A Time-bomb in the Earth's Atmosphere

Ground and satellite readings confirm a decline in global ozone: the stratospheric ozone shield that protects life from damaging ultraviolet radiation is being rapidly depleted. The depletion of the ozone layer is an immediate global environmental problem threatening the survival and development of humanity.

Industrial chemicals such as chlorofluorocarbons (CFCs), widely used as refrigerants in auto air-conditioning, halons, used as fire retardants, aerosol propellants and solvents, foam-blowing agents and others which destroy the ozone layer allow harmful ultraviolet rays to enter the atmosphere, damaging plant and animal life. These chemicals also contribute to global warming. Created and used by man for industrial and commercial purposes, the chemicals appear to be the sole cause for this destructive effect.

Destruction of the ozone layer may be compared to the effect of a bomb that has been primed: its timing mechanism is counting off days, hours and minutes up to the "explosion", which could threaten all civilization with disaster. And the cause of the disaster, if it happens, will not be atomic or hydrogen bombs or laser weapons — it will be nothing more exotic than the ordinary everyday deodorant can and refrigeration systems using CFCs.

When they were first synthesized over 60 years ago, these chemicals were the pride and joy of the chemists who invented them: they were harmless, non-toxic and cheap to produce. Now they are called "killers".

Each one percent drop in ozone is thought to allow a 2 to 3 percent rise in the ultraviolet light reaching Earth. Any large increase would be reason for serious concern. The light is destructive to DNA, the hereditary material, and to proteins. The most dramatic evidence of damage to the global ozone shield appears each spring in the Polar Regions. The continent-wide hole over the Antarctica was first detected by British researches in 1982. A retrospective examination of satellite data reveals that the hole was virtually undetectable prior to 1979. In 1987, a 50 percent reduction in ozone was measured during October. In January 1989, a major international research effort confirmed that conditions similar but less severe than those found in the south polar atmosphere prevailed over the Arctic. The chemistry resembled that found over the Antarctica. As the Antarctic ozone hole dissipates each summer, great masses of ozone-deficient air have spread as far as New Zealand, Australia, and southern Argentina and Chile, resulting in significantly higher radiation exposure for the populations of these nations. In addition, ozone levels over midlatitudes of the northern hemisphere are decreasing. The average levels of ozone in the midlatitudes of the northern hemisphere appear to have decreased by about three per cent.

High concentrations of chlorine and bromine occur where ozone depletion is the most severe. Some scientists conclude that the sudden onset of the ozone hole was triggered when chlorine levels exceeded two parts for billion. This is an example of how sensitive the earth's atmosphere is to man-made chemical effects.

Even if the production and use of ozone-depleting substances is stopped immediately, the chemicals already released will continue to accelerate ozone depletion for ten years. It will require nearly three centuries for the ozone hole to fully heal.

The increased ground-level intensity of ultraviolet radiation that accompanies stratospheric ozone depletion is linked in a way to increases in skin cancer, cataracts and change in the immune system in humans.

We do know enough now to recognize that the continued release of CFCs, halons and other chemicals put all of the earth's human and natural environment at risk. The threat to plant and animal life has direct consequences for humans. Commercially important fish and shrimp species, for example, have been shown to suffer mortality rates when exposed to increases in ultraviolet radiation.

These findings are truly alarming.

Ecologists call for a complete, worldwide phase-out of CFCs and halons, for restrictions on other related gases that contribute to ozone depletion.

How can the transition to a total phase-out be managed? To begin with, approximately one-third of CFCs presently in use can be substituted by CFCs which decay more rapidly and present less threat to the atmosphere; one-third of CFCs can be contained and reused through recycling processes; and one-third of present uses can be phased out by the introduction of non-CFC technologies.

Answer the following questions:

1. What is considered to be the most urgent environmental problem today?

2. Where are the chemicals that destroy the ozone layer used?

3. What scientific data were revealed prior to 1979? in 1982? in 1987? in 1989?

4. What regions are exposed to significantly higher ultraviolet radiation nowadays?

5. What do you know about the levels of ozone over the northern hemisphere?

6. How could the sensitiveness of the earth's atmosphere to man-made chemical effects be illustrated?

7. How long will it require to cure our planet of ozone depletion?

8. How does the production and use of ozone depleting chemicals influence life on Earth?

9. What do ecologists call for?

10. How can the transition of a total phase-out of CFCs be managed?