New measurements show that the atmosphere?s ability to keep itself clean is decreasing. In the past 10 years, levels of an important cleansing chemical have declined markedly in the Northern Hemisphere.
Chemicals are generated in the air by forces such as ultraviolet light and lightening. These chemicals are highly reactive and tend to remove polluting gases. One of the most important of these is the hydroxl radical, OH, which is the water molecule minus one hydrogen atom. The missing hydrogen atom makes it highly reactive so that it easily sucks up pollutants. OH changes pollutants into gases that are easily dissolved in water and thus are removed from the atmosphere during rainfall.