Researchers in North America believe the combination of smog-clad skyscrapers with sunshine could be a key factor in the exacerbation of urban air pollution.

A University of Toronto study, scheduled for presentation before the American Chemical Society, claims exposure to sunlight can trigger the release of nitrogen oxide compounds harboured by the film of pollution that accumulates on the surface of built structures in smoggy urban areas. This finding contradicts the long-standing assumption that…