| In order to make the heavy air pollution response more scientific and accurate, the Ministry of Ecology and Environment of the People's Republic of China formulated the "differentiated response requirement based on performance grading" policy in July 2019. A total of 68 cities in the Beijing-Tianjin-Hebei region and surrounding areas issued heavy air pollution alerts from late September to early October. This was the first time the policy was put into practice. The regression discontinuity in time design was employed to estimate the effects of the policy on air quality in Beijing and 67 other cities. Here, we showed that the policy basically brought about a short-term, substantial air quality improvement in Beijing and 67 other cities. We found that there was a "lag phenomenon" in which three gaseous pollutants (SO2, NO2, and CO) achieved improvement relatively quickly; however, O3 and PM2.5achieved improvement slowly. A parade to celebrate the 70th anniversary of the founding of the People's Republic of China was coincidently held in Beijing on October 1st. Compared with the hypothetical situation in the absence of the heavy air pollution alert, the heavy pollution response measure brought down the concentrations of PM2.5, NO2, and CO by 54.1%, 62.4%, and 25.8%, respectively, in Beijing on October 1st. Without the heavy pollution response measures, the air quality rank on the morning of October 1st would have been unhealthy or very unhealthy while the parade was on-going, but in actuality it was moderate. Further analyses of 67 cities found that PM2.5, PM10, NO2, SO2, and CO were all improved on October 1st, whereas the concentration of O3 increased in a portion of the cities. Our study demonstrates that the "differentiated response requirement based on performance grading" policy is effective. |
