It is generally believed by scientists that chemicals produced by human industry which were not present in the pre-industrial atmosphere are breaking down the ozone by releasing chlorine. These chemicals - Chloro-fluoro-carbon compounds CFCs - have been used in aerosols, refrigerators, plastic foam and electronic manufacturing. Halons in fire extinguishers are also implicated.

CFCs, as well as damaging the ozone layer, add to the warming effect.

Even if the production of CFCs ceased at once the quantity in the atmosphere would continue to rise as existing stocks escaped. The rate of breakdown in the upper atmosphere is slow so that the existing quantity would only reduce slowly, even if no new compounds are added.

Observation of the upper atmosphere above Antarctica has shown a diminution of the concentration of ozone. Ozone is formed by the action of ultraviolet light on oxygen. Its function is to absorb ultraviolet light.

In 1991 scientists observed the same effect over the Arctic. Reduced ozone will put at risk the populations of the northern hemisphere, especially the industrial countries of western Europe and North America. A reduction was observed in 1986 and 1989, however by Fall 1990 the northern hole had disappeared - but it returned in 1991 when scientists reported a serious attenuation of ozone above the northern hemisphere. By early 1992 there were warnings of serious reductions and warnings of dangers to people's eyes in the whole northern hemisphere in winter sunshine. Perhaps this will provoke political leaders into realistic action, which they have been reluctant to take so far.

Life on land, as opposed to life in the depths of the ocean, only became possible when sufficient oxygen had been produced to form an ozone layer. Ultra-violet light damages living processes including plant growth (reduced crop yields, especially of peas and beans) and animal tissues. Increased incidence of cataracts in human eyes can be expected, as well as skin cancers. Blind sheep and rabbits have been reported in Patagonia and southern Chile. (Later research suggests this story is not true but that the blindnessis caused by the disease "pinkeye" )

Sunbathing by people with "white" skins as a social custom might have to be replaced by walks in the rain as a safe recreational activity, but even peoples with higher proportions of skin melanin are at greater risk than before. They may well have a genetic survival advantage, though, especially in Australia. People with African genes may do better than "whites" . Could this end racist discrimination and make people of African descent preferred marriage partners?

1) International agreement to cease production of CFCs, at once.

2) Programs to recover the existing stocks and destroy them (already begun on a pilot scale).

3) Technical innovation in production of refrigerators and air conditioners and phasing out aerosols (a product which is mainly an advertiser's luxury).

4) Replacement in the electronic industry by other cleaning methods.

5) Refrigerators based on solid state cooling by the Peltier effect using bimetallic electrical junctions would not introduce chemicals into the atmosphere, and might well reduce energy needs at the same time. Using the Ammonia cycle or butane might also avoid the use of CFCs.

As countries like India, China and Africa are on the point of delivering refrigerators to millions of people there is a danger that the amount of CFCs produced will actually increase instead of being phased out. The leaders of some of these countries, in tropical zones, may believe they are less at risk from thinning ozone layers, which are concentrated in the polar regions.

This is one of the many disputes between already developed countries and those wishing to "catch up" . The ozone covers us all but the poorer complain that they can't afford environmental controls. (This may not be true, but it is a common argument.)

An international agreement to phase them out rather slowly - by 2000 - has been criticized by scientists as a sign that the politicians and diplomats don't have a sufficient feeling of urgency and are more concerned with the profits of the industrialists who manufacture CFCs than with the effects on the atmosphere. Moreover, the proposed substitutes, which include Hydro-Chloro-Fluoro-carbon compounds - HCFCs - may be just as dangerous ozone destroyers and greenhouse gases. In February 1992, the American president, who was facing an election, announced that the phase out was being brought forward to 1995.

This problem seems on the way to being solved but it will take some years for Ozone layer to be healed.