The human microplastic burden has been linked to stroke, dementia and other serious health risks, experts say.
Brain tissue from deceased donors in a 2016 to 2024 cohort was found to have microplastic concentrations seven to 30 times higher than matched liver or kidney samples, with the cumulative tissue burden rising by around 50 per cent across the eight-year period.
Donors with diagnosed dementia had the heaviest loads. Polyethylene was the most common plastic found, largely appearing as nanoscale, shard-like fragments.
The findings, set out in a new perspective article, draw on brain tissue analysis led by researchers at the University of New Mexico.
The wider article was authored by an international team headed by Dr Julio Licinio.
Dr Julio Licinio, lead author of the article and publisher and CEO of Genomic Press, said: “We are looking at an organ where the highest measured concentrations of microplastics meet the most consequential clinical endpoints in medicine.
“Cognition, mood, stroke, dementia. Treating this as a peripheral environmental concern, when the relevant peripheral organs carry less of the contaminant than the central one, has become difficult to defend.”
The article also highlights cardiovascular evidence that researchers say strengthens the case for treating microplastics as a brain health concern.
Patients undergoing carotid endarterectomy, a procedure to remove fatty plaque from the arteries that supply the brain, were found to have microplastics and nanoplastics inside plaque deposits.
Those whose plaque tested positive for the particles had a roughly fourfold increase in the combined risk of heart attack, stroke or death over 34 weeks of follow-up.
The authors note this is a brain finding as well as a cardiac one, because stroke is a brain outcome.
Animal data are now helping explain how the particles may reach the brain.
Polystyrene nanoparticles given orally to mice were shown to cross the blood-brain barrier, the protective layer that controls what enters the brain from the blood, within two hours of exposure.
The biomolecular corona, a layer of biological molecules acquired in transit, functioned as a passport for entry. Larger particles did not cross, but nanoscale particles did.
The article also focuses on a route for widespread exposure: ultra-processed food. Classified as Group 4 in the NOVA system, ultra-processed foods now supply more than half of calorie intake in the US.
They are also high-throughput routes for microplastic exposure through packaging migration during heating and storage, mechanical wear during industrial processing, and downstream contamination.
Independent of microplastic content, ultra-processed food consumption has been linked in large prospective cohorts to depression, anxiety, cognitive decline, stroke and dementia.
A meta-analysis of 385,541 participants found a 53 per cent increase in the odds of common mental disorder symptoms among those with the highest ultra-processed food intake.
UK Biobank data link the same dietary pattern to increased dementia risk.
The REGARDS cohort showed that a 10 per cent rise in relative ultra-processed food intake was associated with a 16 per cent increase in cognitive impairment risk and an 8 per cent increase in stroke risk, independently of adherence to Mediterranean, DASH or MIND dietary patterns.
Dr Nicholas Fabiano, of the University of Ottawa department of psychiatry and a co-author on the article, said: “The boundary between physical and mental health has always been more administrative than biological.
“Microplastics do not respect that boundary. The same particles that lodge in atheroma also reach the brain.
“The same dietary exposures that raise cardiovascular risk also raise risk for depression and dementia. We are looking at one problem with many clinical faces.”
