechanism and toxicology of pesticide-derived DBPs, screening methods to identify priority DBPs for control, as well as advanced purification technologies for removing DBPs from drinking water. These efforts will contribute to promoting the drinking water safety, improving pesticide management, and preventing associated health risks.