Human brains contain higher concentrations of microplastics than other organs, according to a new study, and the amount appears to be increasing over time.
In the study, published Monday in the journal Nature Medicine, University of New Mexico Health Sciences researchers found microplastics in human brains have increased 50% over the past 8 years. They also found that people with dementia had up to 10 times as much plastic in their brains as everyone else.
Microplastics are tiny fragments of degraded polymers that are found in the environment, including our air, water and soil, a news release explained. Previous studies have already shown these substances have made their way into the human body.
The lead researcher, toxicologist Matthew Campen, said the rate of accumulation they found mirrors the increasing amounts of plastics waste on the planet. And he said in the news release that their findings should trigger alarm about the potential impact on human health.
“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,'” he said.
The study compared liver, kidney and brain tissue samples from autopsies conducted in 2016 and 2024, and found “substantially higher concentrations” in the 2024 brain tissue. The researchers also conducted similar analysis on older and more recent autopsies for people who died with confirmed dementia diagnoses, and found “far greater” concentrations.
While it’s unclear how particles are actually being transported into the brain, Campen said the size of the micro- and nanoplastics, measuring 200 nanometers or less, are not much larger than viruses and therefore small enough to cross the blood-brain barrier.
In the study, researchers detected 12 different polymers, the most common of which was polyethylene, widely used for packaging and containers, including bottles and cups, the release noted.
Campen suspects most microplastics in the body are ingested through food, particularly meat.
“The way we irrigate fields with plastic-contaminated water, we postulate that the plastics build up there,” he said. “We feed those crops to our livestock. We take the manure and put it back on the field, so there may be a sort of feed-forward biomagnification.”
The team also found high concentrations of plastic in meat bought at grocery stores.
As for the higher levels found in the brains of dementia patients, the researchers noted the study was not designed to prove whether that was the cause of symptoms — it may be the reverse, that the disease process allows more accumulation to happen.
“Atrophy of brain tissue, impaired blood–brain barrier integrity and poor clearance mechanisms are hallmarks of dementia and would be anticipated to increase [micro- and nanoplastic] concentrations,” they wrote.
