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. 2022 Nov;22(11):10.4209/aaqr.220047.
doi: 10.4209/aaqr.220047.

Understanding Air Quality Changes after Implementation of Mitigation Measures during a Pandemic: A Scoping Review of Literature in the United States

Sara McElroy  1   2 , Ambarish Vaidyanathan  2
Affiliations

Understanding Air Quality Changes after Implementation of Mitigation Measures during a Pandemic: A Scoping Review of Literature in the United States

Sara McElroy et al. Aerosol Air Qual Res. 2022 Nov.

Abstract

Traffic-related emissions continue to be a significant source of air pollution in the United States (US) and around the globe. Evidence has shown that previous policies implemented to restrict-traffic flows have affected air pollution levels. Thus, mitigation strategies associated with the COVID-19 pandemic that modified population-level mobility patterns provide a unique opportunity to study air pollution change across the US. For instance, to slow the spread of the pandemic, state and local governments started implementing various mitigation actions, including stay-at-home directives, social distancing measures, school closures, and travel restrictions. This scoping review aimed to summarize the existing evidence about how air quality changed through mitigation practices throughout the pandemic in the US. We found 66 articles that fit our inclusion criteria. Generally, the consolidated results revealed that nitrogen dioxide (NO2) and carbon monoxide (CO) decreased across the country. Studies observed mixed directions and magnitudes of change for fine and coarse particulate matter (PM2.5, PM10), ozone (O3), and sulfur dioxide (SO2). Few articles tried to explain this notable heterogeneity in air quality changes by associating contextual factors, such as mobility, traffic flow, and demographic factors. However, all studies agreed that the change in air pollution was nonuniform across the US and even varied within a city.

Keywords: Air pollution; COVID-19; Mitigation measures; Mobility; Public health interventions.

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Figures

Fig. 1.
Fig. 1.
PRISMA Flow chart of scoping review inclusion and exclusion criteria.
Fig. 2.
Fig. 2.
A thematic map of number of studies included in this scoping review, by air pollutants. Studies could examine more than one pollutant. The numbers reflect the total number of studies that examined a particular pollutant.
Fig. 3.
Fig. 3.
Location-specific summary of magnitude and direction of change in air pollutants.
Fig. 4.
Fig. 4.
Methodologies utilized in this scoping review, by location and air pollutant.
See this image and copyright information in PMC

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