Neonicotinoid insecticides in non-target organisms: Occurrence, exposure, toxicity, and human health risks

Pesticides have consistently portrayed a crucial role in the history of modern agricultural production. Neonicotinoid insecticides are classified as the fourth generation of pesticides, following organophosphorus, pyrethroids, and carbamates. Due to their broad-spectrum insecticidal activity, unique neurotoxic mode of action, and versatility of application methods, neonicotinoids have been widely used worldwide since their introduction. Recent studies have shown that neonicotinoids are frequently detected in a variety of food and environmental media around the world, posing considerable safety risks to human health and ecosystems, and therefore have become an emerging contaminant. However, the toxic effects and exposure risks of neonicotinoids to non-target organisms, including humans, have not received sufficient attention. Therefore, based on previous studies, this critical review concisely evaluates the occurrence and exposure levels of neonicotinoids in the environment and the associated risks to human health. The toxic effects of neonicotinoids on non-target organisms are systematically reviewed, including the aspects of acute toxicity, reproductive development, nervous system, immune function, genetics, and others. The potential toxic mechanism of these pesticides is discussed. The existing knowledge gaps are identified, and future prospects for neonicotinoids are proposed to provide scientific guidance for the safe and rational use of neonicotinoids and future research directions.