Microplastics are common in people's everyday environments, and research is ongoing on microplastics in the human body.
Recent study findings revealed that microplastics can be present in the brain's olfactory bulbs.
While there is limited research, there could be certain health implications, such as an increased risk for neurodegenerative diseases because of exposure to microplastics.
Microplastics permeate the environment, and human beings are frequently exposed to them. Research is ongoing about how microplastics accumulate in people and the related health risks.
A study published in JAMA Network Open confirmed that microplastics can be present in the olfactory bulbs of the brain in people, based on their analysis of 15 deceased people.
While more research can help confirm these findings, the results support that the olfactory pathway, which has to do with smell, could be a way for microplastics to enter the brain.
Evidence suggests that microplastics may travel to several areas of the human body, such as the bloodstream and the colon. However, as researchers of this study note, “While MPs [microplastics] have been detected in various human tissues, their presence in the human brain has not been documented.”
This study was an opportunity to look for the presence of microplastics in the olfactory bulbs of the human brain. The olfactory bulbs are a critical component of people's ability to smell. Researchers of this study note that the olfactory pathway from the neurons in the nose to the brain could allow certain substances into the brain.
For this study, researchers examined the olfactory bulbs of fifteen deceased individuals between the ages of thirty-three and one hundred. Before death, all individuals were residents of São Paulo for over five years, and all had undergone coroner autopsy.
The researchers gathered data on underlying diseases and what the participants did for a living from the next of kin. Researchers excluded individuals who had had neurosurgery. They used two stillborns as negative controls but could only analyze one sample from this group. Among participants, two showed evidence of previous ischemic stroke, and one had a subarachnoid hematoma because of a ruptured aneurysm.
The researchers used several methods to avoid outside contamination of samples with microplastics. Overall, researchers identified microplastics in eight of the fifteen individuals. The most common type of polymer they identified was polypropylene, and particles were the most common shape identified.
The results highlight microplastics' presence in another body organ and suggest that the olfactory pathway may be a way for microplastics to reach the brain.
Tracey Woodruff, PhD, professor and director of Environmental Research and Translation for Health (EaRTH) Center at the University of California, San Francisco, who was not involved in the study, commented with her thoughts on the study to Medical News Today:
“It was very thorough. It wasn't very big…so it's not as large as some of the other studies. It's really concerning that we're seeing microplastics measured in brain tissue, note not all of the brain tissue, but we shouldn't be surprised given that microplastics have been measured in all the other human tissues that have been examined to date. [M]icroplastics are everywhere and they're also in us.”
Heather A. Leslie, PhD, an independent scientist specializing in nanoplastic and microplastic analysis and problem-solving based in Amsterdam, who was also not involved in the study, also commented with her thoughts on the study to Medical News Today:
“This study is an important first step in understanding what kind of real-world microplastic accumulation we can expect in human olfactory tissue. The study identified a very low number of plastic particles (between 1 and 4) in half of the cadavers tested, though it is difficult to compare these data to other studies because no microplastics concentrations are reported per gram tissue.”
“More sensitive detection techniques and more rigorous quality control should be applied in the future to see if the results can be replicated,” she added.
More research is required to understand the full health implications of microplastic exposure and its influence on the brain.
“Finding one or two microplastics in parts of the brain does not directly prove there are health implications in a given population, but these data do compel us to find out. Measuring health effects requires additional work to collect the toxicological effect data that tell us which doses are dangerous and which are not,” Leslie noted.
However, microplastic exposure could contribute to certain brain-related issues.
The study authors note that some microplastics are associated with particulate matter, and exposure to particulate matter could contribute to problems like dementia. In addition, exposure to particulate matter and microplastics could lead to problems in brain development.
“A component of particulate matter air pollution is definitely made up of microplastics. We know that exposure to particulate matter air pollution is associated with neurodegenerative effects. [T]here's different studies showing that it can increase the risk of neurodegenerative diseases like Alzheimer's. [T]he fact that we're finding microplastics in the brain means that that can disturb brain function which could increase the risk of neurodegenerative disorders,” Woodruff said.
This research does have some limitations that warrant caution and continued research.
All of the deceased individuals had lived in the same area for over five years, meaning that future studies could include data from people in other regions. It also only included a small number of participants, and a great majority of the participants were male, which does limit the findings. It's possible that the unique health and life circumstances of these people could have impacted the results. Reports from next kin could be inaccurate as well.
The study also only included adults in a specific age range, so additional research with other age demographics could be useful. As this study focused on one specific area, it may also be helpful to look for microplastics in other areas of the brain.
The researchers acknowledge that while the olfactory pathway was the likely route that these microplastics ended up in the olfactory bulbs, multiple entry points were possible. They also note the possibility of confounding because the biological matrix of olfactory bulb tissues is similar to a few polymeric materials.
For some subjects, researchers could not use one specific method of analysis, which could have limited the findings. Researchers couldn't detect nanoplastics, so they may have missed some plastics that were present that could be dangerous to health. They also had some struggles analyzing the stillborn controls.
Furthermore, Woodruff noted, “We know there are exposures to microplastics in the developing fetus.” This warrants caution in making assumptions that using stillborns was an appropriate control.
“I expect much more extensive research on the accumulation of real-world microplastic in the brain in the coming years. If microplastic is found to be widespread in the brain, I am sure it will also spur more neurotoxicological research. More sensitive detection techniques and rigorous quality control should be applied in the future to see if these results can be replicated,” Leslie added.
Still, the results point to a need to address the potential dangers of microplastics. Woodruff noted the following about action at the individual and governmental level:
“For individuals, you can be exposed to microplastics through drinking water, through food consumption, [and] through air. One area that individuals have more control over for microplastic pollution is in food. There's really simple things that people can do: don't microwave in plastics, try and use less plastic containers, [and] eating fresh fruits and vegetables and lower on the food chain improve your resiliency to exposure to toxic chemicals in general. [T]he government should be focusing on looking at the range of options they have to address microplastics from a policy perspective.”
— Tracey Woodruff, PhD
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