People in northern China can breathe easier for the moment, as cold fronts sweep through, clearing the smog. Authorities say frequent cold snaps will help to keep the air clean until the end of the month.

Over the past week, nearly a sixth of China's total land area was smothered by the worst haze of the year. 40 cities issued heavy pollution alerts including Beijing. In the capital, PM2.5 pollutants reached a staggering 500 micrograms per cubic meter, 10 times higher than the healthy level. Schools were temporarily closed and hundreds of flights were cancelled.