When Breathing Becomes Dangerous: Pollution on Brain Health

Authored by Timothy Johnson

Sometimes, even the unconscious act of breathing can be dangerous. The February 3rd, 2023 derailment of a train carrying toxic chemicals near East Palestine, Ohio is a prime example. In the chaos that followed the derailment, authorities agreed that the health effects from airborne toxins on East Palestine residents were unknown and potentially life-long [1]. It’s well known that exposure to air pollution, whether from environmental disasters or everyday urban life, can have detrimental effects on human health. However, emerging research indicates that those negative health effects are much more concerning than previously believed — especially for the brain. Air pollution can affect brains at every stage of life and, therefore, people’s very livelihoods.

A large portion of air pollution research focuses on particulate matter. According to Boda et al., particulate matter (PM) is defined as a mixture of small particles released by combustion or industrial processes [2]. Ultrafine PM can be particularly pervasive in the body. Evidence suggests that it can penetrate the blood-brain barrier — an important junction in the circulatory system responsible for keeping pathogens and toxins out of the brain. Studies have also shown that PM in blood circulation can cross the placental barrier, leading to mother-to-fetus transmission of pollutants [2].

This pervasive nature of PM leads to a number of critical issues for developing brains. During the first natal period, exposure to high levels of PM leads to lower postnatal brain weight [2]. Residential exposure to air pollution during pregnancy is also linked to a decrease in white matter in prefrontal cortex areas associated with attention [3]. Air pollutants even disrupt the normal functioning of the placenta, which can disrupt neurobehavioral development in children [2]. After high exposure to PM, some postnatal neural cell connections appear to operate in a reduced and compensatory manner in the hippocampus, which is a brain structure essential for decision-making and memory. Concerningly, these developmental disorders can often be comorbid with other brain health issues later in life [2].

Even if someone exposed to air pollution avoids developmental disorders, pollution-caused cognitive deficits or mental disorders are common later in life. Cognitive testing and MRI brain imaging show cognitive impairments in adults exposed to air pollution [4]. Verbal cognitive testing on adults exposed to air pollution shows lower average scores and a detrimental effect that gets worse as people age [5]. In terms of mental disorders, sulfur dioxide air pollution is strongly linked to increased psychiatric hospitalizations, and nitric oxide air pollution is significantly associated with an increased incidence of psychotropic drug prescription in adolescents [6]. Studies on chronic PM exposure find a heightened risk of onset and worsened progression of depression in adults [2]. These cognitive deficits and disorders can also couple with developmental disorders and lead to highly exacerbated effects as people enter their later years.

Since dementia and related disorders are some of the most devastating, incurable conditions that modern humans face, the impact of air pollutants on human brain health cannot be understated. Tragically, exposure to air pollutants also increases people’s risk for neurodegenerative disorders. One study found a 138% increase in Alzheimer’s disease risk per incremental increase in exposure to some forms of PM [7]. Another estimated that an entire population of adults aged 55-85 in Ontario, Canada were at hazard risk for incident dementia just by living within 50 meters of major traffic roads [8]. Yet another found that dementia risk increased by up to 50% per incremental change in the mean pollutant levels over five years in the same residential area [9]. 

The effects of pollution on the brain are a series of tragic pathologies and disorders that begin in the womb, cease only with death, and vastly disproportionately affect people of low socio-economic status [10]. For decades now, research on pollution’s human health effects has focused on the lungs and heart, but new findings continue to fortify the idea that the brain is intensely affected by air pollutants. Each piece of literature in this new field of neuroscience concludes by highlighting the urgent need for more research and consideration from officials in government, healthcare, and public health. With the well-being of millions of people around the world on the line, organized anti-pollution efforts, preemptive health screening and care, and well-funded research and educational programming are crucial. Time is lost with every breath, but each breath is also an opportunity to create a safer, cleaner future for all.

Works Cited

1. Dance, S. (2023, February 24). Toxic air pollutants in East Palestine could pose long-term risks, researchers say. Washington Post. https://www.washingtonpost.com/climate-environment/2023/02/24/ohio-derailment-toxic-air-pollution/

2. Boda, E., Rigamonti, A. E., & Bollati, V. (2020). Understanding the effects of air pollution on neurogenesis and gliogenesis in the growing and adult brain. Current Opinion in Pharmacology, 50, 61–66. https://doi.org/10.1016/j.coph.2019.12.003

3. Sunyer, J., & Dadvand, P. (2019). Pre-natal brain development as a target for urban air pollution. Basic & Clinical Pharmacology & Toxicology, 125(S3), 81–88. https://doi.org/10.1111/bcpt.13226

4. Peeples, L. (2020). How air pollution threatens brain health. Proceedings of the National Academy of Sciences, 117(25), 13856–13860. https://doi.org/10.1073/pnas.2008940117

5. Zhang, X., Chen, X., & Zhang, X. (2018). The impact of exposure to air pollution on cognitive performance. Proceedings of the National Academy of Sciences, 115(37), 9193–9197. https://doi.org/10.1073/pnas.1809474115

6. Buoli, M., Grassi, S., Caldiroli, A., Carnevali, G. S., Mucci, F., Iodice, S., Cantone, L., Pergoli, L., & Bollati, V. (2018). Is there a link between air pollution and mental disorders? Environment International, 118, 154–168. https://doi.org/10.1016/j.envint.2018.05.044

7. Jung, C.-R., Lin, Y.-T., & Hwang, B.-F. (2015). Ozone, Particulate Matter, and Newly Diagnosed Alzheimer’s Disease: A Population-Based Cohort Study in Taiwan. Journal of Alzheimer’s Disease, 44(2), 573–584. https://doi.org/10.3233/JAD-140855

8. Chen, H., Kwong, J. C., Copes, R., Tu, K., Villeneuve, P. J., van Donkelaar, A., Hystad, P., Martin, R. V., Murray, B. J., Jessiman, B., Wilton, A. S., Kopp, A., & Burnett, R. T. (2017). Living near major roads and the incidence of dementia, Parkinson’s disease, and multiple sclerosis: A population-based cohort study. The Lancet, 389(10070), 718–726. https://doi.org/10.1016/S0140-6736(16)32399-6

9. Grande, G., Ljungman, P. L. S., Eneroth, K., Bellander, T., & Rizzuto, D. (2020). Association Between Cardiovascular Disease and Long-term Exposure to Air Pollution With the Risk of Dementia. JAMA Neurology, 77(7), 801–809. https://doi.org/10.1001/jamaneurol.2019.4914

10. Calderón-Garcidueñas, L., & Ayala, A. (2022). Air Pollution, Ultrafine Particles, and Your Brain: Are Combustion Nanoparticle Emissions and Engineered Nanoparticles Causing Preventable Fatal Neurodegenerative Diseases and Common Neuropsychiatric Outcomes? Environmental Science & Technology, 56(11), 6847–6856. https://doi.org/10.1021/acs.est.1c04706