Micro- and nanoplastics (MNPs) are everywhere—from the air we breathe to the food we eat—but their impact on human health is not entirely clear. While cell culture and animal studies hint at potential harm, understanding what this means for people is far more complex.
Researchers like Matthew Campen, a biochemist and environmental scientist at the University of New Mexico, investigate how inhaled pollutants, including MNPs, affect cardiovascular and neurological health. He and his team focused on these particles’ accumulation and distribution in human organs.
Their findings, published in Nature Medicine, revealed that MNPs accumulated at higher levels in the brains of deceased individuals compared to livers or kidneys with a greater buildup in individuals with dementia.1 In addition, plastic concentrations were higher in 2024 than in 2016 across these organs, suggesting a steady rise in environmental plastic exposure. These results underscore the urgent need to understand exposure routes, uptake, clearance pathways, and the potential health consequences of MNPs, particularly in the brain.
To investigate the buildup of inhaled microplastics in human organs, researchers analyzed liver, kidney, and brain samples from autopsies conducted in 2016 and 2024. Traditional microscopic spectroscopy methods often miss the tiniest nanoplastics, which are likely to cross the blood-brain barrier and nestle in hidden parts of organs. This can lead researchers to underestimate the scale of tissue pollution with MNPs. To overcome this limitation, Campen and his team turned to pyrolysis gas chromatography-mass spectroscopy, a newer technique for detecting plastic residues in human tissue.
Their findings were striking. The brain tissue contained the highest levels of MNPs, while the liver and kidneys had comparable concentrations. Notably, the 2024 liver and brain samples had significantly higher MNP concentrations than the 2016 samples. Multiple factors, including age, sex, race/ethnicity, or cause of death did not influence these plastic concentrations. However, the year of death was a significant factor.
Curious whether this pattern existed in older brain tissue and if neurological conditions affected plastic accumulation, the researchers expanded their study. Analyzing brain samples from 1997–2013, they found higher plastic concentrations in more recent tissue. Campen’s team also observed greater particle buildup in the brains of individuals with documented dementia compared to those without.
When the team examined the types of plastics present, they found polyethylene was the most common, alongside polypropylene, polyvinyl chloride, and styrene-butadiene rubber. To visualize how these particles accumulate, the team used various microscopy techniques. Their images revealed aged, shard-like plastic fragments embedded in tissues. In the liver and kidney, these fragments ranged from one to five micrometers in size, while brain samples contained even tinier particles less than one micrometer in the parenchyma. In dementia cases, the fragments clustered inside of inflammatory cells and along blood vessel walls.
These findings suggest that environmental MNP levels are rising and may make their way into human organs at increasing rates. While the study uncovered an association between plastic accumulation and certain health conditions, larger and more diverse studies are needed to confirm long-term trends and potential health risks.
- Nihart AJ, et al. Bioaccumulation of microplastics in decedent human brains. Nat Med. 2025.
