Aerial photo taken on Dec. 23, 2016 shows smog shrouded Shanghai, east China. Shanghai issued a blue alert for air pollution on Thursday and maintained the alert on Friday. (Xinhua/Ding Ting)
Aerial photo taken on Dec. 23, 2016 shows smog shrouded Shanghai, east China. Shanghai issued a blue alert for air pollution on Thursday and maintained the alert on Friday. (Xinhua/Ding Ting)