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Ozone Layer Depletion Threatens to Destroy Us

by Mohammad Ahsan Kahir
THE world now knows that danget U looming In the sky. The evidence la overwhelming that the earth's stratospheric ozone layer- our shield against the sun a hazardous ultraviolet rays
any scientist had predicted
According to the previous studies the ozone levels have declined four per cent to eight per cent over the north cm hemisphere tn the past decade But the latest data imply that the ozone layer over some regions. Including the northern most parts of the US, Canada. Europe and Russia, could be temporarily depleted In the late winter and early spring this year by u much as 40 per cen t
That would be almost as bad as the 50 per cent ozone loss recorded over Antarctica. Set entlsts fear that the "ozone hole" over Antarctica, which was discovered tn 1985. may open up very soon leading to a devastating catastrophe.
According to scientists, the concentrations of chlorine monooxide (CIO), a chemical by-product of the chlorofluorocarbons (CFCs). is known to be the chief agents of ozone destruction. It ts discovered that each atom of chlorine could destroy up to 100.000 molecule of ozone at a far faster rate than the gas ts repfenlshcd naturally Besides each CFC molecule la 20.000 times aa efficient at trapping heat aa is a molecule ol carbon dioxide So tt also Increases the greenhouse effect far out of proportion to their concen tratlon in the air
Ozone is a form of oxygen tn which the molecules have three atoms Instead of the normal two and that simple
structure enables ozone to absorb ultraviolet radiation — a process that is crucial to human health
The small amount that docs get through the earth s surface inflicts plenty- of damage Besides causing sunburn the ul travtolct rays (UV) can make the lens of eye cloud up with cataracts, which bring on blindness if untreated. The radiation can cause mutations In DNA, leading to skin cancers, including the often deadly melanoma. In a recent survey, the United Nation's Environment Programme predicted that a 26 per cent rise In the Incidence of nonmelanoma skin cancers worldwide If overall ozone levels drop 10 per cent. Ex cess UV radiation may also al feet the body a general ability to fight off disease
Scientists are also concerned about the potential ef feet of ozone depletion on the earth's climate systems When stratospheric ozone intercepts
UV light, heat is generated That heat helps create stratospheric winds, the driving force behind weather patterns Weather patterns have already began to change over Antarc tica. Each sunless winter, steady winds blow in a circular pattern over the ocean that surrounds the continent, trap ping a huge air mass inside for months at a time. As the sun rises In the spring, this mass, known as a polar vortex, warms and breaks up. But the lack of ozone causes the stratosphere to warm more slowly, and the vortex takes longer to dissipate. This leads to even more ozone destruc tion.
Besides. high doses of UV radiation can reduce the yield of basic crop such as soybeans. UV-b, the most dangerous variety of ultraviolet, penetrates crores of metres below the surface of the oceans There the radiation can kill phyto plankton and tiny shrimplike animals.
Krill, which provides nour ishment to the larger fishes and as a result humans may (act a maritime food shortage In Australia, scientists believe that crops of wheat, sorghum and peas havV been affected
CFCs arc ubiquitous In al most every society They are used in refrigeration and air conditioning, as cleaning sol vents tn factories and as blow Ing agents to create certain kinds of plastic foam In many countries CFCs are still spewn tnto the air as part of aerosol sprays
Though the annual market for CFC has now stood al some 2.2 billion US dollars, efforts for phasing out the CPC have also been made at different times.
Soon after the ozone hole over Antarctica was confirmed in 1985. many of the world s governments reached an unusually rapid consensus that action had to be taken. In 1987, they crafted the landmark Montreal protocol, which called for 50 per cent reduction In CFC production by 1999 Three years later in 1990. as signs of ozone loss mounted, international delegations met again in London and agreed to a total phaseout of CFC by 2000 Some of the countries that resisted CFC control at first are taking thf lead trxiay
Replacing CFCs In newly built equipment, however. Is only half the Job Virtually every existing refrigerator and air conditioner Is a CFC reser voir The chemicals are not a problem as long as they con tlnue to circulate within an appbcances But If the machine Is carelessly drained. Junked or damaged, the CFCs can escape to attack the ozone
Ridding the planet of the millions of tons ozone-deplet Ing chemicals Is not Just a big Job. It may be the biggest Job the nations of the world have ever taken on And It Is not earth that Is fragile II Is w< who are fragile.