Special Issue on Air Quality in a Changed World: Regional, Ambient, and Indoor Air Concentrations from the COVID to Post-COVID Era (VI)

Solaiman Khan  1, Butros M. Dahu1, Grant J. Scott This email address is being protected from spambots. You need JavaScript enabled to view it.1,2 

1 Institute of Data Science and Informatics, University of Missouri, Columbia, MO 65211, USA
2 Department of Electrical Engineering and Computer Science, University of Missouri, Columbia, MO 65211, USA


Received: January 31, 2022
Revised: April 11, 2022
Accepted: May 24, 2022

 Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.

Download Citation: ||https://doi.org/10.4209/aaqr.220053  

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Cite this article:

Khan, S., Dahu, B.M., Scott, G.J. (2022). A Spatio-temporal Study of Changes in Air Quality from Pre-COVID Era to Post-COVID Era in Chicago, USA. Aerosol Air Qual. Res. 22, 220053. https://doi.org/10.4209/aaqr.220053


  • PM2.5, NO2, and CO have been reduced during COVID-19 stay-at-home in 2020.
  • Air quality improvement during COVID-19 was transitory.
  • On average, all air pollutants increased in the post-COVID era except CO.


The COVID-19 pandemic has drastically changed human life and the world's environment. Most of the major cities of the USA went under full or partial lockdown in the first half of 2020. However, it started gradually reopening, and in 2021, most of the public activity restrictions were lifted. Many studies reported a significant improvement in air quality during the COVID-19 pandemic in the USA, corresponding with the reduced human activity. We hypothesized that this improved air quality was followed by the decline to air quality again due to the normalization of human activity in 2021. This study is a novel approach of studying air quality using spatio-temporal analysis at the finer spatial level within a city in the USA. It assessed the change in six air quality parameters from the pre-COVID era to the post-COVID era in Chicago city in Illinois, USA. The study found that reduced human activities during COVID-19, improved air quality by reducing the concentration of some air pollutants, especially PM2.5, NO2, and CO. However, this improvement was transitory, and it reverted in the post-COVID era. Therefore, policies should be formulated and practiced to improve air quality in the long term.

Keywords: COVID-19, Air pollution, Urban air quality, NO2, Particulate matter

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