Part one of term paper
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. Among air pollutants emitted by natural sources, only the radioactive gas radon ...

Part two of term paper
... a risk of lung cancer. Each year industrially developed countries generate billions of tons of pollutants. The level is usually given in terms of atmospheric concentrations or, for gases in terms of parts per million, that is, number of pollutant molecules per million air molecules. Many come from directly identifiable sources; sulfur dioxide, for example, comes from electric power plants burning coal or oil. Others are formed through the action of sunlight on previously emitted reactive mate ...