Occurrence, toxicity and removal of polystyrene microplastics and nanoplastics in human sperm

Polystyrene microplastics, especially those smaller than 10 μm, reduce male fertility in murine models, but whether they affect male reproduction in humans is poorly understood. Here, we studied polystyrene microplastics smaller than 10 μm in human semen samples and evaluated their toxicity to human sperm. We also tested the use of magnetic iron oxide nanoparticles to remove nanoplastics and decrease their toxicity in human sperm. Results show that human semen is contaminated by approximately 3.57 ± 0.32 μg/mL polystyrene microplastics smaller than 10 μm. Polystyrene nanoplastics of 25–100 nm penetrate and damage human sperm at semen-relevant concentrations of 5 and 50 μg of nanoplastic per mL, while 0.5–10 μm polystyrene microplastics bind to the sperm. We also found that 25-nm polystyrene nanoplastics exhibited a synergistic toxicity with bisphenol A on human sperm. Nonetheless, we observed that environmental microplastics released from disposable paper cups do not pose a significant hazard to human sperm under our conditions. Furthermore, magnetic iron oxide nanoparticles can aggregate and coprecipitate with 25-nm polystyrene nanoplastics to eliminate their adverse effects on human sperm.