A Spatio-temporal Study of Changes in Air Quality from Pre-COVID Era to Post-COVID Era in Chicago, USA

ABSTRACT

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 PM_2.5, 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.