A pedestrian wearing mask walks on the West Chang'an Street in Beijing, capital of China, Feb. 28, 2013. A cold front blew away fog and smog which hit Beijing on Feb. 28 morning, but brought dust and sand from Mongolia and North China's Inner Mongolia Autonomous Region. Photo: Xinhua
People visit the Tian'anmen Square amid dust and sand in Beijing, capital of China, Feb. 28, 2013. A cold front blew away fog and smog which hit Beijing on Feb. 28 morning, but brought dust and sand from Mongolia and North China's Inner Mongolia Autonomous Region. Photo: Xinhua
A citizen who has face wrapped up as she rides a motorcycle amid dust and sand in Beijing, capital of China, Feb. 28, 2013. A cold front blew away fog and smog which hit Beijing on Feb. 28 morning, but brought dust and sand from Mongolia and North China's Inner Mongolia Autonomous Region. Photo: Xinhua
A software on a cell phone shows heavy air pollution in Beijing, capital of China, at 10 am on Feb. 28, 2013. A cold front blew away fog and smog which hit Beijing on Feb. 28 morning, but brought dust and sand from Mongolia and North China's Inner Mongolia Autonomous Region. Photo: Xinhua
A pedestrian covers her mouth with a hand as she walks amid dust and sand in Beijing, capital of China, Feb. 28, 2013. A cold front blew away fog and smog which hit Beijing on Feb. 28 morning, but brought dust and sand from Mongolia and North China's Inner Mongolia Autonomous Region. Photo: Xinhua
Tourists brave wind as they visit the Tian'anmen Square in Beijing, capital of China, Feb. 28, 2013. A cold front blew away fog and smog which hit Beijing on Feb. 28 morning, but brought dust and sand from Mongolia and North China's Inner Mongolia Autonomous Region. Photo: Xinhua
Workers try to cover mound with a net amid dust and sand in Beijing, capital of China, Feb. 28, 2013. A cold front blew away fog and smog which hit Beijing on Feb. 28 morning, but brought dust and sand from Mongolia and North China's Inner Mongolia Autonomous Region. (Xinhua/He Junchang)
A train runs amid dust and sand in Beijing, capital of China, Feb. 28, 2013. A cold front blew away fog and smog which hit Beijing on Feb. 28 morning, but brought dust and sand from Mongolia and North China's Inner Mongolia Autonomous Region. (Xinhua/He Junchang)