Severe smog has hit northern China's cities since Wednesday, including the capital, Beijing. Weather authorities have issued an alert for hazardous air and urged residents to reduce outdoor activities.
Beijing is among the most severely hit cities, with visibility down to as low as 500 meters. The national weather authority predicted the smog will disperse beginning Friday, as a cold front is due to arrive.
Before the smog, Beijing enjoyed two weeks of blue skies that coincided with the APEC meetings, with the help of cold fronts and measures such as traffic restrictions and factory closures in the city and surrounding areas.