Microplastics and reproductive health: implications for human health and areas for future research

Microplastics (MPs), conventionally defined as plastic particles 1 μm-5 mm in size, are ubiquitous contaminants, infiltrating both our environment and our bodies. These particles, either manufactured at this scale or formed from the breakdown of larger plastics, possess diverse characteristics that allow them to absorb and release toxic substances, form biofilms, and abrade and inflame tissues. In humans, MPs have been detected in testes, semen, ovarian follicular fluid, placental tissue, and other locations in the reproductive system. Recent studies suggest that MPs may disrupt male and female reproduction through mechanisms involving oxidative stress, inflammation, DNA damage, and endocrine disruption. Over the past 5 years, there has been increasing excitement about MPs research and a burgeoning literature in this area. Despite this growing body of evidence, the full spectrum of MP-associated reproductive toxicity in humans remains poorly understood, with limited research on effects at environmentally relevant exposure levels and in the general population, and a poor understanding of the specific toxicity of different polymer types, sizes, and shapes. As the literature rapidly expands, it is important to take note of current constraints and how research in this field may be optimized for quality. This review summarizes current knowledge about MPs and their reproductive toxicity, highlights emerging research areas, and identifies key challenges and needs for future research on this class of contaminant.