People cross a road on a polluted day in Beijing on December 14, 2015. Authorities issued a yellow alert for pollution on December 14, the first since a red alert last week. AFP PHOTO / GREG BAKER (Photo by GREG BAKER / AFP via Getty Images)
People cross a road on a polluted day in Beijing on December 14, 2015. Authorities issued a yellow alert for pollution on December 14, the first since a red alert last week. AFP PHOTO / GREG BAKER (Photo by GREG BAKER / AFP via Getty Images)