Beginning of Essay
Biology 2B The Problem Contamination of the atmosphere by gaseous, liquid, or solid wastes or by-products that can endanger human health and the health and welfare of plants and animals, or can attack materials, reduce visibility, or produce undesirable odors. ....

Middle of Essay
.... comes from electric power plants burning coal or oil. Others are formed through the action of sunlight on previously emitted reactive materials. For example, ozone, a dangerous pollutant in smog, is produced by the interaction of hydrocarbons and nitrogen oxides under the influence of sunlight. 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. Current information about the problem The tall smokestacks used by industries an utilities do not remove ....