Microplastics are tiny plastic particles, less than 5 millimeters in size, that are pervasive in the environment, including in water bodies, soil, and air. These particles come from various sources, such as the breakdown of larger plastic debris, microbeads in personal care products, and synthetic fibers from clothing. They are so small that they can be ingested or inhaled by organisms, including humans, and accumulate in various tissues and organs.
At the University of New Mexico researchers discovered human testicles had a plastic concentration almost three times higher than that found in the dog testes: 330 micrograms per gram of tissue compared with 123 micrograms.
Microplastics have also been discovered, in placentas and human milk indicating widespread contamination of our bodies.
The ramifications of microplastics in regards to fertility is such that the following can occur:
Endocrine Disruption: Microplastics contain various additives, such as plasticizers and flame retardants, which can interfere with hormonal balance. These chemicals can disrupt the endocrine system, which regulates reproductive functions. For example, exposure to certain plasticizers like bisphenol A (BPA) and phthalates has been linked to reduced sperm quality and quantity.
Microplastics can trigger inflammation and oxidative stress in tissues where they accumulate. In the testicles, inflammation and oxidative stress can damage sperm cells and impair their function. This damage can lead to reduced sperm motility, viability, and DNA integrity, all of which are crucial for fertility.
Direct Physical Damage: Large aggregates of microplastics or sharp-edged particles can physically damage the delicate structures within the testicles. This damage can disrupt spermatogenesis, the process of sperm production, leading to decreased sperm production and quality.
Transport of Harmful Substances in which microplastics have a high surface area, and they can adsorb and accumulate various toxic chemicals from the surrounding environment. These chemicals can include persistent organic pollutants (POPs) like polychlorinated biphenyls (PCBs) and pesticides. When microplastics accumulate in the testicles, they can release these absorbed chemicals, exposing sperm cells to additional toxicants that can further impair fertility.
Epigenetic changes can occur in which microplastics alters gene expression patterns in sperm cells, potentially affecting fertility and even the health of future generations.
While the exact mechanisms through which microplastics affect male fertility are still being studied, accumulating evidence from both animal and human studies suggests that exposure to these ubiquitous pollutants can have detrimental effects on reproductive health.
Ref:
https://academic.oup.com/toxsci/advance-article/doi/10.1093/toxsci/kfae060/7673133 
