The Reproductive Toxicity of Microplastics: From Environmental Contamination to Organ Distribution and Reproductive Hazards

Microplastics (MPs) are ubiquitous in nature, contaminating various environmental media such as soil, air, and water. Moreover, they can be found in drinking water and foods, increasing the risks of human exposure. Studies have reported that MPs can be detected in various human organs, including the reproductive ones. Ovarian follicular fluids and uterine tube tissue have been documented to contain up to 7181 particles/mL and 1.40 particles/g, respectively. Similarly, samples associated with the male reproductive system are also reported with MPs. Specifically, semen and testicular tissue samples contain up to 17 and 11.60 particles/g of MPs, respectively. Growing evidence suggests that MPs can potentially harm the reproductive system by adversely affecting the development and maturation of gametes. They can modulate the cAMP/PKA/StAR pathway to affect FSH and LH. MP-induced ROS production alters the Akt/ESR1/NRF pathway to upregulate IL-1β, IL-6, and TNF-α proinflammatory cytokines. MP-mediated NLRP-3 activation promotes pyroptosis of gonadal germ cells. Therefore, in this comprehensive literature review, the latest data on the environmental distribution of MPs, their entry into the human body, and their accumulation in reproductive tissues are critically examined. The roles of oxidative stress, endocrine disruption, inflammation, and cellular apoptosis in MP-induced reproductive toxicity are also discussed. This review emphasizes the need for further toxicological evaluations and long-term epidemiological studies to fully understand the range of associated risks and highlights knowledge gaps regarding the mechanistic pathways by which MPs trigger reproductive toxicity.