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Methyl Iodide Saga Continues

EPA gives green light to soil fumigant, but California is still assessing risks

by Britt E. Erickson
October 27, 2008 | A version of this story appeared in Volume 86, Issue 43

Credit: Steve Smith/Howard Fertilizer & Chemical
Tomato beds in Florida are being fumigated with methyl iodide and immediately covered with a plastic tarp to help prevent the volatile chemical from being released into the air.
Credit: Steve Smith/Howard Fertilizer & Chemical
Tomato beds in Florida are being fumigated with methyl iodide and immediately covered with a plastic tarp to help prevent the volatile chemical from being released into the air.

AT THE BEGINNING of October, the Environmental Protection Agency approved the use of the highly toxic and controversial fumigant methyl iodide to control soil-borne diseases and pests, primarily in strawberry and tomato fields. The move comes one year after the agency granted the pesticide temporary approval, which was set to expire this month. EPA did not attach any time limitations to the current methyl iodide approval notice.

Despite having been approved by EPA for one year, methyl iodide has not been widely used. Many states, including Florida and California, decided to do their own risk assessments before allowing growers to use the fumigant. Florida finished its assessment and approved the use of methyl iodide last July, requiring additional safety measures beyond those required by EPA. California's assessment is ongoing.

EPA first looked into approving methyl iodide in 2006 as a replacement for methyl bromide, which is a fumigant that is banned under the Montreal Protocol on Substances that Deplete the Ozone Layer but allowed for critical uses for which no alternatives exist. The agency initially dropped its plan because of concerns over methyl iodide's toxicity but changed its position in 2007.

Those who are in favor of using methyl iodide as a replacement for methyl bromide say that if the chemical is handled properly, its toxicity is not a problem and in fact is a necessary characteristic of a fumigant. "If it weren't toxic, it wouldn't do the job that it does on microorganisms," James J. Sims says. "What it means is you have to be careful in handling it." Sims is an emeritus professor of plant pathology at the University of California, Riverside. He pioneered the use of methyl iodide as a soil fumigant in the 1990s. His work eventually led to a patent, which is owned by UC Riverside and licensed to Japan-based Arysta LifeScience, the sole provider of methyl iodide for soil fumigation.

Methyl iodide has several advantages over methyl bromide. It is more reactive and therefore too unstable to make it to the upper atmosphere to damage the ozone layer. And unlike methyl bromide, which is a gas, methyl iodide is a low-boiling liquid, Sims notes. That makes methyl iodide a lot easier to handle, he emphasizes.

Sims also points out that because methyl iodide is so reactive "you can get away with using a little less of it." This is important because iodine is expensive. In the 1990s, "when I was trying to get companies interested in methyl iodide, one of their major concerns was the cost of iodine," Sims says.

At that time, Sims approached the big agricultural chemical companies about licensing methyl iodide, but they were all reluctant to take on a new fumigant. Eventually, Arysta signed on and did a lot of the developmental work, he says. The company was in a unique position in that it belongs to a Japanese conglomerate that owns iodine mines in Chile, Sims notes.

Despite these advantages of methyl iodide, large-scale orders for it haven't yet materialized because of the risk assessments that various states decided to perform. Otherwise, millions of pounds of the fumigant probably would have been injected into soils across the U.S. during the 2008 growing season, says Susan Kegley, a senior scientist with the Pesticide Action Network North America (PANNA), a nonprofit group that has been pushing for a ban on all soil fumigants for years.

This situation may soon change as key agricultural states have completed or are moving along with their assessments.

For instance, after much study and debate, Florida approved the use of methyl iodide to fumigate soils devoted to high-value crops, including tomatoes, strawberries, peppers, stone fruits, tree nuts, vines, and ornamentals. The Florida Department of Agriculture & Consumer Services decided to require labels for methyl iodide with additional safety measures beyond the federal ones. In addition, Florida requires groundwater and air-monitoring studies, as well as reports of all poisoning incidents.

California's risk assessment of methyl iodide began in 2005. According to Lea Brooks, a spokeswoman for California EPA's Department of Pesticide Regulation, the target date to complete that risk assessment is late 2009. Part of the reason it will take so long is that the assessment will undergo multiple layers of peer review. Not only will it be reviewed by the California EPA and the federal EPA, but it will also undergo an external peer review, which will include a provision for public comment, Brooks tells C&EN.

Many people who are concerned about the toxicity of methyl iodide are pleased to see that extra layer of peer review in California's assessment, something they say was lacking in EPA's risk assessment.

AT THE HEART of both the state and federal risk assessments are safety concerns. Even though workers who handle methyl iodide must be trained and wear proper protective gear, including gloves and a respirator, and buffer zones must be established around treated areas, accidents likely will happen. If a spill were to occur, workers and nearby residents would be exposed, opponents say.

Such an accident would be problematic because of methyl iodide's well-documented dangers. It is neurotoxic, suppresses thyroid hormone synthesis, and has caused lung tumors in laboratory animals, Kegley says. She points out that California has classified methyl iodide as a human carcinogen. EPA considers it a possible human carcinogen, she adds, and the International Agency for Research on Cancer says it is not classifiable because of inadequate data.

Methyl iodide is so toxic because it is a strong alkylating agent, says Robert G. Bergman, an organometallic chemist at UC Berkeley. Alkylating agents can chemically modify DNA and can alter gene expression.

Credit: Scott Bauer/USDA
Arysta hopes California will eventually allow methyl iodide to be used on its strawberry fields, which are now typically treated with methyl bromide.
Credit: Scott Bauer/USDA
Arysta hopes California will eventually allow methyl iodide to be used on its strawberry fields, which are now typically treated with methyl bromide.

Bergman is among a group of 54 scientists, mostly chemists, who sent a letter to EPA in September 2007 asking the agency not to approve the use of methyl iodide as a soil fumigant because of fears that it would harm farm workers and people living near agricultural sites where it is applied. Most of the signatories are members of the National Academy of Sciences and five are Nobel Laureates.

"Methyl iodide is pretty damaging to living tissues. It's damaging to DNA and thereby should be considered carcinogenic," adds Ted Schettler, a toxicologist and physician with Science & Environmental Health Network, a nonprofit organization formed by a consortium of environmental groups. Schettler is also one of the scientists who signed the letter to EPA last year. Although Schettler is concerned about the carcinogenic properties of methyl iodide, he says his biggest concern has to do with its effects on the developing brain.

Unfortunately, Schettler says, EPA's risk assessment didn't focus on such concerns. Instead, the agency's assessment concentrated on thyroid effects, he notes. "The agency had no developmental neurotoxicity data. It thought that if it derived a reference dose that protected against the thyroid effects that it would be protecting against any other possible mechanism that would disrupt the developing brain. I just disagree with that," he says.

In their letter to EPA, the 54 scientists asked the agency to assemble "a blue-ribbon panel of independent (conflict-free) scientists such as a committee of the National Research Council to provide peer review and scientific scrutiny" of its methyl iodide safety assessment. Instead, EPA had its own Scientific Advisory Panel (SAP) conduct the review. People like Bergman don't consider that an independent review.

Bergman is also concerned about EPA's Region 10 administrator, Elin D. Miller, who is a former chief executive officer of Arysta. She was hired by EPA in 2006. "If you ask EPA, I'm sure they will tell you that she didn't have anything to do with this decision about methyl iodide," Bergman says. Although Miller was not associated with SAP, the fact that she works for EPA in such a high-level position has people like Bergman raising their eyebrows.

THE BATTLE over methyl iodide has been marked by secrecy on the agency's part. EPA's first attempt to give methyl iodide the green light in 2006 was stymied after officials with the California EPA, labor groups, and environmental activists voiced their concerns about the toxicity of the chemical. When EPA began reconsidering the issue in 2007, it did not publicize its activities.

The agency's moves were brought to light in September 2007, when an anonymous group of government scientists sent an e-mail to PANNA, informing the group that EPA was about to approve agricultural uses of methyl iodide "under the cover of darkness." The e-mail went on to say that the scientists had been told by the federal EPA not to inform the California EPA about the decision. "We find this unethical," the scientists wrote. The e-mail was subsequently posted on the website of the Center for Science in the Public Interest, a consumer advocacy nonprofit focused on health and nutrition issues.

That e-mail is what prompted PANNA to contact Bergman, who was so concerned that he contacted every chemist he knew in the National Academy of Sciences. Many of them agreed to sign the letter he sent to EPA in September 2007. The scientists' concerns did little to sway EPA. Only a few days after the agency received the letter, it approved the use of methyl iodide as a soil fumigant for one year.

EPA's willingness to be open about its handling of the methyl iodide issue has not improved. In fact, had it not been for a news release from Arysta and the aggressive work of PANNA, EPA's latest decision on methyl iodide probably would have gone unnoticed.

Now that EPA has approved methyl iodide as a soil fumigant with no time limitations, all eyes are on California. Because the state is so important for crops like strawberries, it will be a big money-maker for Arysta if California does allow the use of the chemical on its fields. In 2006, more than 6.5 million lb of methyl bromide was applied in California. Arysta is hoping all of that will be replaced with methyl iodide.

Arysta is also working to get approval in New York and Washington states, says Linda Frerichs, a spokeswoman for the company. In addition, it is hoping to market its product—sold under the brand name Midas—in Japan, Australia, New Zealand, Turkey, Morocco, South Africa, and Israel. It is also conducting field trials in Costa Rica, Guatemala, Brazil, and Chile.

When asked whether there are better chemical alternatives to methyl bromide, those concerned about methyl iodide say they are philosophically opposed to using any fumigant in soil. "When we have created an agricultural system that is dependent on highly hazardous chemicals, it seems to me that one way to address the question of alternatives is to ask whether or not we should be redesigning our agricultural system," Schettler says. "That is an important debate that is going on in many places. But it is not one that we'll find the pesticide program of EPA engaging in at all because they somehow have bound themselves off from that conversation and talk simply about alternative chemicals."

Bergman, for one, would like to see more pheromone technology replace toxic pesticides. "Pheromones interfere with the reproductive behavior of the pests that you are after," he explains. "The problem is, they are so sensitive to pheromones that you can control pests with a few grams of the stuff. Nobody is going to make any money on that." Bergman makes the analogy to orphan drugs—those that are not expected to bring in a lot of money because they target diseases that only affect a small population. "You might think about pheromones as orphan pest control," he says.

Although Bergman still has concerns about methyl iodide, he says that he is not an activist and has other things to do besides trying to convince EPA officials to change their minds. "You get a little publicity for a week or two. And then EPA knows it is going to go away," he says. The agency waits you out, and unless you keep pounding at it, the whole thing disappears, he adds. "The inertia is on EPA's side."


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