Fumigant Could Pose Health Risk

Fourteen years ago, as chemicals gobbled up the Earth’s ozone layer, an international treaty ordered a phaseout of a popular pesticide for strawberries and other high-value crops. Now, U.S. officials are poised to replace it with a new pesticide -- one that is highly toxic and has been declared a cancer-causing chemical by the state of California.

The Environmental Protection Agency is expected to approve a new fumigant, methyl iodide, as it eliminates methyl bromide, which damages the ozone layer. With few options for killing diseases and insects in soil, the EPA is faced with a decision that could exchange one toxic hazard for another.

California -- particularly Ventura and Santa Cruz counties -- and Florida have the most at stake. California is the leading producer of strawberries, valued at more than $1 billion a year, and strawberry growers alone could use 3 million pounds of methyl iodide annually to replace methyl bromide.

Fumigants, used to sterilize soil before planting, are considered particularly risky among the hundreds of agricultural pesticides in use today. Because methyl iodide is a gas, it can evaporate from soil and drift into nearby areas.

Last month, based on tests in California and Florida fields, EPA toxicologists concluded that unprotected farmworkers could breathe harmful doses and that low concentrations could drift off fields. But they also determined that the workers would be safe if they wore respirators and that people near the fields would breathe such small amounts that they would face no known health risk. Also, no residue remains in the strawberries or other crops.

The EPA will accept public comments on methyl iodide through Tuesday, with a decision expected possibly as soon as next month.

If the chemical does clear the federal hurdle, it still faces a tougher challenge in Sacramento. The state Department of Pesticide Regulation is conducting its own review of methyl iodide to determine whether it is safe. Imposing the nation’s strictest standards on pesticides, the state agency has in the past rejected some EPA-approved chemicals, and often imposes tighter safety controls.

“It doesn’t matter what EPA says, it has to pass muster in California,” said Glenn Brank, a spokesman for the state pesticide agency. “The registration decision by U.S. EPA will have no bearing on our process.”

Methyl iodide “is highly toxic,” Brank said, and there are “a number of areas of concern -- reproductive and developmental toxicity as well as carcinogenicity.” On the other hand, although “fumigants clearly are problematic, they also are essential, given the lack of alternative soil treatments at present.”

For four years, the EPA has been considering a request from pesticide company Arysta LifeScience to register methyl iodide, also known as iodomethane, as a soil fumigant under the commercial name Midas. If approved, it would be injected into soil, mostly in strawberry fields, but also on fields growing tomatoes, peppers, ornamentals, grapes and several other crops, at a rate of about 175 pounds per acre.

Methyl bromide was the pesticide of choice for these crops until recently. In 1987, the United States and other developed nations signed the Montreal Protocol, which gradually banned a variety of chemicals destroying the ozone layer that blocks the sun’s harmful radiation. Methyl bromide was added to the pact in 1992.

Since then, use of methyl bromide has dropped dramatically. All use was supposed to end last year, but the United Nations granted “critical use” exemptions, amounting to about 15 million pounds in the United States this year, or 27% of the amount used in 1991. Florida uses almost half, with California ranking second.

In testimony before a House committee Wednesday, EPA Acting Assistant Administrator William Wehrum said that the “EPA has made the registration of alternatives to methyl bromide its highest registration priority” so that it can eliminate the ozone-depleting chemical. Wehrum said it is the EPA’s responsibility “to help identify, register and implement safe and effective alternatives.”

But environmentalists say that methyl iodide and other fumigants are too dangerous and that human exposure would be inevitable and could raise the risk of cancer.

“This is an archaic, unsustainable approach,” said Susan Kegley, senior scientist at the San Francisco-based Pesticide Action Network North America, which is leading a campaign against the registration of methyl iodide. “EPA should be helping farmers move into the future by expanding the use of new integrated pest management techniques, not replacing one deadly chemical for another.”

Unlike methyl bromide, methyl iodide poses no threat to the ozone layer, but it can be dangerous if inhaled.

In animal tests, breathing large doses caused miscarriages, thyroid tumors and respiratory tract damage, according to an EPA risk assessment published Jan. 5. When inhaled, it rapidly accumulates in thyroid tissue, and some studies show it can alter thyroid hormones, which are essential to regulating the growth of a healthy fetus.

The Pesticide Action Network said instead of approving new fumigants, the EPA should be doing more to encourage chemical-free approaches to managing pests. In recent years, the EPA, farm groups and chemical companies have invested millions of dollars seeking alternatives to methyl bromide, including about $200 million in research funded by the U.S. Department of Agriculture.

California’s 600 strawberry growers are not taking a position on methyl iodide.

“We are hoping to find something as efficient and cost effective as methyl bromide,” said Mary DeGroat, public relations director for the California Strawberry Commission. But “we’re not proponents” of any particular chemical, she said. “If an alternative comes up that works and is safe, then that’s great news. Whatever the [EPA and state] deem legal and appropriate, we work within those realms in compliance.... If they approve methyl iodide, obviously there would be some training involved. That would be critical.”

Strawberries are grown pesticide-free at organic farms, but it is a more costly and labor-intensive process. “Pesticides generally are not something we try to use or want to use,” DeGroat said. “It’s a necessity for the efficiency of production and conventional growing.”

Artie Lawyer, Arysta’s registration representative, said that EPA approval is likely because the agency’s safety concerns have been addressed by the pesticide company over the years. The company has said it would sell the chemical only to certified applicators who complete a training course on its use.

EPA officials declined to discuss its pending decision because public comments are still being collected. Spokeswoman Enesta Jones said the agency “takes seriously the risks associated with iodomethane” and “will issue the best judgment based on the best available science.”

California and the EPA have classified the chemical’s cancer-causing potential differently -- which could be critical to their decisions.

California in 1988 listed methyl iodide as a chemical “known to cause cancer,” based on a study in which it was injected into rats, not inhaled. The rats developed sarcomas that spread to their lungs.

The EPA’s analysis focused instead on newer studies of inhalation, which can cause thyroid tumors, and gave it a unique classification -- “not likely carcinogenic to humans.” The International Agency for Research on Cancer called methyl iodide “unclassifiable” due to insufficient scientific evidence.

In tests at seven California fields, including in Oxnard and Camarillo, where methyl iodide was applied, EPA toxicologists reported that levels in the air over the fields could be unsafe.

The “safe” level is 0.89 parts per million for cancer risk from long-term exposure and 2.9 ppm for acute respiratory effects, the EPA calculated. In the test fields, the highest dose was just under 2 ppm and on the fields’ perimeter, the maximum was 0.35 ppm.

“Overall, the data indicate that exposures exceed the level of concern for some workers ... when no respiratory protection is used,” the EPA risk assessment says. But if tractor drivers, shovelers and others applying it wear respirators, their exposures are reduced by a factor of ten. In addition, five days after application, farmworkers would need no respirators, the report says.

Bystanders next to fields “could potentially” be exposed but they would be unharmed because the levels measured were too low to trigger cancer or other health effects, the EPA risk assessment says.

If it approves methyl iodide, the federal agency probably will require respirators for applicators, a tarp over the soil, a waiting period before other workers enter the fields and buffer zones around residential areas.

California’s risk report is expected this spring, and then it will be sent to the state’s Office of Environmental Health Hazard Assessment for scientific peer review. The pesticide agency then would decide whether the chemical could be managed safely -- for example, whether county agricultural commissioners have the resources to enforce respirator rules in the fields.

“In addition to scientific findings,” Brank said, “we must determine whether use of the chemical is practical in California under real-world conditions.”