“If all the ozone in the atmosphere were compressed to a pressure corresponding to that at the earth's surface, the layer would be only 3 mm [0.118 in] thick… The thin stratospheric-ozone layer has proved to be an Achilles' heel that may be seriously injured by apparently moderate changes in the composition of the atmosphere.”
You have read in this text many times of the major pollution problems resulting from combustion, especially fossil-fuel combustion. In this chapter we see a global issue – destruction of stratospheric ozone – which does not result from combustion. The chemicals responsible are synthetic chemicals, chlorofluorocarbons (CFCs) and halons. Stratospheric ozone is essential to life on Earth. It absorbs more than 95% of the sun's ultraviolet (UV) radiation, which could otherwise destroy most life. Stratospheric-ozone depletion led to the 1987 Montreal Protocol, the first worldwide agreement to protect the environment. Except for smuggled chemicals, the ban of ozone-depleting chemicals is working. The stratospheric-ozone layer is expected to recover, albeit slowly. Section I below examines the stratosphere and provides background on CFC uses and how ozone depletion was detected. In Section II, we see why the greatest ozone depletion occurs over Antarctica, and describe the increases in UV radiation reaching the Earth.