Acute and chronic exposure to air pollution in relation with incidence, prevalence, severity and mortality of COVID-19: a rapid systematic review

Abstract

Background Air pollution is one of the world’s leading mortality risk factors contributing to seven million deaths annually. COVID-19 pandemic has claimed about one million deaths in less than a year. However, it is unclear whether exposure to acute and chronic air pollution influences the COVID-19 epidemiologic curve. Methods We searched for relevant studies listed in six electronic databases between December 2019 and September 2020. We applied no language or publication status limits. Studies presented as original articles, studies that assessed risk, incidence, prevalence, or lethality of COVID-19 in relation with exposure to either short-term or long-term exposure to ambient air pollution were included. All patients regardless of age, sex and location diagnosed as having COVID-19 of any severity were taken into consideration. We synthesised results using harvest plots based on effect direction. Results Included studies were cross-sectional (n = 10), retrospective cohorts (n = 9), ecological (n = 6 of which two were time-series) and hypothesis (n = 1). Of these studies, 52 and 48% assessed the effect of short-term and long-term pollutant exposure, respectively and one evaluated both. Pollutants mostly studied were PM2.5 (64%), NO2 (50%), PM10 (43%) and O3 (29%) for acute effects and PM2.5 (85%), NO2 (39%) and O3 (23%) then PM10 (15%) for chronic effects. Most assessed COVID-19 outcomes were incidence and mortality rate. Acutely, pollutants independently associated with COVID-19 incidence and mortality were first PM2.5 then PM10, NO2 and O3 (only for incident cases). Chronically, similar relationships were found for PM2.5 and NO2. High overall risk of bias judgments (86 and 39% in short-term and long-term exposure studies, respectively) was predominantly due to a failure to adjust aggregated data for important confounders, and to a lesser extent because of a lack of comparative analysis. Conclusion The body of evidence indicates that both acute and chronic exposure to air pollution can affect COVID-19 epidemiology. The evidence is unclear for acute exposure due to a higher level of bias in existing studies as compared to moderate evidence with chronic exposure. Public health interventions that help minimize anthropogenic pollutant source and socio-economic injustice/disparities may reduce the planetary threat posed by both COVID-19 and air pollution pandemics.

Long-term air pollution and COVID-19 mortality rates in California: Findings from the Spring/Summer and Winter surges of COVID-19

“…Since the beginning of the COVID-19 pandemic, there have been several studies published on the associations between long-term air pollution and COVID-19 mortality; however, many of these studies did not control for potential confounding factors, such as population size or demographics ( Katoto et al, 2021 ; Ali and Islam, 2020 ; Copat et al, 2020 ; Domingo et al, 2020 ). Among studies with some consideration of potentially confounding variables, several have reported positive associations between COVID-19 mortality and long-term air pollution concentrations, primarily PM 2.5 and NO 2 .…”

“…Evidence, including this study, suggests long-term air pollution concentrations to be associated with COVID-19 mortality rates in an area (region, county, census tract, etc. ), indicating that communities with historically higher levels of ambient air pollution have a disproportionate burden of COVID-19 death ( Katoto et al, 2021 ; Ali and Islam, 2020 ; Wu et al, 2020 ; Lopez-Feldman et al, 2021 ; Liang et al, 2020 ; Konstantinoudis et al, 2021 ; Hutter et al, 2020 ). These communities likely face additional stressors, including exposure to higher levels of other risk factors for COVID-19 severity and mortality ( Singh et al, 2020 ; Ssentongo et al, 2020 ; Goodman et al, 2020 ).…”

“…Among modifiable environmental risk factors, long-term exposure to air pollution has risen as a possible risk factor for increased COVID-19 disease severity and mortality ( Katoto et al, 2021 ; Ali and Islam, 2020 ; Wu et al, 2020 ; Lopez-Feldman et al, 2021 ; Tchicaya et al, 2021 ; Liang et al, 2020 ; Konstantinoudis et al, 2021 ; Hutter et al, 2020 ; Dettori et al, 2021 ; Copat et al, 2020 ; Domingo et al, 2020 ). Associations between long-term exposure to air pollution and mortality are well documented ( United States Environmental Protection Agency, 2020 ; United States Environmental Protection Agency, 2019 ) and there are several proposed mechanisms by which long-term air pollution exposure may increase the risk of COVID-19 mortality, including alterations in inflammatory and immune response and contributing to the development of chronic diseases that leave individuals more vulnerable to COVID-19 disease ( Domingo et al, 2020 ; Bourdrel et al, 2021 ; Woodby et al, 2021 ; Comunian et al, 2020 ).…”

Positive association between outdoor air pollution and the incidence and severity of COVID-19. A review of the recent scientific evidences

“… **Studies assessing the effects of acute exposures presented substantial risks of bias. Katoto et al (2021) Role and potential association of air pollution especially particulate matter pollution in the transmission of COVID-19. **There appears to be a positive role of atmospheric particulate matter (PM) pollution and the spread of COVID-19.…”

Environment—lockdown, air pollution and related diseases: could we learn something and make it last?

“…But studies assessing the effects of acute exposures presented substantial risks of bias. 39 Some studies proposed that PM operates as a virus carrier, promoting its transport through the air. Exposure to ambient PM may also reduce the resistance to infection in the population although the degree of influence may depend on the particulate composition.…”