A link between SARS-CoV-2 infection and air pollution is plausible and may impact infection and mortality. This study analyzed the relationship between the concentration of air pollutants (PM 2.5 and NO2) and the COVID-19 outbreak in Italy in terms of transmission, number of patients, severity of presentation and number of deaths.

The authors correlated the numbers of COVID-19 cases, ICU admissions and the mortality rate with the severity of air pollution in regions of Italy. They found that areas in Italy with the highest incidence of cases and deaths are the ones with levels of PM 2.5 and NO2 that are chronically high or with recent increases in the 2 months prior to the outbreak.

This is a correlational study, so the findings are not reflective of a causal relationship. Nevertheless, the findings lend support to a ‘double hit’ hypothesis whereby air pollutants, (such as PM 2.5 and NO2) plus SARS-CoV-2 give a “double-hit” to the lungs leading to acute lung injury by attenuating tissue remodeling and influencing local inflammatory response.