Neonicotinoid Exposure and Reproductive Dysfunction: Mechanisms and Evidence

Abstract: Background: Neonicotinoids are a widely used class of insecticides introduced in the 1990s, primarily valued for their selective toxicity to insect nervous systems. However, mounting evidence suggests that these compounds are not as innocuous to non-target species, including humans, as once thought. Concerns about their persistence in the environment and their detection in human tissues have spurred investigation into their potential systemic health impacts, particularly reproductive toxicity. Objective: This review synthesizes current evidence on the reproductive effects of neonicotinoid pesticide exposure and elucidates the underlying toxicological mechanisms responsible for reproductive dysfunction across genders and species. Methods: A comprehensive analysis of published literature from 2000 to 2024 was conducted using electronic databases such as PubMed, Scopus, and Web of Science. Studies were selected based on relevance to neonicotinoid exposure, reproductive endpoints, and mechanistic insights. Animal model, in vitro, and limited human epidemiological studies were included. Results: Neonicotinoids exert reproductive toxicity through several mechanisms, including endocrine disruption, oxidative stress, apoptosis, and hormonal imbalance. In males, exposure is associated with decreased sperm count, motility, and testosterone levels, along with histopathological changes in testicular tissue. In females, alterations in estrous cycles, folliculogenesis, and hormonal profiles have been observed, often resulting in reduced fertility. Developmental and transgenerational effects—such as fetal growth retardation and epigenetic modifications—further exacerbate concerns. Comparative studies show that imidacloprid and clothianidin are particularly potent in disrupting reproductive function. While mechanistic data in animal models are robust, human studies are sparse but indicate possible associations with adverse reproductive outcomes in high-exposure populations. Conclusion: The evidence implicates neonicotinoids as potential reproductive toxicants with multisystemic effects. There is an urgent need for longitudinal human studies, regulatory reassessment, and mitigation strategies to minimize exposure, particularly in vulnerable populations such as pregnant women and agricultural workers.