The fumigant methyl bromide is nasty stuff. It is lethal to any animal, in large doses. And the effects of long-term but faint exposure are unclear: Lab animals tend to die from even small amounts. On top of that, the gas harms the ozone layer.
Considering methyl bromide's rap sheet, the news that it's due to be banned in the U.S. on Jan. 1, 2001, might seem like a welcome development. But the prospect of a ban has angered thousands of U.S. farmers. For all its unpleasantness, methyl bromide is an important chemical. It is unmatched at sterilizing the soil before planting strawberries, tomatoes, and the like. It is also tops at treating farm commodities before they're shipped across borders. In all, more than 100 crops depend on the chemical in some way.
FISH MEAL. Methyl bromide is so good at controlling pests, in fact, that many nations refuse to accept imports unless they've been dosed with it. If it were withdrawn, farmers in California alone would lose $241 million annually in export sales and reduced yields, the University of California at Berkeley estimates. The upshot: The chemical's death sentence seems likely to be commuted.
Researchers have struggled mightily to find safe alternatives. Yet six years after the deadline was set, dozens of research teams worldwide have found no magic bullet. Nothing safe and economical, it seems, can do everything that methyl bromide does. Indeed, the scientific work has fragmented into a search for narrow, sometimes peculiar alternatives. Plowing broccoli into soil controls a cauliflower fungus; scattered fish meal protects tomatoes. "It's fruit by fruit, bug by bug," says fruit-fly expert Robert Mangan of the U.S. Agricultural Research Service (ARS). "We won't have solutions to every problem."
Environmentalists and concerned citizens who live near farms haven't given up on the ban. And the law is in their favor. Once methyl bromide was found to deplete the ozone layer, the Environmental Protection Agency had no choice under the Clean Air Act but to prescribe a phase-out. That put the U.S. ahead of most other countries, which face a 2010 deadline under an international agreement called the Montreal Protocol. But the government is unlikely to force farmers to swallow gargantuan losses. "It's becoming a desperate situation," declares Peter G. Sparber, lobbyist for the Methyl Bromide Working Group. The group is funded by the chemical's manufacturers, including Great Lakes Chemical Corp. and Albemarle Corp.
Most of the methyl bromide used--about 87%--is injected into soil covered with plastic sheeting. Within 24 hours, it kills parasites, fungi, weed seeds, rodents, and anything else that harms plants. Packers and shippers use much of the remaining 13% on grapes, nuts, and other commodities after harvest, or on storage buildings and containers bound for overseas.
Farmers have tried other chemicals, such as metam sodium and phosphine, but none can match methyl bromide. They've also tried sterilizing soil by sprinkling hot water from truck-mounted boilers--like giant teakettles--and by trapping sunlight in plastic. But such methods offer only sporadic relief.
"EUREKA." Destroying pests in commodities for export is just as difficult. One experimental irradiation process effectively renders bugs infertile, says ARS research entomologist James G. Leesch. But inspectors have no way to distinguish the sterilized survivors from new bugs that enter containers later on. Large-scale irradiation equipment is also expensive and generates wastes.
There is one other promising solution to the dilemma: recapturing the gas to curb emissions. Leesch and GFK Consulting Ltd. in San Clemente, Calif., co-developed an industrial gas mask that fits over the vents of fumigation chambers and traps methyl bromide in activated carbon filters. It could reduce emissions by as much as 95%, they say. That's still a threat to the ozone layer. But it's a big improvement over current methods, which allow 80% of the stuff to escape.
Ultimately, methyl bromide's fate hangs on political interests, rather than a "eureka"-style breakthrough. Given the clout of legislators from the farm states, the chemical will probably survive well into the next century.