A new study finds microplastics in the olfactory bulb, an organ that sits directly below the brain.
Microplastics are tiny polymer fragments that measure less than 5 millimeters up to 1 micrometer. Anything fragment less than 1 micrometer is considered to be a nanoplastic.
Over 80% of microplastics are produced on land and the remaining 20% are from the sea. The primary sources of microplastics are those deliberately produced for consumer and industrial use, like exfoliants in cleansers, cosmetics, drug delivery systems, and industrial air blasting. The secondary sources are those that disintegrate from the macroplastics, such as plastic bags, bottles, food containers, etc. [1]
With the increase in the use of plastics, these microplastics have found ways to enter the human body. Several studies are showing the deposition of microplastics and nanoplastics in human organs, like blood, lungs, liver, kidneys, testes, and even mother’s milk and placenta. [2] A recent preprint study revealed that plastic particles were found in the human brain tissue. [3]
When it comes to the health concerns that these microplastics can cause to the human body, there is still debate and a need for more extensive research.
The lack of consensus stems from sufficient quality assurance, involving issues like nano plastics’ definitions, precision and bias for test methodologies, dose-response relationships, and risk versus exposure assessments.Betsy Bowers, Director of the EPS Industry Alliance (a trade association for the expanded polystyrene industry)
More than plastics per se, it is the harmful chemicals that they contain that can cause adverse health issues.
Experts say that these tiny particles can enter the cells and tissues and deposit harmful chemicals like bisphenols, phthalates, flame retardants, perfluoroalkyl and polyfluoroalkyl substances, and heavy metals. These chemicals can disrupt the endocrine system.
Also, a recent study showed the deposition of microplastics in the carotid artery can increase the risk of heart attack, stroke, or death in the next 3 years of life when compared to people who don’t have it.
Landrigan, the lead author of a March 2023 report from the Minderoo – Monaco Commission on Plastics and Human Health, a global consortium of scientists, healthcare workers and policy analysts charged with following plastics from creation to final product commented on this in another report.
The biggest question is, ‘OK, what are these particles doing to us?’ Honestly there’s a lot we still don’t know. What we do know with real certainty is that these microplastic particles are like Trojan horses — they carry with them all the thousands of chemicals that are in plastics and some are very bad actors.Dr. Philip Landrigan, Pediatrician and Biology Professor, Director, Program for Global Public Health and the Common Good and the Global Observatory on Planetary Health, Boston College
The possible mechanisms can be inflammation, oxidative stress, and metabolic distress caused by these microplastics in the cells they reside in. [1]
There are three main routes through which they gain access to our human body [1]:
Through mouth: by consuming food and drinks stored in plastic containers.
Through the nose: by inhaling airborne microplastics. This can be indoor releases from synthetic fabrics. This can be outdoors from contaminated aerosols from the ocean or airborne fertilizer particles from poor wastewater treatment.
Through skin: by contact with water, health and beauty products containing plastics.
With the rising microplastics (MPs) pollution and the discovery of microplastics in several organs, their presence in the brain was not well documented. This study aimed to find their presence in olfactory bulbs to derive the potential route to the brain.[4]
In the study, the olfactory bulbs of 15 adult cadavers were collected and analyzed for the presence of MPs. They found that 8 out of 15 samples detected MPs. There were 16 different types of polymers found, of which 75% were in particle form and 25% were in fiber form. The size ranged from 5.5 micrometers to 26.4 micrometers. The most common form of plastic was polypropylene (43.8%). The risk of contamination was ruled out with controls.
The human brain has a robust protective gear called the blood-brain barrier (BBB) system, which protects it from harmful substances that travel through the blood. A few animal studies have shown that MPs can breach this BBB system and gain access to the brain.
Another potential route is the inhalation route, which involves the olfactory bulb. The olfactory bulb is connected to the olfactory nerve endings in the nose. Through this connection, it receives odor information. Below the olfactory bulb is a perforated bony structure called a cribriform plate in the upper part of the nose, supporting it. The olfactory bulb is directly connected above to the inferior portion of the brain.
This study finding the presence of MPs in olfactory bulbs supports the idea that this pathway can give access to the MPs to the brain. Several other studies are showing that Mps can cause neurotoxic effects on the brain, causing neurodegenerative disorders and developmental disorders. [4]
The study also found that the predominant type of plastic in olfactory bulbs was polypropylene, the type that is widely used and generally safe for human use. However, polypropylene is the biggest contributor to the release of 1,4-dioxane, which is shown to be carcinogenic for humans. [3]
However, the study was unable to find the source of these MPs and the reason why some deceased didn’t have any MPs in their olfactory bulb.
What we do know from studies published in the literature is that when there is local inflammation of the mucosa (lining in the nasal cavity), it can be easier for microplastics to penetrate. A large proportion of the microplastics present in the air are fibers that come from clothing with synthetic fabrics and everyday objects such as carpets, curtains, etc.Luís Fernando Amato-Lourenco, PhD, Environmental Engineer
Though we cannot eliminate plastics completely, there are steps that we can follow to minimize the exposure. Some advice from the experts are
Avoid using plastic containers for food and drinks. Use stainless steel instead.
Avoid microwaving food in plastics and avoid washing plastics in dishwashers. The heat can release the chemicals.
Avoid using disposable fabrics. Use reusable fabric bags, reusable travel mugs, and silverware when you go outside.
Avoid buying packaged foods and packed water bottles. Carry your own stainless steel water bottles.
Be cautious while buying cosmetics and beauty products that can contain microplastics.
Spread awareness and be informed of the dangers of microplastics.
Rehash/Dr. Shanjitha J. Hussain
References:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7920297/
https://edition.cnn.com/2024/09/16/health/microplastics-nose-wellness/index.html
Amato-Lourenço LF, Dantas KC, Júnior GR, et al. Microplastics in the Olfactory Bulb of the Human Brain. JAMA Netw Open. 2024;7(9):e2440018. doi:10.1001/jamanetworkopen.2024.40018