Scientists Find Microplastics in Human Brain Tissue Above the Nose

Microplastics are inescapable. These miniscule plastic particles have been found at ancient archaeological sites, in freshly fallen snow on Antarctica, at the top of Mount Everest and deep in the Mariana Trench. In the human body, they’ve shown up in blood, baby poop, placentas and lungs.

Now, scientists have also discovered the tiny pollutants in brain tissue, specifically the olfactory bulb that sits above the nose. They shared their findings Monday in the journal JAMA Network Open.

Humans have two olfactory bulbs located in the forebrain, which are connected to each nasal cavity by the olfactory nerve. Olfactory bulbs help detect and process scents and odors, passing information from the nose to the brain.

Microplastics have been found in human brains, according to recent research that has not yet been peer-reviewed. The new findings raise concerns among researchers that the olfactory pathway might allow microplastics to access the brain and potentially reach brain areas beyond the olfactory bulb.

“Once present in [the olfactory bulb], there can be translocation to other regions of the brain,” says study co-author Luís Fernando Amato-Lourenço, an environmental scientist at the Free University of Berlin, to CNN’s Sandee LaMotte. “Translocation depends on several factors, including the shape of the particle, whether it is a fiber or a fragment, its size and the body’s defense mechanisms.”

For the study, the team sampled olfactory bulb tissues from 15 human cadavers. The patients used in the study had died between the ages of 33 and 100.

Eight of the samples contained microplastics, or bits of plastic less than less than five millimeters long. The researchers found 16 total plastic fibers and particles made of polypropylene, polyamide, nylon and polyethylene vinyl acetate. The most common was polypropylene, a type of plastic that’s used widely in clothes, furniture, rugs, packaging and more.

The researchers did not analyze the samples for nanoplastics, which are even tinier particles about 1,000 times smaller than the width of a human hair. But the microplastics they did find were “much smaller than those of several other studies that have determined the presence of microplastics in human organs, such as the placenta, kidneys, liver, etc.,” Amato-Lourenço tells CNN.

The findings don’t come as a surprise to the team, considering the ubiquity of microplastics. In addition, the nose’s job is to prevent dust, particles and other intruders from reaching the lungs, so it makes sense that nasal tissue would also capture plastic fragments.

But it remains unclear whether microplastics can reach the brain via the olfactory pathway. Some microorganisms, such as the brain-eating amoeba Naegleria fowleri, can enter the brain this way, but those incidents are rare.

“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,” says Matthew Campen, a toxicologist at the University of New Mexico who was not involved with the research, to NBC News’ Kaitlin Sullivan. Campen is the lead author of the preprint research that found microplastics in human brains.

Researchers also weren’t able to determine why they found microplastics in some cadavers but not in others. One possible explanation is that inflammation of the nasal cavity lining, called the mucosa, made it easier for plastic particles to enter the nose tissue in only some individuals, per CNN.

The potential consequences of having microplastics in the human body are also mostly unknown, though some studies suggest they could be harmful to human health.

Earlier this year, researchers found a connection between microplastics in human arteries and a higher risk of heart disease. That study, published in the New England Journal of Medicine in March, marked the “first time we’ve seen a human health effect attributed to the particles themselves,” Philip Landrigan, a pediatrician and epidemiologist at Boston College who was not involved with either recent study, said to National Geographic’s Tara Haelle in April.

“Until now, the mantra has always been, ‘Well, the particles are there, but we don’t know anything about what they’re doing,’” he added. “This paper changes that.”

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Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.