A new study published in Nature Medicine has revealed the presence of microplastics – tiny fragments of degraded plastic – in human brain tissue. While previous research has identified microplastics in organs such as the liver, kidneys, and placenta, this study suggests that the brain may be especially vulnerable to these tiny synthetic particles. The findings raise pressing questions about the potential effects of plastic buildup on brain health, particularly in relation to neurodegenerative diseases.
The amount of microplastics and nanoplastics in our environment has grown exponentially over the last 50 years. These tiny plastic particles, ranging in size from microscopic to the width of a pencil eraser, are now found everywhere – in the air we breathe, the water we drink, and the soil where our food grows. While it is known that these particles are making their way into the human body, lodging in organs like the liver, kidneys, and even the placenta, the extent of their accumulation and their potential for harm are not fully understood.
Although some studies in cells and animals have shown negative effects, those studies often used amounts of microplastics much higher than what humans are typically exposed to. A real understanding of the issue requires knowing how much plastic is actually accumulating in different human tissues. Until recently, we lacked reliable methods for measuring these tiny particles, particularly the smallest ones (nanoplastics), in human tissues.
Researchers at the University of New Mexico Health Sciences, led by toxicologist Matthew Campen, developed a new way to detect and measure microplastics in human tissue. They previously used this method to examine placentas and testes. In this new study, they applied the technique to human brain tissue.
The brain tissue samples came from the New Mexico Office of the Medical Investigator, which keeps tissue from autopsies for several years. The researchers compared older tissue samples (from around 2016) with more recent samples (from 2024). All the brain tissue analyzed was from the frontal cortex, the area of the brain located behind the forehead.
To measure the microplastics, the researchers first chemically dissolved the tissue. This created a liquid mixture. They then spun this mixture at very high speeds in a machine called a centrifuge. This process separated out any undissolved materials, including plastics, into a small pellet. Next, they heated this pellet to a very high temperature (600 degrees Celsius), a process that breaks down the plastic.
As the plastics burned, they released gases. The researchers then used a sophisticated instrument called a mass spectrometer to identify the specific types of plastic based on the gases released. This allowed them to determine both the quantity and type of plastic present in the original brain tissue. The team could identify 12 different polymers. In addition to this chemical analysis, the researchers also used powerful microscopes, including a transmission electron microscope, to directly visualize the plastic particles in the tissue.
The researchers found surprisingly high levels of microplastics in the brain tissue. The concentration of plastics in the brain was much greater than that found in the liver or kidney samples. It was also higher than levels previously reported in placentas and testes. The median amount of total plastics for 2024 brain samples was 4917 micrograms per gram, and for 2016 samples, it was 3345 micrograms per gram. For comparison, the 2024 liver and kidney samples were 433 and 404 micrograms per gram, respectively.
Even more concerning was the finding that the amount of plastic in the brain was increasing over time. Brain tissue samples from 2024 had significantly higher levels of microplastics than samples from 2016, representing an approximate 50% increase in just eight years. The predominant type of plastic found in the brain was polyethylene, a common plastic used in packaging, bottles, and cups.
Using electron microscopy, the researchers were able to see very small, sharp-edged plastic particles, some as small as 200 nanometers in size (which is only slightly larger than some viruses). These tiny particles are small enough to potentially cross the protective barrier that normally separates the bloodstream from the brain, although the exact mechanism by which these plastics are entering the brain is still unknown.
To look at trends over a longer time period, the researchers also analyzed brain tissue samples from the eastern United States, dating back as far as 1997. These older samples showed lower levels of microplastics, supporting the idea that plastic accumulation in the brain is increasing over time.
Another striking finding was that brain tissue from individuals who had been diagnosed with dementia contained significantly higher levels of microplastics – up to 10 times more – than brain tissue from people without dementia. While the study does not establish a direct causal link between plastic accumulation and neurodegenerative diseases, it raises important questions. The researchers speculate that microplastics could contribute to neurological conditions by obstructing blood flow, interfering with neural connections, or triggering inflammation in the brain.
“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.”
He believes that food, especially meat, is the primary source of microplastics entering the body, as commercial meat production tends to accumulate plastic particles within the food chain.
“The way we irrigate fields with plastic-contaminated water, we postulate that the plastics build up there,” Campen 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.”
How to Avoid Microplastics and Future Research Directions
A separate commentary on the study, published in Brain Medicine, emphasized the significance of these findings and the urgent need for further investigation. The commentary noted that while the presence of microplastics in the human brain is concerning, scientists still do not fully understand their impact on brain function. It is unclear whether microplastics actively contribute to neurodegenerative diseases or whether people with dementia accumulate more plastic simply because their brains are less able to clear it.
“The dramatic increase in brain microplastic concentrations over just eight years, from 2016 to 2024, is particularly alarming,” said Nicholas Fabiano from the University of Ottawa’s Department of Psychiatry, the lead author of the commentary. “This rise mirrors the exponential increase we’re seeing in environmental microplastic levels.”
“It is important for the public to be aware of the increasing amounts of microplastics in the environment and uptake into our bodies. We should also understand the methods available to help reduce microplastic intake while research continues seeking methods to their removal from our bodies, which continues to be scarce in evidence.”
Animal studies have suggested that microplastics could affect brain health. Experiments on fish have shown that exposure to nanoplastics impairs swimming ability and hunting behavior. In mice, prolonged exposure to microplastics led to memory deficits, inflammation, and reduced levels of key proteins involved in brain function. While these studies indicate potential risks, more research is needed to determine whether similar effects occur in humans.
The commentary also highlighted the increasing presence of microplastics in food and water. People who drink bottled water, for example, ingest significantly more microplastics than those who consume tap water. Heating food in plastic containers has been shown to release billions of plastic particles into food, raising concerns about dietary exposure. Other sources of microplastic ingestion include seafood, processed foods, and even tea bags, which can release millions of tiny plastic particles when steeped in hot water.
“Bottled water alone can expose people to nearly as many microplastic particles annually as all ingested and inhaled sources combined,” said Brandon Luu, an Internal Medicine Resident at the University of Toronto. “Switching to tap water could reduce this exposure by almost 90%, making it one of the simplest ways to cut down on microplastic intake.”
“Heating food in plastic containers—especially in the microwave—can release substantial amounts of microplastics and nanoplastics,” he explains. “Avoiding plastic food storage and using glass or stainless steel alternatives is a small but meaningful step in limiting exposure.”
Efforts to reduce microplastic exposure may help limit their accumulation in the body, but it is unclear whether this would lead to a reduction in brain plastic levels over time. The commentary suggested that more studies should focus on potential methods of eliminating microplastics from the body. Some research has indicated that plastic-related chemicals like bisphenol A can be excreted through sweat, raising the possibility that exercise or sauna use could aid in microplastic removal. However, no direct evidence currently exists to confirm whether the human body can effectively clear accumulated microplastics.
The commentary concludes by emphasizing the need for more research to establish safe exposure limits for microplastics and to understand the long-term health consequences of exposure. Large-scale studies in humans are needed to determine the relationship between microplastic exposure and the development of chronic diseases. Improved methods for measuring microplastics in living humans are also essential for tracking accumulation and assessing the effectiveness of strategies to reduce exposure. It is also important to research ways to remove plastics from the body.
“We need more research to wrap our heads around microplastics—rather than wrapping our brains in them—since this could be one of the biggest environmental storms most people never saw coming,” remarked David Puder, host of the Psychiatry & Psychotherapy Podcast.
The study, “Bioaccumulation of microplastics in decedent human brains,” was authored by Alexander J. Nihart, Marcus A. Garcia, Eliane El Hayek, Rui Liu, Marian Olewine, Josiah D. Kingston, Eliseo F. Castillo, Rama R. Gullapalli, Tamara Howard, Barry Bleske, Justin Scott, Jorge Gonzalez-Estrella, Jessica M. Gross, Michael Spilde, Natalie L. Adolphi, Daniel F. Gallego, Heather S. Jarrell, Gabrielle Dvorscak, Maria E. Zuluaga-Ruiz, Andrew B. West, and Matthew J. Campen.
The commentary, “Human microplastic removal: what does the evidence tell us?,” was authored by Nicholas Fabiano, Brandon Luu, and David Puder.
