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In the first study of its kind, researchers in the Netherlands identified the presence of microplastic particles in human blood.

The study, published Thursday in Environment International, found a “quantifiable mass” of plastic particles in the blood samples of 17 of 22 — or 80% — of the study’s volunteer participants.

Microplastics are small plastic pieces less than five millimeters long. According to the National Oceanic and Atmospheric Administration, they come from a variety of sources, including from larger plastic debris that degrades into smaller and smaller pieces. Microbeads, a type of microplastic, are very tiny pieces of manufactured polyethylene plastic found in health and beauty products, such as some cleansers and toothpaste.

According to the study, the blood samples analyzed by researchers contained four high-production-volume polymers: polyethylene terephthalate (PET), polyethylene (PE) and polymers of styrene, and poly(methyl methacrylate) (PMMA).

The researchers also analyzed the samples for polypropylene but found these values were “under the limits of quantification.”

PET is commonly used in food and beverage containers, including water bottles. PE is used in food packaging, bags and films (such as Saran Wrap), while PMMA, or acrylic, has applications in the human body including dental and eye implants.

“Our study is the first indication that we have polymer particles in our blood — ​it’s a breakthrough result,” Prof Dick Vethaak, one of the study authors, told The Guardian. “But we have to extend the research and increase the sample sizes, the number of polymers assessed, etc.”

Further studies by a number of groups are already underway, Vethaak said.

“It is scientifically plausible that plastic particles may be transported to organs via the bloodstream,” the researchers wrote, although “it remains to be determined whether plastic particles are present in the plasma or are carried by specific cell types (and to which extent such cells may be involved in translocating plastic particles across mucosa to the bloodstream).”

According to the study, plastic particles are bioavailable for uptake into the human bloodstream, but the study’s authors cautioned the fate of these particles in the human body is still unknown and further research is needed.

The researchers asked:

“If plastic particles present in the bloodstream are indeed being carried by immune cells, the question also arises, ‘[C]an such exposures potentially affect immune regulation or the predisposition to diseases with an immunological base?’”

The research was funded by grants from the Common Seas Foundation and Netherlands Organisation for Health Research and Development.

Although this is the first study to find microplastics in blood, research published in December 2021 found concentrations of microplastics in the feces of infants at 10 times that of adults.

Some studies suggest microplastics in air, water and food damage cells and can cause allergic reactions, and recent tests reveal most bottled water contains microplastic pollution, thought to originate from the manufacturing process of the bottles and caps.