Researchers have documented the presence of microplastics and nanoplastics in human brain tissue, with elevated concentrations detected in patients with dementia.
Alexander J. Nihart, of the University of New Mexico, and his colleagues analyzed postmortem tissue samples from human liver, kidney, and brain specimens collected in 2016 and 2024. The analysis revealed median brain microplastics and nanoplastic (MNP) concentrations of 4,917 micrograms per gram in 2024 samples, compared to liver (433 μg/g) and kidney (404 μg/g) tissues.
"Brain samples, all derived from the frontal cortex, exhibited substantially higher concentrations of MNPs than liver or kidney," the research team reported in Nature Medicine.
Brain samples from decedents with confirmed dementia showed median concentrations of 26,076 μg/g. "Notable deposition in cerebrovascular walls and immune cells" was observed in these cases, the investigators wrote. The study found no correlation between total plastics and age. However, "total mass concentration of plastics in the brains analyzed in this study increased by approximately 50% in the past 8 years."
Polyethylene comprised 75% of brain MNPs on average. Using electron microscopy, researchers identified "largely 100-200 nm long shards or flakes" in brain tissue.
The authors emphasized that causality cannot be established between MNPs and dementia. "Atrophy of brain tissue, impaired blood-brain barrier integrity, and poor clearance mechanisms are hallmarks of dementia and would be anticipated to increase MNP concentrations," they wrote.
"These results highlight a critical need to better understand the routes of exposure, uptake and clearance pathways and potential health consequences of plastics in human tissues, particularly in the brain," investigators concluded.
The research represents the first analysis of MNP distribution across major human organs using pyrolysis gas chromatography-mass spectrometry combined with electron microscopy and spectroscopic methods.
The authors declared no competing interests.