New studies show the discovery of microplastics in the brain and debate the related health effects. Experts unpack the evidence, limits of the studies, and what scientists are investigating next.
Microplastics are small pieces of plastic, ranging from one nanometer to five millimeters (a fraction of the width of a human hair to about the size of a grain of rice). Most microplastics come from larger plastic items like bottles, packaging, synthetic clothing, or car tires. Microplastics are found everywhere—in oceans, soil, food, drinking water, and air.
Research has shown that microplastics enter the body through eating food and drinking beverages that have been stored in plastic packaging, breathing in dust from indoor or outdoor air, and using everyday products like synthetic clothing, cookware, and personal care items.
Studies have found microplastics in human blood, lungs, the gut, placenta, and other organs, confirming that exposure is common. Finding microplastics in tissue samples shows that they are present but does not prove that they cause damage or disease.
Until recently, scientists believed the blood–brain barrier—a tightly regulated layer of cells lining the brain’s blood vessels that limits what can enter brain tissue—would protect the brain from microplastics. A new study has shown otherwise.
A research team at the University of New Mexico analyzed brain tissue from deceased individuals and found higher concentrations of microplastic fragments in a part of the brain called the prefrontal cortex than in liver or kidney samples. They also observed that overall microplastic accumulation in the human body appears to have increased over the last decade. Notably, brains from people with documented dementia had higher concentrations of microplastics than those without a dementia diagnosis. The study, published in February 2025 in Nature Medicine, does not prove cause and effect, but it does challenge the idea that the blood-brain barrier is protecting the brain from microplastics.
“There is a significant amount of plastic in the brain, and it is going up over time,” explains study author Matthew Campen, PhD, MSPH, toxicologist and distinguished professor at University of New Mexico College of Pharmacy.
Dr. Campen reminds that causation hasn’t been established and that more research is needed to understand how particles enter the brain and the long-term impact they have on brain structures and connections between brain cells. “We don’t think there is a causal relationship at this time between microplastics and dementia,” he says.
There are plausible explanations for the higher levels of microplastics in brains of people with dementia. For example, neurodegeneration might weaken protective barriers or clearance pathways, allowing more particles to accumulate. Dr. Campen adds that it is not known if microplastics contribute to dementia or if dementia makes the brain more vulnerable to microplastics.
Interestingly, not everyone agrees with the interpretation of the University of New Mexico’s findings. Shortly after publication, a group led by Fazel Monikh, PhD, professor of analytical chemistry at the University of Padua, published an article in Nature Medicine questioning aspects of the methodology and conclusions of the University of New Mexico researchers. Dr. Monikh explains, “The evidence does not yet justify definitive claims about microplastics in the human brain or their health effect. The science is still at a very early stage.”
Dr. Monikh also urges researchers to develop better laboratory methods and standards so results from different labs can be compared reliably: “We are far from being able to confidently say whether plastic particles can penetrate the human brain, how many particles are involved, which size or polymer types are relevant, and under what conditions translocation might occur.”
Research studies have shown that exposure to microplastics can contribute to central nervous system inflammation, which can lead to neurodegenerative disorders like Parkinson’s disease.
Sarju Ganatra, MD, a cardiologist and vice chair of research in the department of medicine at Lahey Hospital and Medical Center in Burlington, MA, led a study that found an association between living in coastal communities with higher levels of microplastics in the ocean and elevated risk for type 2 diabetes, coronary artery disease, and stroke.
He says he is troubled by the emerging evidence, particularly when it comes to brain health. “We don’t know if it is causation, but there is too strong an association to say there is no link whatsoever,” he says.
Dr. Ganatra is also the president of Sustain Health Solutions, which advocates for reducing the amount of plastic used in health care settings. Medical facilities rely on plastic for safety and infection control, from IV tubing and catheters to many single-use medical devices. Although single-use plastic prevents infection, it contributes to plastic waste that eventually fragments into microplastics.
Microplastics are impossible to avoid entirely, but there are reasonable steps you can take to reduce everyday exposure:
These steps may not make your life completely microplastic-free, but they can help lower your exposure as research continues to develop.
