How Air Pollution worsens COVID-19 Pandemic?

By Dr. Shruti Maroo Rathi

Introduction

As India gets ready to celebrate the big festival of Diwali, several states government have decided to ban firecrackers due to the rising cases of coronavirus COVID-19. It is considered that the pollution caused by the bursting of firecrackers increases the risk of COVID-19 patients. 

So, what is the mechanism behind this??

Let’s start from the basic! What causes air pollution?

Air pollution is the result of the presence of toxic gas and contaminating particles in the atmosphere. The gases include carbon monoxide, nitrogen oxides, sulfur dioxides, ammonia, and volatile organic compounds, as well as some gaseous forms of metals. Whereas, Particulate matter includes a mixture of compounds that includes: sulfates, nitrates, elemental carbon, organic carbon, and crustal materials (earth and ash). They are inhalable corpuscles that can cause damage to human health owing to their small size. Their toxicity is then increased as they can adsorb other substances such as heavy metals and polycyclic aromatic hydrocarbons. It is classified as PM2.5 and PM10 based on a diameter of less than 2.5 micrometers or 10 micrometers, respectively. [1]

How is Particulate Matter Related to Spread of Coronavirus?

1.Atmospheric Particulate Matter function as a carrier, or as a transport vector, for the virus.

It creates a microenvironment suitable for its persistence thus increases the effectiveness of the virus spread in the aerosol. [2] Inhalation of these polluting particles (PM10 and PM2.5), can lead to inhalation of the associated microorganisms also which transports the particles & microorganisms deep into the lungs, especially those smaller than 2.5 microns (PM2.5 and UFPs). This allows the virus to develop within the respiratory tract and to cause infections. Recent studies also indicate that microbial community composition and concentration are significantly affected by concentration and dimension of the particle.[3]

2.Particulate Matter Damages Pulmonary Cells Inducing Inflammation and Oxidative Stress

As already discussed, Particulate Matter has small dimensions and, for this reason, it can be inhaled. Long-term exposure to particulate matter causes damage to the lungs’ health. 3 mechanisms have been demonstrated to alter the immune response in lung cells after PM exposure, both in humans and experimental models:

a. Oxidative stress: Exposure to these pollutants induces the production of free oxygen radicals that can induce damage to the cells.

b. Inflammation: Particulate Matter induces the activation of the immune response and thus the cell enters an inflammatory state. An increase in inflammation leads to an increase in angiotensin-converting enzyme 2 (ACEs). These receptors facilitate the entrance of the virus in the cell by combining with Spike proteins present on Coronavirus and leads to infection.[4]

c. Exposure to pollution can reduce the phagocytosis ability of macrophages thus it fails to inactivate the virus.[5] This cellular condition will facilitate the attack of viruses and increases the severity of viral infections in exposed subjects. As respiratory tract cells are the first target of Particulate Matter, as well as the first target of respiratory viruses, pathogens will invade already compromised cells if subjects are exposed to Particulate Matter for a long time which thus will not be able to properly inactivate the viruses.

Conclusion

Delhi, as well as few other areas of NCR, have reported a steep increase in daily cases of Covid-19 in the past few days and 13 percent of this increase has been estimated to be due to air pollution.

Wearing a face mask, maintain social distancing, ensuring hand hygiene and use of air purifiers are some of the effective ways of keeping oneself safe from COVID-19 as well as pollution this winter. Strenuous outdoor exercise during peak pollution hours should also be avoided. For people with respiratory diseases, it is very important to be compliant to their treatment. We must recognize that it is a collective responsibility of people to work together so that we can defeat both COVID-19 and pollution.

The pandemic may end with the vaccination or with herd immunity, however, there are no vaccines against poor air quality and climate change. The remedy is to mitigate emissions. Say No To Fire Crackers this Diwali…!!

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References

[1] E.P.A. Particulate Matter (PM) Pollution. Available online: https://www.epa.gov/pm-pollution/particulatematter-pm-basics (accessed on 22 May 2020)

[2]Setti, L., Passarini, F., de Gennaro, G., Di Gilio, A., Palmisani, J., Buono, P., Fornari, G., Perrone, M.G.,Piazzalunga, A., Barbieri, P., Rizzo, E., Miani, A. Evaluation of the potential relationship between Particulate Matter (PM) pollution and COVID-19 infection spread in Italy. Available online: http://www.simaonlus.it/wpsima/wp-content/uploads/2020/03/COVID_19_position-paper_ENG.pdf

[3] Liu, H.; Zhang, X.; Zhang, H.; Yao, X.; Zhou, M.; Wang, J.; He, Z.; Zhang, H.; Lou, L.; Mao, W.; Zheng, P.; Hu, B., Effect of air pollution on the total bacteria and pathogenic bacteria in different sizes of particulate matter. Environ. Pollut 2018, 233, 483–493.

[4] Comunian S, Dongo D, Milani C, Palestini P. Air Pollution and Covid-19: The Role of Particulate Matter in the Spread and Increase of Covid-19’s Morbidity and Mortality. Int J Environ Res Public Health. 2020;17(12):4487. Published 2020 Jun 22. doi:10.3390/ijerph17124487

[5] Kaan, P.M.; Hegele, R.G., Interaction between respiratory syncytial virus and particulate matter in guinea pig alveolar macrophages. Am. J. Respir Cell Mol. Biol 2003, 28, 697–704.

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