The Effects of Microplastics on Sperm Motility: An In Vitro Experimental Study.

OBJECTIVE: While microplastics such as polyethylene (PE) and polystyrene (PS) have been identified in human semen, their clinical impact is still under investigation; this study evaluates the in vitro effect of PE and PS microplastics on sperm motility parameters and DNA fragmentation in human semen samples DESIGN: Experimental Study SUBJECTS: Post-ejaculate semen samples from men evaluated at a New York fertility center (October 2024 - September 2025) were collected. Samples with normal sperm concentration and morphology were included; those with baseline total motility below 2% were excluded. EXPOSURE: Each sample was divided into 200 μL aliquots and exposed to 0 (control), 1, 2, 4, 8, or 16 μL of 10% PE (34-50 μm) or PS (10 μm) microbead solutions and incubated for 2 hours at 20°C-22°C. MAIN OUTCOME MEASURES: Total motility, progressive motility, average path velocity (VAP), curvilinear velocity (VCL), straight-line velocity (VSL) RESULTS: Thirty-two semen samples were analyzed for motility changes. Within each exposure group, 20 samples had normal baseline motility and 10 had low baseline motility according to WHO 5th edition criteria. Exposure to both PS and PE in both groups resulted in a dose dependent reduction of greater than 10% in VAP and VSL from baseline compared to controls (p <0.05). Total and progressive motility were not significantly impacted. CONCLUSION: In vitro exposure to PS and PE microplastics significantly impaired sperm kinematic parameters (VAP, VCL, and VSL) without affecting overall motility. These findings raising concern regarding environmental exposures and supporting need into further research on their reproductive impact.