Scientists in Brazil Discover Microplastics in Brain Tissue, According to New Study Published on September 16 in JAMA Network Open.
In recent years, researchers have found microplastics in nearly every part of the human body, as well as in blood vessels and atherosclerosis. However, the concern about whether microplastics can reach the human brain has been a significant focus for scientists. The latest study examined a part of the brain known as the olfactory bulb, which is responsible for processing information about smells. Humans have two olfactory bulbs located above each nasal cavity. The olfactory bulb is connected to the nasal cavity by the olfactory nerve, according to NBC.
Microplastics are tiny plastic particles ranging from 5.5 to 26.4 micrometers in size. (Photo: Yahoo).
Some researchers are concerned that the olfactory pathway could serve as an entry point for microplastics to reach the brain, bypassing the olfactory bulb. “Previous studies in humans and animals have shown that air pollution can reach the brain, and pollutants have been found in the olfactory bulb. That is why we think the olfactory bulb could be one of the first points for microplastics to reach the brain,” said the lead researcher, Dr. Thais Mauad, an associate professor of pathology at the São Paulo School of Medicine in Brazil.
Mauad and her colleagues sampled olfactory bulb tissue from 15 deceased individuals aged 33 to 100. Samples from 8 of the cadavers contained microplastics, comprising tiny plastic particles sized between 5.5 and 26.4 micrometers. In total, the research team identified 16 fibers and plastic particles in the tissue samples. The smallest of these was thinner than the diameter of a human red blood cell (approximately 8 micrometers). The most commonly found type of plastic was polypropylene, followed by polyamide, nylon, and polyethylene vinyl acetate. “Polypropylene is everywhere, in household items, carpets, clothing,” Mauad stated. “The places where we have the most contact with plastic particles are in our homes, as our homes are filled with plastic.”
Matthew Campen, a toxicologist at the University of New Mexico, noted that the presence of microplastics in the olfactory bulb is significant but not entirely surprising. “The nose is a crucial barrier to prevent particles and dust from entering the lungs. Therefore, finding plastics in the olfactory system is entirely expected, especially since they are present everywhere else in the body,” Campen commented.
According to Campen, the samples are likely to also contain nano plastics, which are sized between 1 and 1,000 nanometers (1 cm equals 10,000,000 nm). A human DNA strand is about 2.5 nm thick. The presence of microplastics in the olfactory bulb does not necessarily imply that they are present in all areas of the brain, including regions associated with cognition. The research team is still unclear whether microplastics can advance to those areas through the olfactory pathway.
The olfactory system serves as the connection between the nose and the brain. It detects odors by processing tiny odor molecules emitted from various objects like toasted bread or a bouquet of flowers. Odor molecules stimulate the olfactory nerves, and signals are processed in the brain. Other particles may follow a similar route. Although rare, amoebas like Naegleria fowleri, which are larger than the microplastics found in the study, can enter the brain via the olfactory nerve. “We believe if bacteria can pass through this route, microplastics can too,” Mauad stated.
Campen noted that nano plastics are more likely to enter the brain through blood vessels. Blood vessels collect microplastics from the lungs or digestive tract rather than from the olfactory bulb. However, particles have a hard time entering the brain through the bloodstream, even those in pharmaceuticals. This is because the brain is protected by a semi-permeable membrane known as the blood-brain barrier.
Research on microplastics within the body is still in its early stages. Much of what scientists know about the process of the 4,000 chemicals used to create plastics and their degradation is limited to studies on animals. A recent study showed that exposure to microplastics through drinking water for three weeks caused cognitive changes in the brains of mice.
