The banning of the chemicals - which have pervaded modern life in hundreds of uses from aerosol sprays and hamburger cartons to pesticides, dry cleaning and computer maintenance - is the result of the first global environmental treaty, a rare example of governments taking action to prevent a fast emerging problem from developing into a disaster. The making of the treaty is a story with many heroes - the governments themselves, the scientists who detected what was happening and campaigned for action, the embattled United Nations which brokered the agreement and - to a certain extent - industry, which moved rapidly to phase out the chemicals once it was clear they were doomed. But now, at the moment of its greatest triumph, the agreement is being attacked.
The Montreal Protocol on Substances that Deplete the Ozone Layer - to give the treaty its full and cumbersome name - has become the latest target of the ideological right, especially in the US Congress. As a result, the United States, which more than any other country drove through the agreement, now seems bent on undermining it, even though the Vice President, Al Gore, once made "the crisis in the global atmosphere" his own special issue.
Earlier this month a meeting in Vienna of the 150 countries that are party to the treaty barely managed to resist attempts from the US and some Third World countries seriously to water it down. Those attempts were made despite the fact that 1995 saw record depletions of the ozone layer, over both hemispheres.
Last autumn the Antarctic ozone hole, now three times the size of the continental United States, was larger than ever, and expanding faster than ever. Even more ominously, record falls of between 20 and 30 per cent took place in the protective ozone above Europe, North America and Russia last spring.
The ban taking effect tonight covers carbon tetrachloride and methyl chloroform, as well as chlorofluorocarbons (CFCs), of which industrialised countries produced as much as 750,000 tonnes annually only 10 years ago. It comes not a moment too soon. It will take decades for the damage already done to the ozone layer to heal.
OZONE - blue-tinged and pungent - is a form of oxygen with three atoms per molecule instead of the normal two. The added atom makes it poisonous: anyone breathing in more than a trace of it would die. It is an increasingly troublesome pollutant, mainly formed from gases emitted from car exhausts, and is heavily implicated in the asthma epidemic, which now affects one in seven British children. But, safely up in the stratosphere, at altitudes of between about nine and 30 miles, it is as important to life as oxygen itself.
No other known planet has this stratospheric ozone layer. If it had not developed, Earth would have been inhabited by no more, at best, than the most primitive underwater life. If it were to disappear, the Sun's ultraviolet light would sterilise the surface of the globe, annihilating everything except life forms in the depths of the ocean.
The ozone layer forms a fragile shield, curiously insubstantial but remarkably effective. It is scattered so sparsely through the 21-mile deep stratosphere that if it were all collected together it would form a girdle around the earth no thicker than the sole of a shoe. Yet this thinnest of filters effectively screens out almost all the ultraviolet radiation.
The small amount that does get through is the main cause of skin cancer; it also produces blinding cataracts, and affectscrops and the productivity of the ocean. Damaging the ozone layer affects all these dramatically. Elizabeth Dowdeswell, executive director of the United Nations Environment Programme (Unep), which co-ordinates the international rescue efforts, says that it "may ultimately be responsible for many millions of cases of skin cancer worldwide".
It was in the late 1960s that a Dutch canal engineer turned meteorologist, Paul Crutzen, first worked out that we could damage the ozone layer but he had little training in the field and said that at first he "did not dare" to go public. He finally plucked up the courage some years later while working at Oxford University and posted a paper on his findings to a scientific journal.
Another scientist who came to similar conclusions at much the same time - James MacDonald of the University of Arizona - shot himself after being attacked by right-wing United States politicians.
Both Crutzen and MacDonald warned against the effect of supersonic aircraft on the ozone layer - but supersonic aircraft, which fly in the stratosphere, flopped, and so proved too few to make any impact.
Only some years later did CFCs become suspects. For years they had seemed to be miracle substances. Inert and immensely stable, neither flammable nor poisonous, cheap to produce and easy to store, they seemed designed for the modern world. Invented more or less by accident in 1928, they were first used as the working fluid in fridges, then as propellants in aerosols to provide the power behind instant freshness and spray-on sex appeal. The computer revolution found them being used to clean circuitry, while the fast-food revolution saw CFCs being used to puff up the foam for polystyrene cups and hamburger cartons. New Scientist said: "No other chemicals in the home are as harmless as CFCs."
But their very stability, so safe and useful on Earth, enables them to drift into the stratosphere. CFCs do not react with anything on or near the surface. But they do react with intense ultraviolet radiation and this is what causes them to destroy ozone. They remain in the stratosphere for between 74 and 111 years, damaging the ozone shield throughout.
In the autumn of 1973, two scientists at the University of California - Professor Sherwood Rowland and Dr Mario Molina - wondered what happened to CFCs. They thought they would probably have an effect on the ozone layer, but when they worked out the figures they were so shocked that initially they were convinced that they must have made a mistake. They had not. Last year they and Professor Crutzen were jointly awarded the Nobel Prize for Chemistry.
Their findings led to intense debate. Professor James Lovelock - now something of a New Age cult figure for having advanced the "Gaia" hypothesis (named after the Greek Earth goddess) of the planet as a self-regulating entity - was prominent in the CFCs' defence. The United States, Canada, Norway and Sweden phased out use of the chemicals in aerosol cans, apart from essential medical sprays. The EU agreed not to increase its capacity for producing the chemicals - a seemingly helpful step which was, in fact, nothing of the kind, as its capacity then far exceeded its actual production. The UN Environment Programme continued to try to keep the issue on the international agenda, but it faded until there was another unpleasant surprise.
THE surprise came to Dr Joe Farman, a scientist working for the British Antarctic Survey. In October 1982, taking regular measurements of ozone above the project's base at Halley Bay, he suddenly noticed that much of it had disappeared. This seemed impossible.
No one had ever predicted depletion on this scale. Furthermore, a Nasa satellite, Nimbus 7, was measuring ozone and recording no such development.
Dr Farman thought there must be a fault in the instrument he was using and returned next year with a new one. He found even less ozone. The same thing happened in 1984, by which time he was convinced that something was seriously wrong, even though the satellite was still reporting that all was well. He says he was so alarmed that he thought of knocking on the door of 10 Downing Street and asking to see the Prime Minister, but he settled for sending a paper to the scientific magazine Nature.
The paper caused a sensation. The Nasa scientists looked again at their data and found that Nimbus 7 had indeed been recording such ozone levels but had never passed them on because the computers had been programmed to discard very low figures as being spurious, before they were seen by the human eye. Fortunately it had saved the discarded measurements, and the scientists were then able to calculate that there was indeed a hole in the sky over Antarctica that was as big as the continental United States and as deep as Mount Everest is high. It was the reaction to this discovery that made the Montreal Protocol possible.
"We are very lucky that the CFC surprise happened over an uninhabited part of the world," Professor Crutzen says. "If Joe Farman had not taken these measurements or had not published his paper, we might well have done nothing until an ozone hole developed over Europe."
As it was, the world moved with surprising speed. The Montreal Protocol was adopted in March 1987 and amended to impose increasingly stricter controls in 1990 and 1992. The ban on CFCs was agreed three years ago and expanded to include carbon tetrachloride (used in pesticides and dry cleaning) and methyl chloroform (largely used in cleaning metals) as these two were found also to be attacking the ozone layer.
Some governments have taken the threat so seriously that they have moved even faster than the treaty requires. Sweden banned most uses of CFCs in 1991, Austria in 1993 and the European Union phased the chemicals out altogether a year ago, 12 months ahead of the deadline. Industry, after at first resisting regulations, raced to replace the chemicals with substitutes once it became clear that controls were on their way.
The controls have been so rapid and so effective that CFC smuggling is booming, particularly in the United States, where there remains strong demand for the chemicals. Smuggling CFCs into Miami is second only to bringing in cocaine in the profits that can be made. The US government has responded with tough action, so far impounding 1 million pounds of them and convicting 10 smugglers. One, Irma Henneberg, was jailed for 51 months last August.
Some 20 million pounds of the chemicals appear to be smuggled into the US every year, partly because 100 million American cars are cooled by air-conditioning systems built to use them and partly because until now the government has controlled them with a special tax which has quadrupled their prices. The problem is less severe in Europe, which has no CFC tax and where only 10 per cent of the cars have air conditioning. But there are signs that it exists here, too. Duncan Brack, senior research fellow at the Royal Institute of International Affairs, who has made a special study of the issue, says that most of the contraband CFCs seem to come from Russia. He warns that the smuggling threatens the rate of recovery of the ozone layer.
SMUGGLING CFCs, however, is not the biggest threat to the ozone layer. Two others are far more significant: first, that from developing countries, which do not have to phase out CFCs under the treaty until 2010, and, second, that from other chemicals including some of the very substitutes developed by industry to tackle the problem, particularly HCFCs, though they are not as harmful as CFCs. The Third World's use of CFCs has leapt by 50 per cent over the last decade and industry is fighting to limit controls on HCFCs and methyl bromide, an ozone-threatening pesticide.
At this month's meeting in Vienna, the US pressed for a further 20 years' delay before Third World countries had to stop using CFCs, threatening to open the door to further massive damage of the ozone layer. Its intention was to save money: under the Montreal Protocol the rich countries have agreed to provide aid to help poorer nations phase out the chemicals. The US also led opposition to new controls on HCFCs.
This represented an extraordinary turnaround. Under the administrations of Ronald Reagan and George Bush - no friends of environmentalists - the US pushed harder than anyone for measures to save the ozone layer. Now the "greenest" ever US administration - packed with environmentalists from the Vice President (whom President Bush once derided as the "ozone bozo") down - has been leading attempts to undermine it.
The irony was capped when President Reagan's chief ozone negotiator, Richard Benedick, took the rostrum in Vienna to lambaste the "unbelievable" arguments of Clinton's delegation, which included a former leader of Friends of the Earth.
In another strange reversal it was Britain - which had led much of the opposition to the original protocol - which, together with the UN Environmental Panel, saved the day. John Gummer, Secretary of State for the Environment, insisted: "There must be absolutely no question of relaxing current commitments" and rushed around the conference centre putting together an agreement. At one point, in his enthusiasm, he became too "green" even for the environmentally friendly Danish government, which objected that he was going too far. "It has felt very odd to be going around praising Gummer," one male environmental campaigner said. "It was a bit like wearing women's clothes."
The US proposal for longer use of CFCs was fought off and new controls were brought in for HCFCs, though developing countries will still be able to go on using them for another 45 years. Environmentalists fear that, as the economies of countries such as India and China expand, use of these chemicals will increase so fast that the danger to the ozone layer will be even greater than before the treaty was first agreed.
So far about 10 per cent of the Earth's ozone shield has been destroyed. Unep says that if this trend is sustained, as it almost certainly will be, the number of skin cancers will rise by 26 per cent. Other estimates suggest that up to 150,000 more people will go blind each year for every 1 per cent decrease in ozone.
Even at best, we are in for many decades of diminished protection. As the chemicals take years to drift up to the ozone layer, the destruction will go on getting worse at least until the turn of the century. And as they stay in the atmosphere so long, they will continue to do their damage for decades. Even if everything goes well, and international controls continue to get tighter, the ozone hole is not expected to close until after the middle of the next century.Reuse content