Micro- and nanoplastics in human male reproduction: Immune disruption, blood–testis barrier, and clinic-ready biomarkers

Micro- and nanoplastics (MNPs) have recently been detected in the human male reproductive tract, signaling a new dimension of environmental exposure. Mass-based analyses identified polymer particles, predominantly polyethylene, in all archived human testes, while independent semen studies revealed multiple polymer types and a multicenter cohort associated higher mixed burdens in semen and urine with poorer sperm quality. Experimental models support these findings, showing that MNPs induce oxidative stress, activate toll-like receptor and nuclear factor kappa B pathways signaling, trigger NLRP3 inflammasome activity, and disrupt tight-junction proteins that maintain the blood-testis barrier, collectively impairing spermatogenesis and steroidogenesis. However, most human studies quantify particles and conventional semen parameters without simultaneous assessment of immune or barrier biomarkers. This review integrates emerging human evidence and proposes a translational framework that combines particle analytics with a clinic-feasible panel of seminal cytokines, oxidative indices, and extracellular-vesicle markers of junctional integrity. Such integration can determine whether MNP burden maps to measurable immune injury in men, bridging detection with mechanism for reproductive immunology.