AIR POLLUTION

The combustion of coal, oil, and gasoline accounts for much of the airborne pollutants. According to recent estimates by the U.S. government, 20 percent of the homes in the U.S. harbor radon concentrations that are high enough to pose a risk of lung cancer. Ozone has also caused serious crop damage. On the other hand, the discovery in the 1980s that air pollutants such as fluorocarbons are causing a loss of ozone from the earth's protective ozone layer has caused the phasing out of these materials.