Microplastics are abundant in natural environments. Often, they are unintentionally ingested and are subsequently present in human stool samples, according to a study published in Annals of Internal Medicine.

There has been increasing pollution of aqueous, terrestrial, and airborne environments by microplastic particles in recent years, and the presence of these particles in foods and drinking water has begun to be reported. The researchers of the present study examined stool samples from participants who were representative of different geographic locations and dietary patterns. They measured the presence and levels of microplastics to determine whether the particles were ingested involuntarily. Although the health effects of ingested microplastics are still unknown, it is thought that the translocation or absorption of particles into gastrointestinal tissue may be harmful to patients who have increased intestinal permeability as a result of conditions like chronic inflammatory bowel disease.

Stool samples were collected from 8 participants, 3 men and 5 women between the ages of 33 and 65, recruited from locations in Europe and Asia (Japan, Russia, the Netherlands, United Kingdom, Italy, Poland, Finland, and Austria). All participants had normal dietary intake relative to their geographic location and culture. Participants were given stool sampling kits and instructions to document all food intake in the 6 to 7 days prior to stool sample collection and analysis. Stool sampling instructions were strictly predefined to avoid potential contamination with plastics or synthetic fibers.

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Researchers used Fourier-transform infrared microspectroscopy to analyze the presence and shape of 10 common microplastics (polyethylene, polyamide, polystyrene, polypropylene, polycarbonate, polyurethane, polyvinyl chloride, polyethylene terephthalate, polymethyl methacrylate, and polyoxymethylene) in each stool sample.

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Results revealed that all 8 samples tested positive for the presence of microplastics ranging in size from 50 to 500 μm. The median microplastic concentration was 20 pieces (interquartile range, 18-172 pieces) for every 10 g of stool. Each stool sample contained between 3 and 7 microplastic types, and 9 of the 10 targeted microplastic types were detected overall. Polypropylene and polyethylene terephthalate were the most abundant microplastics identified and were present in all 8 samples, with relative frequencies of 62.8% and 17%, respectively. The only plastic not detected in any sample was polymethyl methacrylate.

The study had 2 main limitations. The first was the relatively small sample size of only 8 participants, each of whom provided only 1 stool sample. Additionally, the study was not designed to be able to investigate the ultimate fate of microplastics in the gastrointestinal tract.

The study researchers concluded that various microplastics are commonly and unintentionally ingested, and that this phenomenon is incredibly pervasive, as evidenced by the presence of microplastics in stool samples from such a geographically diverse group of participants. However, further research is needed to investigate the origin, potential gastrointestinal absorption, and effects of microplastics on human health.

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.


Schwabl P, Köppel S, Königshofer P, et al. Detection of various microplastics in human stool: a prospective case series [published online September 3, 2019]. Ann Intern Med. doi:10.7326/M19-0618