China's capital city of Beijing has been swamped by off-the-charts levels of air pollution in January. New images from NASA's Earth Observatory satellite Terra shows the choking layer of smog that has descended over the city.

The first image, from January 14, shows China smothered by a layer of haze. The grey and yellow-tinged clouds visable on the map are areas heavily affected by air pollution. At the time the image was taken, ground sensors at the U.S. Embassy in Beijing recorded PM2.5 measurements of 291. According to the World Health Organization, PM2.5 levels above 25 are considered unsafe.