HOW DO CFCs DAMAGE THE OZONE LAYER?

Most of us don’t think about how our everyday activities might influence the global environment. An example is our use of chlorofluorocarbons or CFCs. These compounds which are useful as propellants in aerosol sprays, refrigerants, coolants, cleaning agents, insulants and plastic foam are the main eaters of ozone present in the ozonosphere. Ozonosphere is the general stratum of the upper atmosphere in which there is an appreciable ozone concentration and in which ozone plays an important part in the radiative balance of the atmosphere. It lies roughly between 10 and 50 kilometers, with maximum ozone concentration at about 20 to 25 kilometers. Ozone, O3, a blue gas is unstable allotropic form of oxygen. It is scarce, even in the astratosphere where it is most concentrated. But each molecule counts. Highly unstable, an ozone molecule readily splits up when hit by ultraviolet radiation. The energy of the life-damaging UV rays is thus converted into harmless heat and never reaches the earth. The breakup leaves a free oxygen atom (O) and an oxygen molecule (O2), the stuff we breathe. The O and O2, in an ongoing cycle, recombine to form new ozone molecules. The chlorofluorocarbons released by us are stable and can live up to 100 years. They are non-toxic and harmless to life. But when they drift slowly upward to reach the stratosphere by convection, they are struck by the high energy short wavelength radiations such as ultra violet rays and this initiates a ozone clearing process. When a CFC molecule is exposed to strong UV radiation in the stratosphere, it is broken apart. This release a chlorine atom, which attacks an ozone molecule, pulls away one of the three oxygen atoms and forms a chlorine monoxide molecule thus destroying the ozone molecule. The destructive process continues further. Free oxygen atoms freeing the chlorine atom to restart the cycle pull the oxygen atoms from the new chlorine monoxide molecule away; thus progressively more ozone molecules are decomposed. It has been estimated that one chlorine atom can eat up to 100000 molecules of ozone. A severe depletion in the ozone layer will result in an increase in the case of skin cancer, eye cataract and suppression of the immune system in humans and other species. Food crops sensitive to UV rays could also be affected. In 1984 a hole in the ozone layer was discovered over Antarctica and more recently a similar hole was discovered which extends over the Arctic, Scandinavia and North America.