Microplastics and nanoplastics (MNPs) from the breakdown of plastic materials pollute the environment and make their way into the human body, raising concerns over potential health impacts.
Research shows that microplastics and nanoplastics are able to cross the blood-brain barrier in mice within 2 hours of ingestion.
Key Facts:
- Polystyrene nanoparticles with a size of 0.293 μm crossed the blood-brain barrier in mice just 2 hours after oral administration
- Molecular simulations found the composition of the particle’s biomolecular corona impacts its ability to enter the membrane of the blood-brain barrier
- Cholesterol enhanced uptake while a protein corona inhibited passage into the membrane
- Accumulation of plastic particles in the brain could lead to neurotoxicity and cognitive issues
Source: Nanomaterials (Basel) (2023)
Increasing Human Exposure to Microplastics & Nanoplastics (MNPs)
The widespread use of polymeric plastics in textiles, tires, packaging, and consumer products has led to ubiquitous environmental contamination as these materials break down into micro- and nanoplastics (MNPs).
Humans ingest significant amounts of MNPs through food and water, leading to the presence of plastic particles in tissues and body fluids.
Understanding whether MNPs can breach protective barriers like the blood-brain barrier (BBB) and their potential health impacts is an emerging area of research.
Plastics Exposure & Health Effects
MNPs are typically defined as plastic particle less than 1 μm in size, ranging down to 1 nm.
Their small size leads to a high surface area to volume ratio, making MNPs potentially more reactive and harmful than larger plastics.
Effects linked to MNP exposure include inflammation, oxidative stress, genotoxicity, lipid peroxidation, protein misfolding, mitochondrial dysfunction, and cell death.
Uptake of MNPs in the Body (Organs & Tissues)
Humans ingest thousands of microplastic particles each year through food, water, and air.
Various studies have detected microplastics in human stool samples, suggesting ingestion.
MNPs less than 130 nm can translocate out of the gastrointestinal tract into the circulatory system and distribute through the body, including crossing the placental barrier.
Microplastics have been found in a number of human organs and tissues:
- Placenta
- Lung
- Liver
- Spleen
- Kidney
Additionally, plastic particles from consumer products have been detected in pulmonary artery blood clots, indicating they can enter and circulate through the cardiovascular system after inhalation.
The ability of MNPs to accumulate in organs depends factors such as particle size, shape, polymer type, and protein corona formation.
Their distribution patterns after translocation from the gut suggests potential for chronic exposure once internalized.
The Blood-Brain Barrier (BBB) Usually Protects the Brain
The blood-brain barrier (BBB) is a selective permeability barrier that protects the central nervous system from harmful substances circulating in the bloodstream.
Structurally, the BBB consists of endothelial cells lining the capillaries in the brain connected by tight junctions that restrict passage of molecules.
The BBB controls exchange of nutrients and waste between the blood and brain parenchyma and excludes entry of toxic metabolites, antigenic proteins, inflammation-inducing molecules, and pathogens.
It plays an essential role in maintaining the micro-environment necessary for healthy neural signaling.
Breach of the BBB Can Lead to Brain Damage
When the BBB is compromised, uncontrolled transport can lead to accumulation of toxic molecules in the brain, resulting in cognitive dysfunction, neuroinflammation, and neurodegeneration.
Nanomaterials like MNPs may be able to bypass the BBB’s protective mechanisms through transcytosis and lipid membrane permeation, raising concerns over brain accumulation and neurotoxicity.
Investigating Uptake of Polystyrene Micro- and Nanoplastics In Vivo (Study)
The featured study explored whether polystyrene (PS) MNPs could cross the BBB after oral administration in mice.
PS, derived from styrene monomers linked into polymer chains, is widely used in disposable plastics and routinely found environmental samples.
Researchers performed short-term 24 exposure studies with three sizes of PS particles fed to mice: 0.293 μm, 1.14 μm, 9.55 μm.
They examined brain tissue sections for the presence of fluorescent PS MNPs via microscopy at 2 hours and 4 hours after oral gavage.
In parallel, computational simulations modeled the interaction of a 5 nm PS nanoparticle with a model lipid bilayer membrane in different biomolecular corona scenarios.
The goal was to elucidate the mechanism enabling nanoplastic transfer through the BBB.
Microplastics & Nanoplastics Cross BBB within Hours of Ingestion
Analysis of mouse brain sections revealed rapid uptake of the smallest 0.293 μm PS nanoparticles within 2 hours, indicating they crossed the BBB soon after ingestion.
Presence of the fluorescent signal diminished from 2 to 4 hours. In contrast, no signal was detected for the larger micron-scale particles.
Molecular dynamics simulations found spontaneous absorption of the polystyrene nanoparticle into the hydrophobic core of the membrane model when coated by a corona of cholesterol molecules.
The corona interacted with membrane lipids, causing deformation enabling entry of the particle into the bilayer.
Without a corona, or with a protein corona, the nanoparticle did not enter the lipid membrane during the microsecond timescale examined.
The protein corona presented an energy barrier inhibiting passage into the membrane.
These discoveries suggest the composition of the biomolecular corona formed on PS MNPs plays a major role in its ability to permeate the BBB.
Specifically, cholesterol enhances nano-plastic uptake while certain proteins block transport.
Accumulation of PS nanoparticles in the brain indicates they are able to bypass the BBB’s protection.
This provides clues to the vector of harm for MNP neurological toxicity observed experimentally.
Health Effects of Microplastic Brain Entry (Possibilities)
The ability of nano-scale plastics to cross the blood-brain barrier and access brain tissue raises major health concerns:
- Neurotoxicity: Plastic particles can damage neurons and glial cells through oxidative stress, inflammation, and mitochondrial dysfunction.
- Neurodegeneration: Misfolding of neuronal proteins induced by nanoparticles could initiate neurodegenerative disorders.
- Cognitive/behavioral issues: Changes in neurotransmitters and enzyme inhibition seen with micoplastics could impair neuronal signaling and alter behaviors.
Documented effects from nanoparticle exposure like inhibition of the important neurological enzyme acetylcholinesterase back up these concerns.
The wide range of critical physiological roles that could be disrupted highlights the need for further research.
How can you reduce your exposure to microplastics & decrease risk of brain damage?
Included below are some strategies that may help decrease exposure to microplastics and nanoplastics – and thus risk of potential brain damage.
- Reduce Plastic Use: Opt for products with minimal plastic packaging. Use reusable bags, bottles, and containers. Avoid single-use plastics like straws and cutlery.
- Choose Natural Fibers: Wear clothing made from natural materials like cotton, wool, or hemp to reduce the release of microplastics from synthetic textiles during washing.
- Careful Selection of Cosmetics and Personal Care Products: Avoid products containing microbeads, often found in exfoliants and personal care products.
- Filter Water: Use water filters that can capture microplastics in drinking water.
- Properly Dispose of Plastics: Recycle plastics whenever possible and dispose of waste responsibly to prevent plastic degradation in the environment.
- Avoid Heating Food in Plastic: Use glass or ceramic containers for microwaving, as heating can cause plastics to release more particles.
- Limit Consumption of Seafood Known to Accumulate Microplastics: Certain fish and shellfish can accumulate higher levels of microplastics.
- Choose Fresh Foods Over Processed: Processed foods are more likely to have been exposed to plastic packaging.
- Exercise regularly: It’s possible that the beneficial effects of regular exercise offset any potential damage from plastic exposure.
What else can be done on a community level to decrease plastic exposures?
- Support Bans on Microbeads and Single-Use Plastics: Advocate for policies that limit or ban the production and sale of products with microplastics.
- Promote and Participate in Community Clean-Up Events: Engage in or organize local beach, river, or park clean-ups to reduce environmental plastic pollution.
- Educate and Raise Awareness: Share information about the impact of microplastics and ways to reduce their usage.
- Support Research and Innovation: Encourage the development of biodegradable alternatives and support companies that innovate in this area.
Takeaways: Plastic Nanoparticles Rapidly Enter the Brain
This research presents compelling evidence that polystyrene plastic nanoparticles can cross the blood-brain barrier in mammals within hours of ingestion.
The findings match computational simulations showing a cholesterol corona enables permeation, while a protein corona blocks transport into the membrane.
Accumulation of plastic particles in the brain could be the vector underlying neurological damage observed with micoplastics in toxicology studies.
Their presence elicits worries over neurotoxicity, cognition issues, and neurodegenerative triggers.
Further investigation needs to explore the long-term fate and impacts of MNPs in brain tissue, mechanisms of membrane transport, interactions with neurons, and other critical questions.
Mitigating health risks will require curtailing environmental plastic pollution and human exposure along with advancing scientific understanding of impacts.
References
- Paper: Micro- and Nanoplastics Breach the Blood-Brain Barrier (BBB): Biomolecular Corona’s Role Revealed (2023)
- Authors: Verena Kopatz et al.