Microplastics Identified in Human Brain Tissue
Post by Meagan Marks
The takeaway
Microplastics and nanoplastics were found in postmortem human brain tissue at concentrations significantly higher than other organ systems analyzed, calling for further research into how these particles accumulate and affect neurological and psychiatric health.
What's the science?
Over the past half-century, the prevalence of microplastics and nanoplastics (MNPs) in our environment has risen exponentially, leading to widespread pollution and potentially harmful effects on our health. MNPs are produced when plastic products—such as clothing, food packaging, and automobile parts—break down into tiny, non-biodegradable polymers, entering ecosystems, food, water, and eventually, our bodies.
Preclinical studies have found MNPs in the organs of animals, and have linked their presence to inflammation, toxicity, and disease. However, the implications for human health remain unclear, especially regarding the average levels of MNPs within the human body, and how they distribute across organ systems. This week in Nature Medicine, Campen and colleagues analyze postmortem human brain, liver, and kidney tissue to assess the relative concentration of MNPs in the brain and how they compare to other organ systems within the body.
How did they do it?
To measure the concentration of MNPs in human brain, liver, and kidney tissue, the authors used pyrolysis gas chromatography-mass spectrometry, a precise technique for detecting and identifying micro and nanoparticles. They first isolated the MNPs from each sample by chemically digesting the tissue, leaving behind non-biodegradable products. The remaining solids were then compacted into a pellet and subjected to several analytical steps to determine both the quantity and identity of the MNPs present. This approach allowed the authors to compare the concentrations of various plastic types within each sample and across different subjects and organ systems. Notably, the authors included samples collected in both 2016 and 2024 to identify trends in MNP levels over the past eight years. Additionally, brain samples from patients with dementia were analyzed to assess MNP levels in neurologically diseased brains. It’s also important to note that all brain samples were taken from the frontal cortex, so more work is needed to explore MNP distributions across other brain regions.
What did they find?
After comparing samples from the liver, kidney, and brain, the authors found that the brain contained 7-30 times as many MNPs (with a median of 3,345 micrograms per gram of sample) as compared to the liver and kidney (with median values of 433 and 404 micrograms per gram of sample, respectively). The majority of the MNPs appeared as plastic shards or flakes and were made of a specific plastic called polyethylene, a common polymer found in food packaging, bottles, and automobile parts. The brain had the highest concentration of this plastic, which made up about 75% of all MNPs.
Interestingly, liver and brain samples from 2024 showed significantly higher concentrations of MNPs compared to the 2016 samples, with certain types of plastic—including polyethylene, polypropylene, polyvinyl chloride, and styrene butadiene rubber—specifically increasing. The total mass of these concentrations within samples had increased by 50% over the past 8 years, suggesting that environmental MNPs may be growing and leading to higher uptake by our bodies.
Additionally, dementia patients had significantly higher MNPs than other brain samples, with a median value of over 26,000 micrograms per gram of sample. This is likely due to a more permeable blood-brain barrier and impaired clearance mechanisms, which are hallmarks of the disease.
What's the impact?
This study found that the brain contains significantly higher levels of MNPs compared to the liver and kidney. While this discovery is important, there is still much work to be done, particularly in understanding how MNPs are taken up and dispersed throughout the brain, how they concentrate in different regions, and how they are cleared from the system. Given the rising levels of MNPs in our environment, it is crucial to investigate their potential role in neurological and psychiatric health.