Road traffic and air pollution: Evidence from a nationwide traffic control during coronavirus disease 2019 outbreak

摘要

Existing estimations of air pollution from automobile sources are based on either experiments or small-scale governmental interventions. China's nationwide traffic control during the coronavirus disease 2019 outbreak provided us a unique opportunity to assess the direct dose-effect relationship between vehicle density and air pollution. We found that, during the coronavirus disease 2019 outbreak, the nationwide reduced air pollution (except for O_3) could be largely explained by traffic control measures. During the traffic control period, every doubling of vehicle density was associated with a decrease of 4.2 (2.0, 6.4) μg/m~3 in PM_(2.5), 5.5 (2.9, 8.1) μg/m~3 in PM_(10),1-5 (0.9,2.0) μg/m~3 in NO_2, and 0.04 (0.02,0.07) mg/m~3 in CO comparing cities with different vehicle densities. Similarly, for every 10% increase in the truck proportion, PM_(2.5) decreased by 12.3 (4.1,20.6) μg/m~3, PM_(10) decreased by 14.3 (4.6,23.9) μg/m~3, and CO decreased by 0.14 (0.05,0.23) mg/m~3. Moreover, the associations between vehicle density and reduction in PM_(2.5), PM_(10), and CO during the traffic control period were stronger and showed near-complete linearity in cities with low green coverage rate (All P < 0.05 for interaction). According to our estimation, PM_(2.5) emissions from every doubling of vehicle density can lead to over 8000 excess deaths per year, 66% of which were caused by cardiopulmonary diseases. This natural experiment study is the first to observe the dose-effect relationship between on-road traffic and traffic-generated air pollution, as well as the mitigating effect of urban greening. Findings provide key evidence to the assessment and control of traffic-generated air pollution and its public health impact.