Temporal trends in the use and concentration of organophosphorus pesticides in Indian riverine water, toxicity, and their risk assessment

Despite the positive aspect of pesticide application in increasing crop productivity and significantly reducing vector-borne diseases, their unregulated and indiscriminate use has prompted severe concerns about the environment in general and human and animal health in particular. When living beings are exposed to organophosphate (OP) pesticides, the principal toxicological consequence is the irreversible acetylcholinesterase enzyme (AChE) suppression. As AChE is involved in signal transmission, it thus causes damage to the respiratory tract and neuromuscular transmission. Therefore, exposure and toxicity studies are critical to reducing pesticide exposure and toxicity to humans and the environment. This study overviews the consumption trend, occurrence, toxicological effects and risk assessment of hazardous OP pesticides. The use of OP pesticides in India was reviewed for the period 2010–2021 using data from the Directorate of plant protection, quarantine and storage, Ministry of Agriculture, and farmer’s welfare. Concentrations of OP pesticides in river/lake water across India were obtained from literature, and risk evaluations for selected pesticides were performed using risk quotients and hazard quotients. Seventeen common pesticides, including insecticides, were evaluated. Annual OP pesticide use was highest for chlorpyrifos and lowest for fenthion, and OP pesticides were found in substantial amounts in freshwater systems in different states as per reports. According to ecotoxicological risk assessment, chlorpyrifos and malathion constituted severe threats to the Indian aquatic environment, while diazinon and ethion posed only moderate risks. Not a single OP pesticide studied posed a significant risk to humans. In India, continued usage of OP pesticides may lead to solid hazards to aquatic habitats; therefore, such concerns should be re-evaluated regularly.