The study, published online in the journal Occupational and Environmental Medicine, showed that both Particulate matter (PM) 2.5 and 10 were significantly associated with an increased Covid-19 infection rate.
Every 1 microgram/cubic metre increase in long term exposure to PM2.5 was associated with a 5 per cent increase in the number of new cases of Covid-19 infection, equivalent to 294 extra cases per 100,000 of the population/year.
“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,” said Giovanni Veronesi from Department of Medicine and Surgery at University of Insubria,Italy.
“Meanwhile, government efforts to further reduce air pollution levels can help to mitigate the public health burden of Covid-19,” Veronesi added.
While population density wasn’t associated with a heightened risk of infection, living in a residential care home was associated with a more than 10-fold heightened risk of the infection.
The associations were even more noticeable among older age groups, indicating a stronger effect of pollutants on the Covid-19 infection rate among 55-64 and 65-74 year olds.
However, as this is an observational study, and as such, can’t establish the cause, they said.
But long term exposure to air pollution also heightens the risk of respiratory and cardiovascular diseases through persistent inflammation and compromised immunity. These same pathways may therefore be involved in the link between air pollution and higher Covid-19 infection rates, the researchers noted.
Further, drug treatment for diabetes, high blood pressure, and obstructive airway diseases, as well as a history of stroke were also associated with, respectively, a 17 per cent, 12 per cent, 17 per cent, and 29 per cent, heightened risk.
For the study, the team looked at long term exposure to airborne pollutants and patterns of Covid-19 infection from the start of the pandemic to March 2021 among the residents of Varese, the eighth largest city in Lombardy – worst affected region in terms of both cases and deaths due to Covid.