镶着金边的乌云:重大突发公共卫生事件与城市空气质量

Every Cloud Has a Silver Lining:Major Public Health Emergency and Urban Air Quality

在新型冠状病毒肺炎疫情期间,中国各地陆续启动的重大突发公共卫生事件一级响应(简称"一级响应")为科学评估社会经济全面管控的环境影响提供了良好契机.本文基于2019年12月至2020年2月中国289个地级及以上城市的日度面板数据样本,采用断点回归法和断点-双重差分法,并利用具有大数据特征的百度迁徙城内出行强度和六大发电集团耗煤量分别表征居民出行强度和经济活动强度,实证考察了该一级响应的启动对城市空气质量的影响及其作用机制,并估算了一级响应启动所带来的公共健康收益.研究发现,一级响应的启动显著改善了空气质量,其中东部城市、北方城市、非工业主导城市及低污染城市的空气污染物浓度下降得更为明显.并且,疫情的严重性会增强一级响应对空气污染的促降效应.机制检验结果表明,一级响应的全面管控措施主要通过减弱居民出行强度和经济活动强度而降低了空气污染,这意味着一级响应相关管控措施尽管具有显著的减排效果,但却是以抑制正常的经济活动为代价的,因而并非经济有效的减排策略.最后,本文通过估算发现一级响应对空气污染的促降效应产生了"额外"的公共健康收益,因其避免的总致死人数为4018~16659人.上述研究结论为中国的大气污染治理提供了重要的经验启示.

During the epidemic period of the Corona Virus Disease 2019(COVID-19),the first-level response to the major public health emergency("first-level response"for short)launched by the governments across China provides a good opportunity to scientifically assess environmental benefits of comprehensive social and economic controls.Based on a daily panel data set from 289 prefecture-level and above cities of China from December 2019 to February 2020,including the Baidu migration index and the coal consumption of six major power generation groups that measure the intensity of residents’egress and the intensity of economic activities,respectively,this paper examines the impact and mechanism of the first-level response on urban air quality using regression discontinuity design and the regression discontinuity difference-in-differences design.We also estimate the public health benefits of the first-level response policy.The results show that the first-level response policy improves urban air quality significantly.Such an air quality improvement effect is more evident in eastern and north cities,non-industrial-based cities,and less polluted cities than other cities.Moreover,the effect is stronger in regions with severe COVID-19 epidemics.The mechanism analysis indicates that the first-level response policy mitigates air pollutant emissions by weakening the intensity of residents’egress and the intensity of economic activities.This implies that the control measures related with first-level response have an anticipated emission-reduction effect,but they are not economically effective.Finally,this paper finds that the mitigation effect of the first-level response policy on air pollution leads to additional public health benefits,and the improved air quality reduces the premature deaths by 4018~16659 persons.The above findings provide some important empirical insights for China’s atmospheric pollution governance.