Background: Microplastics are ubiquitous in natural environments. Ingestion of microplastics has been described in marine organisms, whereby particles may enter the food chain.

Objective: To examine human feces for the presence of microplastics to determine whether humans involuntarily ingest them.

Design: Prospective case series in which participants completed a food diary and sampled stool according to step-by-step instructions.

Setting: Europe and Asia.

Participants: Eight healthy volunteers aged 33 to 65 years.

Measurements: After chemical digestion, Fourier-transform infrared microspectroscopy was used to analyze the presence and shape of 10 common types of microplastic in stool samples.

Results: All 8 stool samples tested positive for microplastics. A median of 20 microplastics (50 to 500 µm in size) per 10 g of human stool were identified. Overall, 9 plastic types were detected, with polypropylene and polyethylene terephthalate being the most abundant.

Limitations: There were few participants, and each provided only 1 sample. The origin and fate of microplastics in the gastrointestinal tract were not investigated.

Conclusion: Various microplastics were detected in human stool, suggesting inadvertent ingestion from different sources. Further research on the extent of microplastic intake and the potential effect on human health is needed.

Primary funding source: None.