Urban air pollution is linked with Covid-19.In 2019, novel infectious coronavirus appeared as an emergent and deadly respiratory disease caused by SARS coronavirus 2 (Onder et al., 2020). It was firstly identified in Wuhan, China and gradually spread all around the globe. According to World meter report, around 56,727,696 cases have been reported and 1,357,809 have died till yet. Considering these numbers, 2.39% appears to be the case-fatality rate all around the world. Various studies on etiology of covid-19 have been conducted since outbreak, however, research on environmental factors contributing to diversity in severity of cases is still lacking (Liang et al., 2020).
“Urban Air Pollution”
In recent past, Weiss et al. (2004), Lin et al. (2006), Heymann et al. (2005) and Qu et al. (2020) have put forward the studies on impacts of environmental and social factors on infectious diseases such as SARS. One among the factor is the “Urban Air Pollution” that is reported to intensify the vulnerability of serious outcomes of outbreak. Morbidity and mortality due to air pollution is already well understood (Liu et al., 2019; Anenberg et al., 2018; Alhanti et al., 2016). This air pollution is caused by, cars, power plants, refineries, industries, chemical plants etc. and are the most common sources of in urban areas, according to USEPA. Since the boost of industrialization, air pollutant prevalence has jumped to a next level. Criteria pollutants such as Sulphur dioxide (SO2), soot, lead (Pb), nitrogen oxides (NOx) and other particulate matter (PM2.5 and PM10) increased in uncontrolled manner causing environmental deterioration and health threats (Fenger, 1999). These air pollutants standard is being used now for research when covid-19 death toll risen. Two death outcomes are needed to be measured, Case-Fatality Rate– number of deaths among covid-19 patients and Mortality Rate– number of covid-19 deaths in the total population.
Ozone (O3), particulate matter (PM2.5 and PM10) and nitrogen oxides (NOx)
In these times of Coronavirus outbreak, ozone (O3), particulate matter (PM2.5 and PM10) and nitrogen oxides (NOx) are of great concern due to their capability to cause respiratory, cardiovascular and immune system dysfunctioning (Ciencewicki et al., 2007; Ayyagari et al., 2007; Liang et al., 2018; Liang et al., 2019; Golan et al., 2018). This is of key interest now that how these pollutants affect the disease onset and case-fatality rate of covid-19.
Pollutants and SARS case-fatality rate
During this covid-19 outbreak, a close correlation has been found between pollutants and SARS case-fatality rate (Cui et al., 2003). Yongjian et al. (2020) demonstrated a temporal increase in Covid-19 cases because of varying air quality for short duration. Liang et al., (2020) explained that nitrogen oxides have positive correlation with case-fatality rate of SARS Covid-19, independent of PM2.5 and ozone, making long-term urban air pollution to be a risk factor in times of Covid-19. In a research conducted by Wu et al., (2020), they concluded the results via ecological regression analysis and found that particulate matter (PM2.5) is closely associated with higher county-level covid-19 cases.
Urban air pollutants
Urban air pollutants not only directly affect the health of individuals, but they also serve as vectors for virus transmission. Coccia et al. (2020) explained that PM2.5 are more involved in virus transmission as compared to man to man transmission. These pollutants are capable to agglomerate with the virus. Setti et al., (2020) suggested that exhaled droplets get fused with PM, making them more persistent in atmosphere due to the decline in diffusion coefficient. This leads to inhalation of virus containing particulate matter (PM 2.5) making the virus containing droplets more contagious.
National Aeronautics and Space Administrations (NASA) and European Space Agency (ESA)
There are several countries like China, Italy, England, France, Czech Republic, Poland, United States of America and Brazil where air pollution data has been estimated and linked with disease onset. According to National Aeronautics and Space Administrations (NASA) and European Space Agency (ESA), no reduction in pollution has been observed in Northern China, however, Southern parts showed a considerable drop in pollution during Covid-19. Same has been identified in Northern Italy during lockdown. In these times, Conticini et al., (2020) found a correlation between death caused by covid-19 and high pollution level. England and France showed the same trend of correlation between mortality rate and pollutant level (Travaglio et al., 2020). Similar study conducted by Wu et al. (2020) in USA suggested that increase of 1 μg/m3 of PM2.5 causes the 15% rise in covid-19 mortality rate. And one-unit increase in PM10 cause an increase of 8% in covid-19 cases (Travaglio et al., 2020).
The Centre for Research on Energy and Clean Air published
The Centre for Research on Energy and Clean Air published a report considering this air pollution and human health in times of Covid-19, that concluded that:
People exposed to high level of pollutants have vulnerable natural defense systems against air borne diseases and so thus against SARS Covid-19.
In many chronic illnesses, air pollution serves to be a vital risk factor to make people seriously ill to be treated in ICU or it may lead to their death due to covid-19.
People with vulnerable respiratory tract systems are at more risk to be hospitalized or die off.
A socio-environmental synthesis approach
In addition to these criteria pollutants (sulphur dioxide, SO2; nitrogen oxides, NOx and particulate matter, PM2.5 and PM10), hazardous air pollutants (HAPs) are of great concern too. According to EPA, HAPs are toxic air pollutants that are posed to cause serious health effects such as reproductive effects or environmental or ecological effects. There are total 187 hazardous air pollutants. A socio-environmental synthesis approach was used by Petroni et al. (2020) to examine top five hazardous air pollutants (HAPS) including Acrolein, acetaldehyde, formaldehyde, diesel particulate matter and naphthalene. They found that HAPs do not affect the respiratory tract directly, but they do reduce the covid-19 patients’ ability to recover. However, in the negative binomial mixed county-level model, they predicted the covid-19 mortality as the function of hazardous air pollutants respiratory toxicity levels and related covariates. They came to a conclusion that a rise in Respiratory Hazard Index (RHI) is linked with 9% more covid-19 cases. In The Conversation, environmental health scientists also stated that the diesel exhaust and industrial exhaust containing acetaldehyde is closely associated with higher cases of Covid-19, same as reported by Petroni et al., (2020).
Thus, it is now confirmed that both Criteria Pollutants as well as Hazardous Air Pollutants (HAPs) have their implications in Covid-19 disease onset and recovery from it. More precisely, long-term and short-term pollution exposure may have direct or indirect systematic paraphernalia on the human body.
The metropolitan cities with high pollution level have both man to man and pollutant to man transmission of novel coronavirus. People like hawker, auto-rickshaw drivers, bus drivers, mechanics, and the people who travels through public transport get more exposed to particulate matter (PM2.5 and PM10), nitrogen oxides (NOx) and ozone (O3) and these pollutants have caused higher agglomeration of virus and thus virus finds its way to get into human body through respiratory tract via inhalation, and not always via man to man transmission.
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