The causal link between air pollution and Covid-19 cases has yet to be conclusively established, but long-term exposure will certainly make people more vulnerable to lung infections, scientists warn as they Skies over much of northern India, including Delhi, are turning smoky and air quality is rapidly deteriorating.
Their concerns arise amid several global studies pointing to the possible connection between higher levels of air pollution and an increase in Covid-19 cases and deaths.
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A study by researchers at Harvard University in the US in September showed that an increase of just one microgram per cubic meter in PM 2.5 is associated with an 8 percent increase in the death rate from Covid-19. .
“Given the current limited literature, rising PM2.5 level in Delhi may be associated with increased Covid-19 cases … Although literature is relatively sparse at this stage,” said Xiao Wu, corresponding author of the Harvard study. PTI.
He said the relationship between long-term air pollution and Covid-19 has been documented in many studies, which indicate that the adverse health impacts of air pollution can make people prone to infection or exacerbate the disease. severity of Covid-19 symptoms once infected.
This is interesting, especially considering that Covid-19 causes viral pneumonia and acute respiratory distress syndrome, and severe inflammation of the heart and circulatory system, the scientist said.
Another study conducted by the University of Cambridge in April found an association between living in an area of England with high levels of air pollution and the severity of Covid-19, caused by the SARS-CoV-2 virus.
“Based on our findings, you would expect to see an association between higher levels of air pollution in India and Covid-19 in winter, similar to what we found in England,” said Marco Travaglio, corresponding author of the Cambridge study.
“If air pollution levels have been consistently above legal limits for several months or years before next winter, I would expect to see a relationship between those levels and the Covid-19 burden in different parts of India in November and going forward, “Travaglio told PTI.
He noted that a key component of PM2.5 toxicity is its composition, which can vary considerably between countries.
“However, the WHO legal limits for PM2.5 are currently set at 10 µg / m³ (micrograms per cubic meter) on an annual average. Levels above 500 μg / m³ are extremely high and can have a considerable impact on people’s health in relation to Covid-19, but also beyond, ”Travalgo said.
The level of small particulate matter (PM2.5) in Delhi has averaged around 180-340 µg / m³ in recent weeks, while that of larger particulate pollutants (PM10) has ranged between 120 and 450 during that time.
Long-term exposure to chronically high levels of PM2.5 weakens the lungs’ ability to fend off infection, making people more susceptible to Covid-19, the scientists said.
Furthermore, studies from Italy have shown that traces of RNA from SARS-CoV-2, the genetic material of the virus, can be found in pollutant particles, meaning that increased air pollution can act as a vehicle to increase the transmission of Covid-19 in very high cases. contaminated places.
The air quality in northern India is expected to deteriorate further from November to February due to various factors such as stubble burning, festive fireworks and low wind speed conditions leading to an increase in vehicular and industrial pollution trapped in the lower atmosphere.
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“In view of this evidence, the high levels of PM2.5 in Delhi may lead to a higher number of Covid-19 cases,” added Travalgo.
Studies in humans have shown that toxic airborne particles can enter the airways and cause widespread infiltration of lung cells.
This chronic state of inflammation can induce or aggravate health conditions such as asthma, chronic obstructive pulmonary disease, cardiovascular disease and diabetes, experts said.
Because these conditions have been widely found to be associated with an increased risk of contracting Covid-19 or suffering from critical illness, air pollution is likely to act as a risk factor to increase susceptibility to Covid-19.
India has the second highest number of cases in the world of more than 7.9 million and the third highest number of deaths with more than 115,000 from the new coronavirus.
The National Center for Disease Control (NCDC) has warned that Delhi is likely to report around 15,000 Covid-19 cases daily in winter due to the prevalence of respiratory illnesses during this season that worsen the symptoms of the disease. On Sunday, the national capital registered 4,136 new cases of Covid-19, the highest peak in a single day in 38 days.
DJ Christopher, chief of pulmonary medicine at Christian Medical College in Tamil Nadu, noted that the increase in the severe form of Covid-19 among patients would lead to an increase in ICU hospitalizations, increasing the burden on the healthcare system. .
“The lung is the gateway to the body and receives the first impact from inhaled pollutants. It triggers an inflammatory response that damages the lung and makes it more susceptible to infection, ”Christopher told PTI.
‘Hopefully the numbers are not that high. There is the possibility that hospital beds will fill up and ICU beds will be scarce, ”he added.
Professor Rajneesh Bhardwaj agreed, saying there is growing scientific evidence that the airborne respiratory droplets that carry the virus travel and pollute the air after an infected person coughs. He added that pollution can help this airborne droplet stay suspended for longer and can increase the spread of Covid-19.
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“PM2.5 are finer particles that remain suspended in the air for a long time and therefore droplets or viral particles can adhere to these particles to increase risk. They can increase the number of cases as pollution increases, especially with high levels of PM2.5, ”Bhardwaj, associate professor at the Indian Institute of Technology, Bombay, told PTI.
He said the government should make contingent plans to treat a large number of expected cases and warned that any health system could be overwhelmed by a greater number of cases.
However, according to pulmonologist Anurag Agarwal, the relationship between air pollution and Covid-19 cases is very complex. While high air pollution generally increases the risk of respiratory infections, it’s hard to say much more, he said. “Studies that found more infections and deaths in high-polluted areas have tried to statistically adjust for higher population density in polluted cities. These adjusted correlations are interesting but they are not proof, ”Agarwal, director of the CSIR Institute for Genomics and Integrative Biology, told PTI.
“However, it is clear that air pollution is bad for health and Covid-19 is more dangerous in sick people. So the message is clear: we must take action to reduce air pollution for many reasons, ”he added.
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