The Impact of COVID-19 Restrictions on Air Quality- Based on Seven Cities in China

Abstract: Many researchers have studied the impact of the COVID-19 restrictions. However, in terms of the air quality impact, few studies have done so for specific cities. In this study, seven cities in China under the first stage of transmission prevention have been selected. The air quality standard indicators discussed are NO2 (Nitrogen dioxide), PM2.5 (fine particulate matter), and AQI (Air Quality Index). To find the causal inference, this study employed the fixed effect model and regression discontinuity in time design while using the high-frequency dataset around the policy date of each city. According to the policy-driven bandwidth for each city, the findings showed that NO2 in every city decreased significantly. In contrast, 2 of 7 cities and 1 of 7 cities did not provide significant results in PM2.5 and AQI respectively. The results are robust after various checks. This study confirmed the conclusions in the previous studies that the COVID-19 restrictions improved the ambient air quality.