The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured an image of the haze spreading from Beijing to Shanghai on 7 December 2013. The expansion of the smog to the south of China is not that common as for the northeast.
The fog has distinguishing features that makes it appear grey and smooth on the images. Ground-based sensors reported a level Particulate Matter smaller than 2.5 microns in the air to be as high as 480 and 355 per cubic meter of air in Beijing and Shanghai. WHO considers levels below 25 to be safe. The Air Quality Index was also with more than 800% above what is considered good.
In some cities, authorities ordered school children to stay indoors, pulled government vehicles off the road, and halted construction in an attempt to reduce the smog, according to news reports.