OZONE LAYER

Ozone is a poisonous colorless gas with an acrid odor. Chemically, it is a variant of normal oxygen, except that ozone has three oxygen atoms per molecule rather than the two found in normal oxygen. There exists a layer of ozone occurring naturally six to thirty-one miles above the earth. This layer of ozone gas surrounding the earth protects living organisms at the earth's surface from the dangerous ultraviolet radiation of the sun. The ozone layer normally absorbs about 98 percent of the ultraviolet rays that continually shower the earth. In small amounts, ozone can be useful as a water disinfectant and a purifier. If, however, ultraviolet rays came to ground level through the shield of the ozone layer, there would be massive lethal consequences for wildlife, crops, vegetation, and profound life-threatening problems for human beings, including cancer and immune system damage.

In 1974 chemists F. Sherwood Rowland and Marle Molina found that chlorine from chlorofluorocarbon (CFC) molecules was capable of breaking down ozone in the ozone layer above the earth. There was evidence that industrial chemicals and chemical exhaust from jet airplanes, as well as large volcanic eruptions, severely threatened the upper atmosphere and the ozone layer. In 1974, when damage to the ozone layer first became apparent, the propellants in common aerosol spray cans were a major source of CFC emissions. CFC aerosols were banned in the United States by 1978, but CFC chemicals remained in widespread use as coolant agents in refrigerators and in air-conditioners as well as in cleaning solvents. During the last decades of the twentieth century there was only a gradual move to ban CFC chemicals from all refrigerant systems, forcing modern industry to deal with alternative systems to stabilize the ozone layer. The question of how much protection is necessary has continued to be a controversial political issue because necessary changes in industrial systems proved to be profoundly expensive. At some level, however, such expenditure is crucial to the existence of human life.

See also: Environmentalism