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An anonymous reader quotes a report from NBC News: Scientists in Brazil found microplastics in the brain tissue of cadavers, according to a new study published Monday in the journal JAMA Network Open. Mounting research over the last few years has found microplastics in nearly every organ in the body, as well as in the bloodstream and in plaque that clogs arteries. Whether these ubiquitous pollutants can reach the human brain has been a primary concern for scientists. The latest research looked at a part of the brain called the olfactory bulb, which processes information about smell. Humans have two olfactory bulbs, one above each nasal cavity. Connecting the olfactory bulb and the nasal cavity is the olfactory nerve. Some researchers worry the olfactory pathway may also be an entry point for microplastics getting into the brain, beyond the olfactory bulb. "Previous studies in humans and animals have shown that air pollution reaches the brain, and that particles have been found in the olfactory bulb, which is why we think the olfactory bulb is probably one of the first points for microplastics to reach the brain," said lead study author Dr. Thais Mauad, an associate professor of pathology at the University of Sao Paulo Medical School in Brazil. Mauad and her team took samples of olfactory bulb tissue from 15 cadavers of people who died between the ages of 33 and 100. Samples from eight of the cadavers contained microplastics -- tiny bits of plastic that ranged from 5.5 micrometers to 26.4 micrometers in size. In total, the researchers found 16 plastic fibers and particles in the tissues. The smallest were slimmer than the diameter of a human red blood cell, which measures about 8 micrometers. The most common type of plastic they found was polypropylene, followed by polyamide, nylon and polyethylene vinyl acetate. "The nose is a major point of defense to keep particles and dust out of the lungs," Campen wrote in an email. "So seeing some plastics in the olfactory system, especially given how they are being found everywhere else in the body, is completely expected." [...] "There is evidence that very small airborne particles can move to the brain via the olfactory bulb, but this is not known to be a major route of trafficking material to the brain," Campen said. Campen notes it's more likely that nanoplastics enter the brain through the bloodstream, which picks up plastic bits from the lungs or digestive tract, rather than the olfactory bulb. "However, it's extremely difficult for particles, even those in pharmaceuticals, to enter the brain through the blood," notes NBC News. "That's because the brain is surrounded by a semipermeable membrane called the blood-brain barrier."