This week various health warnings have been issued in England and Wales due to high levels of air pollution. NASA’s Aqua satellite captured this image of the country shrouded in smog on April 22, 2011:
Earth Observatory explains:
The haze is building up under a high-pressure system, which is trapping still air in place. According to UK Air, much of the pollution is coming from continental Europe, and some of that transport is evident in the image.