COVID-19: Why long-term exposure to air pollution is worrisome

Several countries have seen an exponential rise in the novel coronavirus disease (COVID-19) cases. Most of them have imposed lockdowns in a bid to flatten the curve and contain the virus' (SARS-CoV-2) spread.

A new study has emerged saying people with respiratory conditions such as asthma and chronic obstructive pulmonary diseases (COPD), and those with weaker immunity, are more susceptible.

A recent study in the United States suggested that people living in areas with heavily polluted air are at a higher risk of contracting the disease.

Researchers from Harvard TH School of Public Health in Boston studied patient data from more than 3,000 counties across the US and found that increase in long-term particulate matter (PM) 2.5 exposure had a direct correlation with the death rate associated with COVID-19.

In short, people living in areas with higher levels of PM 2.5 had a higher chance of succumbing to COVID-19.

The study claimed that an increase of only 1 microgram per cubic metre (μg/m³⁾ in PM 2.5 in ambient air led to a 15 per cent increase in mortality rate due to COVID-19.

For instance, if the concentration of average PM levels in New York City were lowered by one unit each year for the last two decades, the financial nerve centre would have seen 248 fewer cases.

A similar study was conducted in northern Italy, a region which has seen one of the highest numbers of COVID-19 cases worldwide so far.

The study suggested that high mortality rates in the area were a result of an older population demographic combined with long-term exposure to pollution.

Death rate in Lombardy, which is far more polluted due to higher economic activity, was at 12 per cent in March 2020; in rest of Italy it was 4.5 per cent during the same time period.

Presence of chronic respiratory tract diseases and other cardio-vascular comorbidities only facilitated easier virus (SARS-CoV-2) transmission and death. Worldwide, hypertension, diabetes, cardiovascular diseases and respiratory symptoms have been the most reported comorbidities for COVID-19.  

This bit of information is particularly troubling for India which is infamous for being one of the 20 most polluted countries in the world.

Monitoring of PM 2.5 levels began as late as 2016 at manual monitoring stations, while the real-time network, which has been monitoring PM 2.5 levels for much longer, has recently expanded.

A quick analysis of the available data showed considerable gaps. However, most of the available data showed very high levels of PM 2.5 as compared to the national standards.

Where does India stand

One may argue that the national lockdown would have led to a decline in pollution levels, hence making people better equipped to fight COVID-19.

While Delhi witnessed the cleanest March in the last five years, the dip is only recent and not sufficient to reverse the damages caused in the past. Also, a rise in COVID-19 cases and high mortality rates continued to persist in Lombardy region in Italy, even after a lockdown and a subsequent dip in pollution levels were observed in the first half of March 2020.

In 2018, Delhi recorded an annual average of 116 μg/m³ of PM 2.5. Though there was a slight drop in 2019 (109 μg/m³), this, too, was well above the prescribed limits of 40 μg /m³.

Further, several studies confirmed that Delhi accounted for a significant number of premature deaths due to ambient PM 2.5. Therefore, people of Delhi and other major cities in India have already had long term exposure to severe air pollution and PM 2.5.

Assuming that the rate of testing and social distancing measures is similar across India, northeast India comes out as an outlier — it continues to report very few cases.

Kerala, another state with cleaner air, has reported a decline in the number of cases despite initially reporting a higher number of infections.

Symptomatic COVID-19 patients have mild, severe or critical symptoms. While critical symptoms have been observed in less than 12 per cent of cases, it is this bracket that is likely to die from the disease.

Though the exact trajectory of the virus and its effects on humans is still under investigation, the medical fraternity at large agrees that death in COVID-19 patients is mainly due to severe lung inflammation (pneumonia), imbalances in immune response and sepsis.

Cardiac arrests have also been observed, though it is yet to be ascertained if the virus attacks the heart muscle or heart attack occurs due to continued lung inflammation. At present, gathering data for this remains a challenge, as autopsies on COVID-19 patients are seen as high risk along with the very high body count.

Interestingly, pneumonia and cardiac arrests have been observed in patients suffering from lower respiratory tract illnesses and COPD and among people living close to mining areas.

Studies in Chhattisgarh and Tamil Nadu have suggested that poor lung capacity in people living closer to power plants puts them at higher risk of contracting the disease.

Though large-scale experimental and epidemiological studies are required to assess the exact role of air pollution in novel coronavirus infections, these preliminary studies suggested long-term exposure only exacerbated the number of infected patients.

Further, in densely populated countries such as India, our fragile healthcare systems are additionally burdened. Similar correlations between air pollution and SARS fatality rates have already been reported in China.

The novel coronavirus is zoonotic and is said to have originated from animals, possibly bats. If forest degradation continues at the current rate, such pandemics will be more frequent due to increased habitat destruction and subsequent higher man-animal interactions.

To prevent such large-scale pandemics, implementation of multi-pronged approaches such as prevention of habitat destruction will have be prioritised. Reduction in air pollution and adoption of cleaner industrial and vehicular fuels are important to build a healthier community.

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