The poop emoji may now be used as a symbol of pollution.

For the first time, small pieces of plastic have been detected in human stool samples, according to results from a pilot study presented at the United European Gastroenterology meeting in Vienna earlier this week.

Eight people ages 33 to 65 from Finland, Italy, Japan, the Netherlands, Poland, Russia, the United Kingdom and Austria documented what they ate for seven days and then submitted stool samples for lab analysis. Throughout the week, all of the participants consumed plastic-wrapped food and drank from plastic water bottles. Six of the participants ate seafood and none of them were vegetarian. Microplastics were detected in all eight samples.

"This is the first study of its kind and confirms what we have long suspected, that plastics ultimately reach the human gut," lead researcher Philipp Schwabl from the Medical University of Vienna said in a press release.

Among 10 different types of plastics the team of Austrian scientists screened for, nine were detected. Particles ranged in size from 50 micrometers to 500 micrometers (about two one-hundredths of an inch). Polypropylene (PP), found in bottle caps and polyethylene terephthalate (PET), used in bottles, were found most frequently.

While the results may seem startling, it’s not the first time microplastic has been detected in remote and obscure places. Plastic particles have been found frozen in Arctic sea ice and in the stomachs of some of the world’s deepest-living sea creatures.

Microplastics are tiny pieces of plastic, about the size of a sesame seed or smaller. Researchers don't know how the study participants ingested or inhaled microplastics, but the possible pathways into the human body are abundant. Microplastics have been detected in air, soil and tap water. They are also prevalent in oceans where plastic trash gets broken down over time in the water and can then works its way up the marine food chain, eventually onto our plates through seafood.

In the ocean, particles can also be a vessel for other pollutants. Specifically, a class of chemicals called polychlorinated biphenyls (PCBs) are known carcinogens that have been released into the oceans. PCBs have been banned in many countries, and an international treaty calls for their eradication by 2025. But they do not easily decompose so their presence has been persistent.

Microplastics tend to be surfaces for other chemicals, such as PCBs to absorb, so they may be coated with pollutants such as PCBs that are also passed up the food chain, says Dr. Scott Fruin, an assistant professor of clinical preventive medicine in the Division of Environmental Health at the University of Southern California.

Researchers explain that due to the limited scope of the study, more work is needed to understand the potential health implications of microplastic in the body, and what foods and activities may put people at greatest risk for microplastic exposure.

"Now that we have first evidence for microplastics inside humans," said Schwabl, "we need further research to understand what this means for human health."