Study Highlights Link Between Atmospheric Pollutants and COVID-19 Incidence

A thorough study targeted the probable connection between a low air quality index and COVID-19 spread in Italy, in Q2 of 2020.

Led by the Euro-Mediterranean Center on Climate Change (CMCC) Foundation, the study points toward the possible short-term correlation between exposure to three familiar atmospheric pollutants (PM₁₀, PM_2.5, and NO₂) and COVID-19 incidence, lethality and mortality rates.

It has been speculated that the spread of SARS-CoV-2, the coronavirus that caused the present pandemic outbreak, is associated with short-term and long-term exposure to atmospheric pollutants, mostly particulate matters (PMs).

People who live in highly industrialized areas and are thus exposed to higher levels of pollution, could exhibit more severe symptoms. Additional studies have indicated that atmospheric pollutants can serve as virus carriers and increase pandemic diffusion.

A study that was published recently in the Environmental Pollution journal looked for any prospective short-term correlation between these two phenomena.

The study was performed in collaboration with the University of Salento and the Italian National Institute of Health (ISS) and focuses on the analysis of concentrations of atmospheric pollutants (NO₂, PM₁₀, PM_2.5) together with the spatio-temporal distribution of cases and deaths (particularly incidence, lethality, and mortality rates) throughout Italy, down to the level of separate territorial areas, which include four of the most affected regions—Piedmont, Lombardy, Veneto, and Emilia-Romagna.

The data analysis has been limited to the first quarter of 2020 to reduce the lockdown-dependent biased effects on the atmospheric pollutant levels as much as possible.

Giovanni Aloisio, Full Professor, Department of Innovation Engineering, University of Salento

“Our results suggest the hypothesis of a moderate-to-strong correlation between the number of days exceeding the annual regulatory limits of PM₁₀, PM_2.5 and NO₂ atmospheric pollutants and COVID-19 incidence, mortality and lethality rates for all the 107 Italian territorial areas under investigation, whereas weak-to-moderate correlations where found when the analysis was limited to four of the most affected regions in Northern Italy (Lombardy, Piedmont, Emilia-Romagna and Veneto),” added Aloisio, who is also the corresponding author of the study, a member of CMCC Strategic Board, and Director of the CMCC Supercomputing Center.

In general, PM_2.5 and PM₁₀ exhibited a higher correlation compared to NO₂ with COVID-19 incidence, lethality and mortality rates. Eventually, PM₁₀ profiles have been further examined together with the variation in COVID-19 incidence rate for three of the most affected territorial regions in Northern Italy (that is, Brescia, Milan, and Bergamo) in March 2020.

All areas exhibited a similar PM₁₀ time trend but a distinct COVID-19 incidence rate variation, which was less severe in Milan than in Bergamo and Brescia.

In the future, the analysis will be extended to consider outbreak dynamics and confounding factors, such as ethnicity, hospital beds, population size, number of individuals tested for COVID-19, weather, socioeconomic and behavioral variables (for example, obesity, income, and smoking habits), days from the first reported case of COVID-19, population age distribution, and days from the issuance of the stay-at-home order, etc.

The study findings indicate that confounding factors must be accounted for to justify why the almost equal PM₁₀ profiles observed in Bergamo, Brescia and Milan during Q1 of 2020 did not produce analogous changes in COVID-19 incidence rates.

Besides, confounders may justify the discrepancies in the statistical significance of correlations identified when a four-region subset is compared with the entire Italian country. Eventually, climate change negatively impacts human health and its prospective role in the pandemic spread warrants additional investigation.

Journal Reference

Accarino, G., et al. (2020) Assessing correlations between short-term exposure to atmospheric pollutants and COVID-19 spread in all Italian territorial areas. Environmental Pollution. doi.org/10.1016/j.envpol.2020.115714.