Effects of the COVID-19 on Air Quality: Human Mobility, Spillover Effects, and City Connections

We quantify the causal effects of the coronavirus disease 2019 (COVID-19) on air quality in the context of China. Using the lockdowns in different cities as exogenous shocks, our difference-in-differences estimations show that lockdown policies significantly reduced air pollution by 12% on average. Based on the first lockdown city, Wuhan, we present three underlying mechanisms driving our findings: anticipatory effects, spillover effects, and a city's level of connection with Wuhan. Our findings are more pronounced in cities whose population was more willing to self-isolate or more susceptible to anxiety, or whose government faces less pressure to stimulate economic growth. Overall, this study contributes to the literature by evaluating the unintended consequences of the COVID-19 outbreak for air quality, and provides timely policy implications for policymakers.