t of haze cut the annual amount of solar energy reaching the surface of the Earth by eight-percent. The type of haze that hangs over the eastern United States and Canada has been linked to acute respiratory ailments in humans. The chemicals contained in haze attack the tissues lining the nose, throat, and lungs.
Spring and summer haze over the eastern United States is composed primarily of concentrated sulfuric acid. Most of this acid may be traced to the release of sulfur dioxide gas during the burning of high-sulfur coal by power plants, oil refineries, and steel manufacturing facilities. Sulfur dioxide emissions in the United States are concentrated in a broad band extending from the mid-Mississippi Valley into the lower Great Lakes region, the mid-Atlantic states, and southern New England.
Once in the atmosphere, sulfur dioxide bonds with oxygen sometimes in reactions enhanced by sunlightùphotooxidationùand sometimes merely in the presence of liquid waterùas in the droplets of clouds or power-plant plumes. These reactions form sulfate aerosols, liquid or solid particles suspended in the air. In the liquid aerosols, the sulfate forms tiny droplets of sulfuric acid. In the solid aerosols, the sulfate is suspended in a salt with ammonium that will readily form sulfuric acid if dissolved in water. The sulfate aerosols readily absorb water vapor from the air. Thus, sulfate aerosols make excellent condensation nuclei, and polluted haze clouds eventually form. Sulfate aerosols are chemically stable, and can remain airborne for days, traveling far from their origin when winds are strong and constant in direction. The main sources of sulfur dioxide are in the Ohio Valley.
In parts of the United States, air pollution is responsible for health problems ranging from skin rashes to anencephalic babies. In addition to anencephalic births, a wide range of other birth defects are attributed to air pollution in parts of t...