The importance of the stratospheric ozone layer, which filters out most of the sun's harmful ultraviolet radiation, in protecting the Earth's surface from the harmful effects of solar ultraviolet radiation has been recognized for many decades. It was not until the early 1970s, however, that scientists began to actually grasp the fact that even relatively small decreases in the stratospheric ozone concentration can have a serious impact on human health--an increased occurrence of skin cancer, particularly in fair-skinned people. The process ....