Association between microplastic exposure and reduced semen quality and the mediating role of gut microbiota

Background Microplastics (MPs) are widely prevalent in the environment and food chain, leading to increased human exposure and potential health risks. Although MPs have been shown to induce reproductive toxicity in animal models, it remains unclear whether exposure to MPs contributes to the decline in human semen quality. This study aimed to investigate the association between MP exposure and semen quality among men visiting assisted reproductive outpatient clinics at tertiary hospitals. Methods This study employed both cross-sectional and case–control designs. The study population comprised men attending the assisted reproductive outpatient clinic of a Grade-A tertiary hospital in Jinan, China, between April 1 and July 31, 2023. Semen quality parameters were assessed using an automated sperm analyzer. Fecal microplastic (MP) levels were quantified via laser direct infrared spectroscopy, and gut microbiota composition was characterized by 16S rRNA gene sequencing. Results The results show that the level of sperm total motility was decreased with the higher number of PS ( β = −0.585, 95% CI = −1.071, −0.098), PVB ( β = −0.775, 95% CI = −1.209, −0.341), and PET ( β = −0.0.480, 95% CI = −0.937, −0.023). Importantly, the gut microbiota of men with abnormal sperm motility is dysregulated, and the gut microbiota plays a potential mediating role in the association between MP exposure and decreased sperm motility. Conclusion This study provides evidence that MP exposure is associated with an increased risk of declined semen quality in men, and suggests a potential mediating role of gut microbiota in this relationship. These findings offer critical insights into the potential etiological clues of poor semen quality and contribute to a deeper understanding of the health risks and mechanistic pathways related to MP pollution.