Plastics — omnipresent in modern life — are falling from the air, circulating in the seas and turning up in the soil.
And new research estimates that tens of thousands of the little particles, often smaller than the eye can see, find their way inside our bodies each year.
The study estimates that adults consume and inhale at least 98,000 of the particles each year, based on a review of previous research about microplastic intake from such things as seafood, honey, bottled water and beer.
Published Wednesday in the American Chemical Society’s journal Environmental Science & Technology, the research likely accounts for a fraction of what Americans actually inhale or ingest.
That’s because the field of study is still in its infancy. Scientists have not studied microplastic content for about 85% of the government-recommended American diet, including pork, beef or the plastic-rich processed goods. (And who doesn’t indulge beyond the government’s nutrition guide?)
It’s also not clear what risk, if any, the consumption of microplastic poses to human health.
What the study does make plain: As worldwide plastic production continues to increase, scientists have found microplastic almost everywhere; the material is entering the food system by myriad means; and scientists are calling for more investigation into what this could mean.
In fact, microplastic has become so ubiquitous in what people drink, eat and breathe, during tests “it would be more surprising to not find plastic in a setting,” said Kieran Cox, the study’s lead author.
The researchers analyzed 26 papers about microplastics and constructed a database of microplastic content using their results, which represented measurements from more than 3,600 samples of items, including air, alcohol, bottled water, honey, seafood, salt, sugar and tap water.
Then, they compared that data with government information on respiration rates, average consumption of water and suggested food intake to determine how much exposure people would have to microplastics.
“Our aim was to get to your government intake of plastics,” said Cox, a doctoral student at the University of Victoria.
The study estimated that adult men, on average, would eat, drink and breathe in 121,664 particles during a year, while women would take in 98,305. Numbers for children were slightly less.
Personal habits could have significant effects on levels of exposure.
Bottled water, on average, contained much higher numbers of microplastic per liter than tap water, according to previous research cited in the study. Drinking only bottled water could increase how much microplastic people consume, Cox said.
“With small choices you can mitigate this quite a bit,” Cox said.
The data does not convey how much microplastic people are consuming by weight. Microplastics are defined as any plastic particles less than 5 millimeters in size. But shape, size and chemical content vary widely, Cox said. Most studies included in his study provided a quantity of microplastics, but not a mass.
Julie Masura, a research scientist at the University of Washington Tacoma who has studied microplastics for more than a decade, said it was important to keep perspective about just how small some of the material is and how little is known about what it could mean.
“The mass concentration is nearly negligible. We’re talking about parts per million and parts per billion,” Masura said.
Masura said other environmental pollutants are found in food and water at higher concentrations.
“We need to be cautious about what it means,” Masura said of the study. “The authors are not really trying to claim that it will cause harms to humans, necessarily. It’s a call to say, ‘Hey, you should know it’s in our food system.’”
Microplastics research has developed rapidly over the past few decades.
“This is an emerging topic and people are doing work on this stuff and trying to see what the implications are on ecosystems and organisms,” Masura said.
Scientists have developed a variety of methods to filter and identify plastics in the environment.
Researchers use vacuum filters to pull material from the air, they float plastic to the surface of ocean samples by adjusting water’s density and they use chemicals to decompose sample organisms but leave inorganic material behind.
Once it’s filtered, scientists can use infrared light to determine what kind of microplastics they’ve found.
“Every plastic has its own absorption of IR (light). It produces this fingerprint,” said Sherri Mason, a researcher and sustainability coordinator at Penn State Behrend, who published data on bottled water and microplastics last year.
The innovations in research have produced dozens of studies on different means of ingestion, but few researchers have stitched the research together or contemplated cumulative effects on people.
That’s why the Environmental Science & Technology paper is important, Mason said.
“I appreciate they were able to pull all these studies together and provide that bigger picture.”
After the release of Mason’s bottled-water research last year, The World Health Organization launched a health review of microplastics in drinking water, according to The Guardian.
The Environmental Science & Technology paper could provide a guide for that work, Mason said.
“There is still so much more that needs to be done,” Mason said. “We really need to do a human-health impact assessment of microplastics. This study is a really nice foundation.”
Cox said he hoped people considered the global impact of plastics.
“Single-use, unnecessary plastic is ending up back in our food chain,” Cox said. “The average person — as plastic increases, if we don’t mitigate this issue — our exposure risk is only going to go up.”