Methyl bromide, a common pesticide and fumigant used to kill everything from worms to termites, is at the top of the agenda of the Multilateral Fund for the Implementation of the Montreal Protocol, that reconvenes next week in Quebec. It is targeted because it harms the ozone layer, exposing the Earth to ultraviolet sunlight.

While the United States is technically in compliance with the protocol, the federal government frequently uses a policy that allows it to apply for critical-use exemptions.

There is no limit to the number a country can request, and the United States has been able to continue with as much as 30 to 40 percent of its original methyl bromide use. Sixty percent of all exemptions are sought by the United States, and this number could increase as other countries curtail their use.

Nationwide, strawberry farmers are the most common applicants for exemption permits, along with farmers of winter tomato crops and other out-of-season vegetables.

The Environmental Protection Agency said it receives about 60 exemption permits each year.

To qualify for a permit, there must be no feasible alternative to methyl bromide use, and the transition would have to cause severe market disruption.

The EPA often requires industries to trim their usage requests before passing applications on to the protocol signers for approval, and methyl bromide use has declined over the past two years.

Yet sometimes there isn't another alternative, says the EPA. In Michigan, for example, alternative chemicals require the soil temperature to be above 40 degrees, which means that if farmers give up methyl bromide, they have to wait an extra month to plant.

Even organic farmers have gone on the record as proponents of methyl bromide, according to the EPA. While they can't fumigate their own cropland, organic growers often prefer to buy plants from nurseries that use methyl bromide because it's critical to start with a clean rootstock.

Yet organic farmers in California insist methyl bromide isn't necessary.

"I've never heard that organic farmers believe methyl bromide should be allowed," said Peggy Miars of California Certified Organic Farmers in Santa Cruz.

Miars said farmers must use organically grown stock plants whenever possible, and she confirms that organic strawberry starts are available. As organic farmers in Northern California have grown several generations of high-yield strawberries without methyl bromide, they say the chemical is never the only option.

"Going organic is not as hard as it sounds," said Michael Cohen, a biologist at Sonoma State University who develops alternative soil treatments.

According to Cohen, canola - a yellow-flowering plant of the mustard family grown to make cooking oil and biodiesel - can be used to replace methyl bromide. The seed meal is distributed in specialized gardening stores as a soil treatment.

After the seed is pressed to make oil, it contains lots of glucosinolates - compounds found in horseradish and wasabi paste that become active in water and release the spicy molecules that make your mouth burn. While methyl bromide sterilizes the soil, killing both bad and good organisms, the seed meal selectively targets certain worms and molds that harm plants.

"It also helps stimulate a soil microbial community that prevents disease," said Cohen. "This makes plants more resistant to fungal infections and doesn't harm the ozone layer like methyl bromide."

Numerous other alternatives are also available, although scientists warn many are highly toxic. The EPA approved methyl iodide (iodomethane) as a replacement for methyl bromide on Oct. 5, despite formal warnings from Nobel Prize-winning chemists that the pesticide is highly toxic.

California used 6.5 million pounds of methyl bromide in 2006 - about 22 percent of the nation's total use. Yet California has the strictest methyl bromide regulations in the nation, according to the Division of Pesticide Regulation.

Methyl bromide is a carcinogen, and while farmworkers are most frequently exposed, the chemical has an uncanny tendency to pop up in the home and office. About 20,000 pounds are used in California each year to kill termites, beetles and other bugs. The chemical can drift through pipes that connect buildings, and sometimes results in illness and even fatalities.

In 1997, a 36-year-old Los Angeles woman died after a building near her apartment was fumigated. Underground pipes connected the building to her apartment, and blood tests confirmed that methyl bromide was well above lethal levels.

The Division of Pesticide Regulation said that most cases of poisoning occur when people break into homes that are tarped for fumigation and that companies turn to methyl bromide only in special cases. The chemical hasn't been applied indoors in San Francisco since 2000.

The Multilateral Fund for the Implementation of the Montreal Protocol plans to discuss a U.N. report that found that of the 191 countries participating in the treaty, more than half are developing nations.

"There are several developing countries that are phasing out methyl bromide earlier than (developed countries)," said Megumi Seki, a senior scientific affairs officer at the U.N. Ozone Secretariat.

While methyl bromide was supposed to be phased out of developed nations by January 2005, countries with fewer resources were given an extra 10 years - yet many have made more substantial reductions than the United States, which is also surpassed by other developed nations.

"Countries such as Spain, Greece, Italy and Australia have climates like California and Florida's, and they grow the same crops - tomatoes and strawberries - yet they have almost successfully eliminated methyl bromide," said David Doniger, a policy director at the Natural Resources Defense Council.

"These exemptions are big enough to drive a truck through," said Edward Parson, a professor of law and natural resources at the University of Michigan. "Technically we may be in compliance, but in essence the U.S. just started calling much of its normal use 'critical,' and began relying on exemption permits."

The Montreal Protocol celebrated its 20th anniversary in September, and is largely viewed as an international success story as atmospheric levels of ozone-depleting chemicals are beginning to drop.

Gases such as methyl bromide accumulate in the atmosphere, where they convert ozone molecules to oxygen. Chlorofluorocarbons (CFCs) - the chemicals found in spray paints and aerosol hairsprays in the 1970s and 1980s - are perhaps the most famous culprits, but methyl bromide is thought to be 50 times more damaging. It binds more tightly to oxygen atoms and prevents them from re-forming ozone molecules.

"We have led the world in reducing CFCs and other ozone-depleting chemicals," Doniger said, "but the combination of methyl bromide and the Bush administration has been toxic."

Because the United States lowered other uses, the protocol's signers have been lenient with methyl bromide requests, but this tide is beginning to turn, Doniger said.

"There are questions regarding how much effort the USA is making," Seki said.

The biggest public-health hazard comes from the chemical's long-term impact on the ozone layer, scientists say. Because methyl bromide is a halogen - a class of chemicals that contain atoms from the 17th column of the periodic table (in this case bromine) - it is slow to degrade in the environment.

Halogens are extremely stable, a trait that makes them appealing to industry, but they are also slow to degrade in the air, soil and water. As UV light from the sun is a primary cause of skin cancer, the EPA projects that declines in methyl bromide, CFCs and other ozone-depleting chemicals could potentially save millions of lives for the next 60 years.