67 Ozone Depletion

Pamela S. Chasek, David L. Downie, and Janet Welsh Brown

Ozone is a pungent, slightly bluish gas composed of three oxygen atoms (O3). Ninety percent of naturally occurring ozone resides in the stratosphere. This “ozone layer” helps to shield the earth from ultraviolet radiation produced by the sun and plays a critical role in absorbing UV-B radiation. Because large increases in UV-B radiation would seriously harm nearly all plants and animals, the ozone layer is considered an essential component of the natural systems that make life on earth possible.

In the 1970s, scientists discovered that certain man-made chemicals, called chlorofluorocarbons (CFCs), posed a serious threat to stratospheric ozone. CFCs release chlorine atoms into the stratosphere that act as a catalyst in the destruction of ozone molecules. Created in the 1920s to replace flammable and noxious refrigerants, CFCs are inert, nonflammable, nontoxic, colorless, odorless, and wonderfully adaptable to a wide variety of profitable uses. By the mid-1970s, CFCs had become the chemical of choice for coolants in air conditioning and refrigerating systems, propellants in aerosol sprays, solvents in the cleaning of electronic components, and the blowing agent for the manufacture of flexible and rigid foam. Scientists later discovered other ozone-depleting compounds, including halons, a tremendous and otherwise safe fire suppressant, carbon tetrachloride, methyl chloroform, and methyl bromide. Each ...

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