Microplastics Have Been Found Throughout the Human Body—Here’s Where

Microplastics Have Been Found Throughout the Human Body—Here’s Where

Microplastics have been found virtually everywhere on Earth, from the distant regions of the Arctic to drinking water.

And, according to a flurry of recent research, these bits of degraded plastic have also been discovered lurking inside us—in the kidneys, liver, and elsewhere throughout the body.

Microplastics range from 5 millimeters in diameter, or about the thickness of pencil lead, to 1 nanometer. Nanoplastics, which have also been found in humans, are even smaller and potentially more dangerous. 

Although research into body-bound plastic’s impact on health is in the early stages, scientists have become increasingly concerned about the substance’s potential effects.

Here are the places found to contain plastic that have experts particularly concerned.

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A study published in 2022 showed that researchers had detected bits of microplastics in nearly 80% of the 22 healthy people who had blood drawn. A few months later, scientists confirmed the presence of microplastics in human lungs. 

Given that plastic fragments are ubiquitous in the air, scientists believe the lungs are often the gateway for microplastics, and even more so, nanoplastics, to enter the body. 

“Nanoplastics are going to penetrate deeper into the body,” Mary Johnson, MD, PhD, a research scientist specializing in environmental health at Harvard T.H. Chan School of Public Health, told Health. “The larger particulate matter lodges into the lungs, but anything 2.5 micrometers or smaller can get into the blood via the lungs.” 

Once in the blood, the plastic particles can circulate in the body and accumulate in tissues.

A study published in the New England Journal of Medicine in March revealed that not only had researchers discovered microplastics and nanoplastics in the plaque of arteries, but that people who had plastic in arterial plaque had a greater risk of stroke or heart attack in the future.

The research included 257 people who needed to remove plaque from their carotid arteries, the blood vessels on the sides of the neck that carry blood and oxygen between the heart and brain.

Because of this build-up, everyone in the study was already at higher risk for cardiovascular disease, stroke, and death. However, after three years, the researchers found that 60% of participants who had microplastics and nanoplastics in their plaque were 4.5 times more likely to have had a stroke or heart attack or to have died of any cause. This was after they adjusted for other risk factors, such as a person’s age and whether they had type 2 diabetes.

“I don’t know how much scarier it can get,” Johnson said. “It was not only found in plaque, but it was associated with an increased risk of stroke, heart attack, and death.”

Although the study showed an association and did not prove causation, Johnson said the research marked a significant milestone. It suggested that plastic detected years earlier may be linked to future health outcomes—something that had previously only been shown in lab studies.

In a study published in January 2021, researchers found microplastics in four of the six placentas they analyzed. Three years later, a different team examined 62 placentas, discovering nanoplastics and microplastics in every single one. 

“The placenta will expose the fetus to these contaminants and possibly induce long-term effects on the development of different organs and biological systems,” Jacques Robert, PhD, chair of the University of Rochester Medical Center’s Department of Microbiology and Immunology, told Health

The research is still too new to determine precisely what effect, if any, placental microplastics have on fetal development. However, Robert said these plastics could impact a baby’s immune system, which can increase their risk for allergies, promote inflammatory and autoimmune diseases, and make them more susceptible to infection.

Research has found that ingested nanoplastic particles can cross the blood-brain barrier, which protects the brain from toxins. So far, researchers have only explored this in mouse models, finding microplastics in the brains of mice fed polystyrene nanoparticles.

“Finding plastic debris in the central nervous system raises questions about the potential impact on brain function, including memory and behavior, as well as microplastic’s influence on diseases such as Alzheimer’s,” Robert said.

Garcia said that while it’s important to limit the amount of plastic we use, it’s virtually impossible to avoid microplastics exposure altogether.

“It’s gone beyond that point,” he said. “It is so ubiquitous in our environment, there isn’t much we can do to completely avoid it.”

Even if we stopped producing plastic today, he added, the 8.3 billion metric tons produced since the 1950s would still be breaking into tiny pieces that infiltrate our environment and bodies.

The reassuring news is that researchers are pushing forward to determine how microplastics affect health.

“We are investigating this so we are all aware of what it’s doing,” Garcia said. “Down the line, if there are any policies that need to be put in place, we want to come from a data-driven source so we can say, ‘this is what we are seeing, what can we do to ensure we have a better future?’”

Moving forward, Johnson said researchers need to work together to standardize how everyone is measuring microplastics and nanoplastics in human tissues.

“There is not one gold standard that’s realistic to be able to replicate yet,” she said, noting that replication of studies such as the plaque one will be key for establishing whether there is a clear link—rather than an association—between plastic and health outcomes.

Future research will also need to examine the mechanism behind how microplastics might damage human health.

Robert said one hypothesis is that cells are unable to metabolize plastic, which may disrupt their ability to carry out duties and cause inflammation that leads to everything from Alzheimer’s disease to a heart attack.

Marcus Garcia, PharmD, a fellow at the University of New Mexico Health Sciences Center Department of Pharmaceutical Sciences, told Health he wants to see research assessing how specific types of plastic—or the chemicals that make them—affect health outcomes. 

“The dose is the poison,” he said. “At what level is it okay for us to have this accumulation? We need to know: At what levels do these create health conditions?”

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