Plastics in the brain: Polymer ingestion likely degenerating human cognition, finds study

22 May 2023 --- Researchers from the University of Vienna, Austria, have revealed that microplastics might enter human brains after surveilling mice’s reaction to ingesting microplastics.

The researchers performed short-term studies in mice with orally administered polystyrene (PS) micro- and nano-particles (MNPs). The nanometer-sized particles reached the brain within two hours after consumption. 

The research focused on microplastic-contaminated drinking water. PS, a common plastic in food packaging, was given to the mice through laced water. The scientists report that exposure to nanoplastics in the brain could harm human health and cognitive functions. 

“Although the environmental impacts of plastic pollution have been widely studied, the potential health consequences of plastic consumption on mammals, including humans, remain to be elucidated,” writes the study. 

Breaking the blood-brain barrier
The nanoparticles entered the mice’s brains by an unknown biological transport mechanism. To understand the transport mechanism, the scientists performed coarse-grained molecular dynamics simulations on the interaction of cholesterol bilayers with a PS nanoparticle. 

They discovered that the composition of the biomolecular corona – a layer of proteins and other biomolecules that can accumulate on the surface of plastic particles when they are exposed to biological fluids – surrounding the plastic particles was critical for passage through the blood-brain barrier (BBB), a wall of blood vessels and tissue that protects the brain from harmful substances. 

The cholesterol molecules enhanced the uptake of these contaminants into the membrane of the BBB, whereas the protein model inhibited it. These opposing effects could explain the passive transport of the particles into the brain.

“Given the widespread use of plastics in our daily lives and the growing concern over the impact of microplastics on the environment and our health, there is an urgent need for more research in this field,” say the scientists. Plastics can break through the BBB demonstrates Austrian researchers.

Assessing toxicity
Computer models show that PS particles can enter the BBB depending on their specific surface corona. The mouse models verified these findings, showing accumulations of specifical signals of nanometer-sized PS particles in brain tissues. 

The researchers highlight the importance of understanding the corona on the surface of plastic particles when assessing their toxicity.

Before entering the body, MNPs acquire an environmental or eco-corona consisting of biomolecules, organic matter and chemical and biological contaminants, contributing to the corona’s complex and variable composition. The type of corona can, therefore, significantly impact their ability to enter the BBB and their overall toxicity.

Ingesting plastic 
It has been previously researched that an average person consumes 39,000-52,000 microplastic particles per year, roughly the size of a credit card per week. 

“In recent years, plastic pollution has become an increasingly important environmental and human health issue,” reports the Austrian study. 

The scientists hypothesize that consuming these plastics can cause potentially severe degenerative consequences and short-term health effects, such as cognitive impairment, neurotoxicity and altered neurotransmitter levels, that can contribute to behavioral changes.

The findings can be read in Nanomaterials journal. 

By Sabine Waldeck