While COVID-19 is a lethal disease by itself, there exist several factors—both internal and external to the human body—that can make the disease even deadlier. The most notable external factor of the lot is air pollution, which can negatively impact the human respiratory system, and effectively exacerbate the health of a person that is regularly exposed to harmful pollutants. Evidence of this fact has been quite visible in Delhi, where the virus-related cases and deaths continue to rise with the pollution levels.

Several scientific studies have already established a positive link between a spike in air pollution and increased COVID-19 death rates, and between local pollution and the risk of contracting the coronavirus. Therefore, the fact that air pollution and COVID-19 make a deadly combo can’t be denied, and if not paid attention to now, this issue has the potential to cause a ‘twindemic’ in the time to come.

To better understand this inextricable link between COVID-19 and air pollution, we spoke to Dr Sachin Gunthe—an associate professor at the Department of Civil Engineering at the Indian Institute of Technology Madras, and a leading expert in this field.

Precisely why does exposure to air pollution increase the risk of severe COVID-19, as claimed by a few studies?

Under the limited epidemiological evidence, many scientific studies have shown a strong positive relation between air pollution and SARS, most closely associated with the COVID-19 case fatality rate. The areas of urban air pollution mainly include the gas phase pollutants such as ozone, carbon monoxide, oxides of nitrogen, and PM2.5 (PM is particulate matter and 2.5 is the upper size limit of these particles in air in micrometer).

Among all these pollutants, PM2.5 is considered most dangerous as it penetrates deeply, reaching the base of the lungs and entering the blood system. Long-term exposure to such a polluted environment leads to dysregulation and compromises the immune system. Therefore, when a person with a compromised immune system acquires COVID-19, the person’s immune system cannot effectively fight the infection, making the individual vulnerable to succumbing to the infection. Thus, air pollution, due to its ability to cause damage at cellular level, can lay the foundation for severe risk of COVID-19 amongst the vulnerable population.

What type of pollutants mainly contribute to aggravating COVID-19?
PM2.5 (also called aerosols), in addition to ozone (O3) and nitrogen dioxide (NO2) may increase the risk of aggravating COVID-19. While PM2.5 is strongly related with the increased risk, few studies conducted in the US have also reported very strong positive relation with NO2 as well.

Since the outbreak, the debate on which climatic conditions most facilitate the spread of the virus has continuously raged. One of your research studies show that the impact of COVID-19 is lower in hotter regions. Is this always the case? And does that mean the situation will worsen during the winter months?
During the very early stages of the pandemic, some relation between the number of cases, temperature,and UltraViolet index was observed, where places with lower temperatures were shown to be having higher cases and vice versa. However, it is important to note that no physiological evidence was examined in that study, and the results were purely statistical.

Further, it was nominally compared with normal influenza, which generally peaks in winter and reduces with warmer temperatures. So it is very difficult to say with any significant level of confidence that COVID-19 has any relation with climatic variables.

Therefore, we can neither deny, nor accept any link with lower temperatures just yet.

It is also important to note that observing the basic hygiene protocols, social distancing, extending full support to pandemic managing departments, and cooperating with government agencies is the best we can do at this stage.

Does climate change have any impact on the pollution levels and the spread of epidemics? If so, could you please elaborate on its effects—both direct and indirect?
The release of pollutants, including that of greenhouse gases, can cause climate change and global warming. Without going into the details at this stage, they are strongly interlinked and are two sides of the same coin. As of now, the increase in pollution is not directly linked with the spread of epidemics, but as mentioned with respect to the points above, prolonged exposure to high pollution does make the population susceptible to certain diseases and infections, as is the case with the severity of COVID-19.

What can residents of Delhi and other highly polluted cities do to minimise the impact of the triple threat of pollution, winter, and COVID-19?
I think the first thing to do is follow the norms set by the agencies (personal hygiene and social distancing), respect the advisories from the medical practitioners, not get paranoid, but at the same time, not adopt a casual attitude towards COVID-19 as well.

As for pollution, simply prevent yourself from burning toxic waste and essentially avoid all activities that give rise to air pollution. And for winter, take proper care of your health, keep your immunity levels high, and do not neglect any symptoms, instead seek medical attention immediately.