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Microplastics Found in Human Stool for First Time, Says Study

Microplastics are fast becoming the oceans’ No. 1 scourge—and a problem for people’s No. 2.

Minuscule fragments of polypropylene (PP) and polyethylene-terephthalate (PET) have been found in human stool for the first time, according to scientists from the Medical University of Vienna and the Environment Agency Austria.

The results of their study, presented at United European Gastroenterology Week in Vienna Tuesday, suggest not only have microplastics infiltrated the human food chain but they’re now a widespread presence.

Researchers analyzed the stool of eight participants from Austria, Finland, Italy, Japan, the Netherlands, Poland, Russia and the United Kingdom. Every single stool sample tested positive for microplastics ranging in size from 50 to 500 micrometers. Though up to nine different plastic varieties were identified, PP and PET popped up most often. On average, researchers uncovered 20 microplastic particles per 10 grams of stool.

“This is the first study of its kind and confirms what we have long suspected: that plastics ultimately reach the human gut,” said lead researcher Philipp Schwabl, a gastroenterologist at the Medical University of Vienna, in a statement. “Of particular concern is what this means to us and especially patients with gastrointestinal diseases.”

Microplastics, he noted, could affect human health by interfering with the immune response of the gut or aiding the transmission of toxic chemicals and pathogens. Other problems might also arise when particles migrate from the gastrointestinal tract to various organs and tissues.

“While the highest plastic concentrations in animal studies have been found in the gut, the smallest microplastic particles are capable of entering the bloodstream, lymphatic system and may even reach the liver,” Schawbl added. “Now that we have first evidence for microplastics inside humans, we need further research to understand what this means for human health.”

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But where did the microplastics come from? Food diaries kept by participants in the week leading up to their stool samplings revealed common exposures such as plastic-wrapped foods or plastic water and soda bottles. (Extra vindication for the anti-single-use-plastics brigade?) None of the participants were vegetarians and six had consumed seafood.

Most microplastics are created when larger plastics in the oceans are broken into smaller pieces by waves, sediment abrasion and degradation in sunlight. In some cases, they’re manufactured to be less than 1 millimeter in diameter, such as with microbeads used in certain cosmetics and personal-care products.

At the same time, tiny plastic fibers can flake off of synthetic clothing, such as those made from polyester, and into wastewater systems during laundry. One study by the University of California, Santa Barbara, posited that a synthetic fleece jacket releases an average of 1.7 grams of microfibers with every wash.

It doesn’t take a huge leap of logic to conclude that the pernicious pieces would eventually wind up in the human gut. Significant amounts of microplastics have been detected in tuna, lobster and shrimp, and a 2014 study estimates shellfish lovers are consuming as many as 11,000 microplastic particles per year. Flying insects, like mosquitoes, aren’t free from the tyranny of microplastics; neither are deep-sea starfish, which scientists recently announced have been ingesting microplastics for the past four decades.

Researchers at the Scottish Association for Marine Science analyzed archived samples from the Rockall Trough, an area of deep sea off the west coast of Scotland, to suss out the scope of microplastic ingestion in stomachs of bottom-dwelling starfish and brittle stars.

“Mass production of plastics only began in the 1940s and 1950s, so it would be reasonable to expect less plastic in our earlier samples, with a subsequent upward trend to the present day levels, but we haven’t seen that. In fact, the level of microplastic ingestion is remarkably similar throughout the time series,” said Winnie Courtene-Jones, a doctorate student and lead author of the study, which will be published in the journal Environmental Pollution in January. “This data shows, for the first time, the long-term prevalence of microplastic pollution in the deep sea and indicated that microplastics may have been present on the seafloor of the Rockall Trough prior to 1976.”

While the results demonstrate plastic pollution isn’t new to the planet, said Bhavani Narayanaswamy, Courtene-Jones’ supervisor and co-author of the report, it also means both old and novel plastics are bedding down for the long haul.

“Previous studies have highlighted the current levels of plastic pollution, or given us a snapshot in time,” he added. “But we need more long-term data like this if we are to find out the true extent of the problem.”