For more than a decade scientists have been warning that the release of man-made chemicals into the atmosphere was depleting the protective, high-altitude layer of ozone that blocks the passage of harmful ultraviolet radiation from the sun. Now researchers at the National Aeronautics and Space Administration say they have conclusive evidence that such a process is indeed taking place.
The findings vindicate the efforts of environmentalists and others over the years to eliminate production of the kinds of chemicals responsible for the destruction of ozone in the upper atmosphere as well as the multinational effort to reduce ozone depletion by the year 2005.
Ozone, an isotope of oxygen that contains three atoms instead of two, is a gas that acts as a shield against UV radiation from the sun. The radiation is invisible to humans but can cause skin and eye damage, kill microorganisms and damage crops.
Scientists have long suspected that man-made compounds called chlorofluorocarbons were responsible for thinning the ozone layer. CFCs are commonly used as refrigerants, propellants in spray cans and as cleaning agents. But when released they rise into the atmosphere, where they form new compounds with the layer of ozone in the upper stratosphere, thus depleting the supply of free ozone molecules.
During the 1970s researchers noticed that the ozone layer over dTC the Antarctic seemed to be thinning each spring. They theorized that seasonal temperature changes allowed chlorine in the CFCs to react with free ozone.
That hypothesis was confirmed this week when satellite measurements detected the presence not only of chlorine compounds but of fluorine, which could only come from CFCs.
Previously, skeptics had argued that the chlorine could have arisen naturally from volcanic eruptions. That was a principal complaint against the 1987 Montreal Protocol, which pledged most of the world's nations to halt production of CFCs by 1996. Critics of the treaty charged the alternatives to CFCs were too costly and the evidence too inconclusive to justify the cost of replacing them.
Now that argument has been laid to rest. Every effort should be made to meet a world-wide goal of returning ozone levels to where they were in 1979. Increased UV radiation is expected to cause about 30,000 additional cases of skin cancer over the next decade. Prevention, in this instance, is clearly the best medicine.