May 11, 2007 -- Grime on windows may contribute to air pollution, a Canadian study suggests.
Scientists from the University of Toronto did several lab tests on window grime, which they call "urban organic films."
Window grime can soak up an inactive version of the smog chemical nitric acid, note the researchers, who included D.J. Donaldson, PhD, of the University of Toronto's chemistry department and department of physical and environmental sciences.
In a lab, Donaldson's team concocted a solution like window grime and smeared it on a microscope slide.
The scientists observed how the window grime's chemistry changed when exposed to light in a series of lab tests.
Light caused a chemical change in the nitric acid, breaking it down and gradually releasing the mixture into the air.
If the same thing happens outside the lab, it could mean that window grime, in sunlight, recycles smog-related chemicals.
The findings are scheduled for publication in the June 15 edition of the journal Environmental Science & Technology.