The Protocol will be reviewed at an international meeting in Copenhagen which ends on 26 November. Like its predecessors, this will take place against a background of alarming new evidence about the threat posed to the ozone layer by emissions of halocarbons.
Last year's record ozone depletion above the Antarctic, which appears to have been catalysed by dust particles from volcanic eruptions in Chile and the Philippines, has already been beaten. In September, the ozone hole appeared earlier than in previous years, and covered a record 8.9 million square miles. Ozone levels fell to 40% of their normal value, and for a few days the ozone hole extended over populated areas in South America, where ozone readings declined to almost half their normal value.
At Copenhagen, industrialised countries appear ready to agree to a ban on all but "essential" uses of halons from 1 January 1994, and of CFCs from 1 January 1996. Developing nations are likely to demand an extra ten years in which to follow suit. "Essential" uses will probably be defined next year.
Although the EC is backing both phase-out dates for the purposes of the Protocol negotiations, earlier bans within the Community are still a possibility. The position may be clarified after the next meeting of EC Environment Ministers in mid-December.
Some progress has been made in the past few weeks towards agreeing a basis for negotiations on the control of HCFCs. These are being pushed by some fluorocarbon producers as CFC substitutes in several applications by virtue of their low ozone depletion potential (ODP).
However, the HCFCs have been under a cloud for more than a year since it was recognised that their ODPs understate their short-term contribution to ozone depletion. This means that they will be causing their maximum damage to the ozone layer at just the time that ozone depletion is expected to be at its height due to the cumulative effect of past and impending releases of CFCs, halons and other chemicals (ENDS Report 198, pp 3-4).
Some environmentalists insist that this phenomenon warrants an early phase-out of the HCFCs as well. The counter-argument from HCFC producers and some user industries is that the transition away from CFCs will be delayed without HCFCs. Environmentalists' response, typified by a new Greenpeace campaign in the UK against the use of HCFCs in supermarket refrigeration systems, is that other substitutes are available (see pp 11-12 ).
The future of the HCFCs will probably be the most hotly disputed issue at the Copenhagen meeting. The baseline for the negotiations was provided by a proposal put forward by the Executive Director of the UN Environment Programme, Dr Mostafa Tolba, at a meeting of officials in late September. The proposal incorporates a production cap, a phase-out deadline with interim reduction targets, and a list of permitted or banned uses of HCFCs.
The production cap proposed by Dr Tolba would involve limiting HCFC production to 1989 levels, together with a small proportion of CFC consumption levels in 1986. Precisely what that proportion should be will be the subject of prolonged negotiations. Until recently, US industry, including the world's leading fluorocarbon producer Du Pont, had opposed the idea of a cap, but the need to prevent uncontrolled short-term growth in HCFC consumption has been accepted by the regulatory community.
Details of the phase-out programme also remain to be agreed. Dr Tolba apparently proposed a progressive reduction in HCFC production from 2000, with a ban taking effect in 2020. However, official views of how rapidly the phase-out should take effect are not identical on either side of the Atlantic.
At a conference in the USA in September, an official from the US Environmental Protection Agency suggested that the outcome of the Copenhagen meeting would be a 25% cut in HCFC production from the maximum figure by 2005, a further reduction of 30-50% by 2010, a possible 90% reduction by 2020, with a ban taking effect in 2030. In contrast, an official from the UK Department of the Environment predicted that the outcome would be a phase-out in 2015 or 2020.
The third key question is which specific uses of HCFCs should be banned or permitted. A decision on this is likely to be deferred to follow-up meetings in 1993-4.
Another controversial issue will be the future of methyl bromide, a common soil, grain and timber fumigant. The chemical emerged on the ozone depletion agenda only at the end of 1991. Subsequent studies have suggested that its global consumption is about 60,000 tonnes annually.
The USA has been leading calls for a ban on methyl bromide by 2000. Its position is dictated by a recent amendment of the Clean Air Act which provides that all chemicals with an ODP of more than 0.2 should be banned from 2000. Methyl bromide has an ODP of 0.7.
The USA's position has run into intense opposition from Israel, a major producer of methyl bromide, and the developing countries, which insist they have no alternative to the chemical in commercially crucial fumigation applications.
The EC will take a negotiating position between these points, arguing for a freeze on production at 1991 levels by 1995. This reflects a compromise reached at the Environment Council on 20 October. The UK is known to have argued at the Council for a 25% reduction in production by 2000, while the Dutch, who are banning the chemical at home because it has polluted soil and groundwater in horticultural areas, urged a 70% reduction by 1995.
However, the southern EC states maintained that no adequate substitutes are available. Their claims were disputed by UK and Dutch officials, who believe that alternatives are available for all but "quarantine" applications, though they generally involve the use of two or three products to tackle different pests in place of the broad spectrum action of methyl bromide.