Microplastics May Be Accumulating in Human Brains, Study Warns

The findings of a new study raise further concerns about the potential health effects from microplastics, which have widely contaminated the environment from the breakdown of consumer products and industrial waste, suggesting that the small pieces of plastic debris are making their way into human brains.

Microplastics include tiny pieces of plastic that are 5 mm long or less. These shards slough off from food wrappers, water bottles and everyday objects in our homes, moving from water and food sources into the body, where they are already known to transfer from the digestive tract to the bloodstream.

In a study published this week in the medical journal JAMA Network Open, researchers found that these small pieces of plastic also appear to be accumulating in the olfactory bulb of the brain, suggesting that microplastics may be building up in other parts of the brain as well.

In this new report, a team of researchers from the São Paolo Medical School in Brazil, led by Dr. Luís Fernando Amato-Lourenço, conducted a case study examining the olfactory bulbs of 15 deceased people, who were residents of São Paolo for a minimum of five years.

Microplastics were detected in eight of the olfactory bulbs of the participants. Humans contain two olfactory bulbs right above the nostrils. They are connected to the olfactory nerve in the brain and are part of the smelling function in humans.

Researchers found the microplastics were made of 16 synthetic polymer particles and fibers, with polypropylene, the most common polymer detected, found in 44% of samples. Polypropylene is a common plastic ingredient used in furniture, rugs and clothing. The next most common plastics were polyamide, nylon and polyethylene vinyl acetate.

The sizes of the particles ranged from 5.5 mm to 26.4 mm and the average fiber length was 21.4 mm. The smallest particle was smaller than the diameter of a human red blood cell, which is 8 mm.

The researchers determined that the tiny plastic particles entered the body through the smell function and accumulated in that part of the brain. They said it is unclear if, once the microplastics reach the olfactory bulb, they are able to travel to other areas of the brain, such as parts that may be key for memory or cognition. This is because they are unsure if microplastics can infiltrate the blood brain barrier.

Previous studies have shown microplastics can pass through that barrier in mice, but note that more research is needed to see if the same is true for humans, and that it may be more likely microplastics enter the brain through the bloodstream.

“The presence of microplastics in the human olfactory bulb suggests the olfactory pathway as a potential entry route for microplastics into the brain, highlighting the need for further research on their neurotoxic effects and implications for human health,” Amato-Lourenço said.

Microplastic Exposure Concerns

A number of studies in recent years have pointed to increasing amounts of health issues that could be caused by microplastics.

In 2021, researchers from Rice University reported that microplastics may be causing antibiotic-resistant bacteria to grow and spread, posing serious health risks for humans. They warned that items breaking down into microplastics become breeding grounds for antibiotic-resistant genes (ARGs) due to microbial and chemical contamination.

These ARGs, protected by bacterial chromosomes, phages and plasmids, can spread antibiotic resistance to other environmental items and humans. This spread decreases humans’ ability to fight infections, contributing to the rise of “superbug” infections that are difficult to treat and can have high fatality rates.

Another study, published in 2020 by researchers from Arizona State University, discovered every organ in the body showed the presence of microplastics. As a result, health experts have expressed concern about a wide range of health effects that humans may experience, including diabetes, obesity, sexual dysfunction and infertility.

A separate study published earlier this year by University of Mexico researchers found microplastics in human testicles, which could impact fertility, sperm count, and lead to other reproductive problems. Other studies show nearly every human has some level of microplastics in their body.