Long-term exposure to air pollution could increase the risk from COVID-19 infection, new findings show today.
Research published in *Occupational & Environmental Medicine* found the association was strongest for particulate matter, with an average annual rise of 1 µg/m3 linked to a 5% increase in the infection rate.
They say while further research is needed to confirm cause and effect, the findings in this observational study should reinforce efforts to cut air pollution.
Lombardy the worst affected region of northern Italy for both cases and deaths and several reasons have been suggested for this, including different testing strategies and demographics.
But the European Union Environmental Agency estimates that most of the 3.9 million Europeans in areas where air pollution exceeds European limits live in northern Italy.
There have been limited studies into airborne pollution as a risk factor for COVID-19 and this research team decided to look at long-term exposure to airborne pollutants and patterns of infection from the start of the pandemic to March 2021 among those living in Varese.
Of the 81,543 residents recorded in December 2017, more than 97% were successfully linked to the 2018 annual average exposure levels for the main air pollutants.
Regional COVID-19 infection data and information on hospital discharge and outpatient drug prescriptions were gathered for 62,848 adults yet to be infected with SARS-CoV-2. Official figures show that 3.5% of the population in the entire region were fully vaccinated by the end of March 2021.
Estimates of annual and seasonal average levels of five airborne pollutants – particulate matter (PM2.5, PM10); nitrogen dioxide (NO2); nitric oxide (NO); and ozone (O3) – were available for 2018 over an area more than 40 km wide.
The average PM2.5 and NO2 values were 12.5 and 20.1 µg/m3, respectively. The corresponding population-weighted average annual exposures in Italy for the same year were 15.5 and 20.1 µg/m3, respectively.
Both PM2.5 and PM10 were significantly associated with an increased COVID-19 infection rate, with every 1 µg/m3 increase in long-term exposure to PM2.5 associated with a 5% increase in the number of new COVID cases – equivalent to 294 extra cases per 100,000 of the population per year.
Similar results were found when they applied seasonal rather than annual averages and these findings were confirmed in further analyses that excluded care home residents and further adjusted for local levels of deprivation and use of public transport. Similar findings were observed for PM10, NO2 and NO.
The research team found that associations were more prevalent among older age groups, those aged 55-64 and 65-74 year olds.
They write: “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.
“Meanwhile, government efforts to further reduce air pollution levels can help to mitigate the public health burden of COVID-19.”
Veronasi G, De Matteis S, Caolri G et al. Long-term exposure to air pollution and COVID-19 incidence: a prospective study of residents in the city of Varese, Northern Italy. *Occupational & Environmental Medicine*. 11 January 2022
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