Few places on Earth — or in our bodies — seem to be free of microplastics.
Researchers in recent months have announced the discovery of microplastics traveling in the bloodstream of a handful of anonymous donors and embedded deep in the lung tissue of about a dozen patients awaiting surgery. Another recent study reported finding microplastics in placentas.
These discoveries have made for a dizzying series of headlines that some might find concerning — but the science remains far from settled.
What recent research makes clear so far is that microplastics are ubiquitous, that these particles enter peoples’ bodies regularly during inhalation or through consumption of food or drinks, and that they find their way into vital body systems.
Some studies of laboratory animals and cells grown outside the body suggest that there are reasons for concern about how these tiny pieces of plastics affect our physiology.
What remains less apparent is what risks to health, if any, these tiny particles pose at the concentrations they’ve been found. Scientists say the flurry of recent studies, and headlines, represent their first steps toward understanding the impact these particles have on our daily lives.
“We’ve identified there are microplastics in the air we breathe. We’ve found microplastics in the lungs. The next step is—so what? Does it matter that there’s plastic in the lungs?” said Laura Sadofsky, a researcher in respiratory medicine at Hull York Medical School in the UK “We don’t know the answer to that question at the moment.”
From 1950 until 2015, plastic production grew about 8.4 percent each year on average, according to an estimate published in the journal Science. Scientists have reported finding microplastic pollution more than 5 miles above sea level (from snow near the summit of Mount Everest) and also in the deepest parts of the ocean (including from seawater in the Marianas Trench).
Dick Vethaak, an emeritus professor of water quality and health at Vrije Universiteit Amsterdam, said scientists are just beginning to grapple with the potential consequences to human health.
“For me the most alarming thing is, we very likely have to deal with increasing concentrations of microplastics in the coming decades,” Vethaak said. “This will take another 10 years, 15 years before we can understand what’s going on here, if we’re dealing with a serious risk.”
What is a microplastic?
Microplastics can be found in the air we breathe, the dust that accumulates on our floors and in the shellfish we buy at the grocery store, studies suggest.
There is no single definition for what a microplastic is, but researchers generally describe them as any particle of plastic less than 5 millimeters in size, but larger than 1 micrometer.
They are often smaller than the tiniest grain of sand or a fraction of the width of a human hair.
The shape, size and chemical composition of these particles also vary, and researchers typically focus on identifying the most common polymers.
It’s the smallest particles that concern the researchers the most, Vethaak said. Researchers suspect they are more likely to penetrate deeply into the body and pass through protective membranes within.
Finding microplastics within the body takes meticulous, careful work. The risk of contamination is ever present.
“There’s plastic in every lab product we use,” said Kurunthachalam Kannan, an environmental chemist and professor in the department of pediatrics at the NYU School of Medicine, who in a recent study found that infants’ exposure to microplastics was about 15 times that of adults. “You have to be very careful in making these kinds of measurements.”
Sadofsky wore a cotton lab coat during experiments.
Much of the research to date on microplastics have been studies with a relatively small number of samples focused on identifying microplastics and determining exposure.
“Exploratory studies,” Kannan said.
Among the most interesting recent findings is Sadofsky’s research, which found microplastics in the lung tissue of living people, Vethaak’s discovery of microplastics in the bloodstream and Kannan’s work showing that infants might be among those most often exposed.
In Sadofsky’s study, researchers collected lung tissue from 13 people who were undergoing chest surgery. They broke down that lung tissue using a powerful acid, then filtered out the synthetic particles.
Then, they characterized the remaining material — much of it plastic — and used analysis technology to characterize the type of plastic. The researchers also ran blank samples with no lung tissue to ensure quality control.
Eleven of the 13 patients’ samples had microplastics in their lungs, with a total of 39 individual pieces of tiny plastic.
“We had a look in the human lungs at the different regions — upper, middle and lower lungs — we found microplastics in all regions of the lungs, including the lower levels,” Sadofsky said.
It’s not clear how well the findings could apply to others.
“They’re in hospital to have operations on their lungs but we have no idea if the microplastics have any effect on their health and we have no idea if the average person in Hull has similar levels of microplastics,” Sadofsky said.
In another study from The Netherlands published last month, researchers processed the blood of 22 anonymous donors, finding microplastics in 17 of the samples.
It was the first time microplastics have been found in blood samples, Vethaak said. It’s not clear how those studied were exposed to microplastics or if it has had any consequences to their health.
“We don’t know too much about their background,” said Vethaak, one of the study’s authors.
Many questions remain unanswered.
“There is plastic circulating in our bodies,” Vethaak said. “Are they excreted? What is the fraction excreted? Are they stuck somewhere in the system? Do they accumulate in certain organs? Do they pass the blood brain barrier or the placenta?”
Risk from microplastics might skew toward certain groups.
Kannan’s lab analyzed the feces of nine babies and 10 adults.
“The infant feces samples contained, on average, 15 times more PET than adult specimens,” Kannan said, referring to polyethylene terephthalate, which is common in clothing and containers for foods.
Kannan suspects babies and other children have much higher exposures because they crawl on floors that could be laden with microplastics, put most everything in their mouths and often rely on plastic sippy cups, teethers and toys.
“There are many sources of exposure for infants,” Kannan said.
Studies involving animals or cells grown in laboratory environments suggest microplastics could cause inflammatory responses, oxidative stress and cell damage. But many of these studies involved highly concentrated exposures or commercial-quality plastic, research says.
The data from the most recent studies could propel more research into microplastics and health.
“None of these studies are associating with any health outcomes. It’s all a measure of ‘are we exposed?’” Kannan said. “The research is in its childhood.”
Kannan said recent findings have laid the groundwork for the US federal government to invest in studies focused on toxicology or epidemiology.
Exposure is now clear, he said. “The question is how toxic are they and at what level are they toxic?”
European researchers are ramping up their efforts.
In 2019, The Netherlands jumpstarted 15 projects on microplastics and then extended additional funding to a microplastics research research consortium last year.
The European Union committed more than $32 million toward five micro- and nanoplastics studies from 2021-2025.