On estimating the additional incidence of COVID-19 among populations exposed to polluted ambient air: methodical approaches and some practical results

This research is vital due to the considerable global medical and demographic losses during the COVID-19 pandemic and the latest research works providing evidence of a correlation between air pollution and spread of the disease, its severity, clinical course and outcomes. Our research goal was to quantitatively estimate the influence of ambient air pollution on SARS-CoV-2 spread among populations in six cities in the Russian Federation. These cities were among priority ones as per air pollution and were included in the “Clean air” Federal project (Bratsk, Krasnoyarsk, Norilsk, Omsk, Cherepovets, and Lipetsk). Our hypothesis was that dynamic features of the infection spread would be different from an expected model of its epidemiologic process under exposure to environmental pollution. Regression and correlation analysis was performed for relationships between a daily deviation in actual incidence from a basic epidemiologic scenario and the average daily concentrations of chemicals in ambient air. The initial data were results obtained from instrument measurements of ambient air quality in the examined cities (approximately 10.8 thousand measurements covering 29 chemicals) and the daily incidence of COVID-19 from April 18, 2020 to July 31, 2021 (77,337 cases). An authentic correlation between COVID-19 incidence and chemical concentrations in ambient air was detected in all six examined cities. The contribution of air pollution to COVID-19 prevalence amounted to 5.0 ± 2.6 % in five cities (Krasnoyarsk, Norilsk, Omsk, Cherepovets, and Lipetsk) over the examined period. In Bratsk, this value was about 33% and it requires additional research for either confirmation or correction. Growth in COVID-19 incidence in the examined territories is associated with particulate matter (PM10, PM2.5) and some other chemicals that can irritate the airway directly or indirectly (sulfuric acid vapors, hydrogen chloride, formaldehyde, hydrogen sulphide, etc.). Target levels were substantiated for several priority chemicals; should these levels be achieved, one would predict a decrease in COVID-19 prevalence by more than 1-3% in the examined cities. We propose that population morbidity and mortality caused by COVID-19 require further studies, including those combined with medical and biological examination regarding efficiency of vaccination and post-vaccination immunity persistence on territories with elevated environmental pollution.