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People come into contact with plastic almost everywhere. A study uncovers a mechanism that allows tiny particles to pass through the blood-brain barrier.
Munich – Plastic is inexpensive and available in large quantities. Nevertheless, it poses a serious threat to people, animals and the environment. A new EU directive will therefore come into force next year. It is almost impossible to escape plastic, as it is used in almost all areas of everyday life. A recent study has now shown that microplastics can even reach our brains.
Study shows: Microplastics enter the brains of mice two hours after ingestion
The Medical University has pointed out in a statement that micro- and nanoplastics (MNP) are “one of the biggest environmental problems of our time”. Research led by Lukas Kenner from the University’s Clinical Institute of Pathology has for the first time uncovered the process by which plastic crosses the blood-brain barrier and enters the brain. The results of this study were published in 2023 in the journal nanomaterials published.
Over time, plastic breaks down into small pieces that enter the environment and the human body. © Sascha Steinach/Imago
The researchers explain in their work that “Humans are constantly exposed to polymer materials, for example in textiles, car tires and packaging.” The resulting degradation products contaminate the environment with micro- and nanoplastics. Through animal experiments, the scientists were able to prove that nanometer-sized particles were detectable in the brains of mice just two hours after the oral administration of polystyrene micro- and nanoparticles (9.55 µm, 1.14 µm, 0.293 µm). Only the smallest particles were able to overcome the blood-brain barrier.
What is the blood-brain barrier?
The AOK explains in a noticethat the blood-brain barrier is a protective mechanism designed to prevent pathogens, cells and harmful substances from entering the brain. It performs a “balancing act” between isolation and supply, allowing some substances to pass through but not others.
In contrast to the rest of the body, the smallest blood vessels in the brain are sealed. These so-called endothelial cells, together with pericytes and astrocytes, form the blood-brain barrier. Although there are other blood-tissue barriers in the body, such as in the intestine, the blood-brain barrier in the brain is particularly “strictly controlled”. The following can enter the brain:
- Blood gas oxygen
- Nutrients such as glucose and amino acids
- Ions
- smaller lipophilic (fat-soluble) molecules
- Hormone
However, undesirable substances such as alcohol and nicotine also pass through the blood-brain barrier. Plastic is now officially included in this barrier. Researchers have not yet identified a mechanism that enables plastic particles to overcome the blood-brain barrier. The decisive factor for the plastic pieces to pass through is therefore the surface structure.
Tiny plastic in the brain increases the likelihood of serious illnesses
According to the university, researchers have already found that microplastics in the gastrointestinal tract can trigger inflammatory and immune reactions and even contribute to the development of cancer. Researcher Lukas Kenner warns: “In the brain, plastic particles could increase the risk of inflammation, neurological disorders or even neurodegenerative diseases such as Alzheimer’s or Parkinson’s.”
Plastic is only classified as nanoplastic when it is less than 0.001 millimeters in size. Nanoplastics have a size of 0.001 to 5 millimeters. Another study has shown that a person who drinks 1.5 to 2 liters of water from plastic bottles every day ingests 90,000 plastic particles per year. Even when using tap water, the number of plastic particles ingested is still considerable, namely 40,000 per year. Just a scratch in a cooking pan can release over 9,000 particles.
Researcher calls for reduction of micro- and nanoplastic particles
Considering his research findings, Kenner says: “To minimize the potential harm of micro- and nanoplastic particles to humans and the environment, it is crucial to limit exposure and restrict their use while further research is conducted into the effects of MNPs.” Chinese researchers have even designed a robot to combat microplastics.
