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Air Pollution: The Invisible Killer

The human health consequences of air pollution are often forgotten in conversations surrounding climate change. Yet, research has already shown that air pollution is responsible for millions of deaths worldwide. For example, one study found that in 2012, the fine particulate matter emitted from fossil fuel was responsible for 10.2 million excess deaths globally [9]. Fine particulate matter (PM2.5) is responsible for a plethora of diseases, such as chronic obstructive pulmonary disease (COPD), cardiovascular diseases, lung cancer, atherosclerosis, and more. Highlighting the dangerous effects of air pollution on human mortality will hopefully push policymakers to seriously consider these impacts when creating policy related to infrastructure, transportation, and other areas that intersect with climate change.

PM is broadly defined as the mixture of solid and liquid particles in air, and PM2.5 specifically defines particles that are 2.5 micrometers and smaller, allowing for them to enter the bloodstream and lungs [4]. PM2.5 originates from a variety of sources, such as fossil fuels, automobiles, power plants, and wildfires. Fossil fuels are directly tied to climate change through the production of greenhouse gasses, of which 40% are created by the industrial sectors globally [1]. As forests become drier with less precipitation and warmer air temperatures, the possibility of wildfires increases [2]. Thus, fossil fuels are not only generating their own PM2.5 but are exacerbating wildfires that also produce PM2.5. In addition, smoke from wildfires can travel thousands of miles, settling in areas seemingly unaffected by the fires.

Of note, the concentration of PM2.5 in urban areas has decreased globally since 2000. However, 2.5 billion urban inhabitants still live in urban areas where the PM2.5 concentrations exceed the World Health Organization’s standards, highlighting the very real exposure risk that many people, often unknowingly, still have to it [8].

PM2.5 is harmful to a variety of human physiological systems. One of its most detrimental effects is that it has been found to induce oxidative stress in cells, leading to damage of respiratory epithelial cells [6]. Additionally, PM2.5 has been found to stimulate inflammation of the respiratory system, exacerbating conditions such as COPD and asthma [5]. Furthermore, PM2.5 contains carcinogenic agents, triggering mutations and changes in biochemical processes across human cells, ultimately leading to a variety of cancers [6]. The structural and chemical changes caused by PM2.5 subsequently increase the risk of the aforementioned diseases, and many more.

Both small and large scale studies have been conducted to grasp the true effects of PM2.5 on humans. One study in Massachusetts found that, although long-term exposure has a much greater association with mortality, even short-term exposure to toxins like PM2.5, ozone, and nitrogen dioxide were significantly associated with an increase in mortality [10]. Of note, another study conducted with US veterans over a span of 10 years found that 99% of deaths from non-accidental causes were associated with PM2.5 concentrations that were below the Environmental Protection Agency’s national standards, bringing up the question as to whether the threshold for danger to human health should be changed [3].

Fossil fuel related emissions have been found to account for 65% of excess deaths globally, and models that estimate the benefits of a phaseout of these fuels have shown that 3.61 million lives per year could be saved [5]. Of note, the avoidable mortality that would result from this phaseout is higher than the avoidable mortality from issues like unsafe water and sanitation. Clean energy sources, which are already being explored with more urgency, would ultimately save the lives of millions. They could also reverse the detrimental effects that fossil fuels have had on the environment, such as the increase in droughts, thus highlighting their importance on a global scale [5]. In return, this would also benefit the fight against unsafe water and food insecurity, creating a positive cycle of environmental regeneration that benefits humans in invaluable ways.

Climate change is a prominent threat but is rarely discussed in the context of human health, which is a great disservice to communities and people worldwide. Numerous studies have concluded that air pollutants are significantly associated with a large portion of deaths worldwide—deaths that could have been avoided in many cases. Further research has shown the link between air pollutants and its damaging effects on bodily processes and pathways. The approach of framing the issue of climate change in a human health perspective has not been widely implemented. However,it is one possible path to incentivizing the need to phase out industries that directly fuel the vicious cycle of climate change, which leads to the death of many innocent lives and crippling even more.


1. Anderson, A., Lebling, K., Byrum, Z., & Dellesky, C. (2021, December 7). A new industrial revolution for a livable climate. World Resources Institute. Retrieved April 14, 2022, from

2. Borunda, A. (2021, May 3). The science of how climate change impacts fires in the West. National Geographic. Retrieved March 15, 2022, from

3. Bowe B, Xie Y, Yan Y, Al-Aly Z. Burden of Cause-Specific Mortality Associated With PM2.5 Air Pollution in the United States. JAMA Netw Open. 2019;2(11):e1915834. doi:10.1001/jamanetworkopen.2019.15834

4. Environmental Protection Agency. (n.d.). Particulate Matter (PM) Pollution. EPA. Retrieved March 31, 2022, from

5. Lelieveld, J., et al. “Effects of Fossil Fuel and Total Anthropogenic Emission Removal on Public Health and Climate.” Proceedings of the National Academy of Sciences, vol. 116, no. 15, 2019, pp. 7192–7197.,

6. Li, T., Hu, R., Chen, Z., Li, Q., Huang, S., Zhu, Z., & Zhou, L. F. (2018). Fine particulate matter (PM2.5): The culprit for chronic lung diseases in China. Chronic diseases and translational medicine, 4(3), 176–186.

7. Rappold, A. G., Stone, S. L., Cascio, W. E., Neas, L. M., Kilaru, V. J., Carraway, M. S., Szykman, J. J., Ising, A., Cleve, W. E., Meredith, J. T., Vaughan-Batten, H., Deyneka, L., & Devlin, R. B. (2011). Peat bog wildfire smoke exposure in rural North Carolina is associated with cardiopulmonary emergency department visits assessed through syndromic surveillance. Environmental health perspectives, 119(10), 1415–1420.

8. Southerland, V. A., Brauer, M., Mohegh, A., Hammer, M. S., van Donkelaar, A., Martin, R. V., Apte, J. S., & Anenberg, S. C. (2022). Global Urban Temporal Trends in fine particulate matter (PM2·5) and attributable health burdens: Estimates from Global Datasets. The Lancet Planetary Health, 6(2).

9. Vohra, Karn, et al. “Global Mortality from Outdoor Fine Particle Pollution Generated by Fossil Fuel Combustion: Results from GEOS-Chem.” Environmental Research, vol. 195, 2021, p. 110754.,

10. Wei, Yaguang, et al. “Causal Effects of Air Pollution on Mortality Rate in Massachusetts.” American Journal of Epidemiology, vol. 189, no. 11, 2020, pp. 1316–1323.,

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