Release of chlorofluorocarbons (CFCs) and several related chemicals to the atmosphere may lead to reductions in the concentration of stratospheric ozone and contribute to changes in the earth’s climate through the “greenhouse effect.” Each effect could threaten existing ecosystems and human welfare: Depletion of stratospheric ozone could increase the quantity of ultraviolet radiation reaching the earth’s surface, potentially increasing human skin cancer incidence, promoting cataracts and suppressing immune responses in humans and other animals, and causing other adverse effects to animals, crops and other plants, and valuable materials. The “greenhouse effect” is expected to cause a general global warming that would affect climate and weather patterns, sea levels, agricultural productivity, and the geographic distribution of plant and animal species (see Chapter 18). 1