Microplastic-induced male reproductive toxicity: animal models, key design parameters, and mechanistic insights

Microplastics (MPs) are pervasive environmental contaminants detected across air, water, soil, and food chains. Their presence in human reproductive tissues has raised concern that MP exposure may contribute to the global decline in male reproductive health. This review summarizes recent progress in animal models used to investigate MP-induced male reproductive toxicity, with particular attention to key design variables, including animal strain and age, polymer type, particle size, dose, exposure route, and exposure duration, as well as the rationale for their selection. We also summarize the major mechanisms implicated in MP-associated reproductive toxicity, including oxidative stress, inflammation, endocrine disruption, programmed cell death, mitochondrial dysfunction, and epigenetic alterations. Current models remain highly heterogeneous, often rely on exposure doses with limited environmental relevance, and provide incomplete mechanistic resolution. Future work should prioritize standardized model design, multi-omics integration, and improved monitoring of human MP exposure and epidemiological surveillance of male reproductive outcomes. Collectively, this review aims to support the refinement of animal models and provide an integrated mechanistic framework for toxicological assessment of MPs.