Alarming Rise in Microplastics Levels in Our Brains

Microplastics have been detected in human brains at far higher concentrations than in other bodily organs—and levels are increasing, having risen 50 percent in eight years. This is the conclusion of a team of researchers from the University of New Mexico (UNM), who said the findings should trigger alarm. The rate of microplastic accumulation in our brains, they said, mirrors the increasing amount of plastic waste across the Earth. "This really changes the landscape. It makes it so much more personal," UNM toxicologist professor Matthew Campen said in a statement. "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'." Microplastic (smaller than 5 millimeters in size) and nanoplastic (under 0.001 millimeters) pollution have become ubiquitous in the environment and can get into the very food we eat. These particles have been found in various bodily organs—including the kidney, liver, placenta and testes—although not at such concentrations as now seen in the brain, the team said.

In their study, Campen and colleagues studied samples of human brain tissue donated by the New Mexico Office of the Medical Investigator (OMI) that were collected via autopsy. All of the samples were collected from the so-called frontal cortex—the brain region found above and behind the eyes that had been linked to various capabilities from abstract thinking through to motor function. As the OMI is required by law to retain tissues from autopsies for seven years before disposal, the samples dated back to 2016. The team compared the oldest samples with tissue collected in 2024. The team's analysis involved chemically dissolving tissue from the samples into a kind of slurry, and then separating out the undissolved plastic by spinning the slurry in a centrifuge. They then used a mass spectrometer to determine the chemical makeup of the plastics that had previously been in the brain tissue. The researchers identified 12 different types of plastic within the samples. The most common was polyethylene, which is used, among other things, to make plastic bottles and cups. Microplastics tend to gather in fat cells in the insulating sheath that wraps around the brain's neurons and helps to regulate signal transmission—this accumulation may explain why microplastic concentrations in the brain are higher than in other organs, the team said.

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Examining tissues with the highest polymer concentration via a transmission electron microscope, the team found that the samples contained clusters of sharp plastic shards that were only two-to-three times the size of viruses, at just 200 nanometers across. For comparison, a strand of human hair would typically be around 90,000 nanometers in diameter—some 225 times thicker. Such nanoplastics are small enough that they can cross the blood–brain barrier, the membrane that evolved to protect the central nervous system from toxins. It's unclear at present how the particles are being transported in the brain, the researchers said. What is also unclear, Campen cautions, is what affect the microplastics might be having in the brain—but previous studies have linked microplastic exposure in the body to various health complications. A study presented last week, for example, found an association between microplastic concentrations in the placenta and the risk of preterm birth. While plastic is considered biologically inert—which is why it can be used in implanted medical devices—it is possible that the physical presence of the particles is the issue. "We start thinking that maybe these plastics obstruct blood flow in capillaries," Campen said. "There's the potential that these nanomaterials interfere with the connections between axons in the brain. They could also be a seed for aggregation of proteins involved in dementia. We just don't know." The team reported that the brain tissue samples from the subjects who had been diagnosed with dementia contained as much as 10 times more plastic than their peers. However, it should be noted that only 12 dementia patients' samples were analyzed—and the study can draw no conclusions as to whether microplastics cause dementia symptoms, or whether the plastic accumulation was accelerated by the disease itself. Campen said most of the microplastics that end up in our bodies arrive there via food—meat in particular, as commercial meat production concentrates plastics across the food chain. The team's studies of store-bought meat would appear to support this hypothesis, with high concentrations of plastics recorded. "The way we irrigate fields with plastic-contaminated waste, we postulate that the plastic builds 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." Microplastic and nanoplastic pollution in the environment is fated to grow, the researchers warn—for even were we to cease plastic production tomorrow, existing polymers would still be around to decompose into micro- and then nanoscopic particles.

The findings have been met with mixed responses from scientists not involved in the research. "Without doubt the increasing presence of plastic particles in the environment and potential negative effects on humans are a concern," said environmental toxicologist professor Theodore Henry of Heriot-Watt University in the U.K. "The difficulty in assessing the accumulation of plastic particles in internal organs because of a lack of analytical methods is addressed to some extent in this paper and this advancement is noteworthy. "The authors of this article correctly note in their conclusion that their results of detection of plastic polymers in tissues are associative and not linked to any negative health outcome." Chemist professor Oliver Jones of the Royal Melbourne Institute of Technology in Australia, however, noted that the study's methodology had some limitations. "The authors tested 28 brain samples from 2016 and 24 from 2024, which is only 52 samples in total. There is not enough data to make firm conclusions on the occurrence of microplastics in New Mexico, let alone globally," he said. "Only data from two years—2016 and 2024—are presented," he added. "You simply can't make a trend from data from just two years. Data from 2017–2023 would be needed to say if there was an actual trend or if it was just a random variation. "Overall, the work is interesting, but the low sample numbers and potential analytical issues mean that care should be taken when interpreting the results." Newsweek has contacted Campen for additional comment. Do you have a tip on a health story that Newsweek should be covering? Do you have a question about microplastics? Let us know via science@newsweek.com.

Reference:

Nihart, A. J., Garcia, M. A., El Hayek, E., Liu, R., Olewine, M., Kingston, J. D., Castillo, E. F., Gullapalli, R. R., Howard, T., Bleske, B., Scott, J., Gonzalez-Estrella, J., Gross, J. M., Spilde, M., Adolphi, N. L., Gallego, D. F., Jarrell, H. S., Dvorscak, G., Zuluaga-Ruiz, M. E., Campen, M. J. (2025). Bioaccumulation of microplastics in decedent human brains. Nature Medicine. https://doi.org/10.1038/s41591-024-03453-1