Dirty windows in urban areas may be hidden contributors to air pollution

In the report, D. J. Donaldson and colleagues point out that air pollution researchers have been focusing on urban surface films, often termed "window grime," as a potential contributor to air pollution. The films contain nitrogen compounds, which disappear at rates that can't be explained by obvious losses due to rain washout. In addition, traditional models of urban air pollution suggest that there must be an important but unrecognized source for one nitrogen compound involved in smog formation.

Their study presents experimental evidence suggesting that windows and other surfaces in urban areas may be sites where "inactive" nitrogen oxides may be transformed into "active" forms and be released to the atmosphere. This transformation may occur in a process triggered by sunlight shining on film-covered surfaces, the report notes.-American Chemical Society