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May 27, 20235 min read

Brain Invaded by Microplastics: A New Challenge for Our Nervous System

Written by Mariana Mastache-Maldonado

Plastics are ubiquitous in modern life, and their versatility has made them an essential material in a wide range of products, from packaging to microchips. However, the chemical properties that make them durable also make them difficult to dispose of, with some taking tens of thousands of years to break down.  


While we may assume that this is the end of the story, the path of plastic is far more complex than we might imagine. The mass production of cheap plastic goods has created a culture of single-use and discarded goods, resulting in a staggering number of plastic bottles sold each year.




As we can see from the 2019 Reuters report, if all of these bottles were piled together, they would be taller than the world's tallest building. Unfortunately, plastic pollution is not limited to its sheer volume, as plastics that cannot easily degrade break down into smaller particles that pollute all of the ecosystems.




Understanding Micro and Nano Plastics: What You Need to Know


Plastic pollution has become an environmental crisis, and the tiny fragments of plastic, known as micro and nano plastics, have been shown to pose a threat to the food chain. These polymers are smaller than 5mm and even smaller than a millimeter, respectively.

Microplastics have been found in drinking water, canned products, and honey, and have even been discovered in human blood.


Studies suggest that exposure to micro and nano plastics could lead to respiratory difficulties, inflammatory effects, and autoimmune diseases, and could even cause the transmission of toxic chemicals or medicines to ecosystems, leading to antibiotic resistance. However, the long-term effects of this involuntary deposit of plastics in our bodies are still being studied, and more research is needed to understand their impact fully. It should be mentioned that the data is, for now, limited due to the complications to extract, characterize, and quantify the plastics.


How Plastics and Our Brains Can Clash


The detrimental impact of micro- and nano-plastics on our brains is a concerning issue that has been gaining attention in scientific research. Despite the blood-brain barrier being a crucial defense mechanism to protect our central nervous system from harmful agents, micro- and nano-plastics have managed to breach this barrier and enter one of the most vital organs in our body.


Analogous to a bouncer at a disco, the blood-brain barrier selectively allows certain substances to pass through while keeping out toxins, pathogens, and other damaging agents. However, micro- and nano-plastics have defied this barrier due to their small size and have been found to accumulate in the brain, particularly in the hippocampus, which plays a significant role in memory formation and is often affected in conditions like Alzheimer's disease.




Studies conducted on animals, such as the research published by Lee et al. in 2022, have shown that exposure to polystyrene microplastics (widely used in food containers and single-use items) can impair learning and memory in mice. The presence of these plastics in the hippocampus has been associated with neuroinflammation and disruption of synaptic plasticity, the process that underlies changes in the strength of connections between neurons and is crucial for learning.


The impact of micro- and nano-plastics on the nervous system extends beyond memory impairment and may even emulate neurodegenerative diseases. In their article titled "Brain single-nucleus transcriptomics highlights that polystyrene nano plastics potentially induce Parkinson’s disease-like neurodegeneration by causing energy metabolism disorders in mice," Liang and colleagues discuss their findings on how polystyrene nano plastics disrupt energy metabolism in the nervous system and striatum, potentially leading to neurodegeneration similar to Parkinson's disease.





It is worth noting that Parkinson's disease is characterized by a significant loss of dopamine and complex changes in neurons in the striatum, which was also affected in the mouse study. This progressive disorder manifests in involuntary movements like tremors, stiffness, and difficulty with balance and coordination and may also involve behavioral changes.

 

The researchers observed similar findings in their study on nano plastics and Parkinson's disease, including damage to the integrity of the blood-brain barrier and weakened neurobehavioral activity, grip strength, and balance, among other aspects.

 

Furthermore, in a 2020 articlei Minne Prüst, Jonelle Meijer, and Remco Westerink reported that exposure to micro- and nano-plastics can alter levels of neurotransmitters, leading to behavioral changes and increased vulnerability to neuronal disorders in exposed individuals.

 

These findings highlight the potentially grave consequences of micro- and nano-plastic contamination on the nervous system, with implications for neurodegenerative diseases and behavioral alterations.


Plastic in Our Lives: The Risks and Challenges

 

As we currently understand, there are limitations in our knowledge regarding the risks associated with plastic exposure to the brain, and many unanswered questions remain, which we hope to address in future research.

 

However, there is sufficient scientific evidence to warrant a precautionary approach when it comes to exposures to small plastic polymers, as it is known that contact with environmentally hazardous materials is a risk factor for the development of neuropsychiatric and neurological disorders.

 

At the same time, plastic is an integral part of our daily lives and plays a crucial role in various fields, such as the development of medical devices that improve our quality of life and iconic spaceships. It is challenging to imagine a reality without these materials.

 

Therefore, should we adopt a resigned attitude? Certainly not. It is important to embrace a perspective that rejects both the single-use culture and the mass production of cheap and low-quality materials.

 

Individual actions also matter choosing reusable containers that are not made of plastic in our daily lives, buying food in bulk, and exploring other viable alternatives. In the social sphere, it is crucial to demand improvements from authorities in managing and handling these materials.



References:

  1. Campanale, C., Massarelli, C., Savino, I., Locaputo, V., & Uricchio, V. F. (2020). A detailed review study on potential effects of microplastics and additives of concern on human health. International journal of environmental research and public health, 17(4), 1212.

  2. Cverenkárová, K., Valachovičová, M., Mackuľak, T., Žemlička, L., & Bírošová, L. (2021). Microplastics in the food chain. Life, 11(12), 1349.

  3. Lee, C. W., Hsu, L. F., Wu, I. L., Wang, Y. L., Chen, W. C., Liu, Y. J., & Huang, C. C. Y. (2022). Exposure to polystyrene microplastics impairs hippocampus-dependent learning and memory in mice. Journal of Hazardous Materials, 430, 128431.

  4. Liang, B., Huang, Y., Zhong, Y., Li, Z., Ye, R., Wang, B., & Huang, Z. (2022). Brain single-nucleus transcriptomics highlights that polystyrene nanoplastics potentially induce Parkinson’s disease-like neurodegeneration by causing energy metabolism disorders in mice. Journal of Hazardous Materials, 430, 128459.

  5. Mariano, S., Tacconi, S., Fidaleo, M., Rossi, M., & Dini, L. (2021). Micro and nanoplastics identification: classic methods and innovative detection techniques. Frontiers in toxicology, 3, 636640.

  6. Prüst, M., Meijer, J., & Westerink, R. H. (2020). The plastic brain: neurotoxicity of micro-and nanoplastics. Particle and fibre toxicology, 17(1), 1-16.

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