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Air pollution and COVID-19
1. AIR POLLUTION AND COVID-19
Kripa Thapa Magar
MPH 1st Year, CDPH, IOM
1
2. Outline of the Presentation
โข COVID-19 Introduction
โข Effect of the COVID-19 prohibitory
orders/lockdown on ambient air quality
โข Air pollution and COVID-19 association
2
3. COVID-19: At a glance
โข Caused by severe acute respiratory syndrome corona virus
2 (SARS-CoV-2)
โข First identified in Wuhan, China on 31st December 2019
โข First case in Nepal on January 23, 2020 (Magh 10th, 2076)
โข WHO declared COVID-19 a PH Emergency of International
Concern on 30th January 2020 and a Global Pandemic on
11th March 2020
โข Variant of concern: Alpha (UK) , Beta (South Africa),
Gamma (Brazil), Delta (India) and Omicron (South Africa)
3
5. Recent Updates of COVID-19 cases
Nepal
Globally
273,900,334 confirmed cases and 5,351,812 deaths
5
6. COVID-19 Lockdown Impact on Air Quality
First corona virus
lockdown in
Wuhan on 23rd
January 2020 until
June
Something
good that
came out of
COVID-19
6
7. โข Research done on 597 major cities worldwide between January 1, 2020,
and July 5, 2020 found that NO2 air quality index value falls more
precipitously (23โ37%) relative to the pre-lockdown period, followed by
PM10 (14โ20%), SO2 (2โ20%), PM2.5 (7โ16%), and CO (7โ11%), but the
O3 increases 10โ27% (Liu et al., 2021).
โข Decline in the population-weighted concentration of ground-level nitrogen
dioxide (NO2: 60%), and fine particulate matter (PM2.5: 31%), with marginal
increases in ozone (O3: 4%) in 34 countries during lockdown dates up until
15 May was observed (Venter et al., 2020).
โข A study done in Portugal revealed that traffic related NO2 and SO2
decreased by 15-71% & 35% respectively during lockdown period, whereas
ozone concentrations slightly increases (Slezakova & Pereira, 2021).
7
8. Fig: The global trend of air pollution (PM2.5)
Notes: The solid red line indicates the date of Wuhan lockdown (January 23, 2020), and the black dash
line indicates the date that this novel corona virus received an official name from WHO (February
11, 2020) (Liu et al., 2021).
8
9. COVID-19 containment measures resulted in up to 50% reduction in the
AQI over South Asian megacities (M. Mishra & Kul Shrestha, 2021)
9
10. Figure: A before/after comparison of the NO2 tropospheric column over the four Hindu
Kush Himalaya (HKH) cities for January 2020 and April 2020; Clockwise from top
left: (a) Delhi, India b) Dhaka, Bangladesh c) Kathmandu, Nepal, and d) Lahore,
Pakistan (Sudip Pradhan & Utsav Maden, n.d.).
10
11. The Centre for Research on Energy and Clean Air reported that quarantines and
travel bans to contain coronavirus resulted in a 25 per cent reduction of
carbon emission in China (Sakshi Mishra, 2020).
Fig: A map shows the sharp
decline in emissions over
China between early January
and late February as parts of
the country went on
lockdown in an attempt to
contain the COVID-19
coronavirus. (Image credit:
NASA Earth Observatory)
11
13. โข The expected premature deaths due to improved air
quality decline by around 99,270 to 146,649 among
76 countries and regions (Liu et al., 2021).
13
14. Lockdown in Nepal
โข First lockdown: Chaitra 11, 2076 to Shrawan 6,
2077 (for 4 months)
โข Second lockdown: Baisakh 16, 2078 to Bhadra
16, 2078 (for 4 months)
14
15. Everest from Kathmandu
Valley: A Rare Sight
Mt Everest (arrow) hidden
behind Mt Kang Nachugo and
Mt Chobutse from Chobar in
Kathmandu on 10 May (Awale,
n.d.). Locals believe that this is
the first time in about 40-50
years that Everest was visible
from the valley (World, n.d.).
Photo: Abhushan Gautam
15
16. Figure: PM mass concentration (percentage change) for 2017-19
(averaged), and 2020 from April to August (A. Mishra et al., 2021)
16
18. COVID-19 and Air Pollution: A Dangerous
Association?
Air Pollutants Role in Transmission of COVID-19
โข Air quality index was significantly correlated with COVID-19 incidence
in both Wuhan and Xiaogan. COVID-19 incidence was prominently
correlated with PM2.5 and NO2 in both cities (Li et al., 2020).
โข Evidence from 219 Chinese cities suggests that the corona virus
further spreads by 5โ7% as the AQI increases by 10 units (Zhang et
al., 2020).
18
19. Setti et al.
suggest that PM
could act as a
carrier for
droplet nuclei,
boosting the
spread of the
virus (Setti et al.,
2020).
Figure: Scheme of possible enhancement of viral transmission
through stabilized human exhalation on PM
19
20. โข Coccia et al. demonstrated that the accelerated
transmission dynamics of COVID-19 resulted mainly
from transmission by contaminated air to man, besides
the transmission from man to man (Coccia, 2020).
โข The highest incidences of COVID-19 occurred in cities
located in Northern Italy. The lowest incidences were
observed in Southern Italy. 39 out of 41 Northern Italian
Provinces resulted in the category with highest PM10
levels, while 62 out of 66 Southern Provinces presented
low PM10 concentrations (Setti et al., 2020).
โข A 10-ฮผg/m3 increase in PM2.5, PM10, NO2, and O3 was
associated with a 2.24%, 1.76%, 6.94%, and 4.76%
increase in the daily counts of confirmed cases,
respectively (Zhu et al., 2020).
20
21. Air Pollutants Role in the Susceptibility &
Severity of COVID-19
โข Study conducted in Northern Italy suggest that an increase in
one unit of PM2.5 (mcg/m3) is associated with a 9% increase in
COVID-19 related mortality (Coker et al., 2020).
โข In the US, a study shows that an increase of 1 mcg/m3 in
PM2.5 is associated with a 15% increase in the COVID-19
mortality rate (Wu et al., 2020).
โข Study conducted in UK found that 0.5% increase in COVID-19
mortality risk for every 1 mcg/m3 increase in NO2
(Konstantinoudis et al., 2021).
21
22. โข Out of the 4443 fatality cases, 3487 (78%) were in five
regions (have the highest NO2) out of 66 administrative
regions of Italy, Spain, France and Germany (Ogen, 2020).
โข In England, a study suggests that individuals exposed to
chronic high levels of air pollution may be more susceptible
to SARS-CoV-2 infection as a result of compromised
immune defence responses due to pollution (Travaglio et
al., 2020).
22
23. PM Exposure
Effects of PM on COVID-19 have been associated with:
o Inflammatory effects and immune dysregulation;
o Oxidative stress and cytotoxicity of polycyclic
aromatic hydrocarbons (PAHs);
o Dysfunctional surfactants;
o Ace-2; and
o Metabolic pathways (Zhao et al., 2021).
23
24. NO2 Exposure
Effects of NO2 levels on COVID-19 have been associated with
(1) Inflammatory effects and immune dysregulation;
(2) Increasing pulmonary epithelial permeability;
(3) Metabolic pathways; and
(4) Monocyte enrichment (Zhao et al., 2021).
24
25. References
1. Archived: WHO Timeline - COVID-19. (n.d.). Retrieved 18 December 2021, from https://www.who.int/news/item/27-04-2020-who-timeline---covid-
19
2. Awale, S. (n.d.). Nepal lockdown proves air quality can be improved. Retrieved 18 December 2021, from
https://www.nepalitimes.com/banner/nepal-lockdown-proves-air-quality-can-be-improved/
3. Baral, B., & Thapa, K. (2021). Effect of COVID-19 Lockdown on Ambient Air Quality In Major Cities of Nepal. In Journal of Health and Pollution (Vol.
11). https://doi.org/10.5696/2156-9614-11.29.210211
4. Coccia, M. (2020). Diffusion of COVID-19 Outbreaks: The Interaction between Air Pollution-to-Human and Human-to-Human Transmission Dynamics
in Hinterland Regions with Cold Weather and Low Average Wind Speed (SSRN Scholarly Paper ID 3567841). Social Science Research Network.
https://doi.org/10.2139/ssrn.3567841
5. Coker, E. S., Cavalli, L., Fabrizi, E., Guastella, G., Lippo, E., Parisi, M. L., Pontarollo, N., Rizzati, M., Varacca, A., & Vergalli, S. (2020). The Effects of Air
Pollution on COVID-19 Related Mortality in Northern Italy. Environmental and Resource Economics, 76(4), 611โ634. https://doi.org/10.1007/s10640-
020-00486-1
6. Konstantinoudis, G., Padellini, T., Bennett, J., Davies, B., Ezzati, M., & Blangiardo, M. (2021). Long-term exposure to air-pollution and COVID-19
mortality in England: A hierarchical spatial analysis. Environment International, 146, 106316. https://doi.org/10.1016/j.envint.2020.106316
7. Li, H., Xu, X.-L., Dai, D.-W., Huang, Z.-Y., Ma, Z., & Guan, Y.-J. (2020). Air pollution and temperature are associated with increased COVID-19
incidence: A time series study. International Journal of Infectious Diseases: IJID: Official Publication of the International Society for Infectious Diseases,
97, 278โ282. https://doi.org/10.1016/j.ijid.2020.05.076
8. Liu, F., Wang, M., & Zheng, M. (2021). Effects of COVID-19 lockdown on global air quality and health. Science of The Total Environment, 755, 142533.
https://doi.org/10.1016/j.scitotenv.2020.142533
9. Mishra, A., Pant, B. P., Shakya, S., Tiwari, P., Pandit, D., & Poudyal, K. N. (2021). Impact of COVID-19 lockdown on particulate matter (PM2.5)
concentration in Kathmandu, Nepal. International Journal of Environmental Studies, 0(0), 1โ9. https://doi.org/10.1080/00207233.2021.1974757
10. Mishra, M., & Kulshrestha, U. C. (2021). A Brief Review on Changes in Air Pollution Scenario over South Asia during COVID-19 Lockdown. Aerosol and
Air Quality Research, 21(4), 200541. https://doi.org/10.4209/aaqr.200541
25
26. 11. Ogen, Y. (2020). Assessing nitrogen dioxide (NO2) levels as a contributing factor to coronavirus (COVID-19) fatality. Science of The Total
Environment, 726, 138605. https://doi.org/10.1016/j.scitotenv.2020.138605
12. Sakshi Mishra. (2020). Origin and Impact of Covid 19. https://www.slideshare.net/sakshioo1/origin-and-impact-of-covid-19?qid=b9c1986a-5eca-
4729-919e-e8cfc183864d&v=&b=&from_search=3
13. Setti, L., Passarini, F., Gennaro, G. D., Barbieri, P., Perrone, M. G., Piazzalunga, A., Borelli, M., Palmisani, J., Gilio, A. D., Piscitelli, P., & Miani, A.
(2020). The Potential role of Particulate Matter in the Spreading of COVID-19 in Northern Italy: First Evidence-based Research Hypotheses (p.
2020.04.11.20061713). https://doi.org/10.1101/2020.04.11.20061713
14. Siciliano, B., Dantas, G., da Silva, C. M., & Arbilla, G. (2020). Increased ozone levels during the COVID-19 lockdown: Analysis for the city of Rio de
Janeiro, Brazil. The Science of the Total Environment, 737, 139765. https://doi.org/10.1016/j.scitotenv.2020.139765
15. Slezakova, K., & Pereira, M. C. (2021). 2020 COVID-19 lockdown and the impacts on air quality with emphasis on urban, suburban and rural zones.
Scientific Reports, 11(1), 21336. https://doi.org/10.1038/s41598-021-99491-7
16. Sudip Pradhan, B. B., & Utsav Maden. (n.d.). Monitoring air quality from space during the COVID-19 pandemic. ICIMOD. Retrieved 19 December
2021, from https://www.icimod.org/article/monitoring-air-quality-from-space-during-the-covid-19-pandemic/
17. Travaglio, M., Yu, Y., Popovic, R., Selley, L., Leal, N. S., & Martins, L. M. (2020). Links between air pollution and COVID-19 in England (p.
2020.04.16.20067405). https://doi.org/10.1101/2020.04.16.20067405
18. Venter, Z. S., Aunan, K., Chowdhury, S., & Lelieveld, J. (2020). COVID-19 lockdowns cause global air pollution declines. Proceedings of the National
Academy of Sciences, 117(32), 18984โ18990. https://doi.org/10.1073/pnas.2006853117
19. World, R. (n.d.). Mount Everest visible from Kathmandu for the first time in decades, see exclusive pictures. Republic World. Retrieved 18
December 2021, from https://www.republicworld.com/india-news/general-news/majestic-mount-everest-visible-from-kathmandu-amid-
lockdown.html
20. Wu, X., Nethery, R. C., Sabath, B. M., Braun, D., & Dominici, F. (2020). Exposure to air pollution and COVID-19 mortality in the United States: A
nationwide cross-sectional study. MedRxiv, 2020.04.05.20054502. https://doi.org/10.1101/2020.04.05.20054502
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cities. The Science of the Total Environment, 741, 140244. https://doi.org/10.1016/j.scitotenv.2020.140244
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Evidence-Based Medicine, 14(2), 123โ138. https://doi.org/10.1111/jebm.12430
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Why ozone concentration increases?
A detailed analysis of NMHC/NOxย ratios and trajectories of air masses in the city of Rio de Janeiro, showed that the relatively high ozone concentrations were a consequence of higher ratios (due to a sharper decrease in NOxย than for hydrocarbons) and also to the possible increase in the reactivity of the VOC mixture (Siciliano et al., 2020).
The paper examines a novel COVID19 government response tracker dataset, combining the daily air pollution data and weather data across 597 major cities worldwide between January 1, 2020, and July 5, 2020
Figure shows the daily changes in PM2.5 individual AQI (converted from corresponding concentrations based on the US EPA standard) of study area cities during the sample period and at the same time frame in 2019, which suggests that cities experienced a similar air pollution level before the date of Wuhan lockdown (the first city in the world to impose city lockdown policy) when the COVID-19 had not spread worldwide, and few cities were put under strict lockdown compared with the same period last year. However, the difference significantly increased, especially after March 2020, when more cities were locked down, indicating an air quality improvement occurred after city lockdowns.
It could be possible to look at the airborne route of transmission, and specifically to particulate matter, as a โhighwayโ for the viral diffusion, in which the droplet nuclei emitted by the exhalations are stabilized in the air through the coalescence (merging) of aerosol with the PM at high concentrations in stability conditions (optimal conditions of temperature and humidity to stabilize the aerosols in airborne). In fact, the fate of a smalls droplet of a virus, under normal conditions of clean air and atmospheric turbulence, evaporates and /or disperses quickly in atmosphere. On the contrary in conditions of atmospheric stability and high concentrations of PM, viruses have a high probability of creating clusters with the particles and, by reducing their diffusion coefficient, enhancing their residence time and amount in atmosphere and promoting contagion.
PM could increase the severity of COVID-19 through directly damaging the immune response of the lungs to infection or indirectly aggravating respiratory or cardiovascular diseases. Excessive inflammatory response results in a massive release of pro-inflammatory cytokines, also known as โcytokine storms,โ which has a significant impact on COVID-19โs severity and mortality.ย
Exposure to these pollutants induces the production of free radicals that induce damage the cells
Third, surfactants decrease surface tension of lung air-fluid interface and prevent alveolar collapse at the end of expiration.87ย Lack of surfactants can lead to ARDS.87ย Experimental studies suggested that physical interaction between PM and surfactant can change the biomechanical function of surfactant.88ย In mice, PM can cause alveolar collapse.89ย On the one hand, PM could compromise the integrity of human respiratory barrier and weaken the host defense.
Fourth, ACE2 plays a key role in viral entry into respiratory epithelial cells.91ย In addition to its physiological function, ACE-2 could serve as a receptor for SARS-COV2. ACE-2 is overexpressed upon chronic exposure to NO2ย and PM2.5ย in mouse experiments.
Fifth, eight metabolic pathways in glycerophospholipid, propanoate, sphingolipid, and glutathione metabolism have been associated with long-term exposure to PM2.5.80ย These pathways are associated with oxidative stress, inflammation, immunity, and nucleic acid damage and repair (Zhao et al., 2021).
Many studies have reported the effect of NO2ย on immune inflammation. A prospective study in nonsmokers showed that higher exposure to NO2ย was associated with IL-17.100ย NO2ย exposure can promote neutrophil and eosinophil recruitment, and a mixed Th2/Th17 response upon antigen challenge.101ย Similarly, NO2ย exposure can boost the production of IL-6 and NF-ฮบB activation.102,ย 103ย NO2ย can function as an adjuvant and induce an antigen-specific Th2 immune response.104ย Inhalation of 15ย ppm NO2ย for just 1ย hour can induce MCP-1 within the lungs,105ย indicating that NO2ย can promote DC recruitment. After NO2ย exposure, CD11c+ pulmonary cells secreted increased amount of IL-1ฮฑ, IL-1ฮฒ, IL-12p70, and IL-6, and increased Th2 cell activity.104ย In addition, high-level NO2ย exposure can induce endothelial dysfunction and oxidative stress disturbances.106ย Thus, it is possible that NO2ย exposure contributes to inflammation and immune disorders and exacerbate SARS-COV-2โinduced lung damage.
High concentrations of NO2ย lead to bronchoconstriction and bronchial hyperreactivity and may also result in damage and inflammation of the airway epithelium. Studies have showed that NO2ย exposure disrupts tight junctions in the lungs and increases epithelial permeability and human bronchial epithelial cell dysfunction.107,ย 108ย In addition, NO2ย exposure reduced the ability of alveolar macrophages to inactivate influenza virus.109
Nassan etย al found significant associations between long-term exposure to NO2ย and 15 blood metabolites using an untargeted metabolomic approach. Short-term exposure to NO2ย was related to 100 unique metabolites and four perturbed metabolic pathways (glutathione, glycerophospholipid, beta-alanine, and taurine and hypotaurine metabolisms).80
Monocytes are key white blood cells of the innate immune system and play a central role in inflammasome activation and cardiovascular diseases. Exposure to NO2ย was positively associated with monocyte levels and diastolic blood pressure after full adjustment.106ย Thus NO2ย may promote monocyte enrichment and DNA methylation in monocytes, which subsequently affects diastolic blood pressure and ultimately aggravates COVID-19 (Zhao et al., 2021).
