What impact has air pollution on COVID-19?

The particulate matter in the air seems to increase the spread of the virus

By Vibha Varshney
Published: Wednesday 12 January 2022
The particulate matter in the air seems to increase the spread of the virus. Photo: iStock

Many studies have linked COVID-19 morbidity and mortality to ambient air pollution. The latest links the high incidence of the disease in northern Italy to air pollution. 

The study, published in the journal Occupational & Environmental Medicine January 11, 2022, shows that an average annual rise of 1 microgram per cubic metre (µg / m3) could be linked to a 2-5 per cent increase in the rate of COVID-19 incidence. 

The researchers — led by Giovanni Veronesi from the Research Center in Epidemiology and Preventive Medicine, University of Insubria, Varese — calculated that this resulted in an extra 294 cases per 100,000 people each year among the residents of Varese, the eighth-largest city in Lombardy in the northern part of Italy.

The researchers linked everyone who had reached the age of 18 years on December 31, 2019, to the average annual exposure to particulate matter (PM) 2.5, PM10, nitrogen dioxide, nitrogen oxide and ozone. Yearly average PM2.5 exposure was 12.5 μg / m3.

As many as 4,408 cases of COVID-19 were recorded among 62,848 residents. 

When correlated with the level of exposure, the researchers found that PM2.5 was associated with a 5.1 per cent increase in the rate of COVID-19. While similar findings were observed for PM10, NO2 and NO, ozone was associated with a 2 per cent decrease in disease rate. 

“Our findings provide the first solid empirical evidence for the hypothesised pathway linking long-term exposure to air pollution with the incidence of COVID-19, and deserve future generalisation in different contexts,” the researchers concluded. 

This is not the first time that such a link has been observed, though the mechanism of action is not well understood. Various theories suggest that air pollution could be working indirectly by exacerbating chronic diseases, such as cardiopulmonary diseases and diabetes. 

Studies have also shown that air pollution can decrease immune response and help the virus gain entry into a cell and replicate. 

Viruses may persist in air through complex interactions with particles and gases depending on chemical composition, electric charges of particles and meteorological conditions such as relative humidity, ultraviolet (UV) radiation and temperature. By reducing UV radiation, air pollutants may promote viral persistence in the air.

In India, Manas P Roy, a public health expert with the Union Ministry of Health and Family Welfare looked at data on air quality parameters (SO2, NO2, PM2.5, and PM10) and COVID-19 from 30 states. However, this study, published in European Review for Medical and Pharmacological Sciences, could see the impact of air pollution on the pandemic only in certain locations.

Relationship between PM10 and COVID-19 cases per million in selected states. Source: European Review for Medical and Pharmacological Sciences

Exposure to air pollution may also increase risks for intensive care unit (ICU) admissions or deaths among COVID-19 patients, according to a study. The researchers analysed more than 6,5000 Covid-19 patients admitted to seven New York City hospitals and correlated them with the air pollution exposure using their residential addresses. 

The team then assessed patient outcomes including mortality, ICU admission and intubation. 

They found that chronic exposure to PM2.5, even at levels below current regulatory thresholds, was associated with an 11 per cent higher risk of mortality and 12 per cent higher risk of admission to the ICU. 

“The COVID-19 pandemic has brought to the forefront the critical role of the environment on health disparities. These data suggest that long-term exposure to air pollution, even at concentrations below US Environmental Protection Agency regulatory standards, is associated with higher COVID-19 morbidity and mortality among hospitalised patients,” said Alison Lee, author of the study published in the American Journal of Respiratory and Critical Care Medicine December 8, 2021. 

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