Ozone Layer Protection and You

What is meant by "ozone hole" ?

Since about 1975, scientists have detected a severe drop in ozone concentration in the layer over the Antarctica each spring. The situation then reached an alarming scale in 1987 when an international expedition found that half of the Antarctica¡¦s ozone have disappeared over a region twice the size of the United States, creating an enormous ¡§hole¡¨ in the ozone layer.  Concentrations of ozone fell by as much as 50% of the norm at altitude of 18 km.  At mid-latitudes in the Northern Hemisphere, up to 3% decrease in ozone concentration was also observed.

 

Why it concerns you?

The ozone molecules form a protective layer which extends from about 16 km to 50 km up above the earth at low latitudes, and from about 8 km to 50 km at high latitudes. The ozone molecules absorb the sun¡¦s ultra violet radiation (UV) which will be harmful to us if it reaches the earth surface.  With more UV radiation reaching the earth surface due to ozone depletion, human health and the environment will be adversely affected. The most significant effects will be the increased incidence of skin cancer, eye cataracts, damage to the human immune system and to the ecology of the earth.

What causes this phenomenon?

Scientists have reached consensus that ozone depletion in the stratosphere is caused by ozone depleting chemicals.  These chemicals contain chlorine or bromine atom with inherent chemical stability and have long lifetime in the atmosphere, in the range of 40 to 150 years. These chemicals and other trace gases drift up into the stratosphere and become involved in chlorine-releasing reactions. The chlorine atoms then react with the ozone molecules in the presence of sunlight and destroy the ozone molecules. Just one chlorofluorocarbon molecule can destroy tens of thousands of ozone molecules.

These ozone-depleting chemicals are extensively used man-made chemicals including the followings: -

What are these ozone depleting substances (ODS) used for?

 The following are the common usage of CFCs and HCFCs :

Halons are used as fire extinguishing agents. Bromochlorodifluoromethane (BCF) is commonly used in portable fire extinguishers. Bromotrifluoromethane (BTM) is used in fixed fire-fighting installations. 1,1,1-trichloroethane is commonly used as a:

Carbon tetrachloride is used as a cleaning agent in textile and electronics industries.

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