Satellite-detected tropospheric nitrogen dioxide and spread of SARS-CoV-2 infection in Northern Italy
Tommaso Filippini, Kenneth J. Rothman, Alessia Goffi, Fabrizio Ferrari, Giuseppe Maffeis, Nicola Orsini, Marco Vinceti
Abstract
Following the outbreak of Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS-CoV-2) last December 2019 in China, Italy was the first European country to be severely affected, with the first local case diagnosed on 20 February 2020. The virus spread quickly, particularly in the North of Italy, with three regions (Lombardy, Veneto and Emilia-Romagna) being the most severely affected. These three regions accounted for more than 80% of SARS-CoV-2 positive cases when the tight lockdown was established (March 8). These regions include one of Europe's areas of heaviest air pollution, the Po valley. Air pollution has been recently proposed as a possible risk factor of SARS-CoV-2 infection, due to its adverse effect on immunity and to the possibility that Journal Pre-proof J o u r n a l P r e -p r o o f 2 polluted air may even carry the virus. We investigated the association between air pollution and subsequent spread of the SARS-CoV-2 infection within these regions. We collected NO 2 tropospheric levels using satellite data available on the European Space Agency before the lockdown. Using a multivariable restricted cubic spline regression model, we compared NO 2 levels with SARS-CoV-2 infection prevalence rate at different time points after the lockdown, namely March 8, 22 and April 5, in the 28 provinces of Lombardy, Veneto and Emilia Romagna. We found little association of NO 2 levels with SARS-CoV-2 prevalence up to about 130 mol/m 2 , while a positive association was evident at higher levels at each time point. Notwithstanding the limitations of the use of aggregated data, these findings lend some support to the hypothesis that high levels of air pollution may favor the spread of the SARS-CoV-2 infection.