NBC News
Brazilian scientists have found microplastics in the brain tissue of cadavers, according to a new study published Monday in the scientific journal JAMA Network Open.
In recent years, more and more research has been carried out on the presence of microplastics in almost all organs of the body, as well as in the bloodstream and in the plaque that clogs the arteries. The possibility of these ubiquitous pollutants reaching the human brain has been a major concern for scientists.
The latest research has focused on a part of the brain called the olfactory bulb, which processes information about smell. Humans have two olfactory bulbs, one above each nasal cavity. The olfactory nerve connects the olfactory bulb and the nasal cavity.
Some researchers have been concerned that the olfactory pathway may also be an entry point for microplastics on their way to the brain, beyond the olfactory bulb.
“Previous studies in humans and animals have shown that air pollution reaches the brain, and particles have even been found in the olfactory bulb, so We think that it is probably one of the first points through which microplastics reach the brain” said Dr. Thais Mauad, senior author of the study and associate professor of Pathology at the School of Medicine at the University of São Paulo, Brazil.
We think that it is probably one of the first points through which microplastics reach the brain.”
Dr. Thais Mauad Author of the study and Prof. of Pathology, University of São Paulo
Mauad and his team took tissue samples from the olfactory bulb of 15 carcasses of people who died between the ages of 33 and 100 Samples from eight of the bodies contained microplastics, tiny pieces of plastic between 5.5 and 26.4 micrometers in size.
In total, the researchers found 16 plastic fibers and particles in the fabrics. The smallest were thinner than the diameter of a human red blood cell which measures about 8 micrometers. The most common type of plastic found was polypropylene, followed by polyamide, nylon, and polyethylene vinyl acetate.
“Propylene is everywhere, in furniture, carpets, clothing,” Mauad explained. “We know that the place where we are most exposed to particles is indoors, because “All our houses are full of plastic.”
Matthew Campen, a toxicologist at the University of New Mexico who has studied microplastics in the brain, said the presence of microplastics in the olfactory bulb “is unique but not terribly surprising.”
“The nose is an important defense point to keep particles and dust out of the lungs,” Campen wrote in an email. “So seeing some plastics in the olfactory system, especially considering they are found everywhere else in the body, is completely expected.”
All our houses are full of plastic”
Dr. Thais mauad
Although it was not mentioned in the study, Campen believes it is likely that the samples also contained many nanoplastics, whose size ranges from 1 to 1,000 nanometers. A strand of human DNA is about 2.5 nanometers thick (a micrometer is 1,000 times larger than a nanometer).
The presence of microplastics in the olfactory bulb does not automatically mean that there are microplastics in other parts of the brain, such as regions related to cognition. It is not yet clear whether these particles can actually reach these parts of the brain via the olfactory bulb.
“There is evidence that very small airborne particles can reach the brain through the olfactory bulb, but this is not known to be a major route for trafficking such material to the brain,” Campen said.
The olfactory system is the pathway between the nose and the brain. This system detects odors by processing the tiny odor molecules given off by various objects, such as baked bread or a bouquet of flowers. These molecules stimulate the olfactory nerves, and the signals are processed in the brain as odor. Other particles can travel along these same pathways. Although rare, amoebas such as the Naegleria fowleri –larger in size than the microplastics found in the study– can reach the brain through the olfactory nerve.
“We thought that if bacteria can go through this pathway, microplastics could too,” Mauad said.
Campen explained that it is more Nanoplastics are likely to enter the brain through the bloodstream, It collects bits of plastic from the lungs or digestive tract, rather than the olfactory bulb. However, it is extremely difficult for particles, even from pharmaceuticals, to enter the brain through the blood. This is because the brain is surrounded by a semipermeable membrane called the blood-brain barrier. Research into microplastics in the body is still in its infancy. Whether these microscopic bits of plastic can cross the blood-brain barrier in humans is still a big question mark.
Most of what scientists know about the harmful health effects of the 4,000 chemicals used in making plastic and their health hazards has been limited to animal studies. A recent study showed that Exposure to microplastics through drinking water for three weeks caused cognitive changes in the brains of mice. The particles were also able to cross the blood-brain barrier.
Earlier this year, research was the first to link the presence of microplastics with higher mortality rates in people who had higher levels of microplastics in arterial plaque.
“We know that there is an inflammatory response when cells are exposed to microplastics in the lab,” said Dr. Mary Johnson, an environmental health researcher at Harvard’s T.H. Chan School of Public Health who was not involved in the research.
Johnson noted that neurological diseases, including dementia, has been linked to air pollution.
“The question is whether microplastics could be part of the puzzle,” he said. “Part of the concern is not just the particle itself, but the fact that “These plastics contain additives, some of which we know are potentially toxic.”