The Montreal Protocol has been one of the most successful global environmental treaties, securing the phase-out of most ozone-depleting chemicals in developed countries, with developing countries due to begin following suit from the end of this decade.
According to the UN Environment Programme, the result of this activity has been ten times less ozone depletion in the northern and southern hemispheres than would otherwise have occurred. This translates this into the avoidance of 19 million cases of non-melanoma cancer, 1.5 million cases of melanoma and 130 million cases of eye cataracts.
But the long lifetimes of some ozone depleters, and continued usage in lesser quantities, mean that their concentrations in the stratosphere are only now levelling off. Complacency about the recovery of the ozone layer has been discouraged by this year's ozone hole over Antarctica, which was the second largest on record, and by continuing concern that the recovery process may be slowed by climate change.
Moreover, at the meeting of Montreal Protocol parties, held in Nairobi, Kenya, on 10-14 November, it became evident that all is not going to plan. For the first time, discussions of an item had to be abandoned, with negotiators agreeing to meet next March at an extraordinary session in Montreal to try again for a consensus.
By this year, production and consumption of the chemical by developed countries is due to be cut to 30% of the 1991 level. Remaining usage is due to cease by the end of 2005 - though parties are able to apply for "critical use" exemptions where there are no technically or economically feasible alternatives and where the unavailability of methyl bromide would cause "significant market disruption".
The US angered other delegations by asking for 16 critical use exemptions, amounting to 9,920 tonnes of methyl bromide for 2005 - two-thirds of the total requested by all parties - and 9,445 tonnes in 2006. If granted, the exemptions would mean that the US could maintain methyl bromide consumption at 39% of the 1991 level for three more years.
The US Natural Resources Defense Council accused the Bush administration of "violating the treaty". It said that the applications abused the critical use exemptions process and "punished the responsible growers who have invested time and money into adopting safer alternatives."
The US critical use nominations cover a variety of crops, including peppers, strawberries, sweet potatoes and tomatoes. It even sought an exemption of 352 tonnes per year for spraying turf grass for golf courses.
On several of the US applications, the Protocol's Methyl Bromide Technical Options Committee (MBTOC) did not give a positive recommendation. In some cases it said it could not see why alternatives employed elsewhere could not be used, and in others it had not been given the specified information to enable it to make a judgment.
Belgium, France, Greece, Italy, Portugal, Spain and the UK also asked for exemptions for methyl bromide for use on a variety of fruit and vegetable crops. Around 15 of the applications were for cut flower nurseries.
The UK asked for 12 tonnes per year for ornamental tree nurseries, which MBTOC recommended should be halved. It requested 80 tonnes per year for strawberry and raspberry growing, and for some 50 tonnes per year for fumigation of various mills and processing plants. Again, MBTOC questioned whether alternatives were not available for these applications.
Commenting on the failure of the meeting, UNEP's executive director Klaus Toepfer said: "Unfortunately and despite a great deal of discussion, governments could not find consensus on this complex issue....They felt they needed more time to find an agreement which balances the interests of farmers and other users of methyl bromide with international agreements to repair the Earth's protective shield."
The US complained about other parties' responses to its applications - objecting in particular to an EU proposal that critical use exemptions should be capped for each country at 30% of their 1991 production and consumption level.
A US representative told the meeting that the introduction of a 30% cap at this stage would be "unfair" - and warned that unless the US request was granted the Protocol would be seriously undermined.
Indeed, the US agricultural industry is already working hard to ensure that it is not held hostage to the Protocol. On 29 October, Congressman George Radanovich backed by 21 others tabled a Bill to authorise the Environmental Protection Agency to override the USA's obligations under the Montreal Protocol should parties deny its critical use applications. The amendment is based closely on one proposed by farming groups earlier this year.
The groups argue that, without the exemptions, the costs and difficulties of using alternatives could leave them unable to compete against developing country growers who will not be obliged to stop using methyl bromide until 2015.
Some in Nairobi remarked that developing countries had not been as indignant as expected about developed countries reneging on their obligations - possibly because this will leave them with an excuse to follow suit in years to come.
One estimate is that illegal trade could amount to as much as 15% of total CFC production, and HCFC trading is also increasing.
Ezra Clarke of the EIA warned: "Ultimately, as long as CFCs are being produced, this illicit trade will exist....The only real solution is to speed up the final phase-out of ODSs."
However, New Zealand and the USA argued that CFC-free inhalers are too expensive for some people - and developing countries also objected to pressure on this front.