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Microplastics likely block blood circulation, causing impaired brain function, according to a new study conducted in mice.
The study, published in Science Advances, used imaging techniques to work out the mechanism through which microplastics impact the brain.
Microplastics are plastic particles measuring less than 5 millimetres in diameter. They originate from small plastic pellets produced for specific purposes, and when larger plastic products in the environment degrade, weather, and fragment over time.
These micron-sized particles are everywhere, from oceans to land and from Antarctic ice to human settlements. They can be transported through the atmosphere, eventually making their way into our bodies.
But “what is the mode of microplastics affecting the brain and the mechanisms that they exert their effects remain uncertain,” the researchers wrote in the study.
The researchers tried to find answers by imaging microplastics in the mouse brain while the animal was awake.
The imaging tracked microplastic movement in the body and observed these particles in the blood vessels of the mouse cerebral cortex, a part of the brain that controls awareness, communication, memory, sensation, understanding, and the initiation of voluntary movement.
Their analysis suggested that immune cells detect these microplastics and engulf them in the blood stream. This, in turn, obstructs blood vessels, affecting blood flow, impairing brain function and affecting cognitive function in mice. The body is also unable to clear this for at least a week.
Further, microplastics could also potentially block movement in mice. These animals also display abnormalities in neurobehavioral regulation, resembling depressive states. Weight loss in mice was also observed. This could potentially be explained by altered movement, causing changes in feeding behaviour.
Previous studies have shown that microplastics affect the brain through two routes. The first is that these particles indirectly control brain function through peripheral organs. Second, they could be crossing the blood brain barrier, which acts as a filter, preventing toxins and pathogens in the blood from entering the brain.
The researchers say that the mechanism proposed in this study could be the third type of potential control through which microparticles affect brain function.
The study also warns that it is too early to extrapolate the findings in mice to humans. Humans and mice have different immune systems, cardiovascular and cerebrovascular (blood flow to the brain) circulatory systems.
Further, the circulating blood volume in humans is roughly 1,200 times greater than that of mice. There are also differences in the diameters of blood vessels, which would greatly reduce the degree of the obstruction in humans, the study noted. While the internal diameter of the coronary arteries in the human heart is about 4 mm, it is less than 100 micrometres in mice.
“Consequently, there is uncertainty regarding whether microplastics will induce or influence the obstruction in human blood vessels,” the researchers wrote in their paper.
Still, the researchers highlighted that the potential impact of microplastics on neurological disorders such as depression and cardiovascular health in humans, is concerning.
The researchers call for increased investment in this area of research to fully comprehend the health risks posed by microplastics in human blood.