Did the COVID-19 lockdown affect air quality? Evidence from Viet Nam

Against the backdrop of the COVID-19 pandemic, most countries implemented a partial or full lockdown as a preventive measure. Although lockdown caused an economic contraction, it unexpectedly improved the environment, especially air pollution. This paper quantifies the impact of the lockdown on air quality by utilizing the air quality data and the lockdown periods in 11 cities and provinces in Viet Nam in 2022 and 2021. Our main empirical framework examines how lockdown measures affected air quality across different locations in Viet Nam during this period. To address the heterogenous effects of lockdown, we conducted a subsample analysis on locations. Utilizing a linear model with time- and location-fixed effects, our analysis revealed that implementing an extra day of lockdown resulted in a decrease of 1.018 ppm in the CO level, while a stricter full lockdown for an additional day led to a drop of 1.369 ppm. These findings remained consistent even when examining the subsamples by location.