Effects of chronic exposure to ambient air pollutants on COVID-19 morbidity and mortality - A lesson from OECD countries

BACKGROUND: Exposure to ambient air pollution is related to 4.2 million premature deaths per year worldwide and is associated with a variety of adverse health outcomes, such as respiratory and cardiovascular morbidity. Furthermore, exposure to air pollution can increase human sensitivity to respiratory pathogens via damage to the respiratory tract or via airborne transmission on the surface of particulate matter, and might be an additional factor influencing COVID-19 morbidity and mortality rates. The aim of this study was to examine the association between populations' exposure to air pollution and the morbidity and mortality rates from COVID-19. METHODS: We examined the association between population-weighted long-term exposure to PM(2.5) and NOx, and the morbidity and mortality over time following the detection of the first COVID-19 positive case in 36 OECD countries. Pearson and Spearman correlations between daily COVID-19 morbidity and mortality (Jan–Jun 2020) on the 10(th), 20(th), 40(th), 60(th) and 80(th) days since first confirmed case in the country, and demographic, health, economic, and environmental data were calculated. Multivariate linear regression were used to examine the associations between demographic, health, economic and air pollution features and the rate of confirmed cases and deaths on the 60(th) and 80(th) days following the first confirmed case. RESULTS: PM(2.5) concentrations in 2015–2017 were positively correlated with COVID-19 morbidity and mortality on the 10(th), 20(th), 40(th) and 60(th) days since the first confirmed case in all countries. NOx concentrations in 2015–2017 and country's density (population/Km(2)) were positively correlated with COVID-19 morbidity and mortality on the 60(th) day. All multivariate linear regressions consisting PM(2.5) concentrations models were statistically significant. Our models also emphasize the importance of the relative number of hospital beds in decreasing the morbidity and mortality of COVID-19. CONCLUSIONS: The adverse health outcomes stemming from long-term exposure to various air pollutants has long been known to the scientific community. According to our results and previously published studies, it appears that long-term exposure to air pollutants concentrations exceeding WHO guidelines, such as PM(2.5) and NOx, might exacerbate morbidity and mortality rates from COVID-19. These results should raise a red flag globally among decision makers about the urgent need to reduce air pollution and its harmful effects.