Key Points:
- The brain accumulates 7 to 30 times more microplastics than the kidney and liver.
- More studies are needed to confirm if microplastics contribute to neurodegeneration and Alzheimer’s disease.
Plastic is one of the many products made from crude oil. Air pollution, a byproduct of burning oil, has well-known health consequences, such as premature death. Now the health consequences of other crude oil byproducts are coming to light.
Microplastics and nanoplastics are microscopic and nano-sized pieces of plastic that are purposely made for cosmetic products or are a byproduct of plastic debris. They have been found in human placentas, testis, and blood vessels, increasing the risk of heart attack and stroke. Some individuals, such as electric vehicle and rocket manufacturer Elon Musk, believe that microplastics and nanoplastics pose no health risk.
However, considering the presence of plastic in humans was only discovered this year, it is too early to make definitive conclusions on whether they are harmful. This could be why the World Health Organization has said there is limited evidence that microplastics cause significant harm to humans. It could be that foreign objects lodged within organs and tissues pose a health risk. Moreover, measuring microplastics in different tissues of the body is an active field of research. A recent preprint study from University of New Mexico showed that microplastics accumulate in human liver, kidney, and brain.
Scientists Discover Plastic in Human Brain, Liver, and Kidney Samples
Tissue samples are routinely collected during autopsy procedures and stored for later use. Taking advantage of this, University of New Mexico researchers procured post-mortem human liver, kidney, and brain samples acquired in 2016 and 2024. Unfortunately, limited demographic data was obtained on the individuals the samples were taken from, although their average age was around 50 and both males and females were well represented.
The samples were carefully mixed and the microplastics isolated to determine their concentration. The results showed that the liver and kidney samples exhibited similar microplastic concentrations. Moreover, the brain samples, which were taken from the frontal cortex — the part of the brain responsible for reason and self-control, had 7-to-30-fold higher concentrations of microplastics than both the liver and kidney. These findings suggest that the brain accumulates dramatically more microplastics than other organs.
The authors reason that since plastics are lipophilic — attracted to fat, they tend to accumulate more in fat. The brain has the second highest amount of fat, only after fat tissue, which may be a contributing factor to high brain microplastic concentrations. Furthermore, the brain receives 25 to 30% percent of the blood pumped from the heart, suggesting that more microplastics from our blood can make it to the brain relative to other organs and tissues. More studies will be needed determine why microplastics accumulate in the brain more than other tissues.
The Etiology of Alzheimer’s
The cause of Alzheimer’s disease (AD) in 95% of patients is unknown. In other words, scientists have yet to figure out what causes AD. Moreover, many pharmaceutical drugs have failed to treat AD for the same reason. These failed drugs target amyloid-beta accumulation, a hallmark of AD that is worsened with nanoplastics. Furthermore, microplastics have been shown to promote the progression of AD by inducing brain inflammation in a mouse model.
Inflammation is thought to be one of the underlying causes of aging. Moreover, brain inflammation has been proposed as the central cause of AD. It follows that if microplastics accumulate in the brain and trigger inflammation, they may at least contribute to the progression of cognitive impairment and AD. Of course, more studies are needed to determine if this is true, but the idea that microplastics are a major contributor to the uptick in AD incidence in the past few decades is plausible.
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