Abstract
The ubiquity of microplastics (MPs) in the environment has raised significant concerns, yet their potential impacts on human health are not fully elucidated. This study aimed to quantify human exposure to MPs in feces and evaluate their associations with oxidative stress and cardiopulmonary function. A panel study was conducted in 16 male college students with three-round visits. Fecal MPs were quantified using infrared micro-spectroscopy, and health effects were assessed through urinary biomarkers of oxidative damage (MDA and 8-OHdG) and cardiopulmonary function tests. Associations between MP exposure and health outcomes were analyzed using linear mixed-effect models. We found that fecal MP amount across 48 samples from 16 participants showed high intra-individual variation and poor reproducibility (ICCs < 0.4). MPs in feces were predominantly identified as sheets and fragments in the 100-200 μm size range, with polyamide (PA), polyester, polyethylene (PE), and polypropylene as the primary polymer types. Significant relationships were observed between fecal MP amount and oxidative damage biomarkers. Each one-unit increase in MPs corresponded to a 0.827 increase in MDA (95% CI: 0.116, 1.54) and a 1.11 increase in 8-OHdG (95% CI: 0.235, 1.98), with fibrous shapes and specific polymers (PE and PA) being the primary drivers. No significant associations were found between MP exposure and lung function or blood pressure. These findings indicated that MP exposure was significantly linked to increased oxidative damage, highlighting a pressing public health concern regarding their subclinical biological effects.