A citizen wearing mask walks on a bridge amid fog and smog in Tianjin, North China, Feb. 28, 2013. The fog hit Tianjin on Feb. 28 morning, causing heavy air pollution in the city. (Xinhua/Yue Yuewei)
Children wearing masks walk on a bridge amid fog and smog in Tianjin, North China, Feb. 28, 2013. The fog hit Tianjin on Feb. 28 morning, causing heavy air pollution in the city. (Xinhua/Yue Yuewei)
Motorcars run on a road amid fog and smog in Tianjin, North China, Feb. 28, 2013. The fog hit Tianjin on Feb. 28 morning, causing heavy air pollution in the city. (Xinhua/Yue Yuewei)
Citizens wearing masks walk amid fog and smog in Tianjin, North China, Feb. 28, 2013. The fog hit Tianjin on Feb. 28 morning, causing heavy air pollution in the city. (Xinhua/Yue Yuewei)
A policeman directs traffic amid fog and smog in Beijing, capital of China, Feb. 28, 2013. Beijing was again hit by heavy fog and smog on Feb. 28 morning. (Xinhua/Wang Yueling)
A citizen does morning exercises amid fog and smog in Beijing, capital of China, Feb. 28, 2013. Beijing was again hit by heavy fog and smog on Feb. 28 morning. (Xinhua/Wang Yueling)
Motorcars have to turn on fog lights amid fog and smog in Baoding, North China's Hebei Province, Feb. 28, 2013. The province was hit by heavy fog on Feb. 28 morning and the local meteorological bureau has issued an orange alert for the fog. (Xinhua/Zhu Xudong)
A citizen rides a bicycle amid fog and smog in Baoding, North China's Hebei Province, Feb. 28, 2013. The province was hit by heavy fog on Feb. 28 morning and the local meteorological bureau has issued an orange alert for the fog. (Xinhua/Zhu Xudong)
Citizens ride bicycles amid fog and smog in Baoding, North China's Hebei Province, Feb. 28, 2013. The province was hit by heavy fog on Feb. 28 morning and the local meteorological bureau has issued an orange alert for the fog. (Xinhua/Zhu Xudong)