About a third of the air pollution in China's smog-hit capital comes from outside the city, official media reported Wednesday, citing a watchdog body.
Chen Tian, chief of the Beijing Environmental Protection Bureau, said that about 28-36 percent of hazardous airborne particles known as PM2.5 came from surrounding provinces such as Hebei, home to seven of China's 10 most polluted cities in 2013, according to official data.