When Crises Collide: The Link Between Air Pollution and Respiratory Disease

Air pollution is a direct consequence of increasingly industrialized societies, and it poses a threat to the health of millions of people worldwide. Toxic air pollutants range from nitrous oxide (N2O) from vehicle exhaust, to small particulate matter (PM) from burning wood (1). The World Health Organization estimates that 9 in 10 people on earth breathe highly polluted air, and that seven million premature deaths are caused every year by exposure to air pollution (2). On top of direct effects, mounting evidence shows that air pollution increases the risk of several severe diseases including asthma, stroke, heart disease, and lung cancer (2); for example, a recent paper shows that long term exposure to air pollution increases risk of dementia (3). One striking correlation is with respiratory disease - air pollution increases the risk of contracting respiratory illnesses spread by viruses, and makes the viral infection more severe. At this specific point in history, a correlation between pollution and infectious disease is especially notable. COVID-19 is a respiratory illness spread by a new type of coronavirus, previously not seen in humans and now spreading exponentially across the planet (4, 5). Because air pollution raises the risk of contracting infections like this (1, 6), it is incredibly likely that those exposed to high levels of pollutants will be more severely impacted by COVID-19 (4, 6). Already, a study hinting that people who smoke may be more susceptible to infection raises the possibility of a link between lung damage and COVID-19 (7). While there is no data currently available relating air pollution to COVID-19 severity, research from the SARS epidemic in the early 2000’s showed that people living who contracted the SARS illness were twice as likely to die from the condition if they lived in an area with high air pollution (8). How does this happen? Researchers believe that harmful particles in polluted air, like N2O and PM, damage the body’s natural response to infectious disease (1,6). Viruses infect people by entering their cells and hijacking the cell’s normal machinery, to force production of thousands of virus replicates which can then go on to infect other cells (9). The natural immune response consists of specialized white blood cells (WBCs) - these can recognize and destroy the virus infected cells. Air pollution damages WBCs, and reduces their ability to kill virus infected cells (10). Further, it has been shown that exposure to air pollution increases inflammation in the lungs, and leads to a body-wide ‘priming’ of the immune system - an effect which can lead to a more severe inflammatory response to infection (6). These combined effects help to worsen the course of the disease (6). With air pollution rapidly increasing in cities worldwide (11), the negative health impacts will continue to rise. Considering the previous research, it is highly likely that dangerous levels of air pollution are contributing to the severity of the COVID-19 pandemic. Further, the frequency of global epidemics is increasing (12), and it is nearly certain that increasing air pollution will increase the severity of disease and the economic burden of future epidemics (4, 11, 12). Evidently, reducing levels of air pollution in global cities is an urgent measure needed to ensure the basic health of people worldwide (1, 6, 11). So, what can we do? Air pollution is a problem on both local and global scales, and thus requires a variety of solutions. In a 2017 report, the UN recommends several strategies for governments to reduce air pollution. These include investments in air quality assessment programs to monitor the situation, providing accessible hybrid and electric vehicles, developing effective public transport systems, investing in clean and renewable energy sources, protecting existing ecosystems, and expanding green space in cities (13). These suggestions could be implemented in Canada on a national, provincial, or municipal scale - some of them, like electric vehicles and land protection, have already begun. However, we can always do more. Reducing air pollution is not just an environmental issue, and the pandemic we are faced with today may owe some of its effects to the impacts of pollutants like N2O and PM on our lungs and immune systems. This shows that the crises we experience are not separate problems - they collide, intertwine, and affect each other’s outcome. Cleaning up our air, then, also means reducing the impact of future viral pandemics and ensuring a safer living environment for everyone.

References

1. Ciencewicki J, Jaspers I. Air Pollution and Respiratory Viral Infection. Inhalation Toxicology 2007;19:1135–46. doi:10.1080/08958370701665434.

2. Air Pollution. World Health Organization. Accessed 1 April 2020, available from https://www.who.int/health-topics/air-pollution#tab=tab_2

3. Grande G, Ljungman PLS, Eneroth K, Bellander T, Rizzuto D. Association Between Cardiovascular Disease and Long-term Exposure to Air Pollution With the Risk of Dementia. JAMA Neurology 2020. doi:10.1001/jamaneurol.2019.4914.

4. Schlanger S. Now is the time to take care of your lungs. Here’s how. The New York Times, 2020. Accessed April 1 2020, available from https://www.nytimes.com/2020/03/27/climate/climate-pollution-coronavirus-lungs.html

5. Coronavirus Resource Centre. Johns Hopkins University & Medicine, 2020. Accessed 1 April 2020, available from https://coronavirus.jhu.edu/

6. Croft DP, Zhang W, Lin S, Thurston SW, Hopke PK, Masiol M, et al. The Association between Respiratory Infection and Air Pollution in the Setting of Air Quality Policy and Economic Change. Annals of the American Thoracic Society 2018. doi:10.1513/annalsats.201810-691oc.

7. Cai G, Cui X, Zhu X, Zhou J. A Hint on the COVID-19 Risk: Population Disparities in Gene Expression of Three Receptors of SARS-CoV. Preprints, 2020. doi:10.20944/preprints202002.0408.v1. (This article is not peer-reviewed).

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9. Cohen FS. How Viruses Invade Cells. Biophysical Journal, 2016;110:1028–32. doi:10.1016/j.bpj.2016.02.006.

10. Müller L, Chehrazi CV, Henderson MW, Noah TL, Jaspers I. Diesel exhaust particles modify natural killer cell function and cytokine release. Particle and Fibre Toxicology, 2013;10:16. doi:10.1186/1743-8977-10-16.

11. Vidal J. Air pollution rising at an 'alarming rate' in world's cities. The Guardian, 2016. Accessed 1 April 2020, available from https://www.theguardian.com/environment/2016/may/12/air-pollution-rising-at-an-alarming-rate-in-worlds-cities

12. Managing epidemics: Key facts about major deadly diseases. Geneva: World Health Organization; 2018. Accessed 1 April, 2020, available from https://www.who.int/emergencies/diseases/managing-epidemics-interactive.pdf

13. United Nations Environment Programme. Towards a Pollution-Free Planet Background Report. United Nations Environment Programme, 2017, Nairobi, Kenya. Available from http://wedocs.unep.org/bitstream/handle/20.500.11822/21800/UNEA_towardspollution_long%20version_Web.pdf?sequence=1&isAllowed=y