Although global dissemination of COVID-19 is multidimensional and non-homogenous, we hypothesize air pollution to be a mitigating factor.
Air pollution, as quantified by particulate matter (PM) 2.5 and PM 10.0, is known to cause respiratory disease1,2 and impact its acute and long-term outcomes. In terms of deleterious effects on the respiratory tract, smoking and the individual components of air pollution (such as SO2, NO2, CO2, and CO) share a common pathogenesis. The lungs of almost all 20 million residents of New Delhi, India, are burdened with cumulative effects of air pollutants, an equivalent of smoking 25 cigarettes a day.3
Air pollution also impairs immunity.4,5 We ponder whether air pollution provided the noxious backdrop that impaired immunity in the thousands of early COVID-19 victims in Wuhan and in other parts of China. With their lowered immunity, these patients became more susceptible to COVID-19. In addition, patients with pollution-dampened immunity may have worse outcomes of their viral infection.
In expanding our observation of the rapid spread of COVID-19 in Iran and northern Italy, we again found air pollution to be a common denominator (An air quality index [AQI] score of 50 or below represents good air quality: Wuhan 147, Iran 77, Italy 78). India presents a confounding variable to our hypothesis and we speculate whether under-reporting and under-testing explain the low incidence of the disease in the country.
Two suggestions emerge from these observations: 1) Larger institutions should research the longitudinal relationship between COVID-19 and air pollution; 2) The World Health Organization (WHO) and other global health regulatory agencies should consider labeling air pollution as a risk factor for COVID-19.
The authors can be contacted via Dr. Sameer Mehta at email@example.com
- Wonjun J, Yu-Rang P, Hae-Reong K, et al. Prolonged effect of air pollution on pneumonia: a nationwide cohort study. European Respiratory Journal. 2017; 50(61): OA467. doi: 10.1183/1393003.congress-2017.
- Dasom K, Zi C, Lin-Fu Z, Shou-Xiong H. Air pollutants and early origins of respiratory diseases. Chronic Dis Transl Med. 2018 Jun 7; 4(2): 75-94. doi: 10.1016/j.cdtm.2018.03.003.
- Balakrishnan K, Dey S, Gupta T, et al. The impact of air pollution on deaths, disease burden, and life expectancy across the states of India: the Global Burden of Disease Study 2017. Lancet Planet Health. 2019 Jan; 3(1): e26-e39. doi: 10.1016/S2542-5196(18)30261-4.
- Gawda A, Majka G, Nowak B, Marcinkiewicz J. Air pollution, oxidative stress, and exacerbation of autoimmune diseases. Cent Eur J Immunol. 2017;3, 305-312. https://doi.org/10.5114/ceji.2017.70975.
- Glencross DA, Ho TR, Camiña N, et al. Air pollution and its effects on the immune system. Free Radic Biol Med. 2020 Jan 30. pii: S0891-5849(19)31521-7. doi: 10.1016/j.freeradbiomed.2020.01.179. [Epub ahead of print]