Microplastics Found in Human Brains Raise Health Concerns

More plastics in the environment seem to mean more in our bodies, though its impact is unclear

Elise Ceyral,

AARP

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Published February 12, 2025

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Inside the human body, you’ll find muscles, bones, blood and organs — but plastic?

As plastics have become a central part of our lives, health professionals have grown increasingly wary about the levels of tiny plastic particles in our bodies. Microplastics are smaller than a sesame seed. Nanoplastics are even smaller, small enough to enter the body’s cells.

Recent studies have found them in human lungs, kidneys, livers, bladders and more. A new study in Nature Medicine found them at alarming levels in the brains of people who had died with dementia and without dementia.

In autopsy tissues, the researchers found higher levels of the plastic particles in brain samples than in liver and kidney samples — seven to 30 times higher. And brain tissue from people who died more recently, in 2024, had 50 percent more plastic than from people who’d died eight years earlier, in 2016. The overall weight was estimated at seven grams, about the weight of a small plastic spoon.

“I have yet to encounter a single human being who says, ‘There’s a bunch of plastic in my brain and I’m totally cool with that,’” Matthew Campen, professor of pharmaceutical sciences at the University of New Mexico and a lead author of the Nature Medicine study, said in a news release.

The higher levels seen in 2024 than in 2016 seem to mirror the rise in global plastic production, the researchers say. Some microplastics come from the breakdown of larger plastic items, such as synthetic clothing and food packaging, while others are created small, such as microbeads, added to beauty products before the U.S. government ban took effect in 2019. The tiny particles can enter our bodies through the air we breathe, the foods we eat, water we drink, as well as skin contact.

“We now hypothesize that most of the plastics we are seeing like these are actually extremely old degradation products,” Campen said in a news conference.

The brains of people diagnosed with dementia had higher plastic levels

In a subset of autopsy tissues from people diagnosed with dementia, levels of the tiny plastics were about five times higher than in the brains without dementia. But it remains unclear whether microplastics increase the risk for the disease or whether dementia somehow leads to the accumulation of microplastics in the brain.

“The findings for dementia thus far don’t prove a causal relationship,” says Gary Small, M.D., chair of psychiatry at Hackensack University Medical Center and behavioral health physician in chief at Hackensack Meridian Health. Small did not participate in the study.

“We do know that with dementia, there’s damage to the blood-brain barrier, which means that potential toxins [including microplastics] from the bloodstream can leak into the cerebrospinal fluid to get to the brain. So maybe we’re seeing higher counts because of that leakage,” he says. “Or it could be that the nanoplastics are causing damage.”

Either way, such high levels of microplastics are concerning, Campen said in a news release. “I never would have imagined it was this high. I certainly don’t feel comfortable with this much plastic in my brain.”

In 2024, a study published in the New England Journal of Medicine found microplastics in nearly 60 percent of the participants’ carotid arteries. These people experienced a 4.5 times higher risk of heart attack, stroke and death at a 3-year follow-up.

Science-backed ways to reduce your risk for dementia

Whether microplastics are harmful to your brain is an open question. But as researchers look for answers, there are key lifestyle behaviors you can adopt now to help lower your risk of cognitive decline. Here are a few important ones. For the full list, go here:

Get your hearing checked. Hearing loss may reduce neural stimulation and increase social isolation. AARP offers an at-home hearing test.
Keep your cholesterol in check. High levels of LDL — or “bad” — cholesterol in the brain raise stroke risks and boost two proteins, amyloid and tau, that are known to clump up in Alzheimer’s disease.
Prevent or reduce high blood pressure. Blood pressure is considered elevated when it rises above 120 mm Hg systolic (the top number) and above 80 diastolic mm Hg (the bottom number). Some ways to lower blood pressure include a healthy diet, regular exercise and maintaining a healthy weight.
Exercise regularly. “When you exercise, it gets your heart to pump oxygen and nutrients to your brain and improves the brain circulation of these essential nutrients,” Small says. This could help reduce your risk for dementia.
Stimulate your brain. Avoid activities that leave you mentally passive, says Dylan Wint, M.D., director of the Cleveland Clinic’s Lou Ruvo Center for Brain Health in Las Vegas. Hours sitting in front of the TV, he says, might not make you feel very stimulated. More mentally engaging activities include reading, learning a new language, or picking up a new instrument.
Stay connected to others. People who are socially isolated are at higher risk for dementia. Strong relationships support cognitive health.
Cut back on alcohol. Alcohol raises your risk for obesity, depression and hypertension. Recent studies suggest no amount of alcohol is good for the brain.