A series of studies suggest that regions with higher pre-pandemic levels of air pollution had a higher incidence of COVID-19 cases and deaths. However, the reasons for this associations are not yet clear; air pollution could favor airborne transmission of the virus, or it could increase an individual’s susceptibility to infection or disease. “The problem is that previous studies were based on reported cases, which had been diagnosed, but missed all the asymptomatic or undiagnosed cases,” says Manolis Kogevinas, ISGlobal researcher and first author of the study.
The study included 9,605 participants among which there were 481 confirmed cases (5%). In addition, blood samples from over 4,000 participants were taken to determine the presence and quantity of IgM, IgA and IgG antibodies to five viral antigens. Of these, 18% had virus-specific antibodies, but no association was found between infection and exposure to air pollutants. However, among those who were seropositive (i.e. got infected), an association was found between higher exposure to NO2 and PM2.5 and higher levels of IgG specific for the five viral antigens (an indication of higher viral burden and/or symptom severity).
For the total study population (the 9,605 participants), an association was found between higher exposure to NO2 and PM2.5 and disease (symptoms), particularly for severe cases that ended in the hospital or in intensive care. The association with PM2.5 was stronger for men over 60 years of age and people living in socioeconomically deprived areas.
“Our study provides the strongest evidence globally on the association of ambient air pollution and COVID-19,” says Kogevinas. “These results are in line with the association between air pollution and hospitalization described for other respiratory diseases such as influenza or pneumonia”. Air pollution could also contribute by favouring the development of cardiovascular, respiratory or other chronic conditions, which in turn increase the risk of severe COVID-19.
Release date: 17 November 2021
Source: Barcelona Institute for Global Health (ISGlobal)