Startling! China's smog event by the numbers

Smoggy and hazy weather enveloped 17 provinces and municipalities in central and east China since Jan. 12, 2013, including Beijing, Tianjin, and Hebei. Most of the cities were "gravely polluted". Residents living in the smog-shrouded areas were advised to stay indoors as much as possible and to wear masks when going out. (china.org.cn)