Environmental pollutants and testicular toxicity in male reproductive health: Basic evidence and translational prospects - A narrative review.

Global sperm concentration has declined by over 50% in the past five decades, with environmental pollutants identified as a critical driving factor. This review focuses on testicular-level evidence regarding the effects of microplastics, bisphenol compounds, and air pollution on male reproductive health, with an emphasis on spermatogenic and testicular somatic cell mechanisms. Microplastics have been detected in human testicular tissue, with a causal pathway established linking gut microbiota dysbiosis, immune activation, and blood-testis barrier disruption. Bisphenol A substitutes show comparable or greater reproductive toxicity than BPA, with BCAT1-mediated ferroptosis identified as a novel testicular injury mechanism. For air pollution, spermatogenesis stage I (70-90 days prior to semen collection) has been pinpointed as the critical PM2.5 exposure vulnerability window, with metal constituents of traffic-derived PM2.5 as the primary toxicity drivers. Future research should prioritize prospective cohort studies and clinical intervention trials targeting these emerging mechanistic pathways.