Association Between Incident COVID-19 Infection and Exposure to Airborne Pollutants

Portrait Of Woman coughing with protection mask and standing on road in city . Epidemic , pollution and allergy .
Researchers conducted a study to investigate the association between long-term exposure to airborne pollutants and the incidence of COVID-19 infection among adults in Italy.

Results of a prospective observational study found an association between long-term exposure to air pollutants and an increased rate of incident COVID-19 infection among individuals in Italy. These findings were published in Occupational and Environmental Medicine

In this prospective study, researchers enrolled individuals from Varese, Italy who were aged 18 years and older as of December 21, 2019. The researchers aimed to investigate the association between the rate of incident COVID-19 infection and long-term exposure to air pollutants. Residential addresses were assessed to link enrolled individuals to the mean annual exposure to outdoor concentrations of fine particulate matter (PM2.5 and PM10), nitrogen dioxide (NO2), nitrogen monoxide (NO), and ozone (O3). A Poisson regression model was used to identify potential confounding variables and determine the association between demographic and clinical features and incident COVID-19 infection.

Among a total of 62,848 individuals included in the final analysis, 4408 developed incident COVID-19 infection (incidence rate, 6005 per 100,000 person-years). Of patients with incident COVID-19 infection, the median age of onset was 53.2 years and 45.6% were men. The researchers found that the rate of incident COVID-19 infection was increased among individuals residing in a residential care home (rate ratio [RR], 10.6; 95% CI, 9.0-12.4). In addition, individuals taking antidiabetic or antihypertensive medications, and those with obstructive airway diseases or a history of stroke, were associated with a 17%, 12%, 17%, and 29% increase in the rate of incident COVID-19 infection, respectively.

The researchers analyzed the demographic and clinical characteristics of individuals included in the study. After adjustment for age, sex, and residing in a residential care home, an increase in the rate of incident COVID-19 infection was found to be significantly associated with exposure to both PM2.5 (RR for 1 μg/m3 increase, 1.051; 95% CI, 1.027-1.076) and PM10 (RR, 1.040; 95% CI, 1.021-1.060). In addition, increased exposure to O3 was associated with a 2% decrease in the rate of incident COVID-19 infection (RR, 0.980; 95% CI, 0.970-0.990). Of note, additional adjustments for medication use and chronic conditions did not significantly change these results. In regard to age, the researchers found a significant association between individuals aged between either 55 and 64 years or 65 and 74 years and an increase in the rate of incident COVID-19 infection.

Limitations of this study include its observational design and the inability to account for potential confounders such as the role of mobility, social interaction, and humidity and temperature. In addition, these findings may not be generalizable to other patient populations due to the inclusion of only individuals aged 18 years and older.

According to the researchers, “ambient pollutants also may sustain SARS-CoV-2 infectivity after the pandemic period, thus exacerbating the already unfavorable health profiles among [individuals residing] in more polluted areas.” They concluded that “future studies are needed to [confirm causality and to] investigate the role of air pollution [on COVID-19] susceptibility in [pediatric populations].”


Veronesi G, De Matteis S, Calori G, Pepe N, Ferrario MM. Long-term exposure to air pollution and COVID-19 incidence: a prospective study of residents in the city of Varese, Northern Italy. Occup Environ Med. Published online January 10, 2022. doi:10.1136/oemed-2021-107833.