Methyl bromide and ozone depletion

Several organic gases have been implicated in the depletion of the ozone layer. Most attention has been focused on the CFCs and haloes, but methyl bromide has now come under increasing scrutiny. Methyl bromide is a highly toxic pesticide. It has been used for the last 50 years as a fumigant for controlling pests in the soil, in harvested durable and perishable crops, and in processed commodities. World-wide the greatest use of methyl bromide is in soil disinfestation to control a broad range of pests including nematodes, soil pathogens and weeds. Methyl bromide is the only quick-acting fumigant available for commodity disinfestation, and one of its major uses in this field of application is quarantine fumigation to prevent the spread of damaging pests through international trade. Although other chemicals or alternative methods of pest control have been developed since its introduction methyl bromide has been retained where no suitable or costeffective alternatives have been available. Under the terms of the Montreal Protocol there is a ten-year grace period for developing countries to allow the transfer of technology that will permit ozone-depleting chemicals to be phased out. Consideration will need to be given to the availability of alternative pest management techniques that might be introduced. For soil treatment there is unlikely to be a single alternative to the broad spectrum of activity of methyl bromide, and a combination of techniques, including chemicals, may be necessary. The greatest problem, however, may lie in finding an alternative to quarantine fumigations, where short-period treatments are essential. Two-hour treatments are commonly employed for perishables such as fruit and cut flowers and it may be that, where no alternatives can be found, special consideration will have to be given to the indefinite retention of methyl bromide. Systems would need to be developed to recover the fumigant, either for recirculation or chemical breakdown with nil emission to the atmosphere. R W Taylor NRI Central Avenue Chatham Maritime Chatham Kent ME4 4TB UKSeveral organic gases have been implicated in the depletion of the ozone layer. Most attention has been focused on the CFCs and haloes, but methyl bromide has now come under increasing scrutiny. Methyl bromide is a highly toxic pesticide. It has..