Methyl bromide update

by Teresa Acklin
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   Methyl bromide now is a controlled substance under the terms of the Montreal Protocol, an international agreement that controls ozone-depleting and potential ozone-depleting substances.

   Under this agreement, world production of methyl bromide for fumigation has been capped at the 1991 level, and signatory countries have agreed to ensure that this level of production and use is not exceeded. In addition, the European Union has introduced a further control measure that in 1998 will reduce the availability of methyl bromide in E.U. countries by another 25%.

   Currently, an exemption from these controls exists for methyl bromide that is used for “quarantine or pre-shipment” purposes. The precise definition and mechanism for monitoring and controlling this exemption is still under debate, but it is very likely it will apply only to uses that are specifically requested by a government authority, e.g. port, health, forestry or other commissions.

   During the past three years, the United Nations Environment Program (UNEP) organized a worldwide Science Panel and a Technology Panel to assess all aspects of methyl bromide. The panels' reports now have been published, and they provide the basis for future assessment.

   The Science Panel report concludes that methyl bromide will destroy ozone but that a massive degree of uncertainty exists regarding the amount produced naturally (e.g., by oceans, which also act as sinks) and the amount produced from other sources (e.g., leaded gasoline, forest burning). The actual effect on the amount of methyl bromide emitted by controlling one source, such as fumigation, is therefore very uncertain.

   The Technology Panel assessed all the possible alternative treatments and also assessed the options to reduce emissions from current use.

   In late November, a full meeting of the Montreal Protocol will take place in Vienna, Austria, during which future controls on methyl bromide will be considered. All decisions will be made by consensus, and a number of preliminary meetings are being held to try to reach consensus before the November meeting.

   In April, the E.U. management committee met to discuss the E.U. position. At this meeting, the Scandinavian countries, which use hardly any methyl bromide, wanted a complete ban imposed within five years or so. Some of the Mediterranean countries wanted no further controls.

   In May, many of the countries represented on the Montreal Protocol met at a preliminary meeting in Nairobi, Kenya, where a wide divergence of views surfaced.

   The United States and the Netherlands proposed a phased-out ban by 2001 with exemptions for essential quarantine use; other E.U. countries were divided, with Spain wanting no further controls and the Scandinavian countries wanting a ban; and developing countries, especially in Africa, Asia and South America, wanted no further controls.

   Another preliminary meeting among Montreal Protocol countries to work on these differences was scheduled for August. The most influential groups within the Montreal Protocol are the United States and the European Union.

   The United States is in a different position than other countries because of its Clean Air Act. Under this act, all ozone-depleting substances must be phased out within a defined period. If methyl bromide continues as a controlled substance under the Act, it will be banned in the United States by the end of 2001.

   At present, opinions between the U.S. Department of Agriculture and the U.S. Environmental Protection Agency, which administers the Clean Air Act, differ widely on this subject. The end result will probably depend on whether science or politics provides the most acceptable argument.

   Although many “technically feasible” alternatives to methyl bromide are listed in the UNEP report, many are not practical or viable.

   For grain and commodity fumigation and some pre-shipment and quarantine fumigation, phosphine gas could be used much more widely. But it has the disadvantage of taking much longer, with the associated difficulties of ensuring safety over a long period and incurring additional costs. Almost all other alternatives are likely to take longer and be significantly more costly or, if not, they may be significantly less effective.

   Work on more sophisticated methods of using phosphine to reduce these difficulties is progressing and is likely to make phosphine a more viable option before long. For fumigation of flour mills, there are alternatives in some situations, but as the UNEP report says, “With regard to treatment of structures for pests in most situations there is currently no alternative to methyl bromide.”

   Meanwhile, the most sensible approach would be to minimize leakage of methyl bromide in all its uses by using better sheeting and improved sealing, together with more accurate application and monitoring systems. This offers the prospect of reduced dosage and therefore reduced emissions without sacrificing effectiveness.

   Chris Watson, managing director of Igrox Ltd., London, is a member of the United Nations Environment Program Methyl Bromide Options Committee.