As if the grime so common to buildings, statues and other outdoor surfaces in urban areas isn’t bad enough, it gets even worse when exposed to sunlight. Researchers from the University of Toronto have determined that the sun triggers the release of smog-forming nitrogen oxide compounds from urban grime, according to an article at Phys.org. The findings dispel a long-held belief by many scientists that the nitrates become inactive when trapped in grime.
Urban grime is defined in the article as a “mixture of thousands of chemical compounds spewed into the air by automobiles, factories and a host of other sources,” with some of those compounds being nitrogen oxides. The study indicates that the current understanding of air pollution is incomplete, according to the researchers, who presented their findings at the 250th American Chemical Society National Meeting & Exposition last month.