rally during lightning storms by the passage of electricity through the air. Photochemical smog contains ozone formed by a complex series of chemical reactions of other pollutants with the air (Breur, 1983, p. 34). Ozone occurs high in the stratosphere in an "ozone layer," where it forms and breaks down in an ozone cycle of reactions.
Carbon dioxide (CO2) is a small but essential component of the earth's atmosphere. In recent decades, the concentration of CO2 in the atmosphere has been increasing in a manner that corresponds closely to the increasing global use of fossil fuels (Council on Environmental Quality, 1982, p. 3). The burning of fossil fuel--oil, natural gas, and coal--release CO2 , about one-half of which appears to be retained in the atmosphere. The burning of fossil fuels is also a cause of the deteriorating ozone layer (pp. 4-5).
Ultraviolet (UV) radiation is the most direct and harmful of the effects resulting from a depleted ozone layer. The ozone layer decreases ultraviolet radiation, and, since ambient outdoor levels of UV radiation are a risk factor for skin cancer, expected atmospheric changes may increase this risk (Council on Environment, 1986, p. 53).
The "greenhouse effect" occurs when
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