Association of mixed exposure to microplastics with sperm dysfunction: a multi-site study in ChinaResearch in context

Summary: Background: Microplastics are environmental pollutants detected in various human organs and tissues. These particles originate from multiple sources including the degradation of larger plastic items and the intentional inclusion in consumer goods. Potential risks for human health resulting from microplastics exposure have also been reported. However, the distribution in the male reproductive system and its effect remains largely unknown. This study aims to investigate the presence of multiple microplastics in human semen and urine and their association with sperm quality in a multi-site study across China. Methods: We conducted a cross-sectional study involving 113 male participants from three regions in China. Semen and urine samples were collected and analysed using Raman microscopy to detect eight types of microplastics: polystyrene (PS), polypropylene (PP), polycarbonate (PC), polyethylene (PE), polyvinyl chloride (PVC), polytetrafluoroethylene (PTFE), polyethylene terephthalate (PET), and acrylonitrile butadiene styrene (ABS). Semen quality parameters, including total sperm count, concentration, motility, and morphology, were assessed. Statistical analyses, including single and multi-variable models, were used to evaluate the relationship between microplastic exposure and semen quality, with a focus on PTFE, after adjusting confounding factors of age, body mass index (BMI), smoking, alcohol drinking, and sites. Findings: Microplastics were detected in all semen and urine samples, with participants typically exposed to 3–5 different types. The detection rates of PS, PP and PE were the highest. Notably, PTFE exposure was significantly associated with decreased semen quality. Participants exposed to PTFE showed reductions in total sperm count [188.90 ± 163.71 vs. 207.67 ± 132.36 million, p = 0.091], sperm concentration [52.13 ± 47.47 vs. 58.32 ± 37.26 million/mL, p = 0.041], and progressive motility [40.29% ± 19.06 vs. 34.11% ± 17.02, p = 0.083]. The multi-linear regression analysis indicated that each additional type of microplastic exposure was associated with a significant decrease in total sperm number [β = −15.4 (95% CI: −25.6, −5.2)], sperm concentration [β = −7.2 (95% CI: −12.4, −2.0)], and progressive motility [β = −8.3 (95% CI: −13.5, −3.1)]. Latent category analysis further refined these groups by types of microplastic exposure, highlighting specific types more strongly associated with decreased semen quality (OR = 3.5, 95% CI: 1.8, 6.9, p