a discovery that worries USP researchers!

Wednesday 22nd January 2025 02:15 AM

On the left, a microscopic image of a microplastic particle (blue) in a lung and, on the right, in brain tissue. Credit: Fernando Amato Lourenço / Free University of Berlin.

They are widespread around the world, invisible but omnipresent: in cities, forests and oceans. In the organisms of fish, birds and even inside us. Microplastics have become an unavoidable reality, alongside the rapid growth in global production of these materials. Recent research by the University of São Paulo (USP) has revealed that microplastics have reached one of the human body’s best-guarded frontiers: the brain.

The study, published in a recent issue of the journal JAMA Open Network, is the result of cooperation between a team of specialists from the USP School of Medicine, the State Research Support Foundation of São Paulo (FAPESP) and Plastic Soup, a Dutch non-governmental organization.

Researchers have identified plastic particles in the brains of eight people. The deceased, who had lived in the city of São Paulo for at least five years, were autopsied at the death verification service in the capital.

The samples were taken from a specific part of the organ called the olfactory bulb. In the human brain, the olfactory bulbs are the part of the central nervous system responsible for first receiving odor-related information. As they are in contact with the neurons located at the back of the nose, they can serve as an entry route for microplastics and other particles.

The samples were subjected to rigorous analysis and infrared radiation.

To guarantee the integrity of the results and prevent the risk of external contamination, strict hygiene protocols have been adopted. The samples were stored in plastic-free containers and even the analysis team’s clothing was limited to cotton clothing.

After processing the samples, they were sent to the National Center for Energy and Materials Research (CNPEM) in Campinas. There they were subjected to a special workstation powered by Sirius, one of the brightest active sources of synchrotron radiation in the world. Illuminated by infrared radiation, the samples revealed different types of microplastics.

Microplastics found in the brain are commonly used in industry and commerce.

Polypropylene (PP) was the most common particle type (44%) in the olfactory bulb fragments analyzed in the research. This petroleum-derived microplastic is widely used in the packaging and composition of personal-use products such as disposable masks, vehicle parts and medical equipment. Other microplastics identified in the samples include polyamide (PA), polyethylene vinyl acetate (Peva), and polyethylene (PE).

Global production of plastics has been increasing since the 1950s and has grown by 50% per decade over the past 20 years. Credit: Romaset / Getty Images Plus

In each of the fragments, 1 to 4 microplastic particles were found, ranging in size from 5.5 µm to 26.4 µm (micrometer). A micrometer is a measurement corresponding to one millionth of a meter. In these dimensions, the microplastics detected by the research resemble medium-sized bacteria and are slightly smaller than a human cell.

Science studies the health effects of microplastics

“The detection of microplastics in the brain is a cause for concern because it is the most protected organ in the human body,” explains chemist Henrique Eisi Toma of the USP Institute of Chemistry. The brain is protected by a membrane composed of three types of cells, the blood-brain barrier, which blocks the flow of compounds carried by the blood.

The culture of disposable plastic and improper waste disposal contribute to the circulation of microplastics around the world. Credit: Md. Akhlas Uddin / Pacific Press / Lightrocket via Getty Images

“Micro and nanoplastics are an important issue that must be treated with caution. Everyone is exposed to them, but their effects on human health are not yet well understood,” says the expert. Nanoplastics are a category of even smaller particles (1 nanometer is one thousandth of a micrometer), comparable to the size of viruses.

In the human body, the absorption of micro- and nanoplastics often occurs through the use of products containing these small particles, such as cosmetics and paints, and through the breakdown of plastics into smaller sizes under the action of light, heat, humidity, among other processes.

According to a report from Pesquisa Fapesp, “these synthetic materials can affect organs and tissues due to their chemical composition, geometry or the microorganisms they can carry, but the impact of each of these factors is unknown at this stage.”

Article references:

Fapesp Research. USP team identifies microplastics in the human brain. 2025

JAMA Open Network. Microplastics in the Olfactory Bulb of the Human Brain. 2024