At autopsy, eight out of fifteen human brains contained microplastics.
The olfactory bulb contained 16 different polymer fibers and particles.
The olfactory path may be an entry point for microplastics in the brain.
A case series revealed that microplastics were detected in the olfactory bulb of eight out of fifteen human brains during autopsy.
Luis Fernando Amato – Lorenco, PhD and his co-authors from Freie Universität Berlin, Germany, identified 16 different synthetic polymer fibers and particles.
Researchers in JAMA Open wrote that most microplastics (75%) were particles, and 25% were fibres. The majority of particles were fragments from polymers commonly used for clothing and packaging like nylon and polypropylene.
Amato-Lourenco said that the findings indicate the olfactory path is a possible entry route for microplastics to the brain. This is the first study that has detected and characterized microplastics within the human brain’s olfactory bulb, he added.
Amato-Lourenco, who spoke to MedPage Today, said that although microplastics were found in organs such as the lungs and intestines, there had never been any direct evidence of their presence in brain tissue.
Philip Landrigan MD, Boston College, not involved in the study, noted that microplastic pollution was a growing concern for health.
He noted that recent research found a higher risk for combined stroke, myocardial ischemia, or death in nearly three years among people with microplastics and Nanoplastics in the atherosclerotic calcification of surgically removed carotid calcification specimens.
Landrigan, MedPage today, said: “Unfortunately microplastics are everywhere in the environment.” They are found everywhere. The Mariana Trench is 6 miles below the surface of Pacific Ocean. In polar ice cap. They have been found in the Himalayas and Alps. They get into our food chain and us from the ocean.
Landrigan pointed out that the olfactory bulbs are among the oldest parts of the brain, in terms of evolution.
It sits in front of the rest the brain of the skull. He said it’s a small bulb of tissue inside the nose that is separated from the nasal cavities by a thin bone piece. This piece of porous bone is what allows us to smell. Scientists have speculated that the olfactory bones may be the point of entry for foreign substances to the brain.
Most microplastics, defined by the Environmental Protection Agency as plastic particles ranging between 5 mm and 1 nanometer (nm), are likely to be stopped from reaching the brain. Nanoplastics are particles smaller than one um or 1,000 nm. According to the EPA, a strand human hair measures about 80,000 nm in width.
There are no published studies that have shown the presence of microplastics within the human brain. Researchers at the University of New Mexico used a new analytical chemistry technique to identify microplastics and nanoplastics from autopsy samples. They found that brains contained higher concentrations of these materials than livers and kidneys. Many particles were in the nanoscale.
Amato-Lourenco, along with his colleagues, analyzed olfactory bulbs tissues from dead individuals obtained during routine autopsies by coroners. Participants were 15 adults who lived in Sao Paulo (Brazil) for at least 5 years. Previous neurosurgical interventions were excluded.
The median age at death was 69.5 years. Twelve of the dead individuals were men. Researchers also collected samples of olfactory bulb tissue from two stillbirths humans who were 7 months pregnant as negative controls.
Two methods were used to determine the presence of microplastics within the olfactory bulbs: direct tissue examination, followed by digested tissues filtration and infrared spectrum. All procedures were conducted with a plastic-free method: the staff wore lab coats made of 100% cotton, and latex gloves that had been cleaned. No textile or plastic bracelets, rings, or watches were permitted.
Researchers said that polymeric materials were not present in the procedural blank or negative control filters. This indicates a minimal risk of contamination. The researchers found that one stillborn sample did not contain microplastics, while the other was insufficient for analysis.
Amato-Lourenco, along with co-authors, wrote that “Our data support our hypothesis that the olfactory path is an important entry point for air pollutants.”
While this seems to be the case, they admit that “we cannot exclude the possibility of multiple entrance routes.” “Microplastics could have reached the olfactory bulbs either via systemic circulation or by crossing the blood brain barrier.
Landrigan pointed out that the case-series adds a lot to the growing literature on microplastics.
He said, “I believe there will be more information over the next few year about how microplastics get into the body of humans — and what happens to them once they are there.”
The study was funded by the Alexander von Humboldt Foundation of Germany, the Plastic Soup Foundation and the Brazilian Research Council.
Amato-Lourenco, and the co-authors, reported that they had no conflict of interest.
Landrigan has reported on his relationships with the Minderoo Foundation and Ramazzini Institute.