Microplastics — tiny bits of plastic waste less than 0.197 inches (5 millimeters) in size — are an increasingly worrisome phenomenon in the world's oceans, where scientists have found them in the bodies of dozens of aquatic species, including shrimp, mussels and fish that end up on human dinner tables. Scientists have suspected for a while that the miniscule pollution was getting into people's bodies as well.
And now for the first time, in a pilot study presented at the United European Gastroenterology conference in Vienna, researchers have found evidence of just how widespread human ingestion of microplastics might be. Researchers from the Medical University of Vienna and the Environment Agency Austria gathered stool samples from eight human subjects in eight different countries: Finland, Italy, Japan, the Netherlands, Poland, Russia, the United Kingdom and Austria. All eight of the subjects turned out to have microplastic in their poop — on average, 20 particles per 0.35274 ounces (10 grams) of feces.
In some cases, the subjects' fecal stool samples contained as many as nine different types of microplastics, with polypropylene (PP) and polyethylene terephthalate (PET) being most common.
We Are Eating Plastics
The study didn't pinpoint how the microplastics got into the subjects' gastrointestinal tracts. That said, each subject kept a food diary in the week leading up to the stool sample being collected. The records showed that six of the eight ate seafood, and all either consumed food that had been wrapped in plastic or else drank from plastic bottles.
"We don't know, but food and food packaging are likely sources of ingested microplastics," Dr. Philipp Schwabl, a gastroenterologist at Medical University of Vienna and the study's lead author, says in an email interview. Microplastics have been detected in liquids stored in PET bottles, Dr. Schwabl says. And a study published in the journal Water Research in February 2018 found that microplastics were present in 38 different bottled waters.
In addition to packaging, another big source of microplastics may be indoor dust containing plastic fibers, which we're inhaling and eating as it settles onto our food.
Exactly what the findings mean is still unclear, since relatively little is known about the effect of microplastics on human health.
"There is no evidence yet that microplastics do any harm to humans," Dr. Schwabl says. "However, animal studies showed that orally ingested microplastics might transmigrate through the gut, as microplastics have been detected in animals in blood, lymph and liver. Maybe patients with inflammatory bowel diseases might be more susceptible to microparticle uptake. However, larger trials are needed to elucidate this."
The small-scale study isn't meant to be the last word on the subject. "Now that we know how abundant microplastics are, we aim to perform follow-up trials to analyze microplastics contamination on a larger scale," Schwabl says.
Another scientist not connected with the study wasn't surprised by its findings. Rolf Halden, director and professor at the Biodesign Center for Environmental Health Engineering at Arizona State University, says that humans have been exposed to plastic fragments since the 1940s. There is now so much plastic in the environment "that the exposure is almost ubiquitous," he adds.
A Cancer Link?
Halden explained that one big concern is that tiny particles might accumulate in human tissue, where they would cause inflammation and potentially lead to cancer. "But there aren't a lot of studies right now," he notes.
Halden, who participated in the 2014 U.S. Environmental Protection Agency forum on possible human health risks from microplastics in the marine environment, says that while seafood might be a possible source, it's more likely that people are inhaling and ingesting microplastic directly from consumer products. Those include the synthetic textiles that often cover our bodies, as well as carpeting and plastic items in our indoor surroundings.
Humans are part of the environment in which they live, and our bodies are constantly interacting with it, Halden explains. "We're in constant chemical communication with it, wherever we are," he says.
Halden emphasizes that the study "does not need to be a reason for alarm, but it certainly constitutes an incentive to study exposures and associated effects in greater depth."