Oxygen is usually found in the air and dissolved in water as O2, i.e. the two-atom form of oxygen. At ground level, however, ozone is a pollutant, irritating eyes, nose and throat, and damaging the respiratory system. It is especially harmful to people with cardiorespiratory problems. Ozone also corrodes some metals.
Ozone shields life on earth from the sun's UV radiation.
Plants and animals living at different altitudes are adapted to different amounts and wavelengths of UV radiation. Some scientists believe that the evolution of life on earth has been made possible by the existence of the protective ozone shield. In 1982 a team from the British Antarctic Survey working in Antarctica found that much of the ozone overhead had vanished. The report of their findings caused a sensation, as ozone depletion of this scale was totally unforseen. It is now known that a depletion, often termed a hole, of the ozone layer over Antarctica occurs each spring, and lasts for approximately six weeks.