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Welfare Effects - Stratospheric Ozone Depletion
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The stratosphere, located about 6 to 31 miles above the earth, contains a layer of ozone gas that protects living organisms from harmful ultraviolet-B radiation (UV-B) from the Sun. UV-B (280 to 315 nanometer wavelength) has been linked to many harmful effects including various types of skin cancer, cataracts, and harm to some crops, certain materials, and some forms of marine life. In the mid-1970s, it was discovered that some human-produced gases could cause stratospheric ozone depletion. Gases containing chlorine and bromine accumulate in the lower atmosphere, are eventually transported to the stratosphere and then converted to more reactive gases that participate in reactions that destroy ozone. Ozone depletion allows additional UV-B radiation to pass through the atmosphere and reach the earth's surface, leading to increases in UV-related health and environmental effects.
Several substances have been associated with the stratospheric ozone depletion, including chlorofluorocarbons (CFCs), halons, carbon tetrachloride, methyl bromide, and methyl chloroform. One example of ozone depletion is the annual ozone "hole" over Antarctica that has occurred during the Antarctic spring since the early 1980s. Rather than being a literal hole, the ozone hole is a large area of the stratosphere with extremely low amounts of ozone. Ozone levels fall by over 60% during the worst years. Even over the United States, ozone levels are about 3 percent below normal in the summer and 5 percent below normal in the winter.
More information on stratospheric ozone depletion can be found
at
http://www.epa.gov/air/ozonedep.html 
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