Images Dated 30th November 1998

Photochemical air pollution over Vancouver, Canada

Air pollution over Vancouver. View of the city of Vancouver, Canada, showing photochemical air pollution (smog). The pollution results from hydrocarbons and oxides of nitrogen, mainly from motor vehicles exhausts, reacting together in the presence of sunlight. Here, the pollution has been trapped by an inversion layer, a very stable atmospheric condition in which air temperature increases with altitude. The hazy smog limits visibility, damages plants and irritates the eyes. High levels of smog pose a very serious health hazard, especially to the very young and old, and those with existing respiratory complaints. For Vancouver on a clear day see image E780/739

© KAJ R. SVENSSON/SCIENCE PHOTO LIBRARY