Despite the protests of more than 50 scientists, including five Nobel laureates in chemistry, the U.S. Environmental Protection Agency on Friday approved use of a new, highly toxic fumigant, mainly for strawberry fields.
The new pesticide, methyl iodide, is designed for growers, mainly in California and Florida, who need to replace methyl bromide, which has been banned under an international treaty because it damages the Earth's ozone layer.
In a letter sent last month to EPA Administrator Stephen Johnson, 54 scientists, mostly chemists, warned that "pregnant women and the fetus, children, the elderly, farmworkers and other people living near application sites would be at serious risk."
Methyl iodide is a neurotoxin and carcinogen that has caused thyroid tumors, neurological damage and miscarriages in lab animals.
But EPA officials said Friday that they carefully evaluated the risks and decided to approve its use for one year, imposing restrictions such as buffer zones to protect farmworkers and neighbors.
"We are confident that by conducting such a rigorous analysis and developing highly restrictive provisions governing its use, there will be no risks of concern," EPA Assistant Administrator Jim Gulliford said in a letter sent Friday to the scientists.
Growers, particularly those who raise strawberries and tomatoes, have been searching for 15 years for a new soil fumigant to replace methyl bromide. Fumigants are valuable to growers because they can be injected into the soil before planting to sterilize the field and kill a broad spectrum of insects and diseases without leaving residue on crops.
But fumigants are among the most potentially dangerous pesticides in use today because the toxic gas can evaporate from the soil, exposing farmworkers and drifting into neighborhoods.
Methyl iodide will be manufactured by Tokyo-based Arysta LifeScience Corp. and marketed under the name Midas. Its use will be allowed on fields growing strawberries, tomatoes, peppers, ornamentals, turf, trees and vines.
California growers can use the new pesticide only if it is also approved by the Department of Pesticide Regulation. The state agency often imposes tighter restrictions than the EPA, and last year its top officials expressed concerns to the EPA about methyl iodide.
"We are conducting our own risk assessment of methyl iodide, and we expect that process to continue for several months before we make a decision whether or how it can be used safely in California," said Glenn Brank, a spokesman for the state Department of Pesticide Regulation.
Robert Bergman, the Gerald E. K. Branch Distinguished Professor at UC Berkeley's chemistry department, led the effort by scientists to persuade the EPA to reject methyl iodide. Among the signatories were five Nobel laureates: Robert H. Grubbs of the California Institute of Technology; Roald Hoffmann of Cornell University; Williams S. Knowles, formerly of Monsanto Co.; John B. Fenn of Virginia Commonwealth University; and Richard R. Ernst of the Swiss Federal Polytechnic Institute.
Many of the chemists -- who use small amounts of methyl iodide in their laboratories to attach molecules and are careful to avoid exposure -- said they are shocked that the EPA is allowing its use as a pesticide because it can drift into neighborhoods and pollute groundwater.
"It is potentially really toxic, and it's certainly very reactive. From what we know about its chemistry, we know this stuff reacts with DNA. It mutates it. So it's prudent to be as careful as you can with it," Bergman said in an interview Friday.
Bergman said he was disappointed, but not surprised, by the EPA's decision because top officials there seemed unswayed in discussions with him and two other scientists earlier this week.
The scientists had asked for an independent review by the National Research Council, but the EPA rejected that because its own scientific advisory panel already had reviewed it.
"If they're right, they shouldn't be afraid of an independent review," Bergman said. "I don't know what the motivation is to get this stuff approved so fast. If there is any possibility that it would be dangerous, do you not approve it, or do you approve it and then decide, after something happens, to change your mind? There is serious potential for accidents."
Bergman said he is particularly concerned about neighborhoods in Ventura County and other areas where homes have been built next to farm fields.
EPA officials called their review, which lasted four years, "one of the most thorough analyses ever completed on a new pesticide."
The manufacturer, Arysta, has spent eight years and more than $11 million collecting toxicological and environmental data to persuade the EPA to register methyl iodide as a pesticide.
Arysta's former chief executive, Elin Miller, is now a top official at the EPA and was appointed administrator of its northwest region last year.
The EPA last year dropped its plan to approve methyl iodide after objections from the United Farm Workers, environmental groups and California pesticide officials. But after reviewing additional data, a one-year approval was granted.
EPA scientists reviewed data from test fields in Ventura County, Watsonville and Florida where methyl iodide was applied. They concluded that the amounts people might be exposed to "are well below those that would cause thyroid effects leading to cancer" or other effects in fetuses, children or adults.
"We evaluated the probability of being exposed to concentrations that could possibly lead to adverse health effects and found that those levels would not be reached under the stringent use conditions that will be imposed," the EPA's Gulliford wrote to the scientists.
Use of certified commercial applicators will be required, and buffer zones must be maintained around fields to protect workers and bystanders. The buffers range from 25 to 500 feet depending on the size of the field and the amount of fumigant used.
Shovelers, tractor drivers and other employees of companies applying the fumigant must be trained and wear respirators, and farmworkers cannot enter the fields for five days after it is applied.
Use is prohibited within a quarter-mile of a school, day-care facility, nursing home, hospital, prison or playground.
Strawberry growers alone could use 3 million pounds of methyl iodide annually to replace methyl bromide. Only areas with special "critical use" exemptions, largely in California and Florida, are still allowed to use some methyl bromide.
The California Strawberry Commission, in a letter to the EPA last year, called methyl iodide a "highly promising alternative" that is "essential to our continued transition away" from methyl bromide.
Many California growers, however, say they will not use fumigants because they are expensive and the state requires many safeguards, such as tarps and buffer zones.
EPA officials said the approval is limited to one year because the agency is developing new regulations for all fumigants. California also has proposed new restrictions on fumigants after facing a court order to control smog-forming emissions.