Methyl iodide, also known as iodomethane, will be allowed to control soil pests "under highly restrictive provisions governing its use," the EPA said in a statement.
"When used according to EPA's strict procedures, iodomethane is not only an effective pesticide, but also meets the health and safety standards for registering pesticides," the agency said.
Methyl iodide was developed by Tokyo-based Arysta LifeScience Corp. as an alternative to the widely used fumigant methyl bromide, which has been banned under an international treaty because it depletes the ozone layer. Like methyl bromide, the new product, to be sold under the name MIDAS, kills off weeds and soil pests before planting a wide variety of fruits and vegetables.
The EPA said its decision was based on four years of risk assessment studies, constituting "one of the most thorough analyses ever completed by the agency for a pesticide registration action."
"The agency concluded that there are adequate safety margins and the registration of iodomethane does not pose unreasonable risks," the agency said. Last week, however, a group of 54 scientists, including six Nobel Prize winners, sent a letter to EPA urging that the pesticide not be registered for use because of the potential danger to pregnant women and children, the elderly and farmworkers.
California's Department of Pesticide Regulation lists the chemical as a carcinogen and also had expressed objections. Officials have said that whatever EPA's action, use of the new product in California would not be possible before the state concludes its own review in a year or so.
The approval brought immediate reaction from critics. It "will put farmworkers, farmers and rural families at risk," Erik Nicholson of the United Farmworkers of America said in a statement with the Pesticide Action Network of North America. He said the EPA instead should "focus on alternatives that don't view us as disposable human beings who can risk cancer and miscarriages in the name of supposed economic gain."
Robert Bergman, a University of California chemistry professor who was the lead author on the scientists' letter, called the EPA's decision outrageous.
"I think its pretty clear these guys never had any intention of taking our concerns seriously," he said. "They have intended to approve this stuff from day one and we were just a bump in the road."
In a letter Friday to Bergman, EPA Assistant Administrator Jim Gulliford said the EPA's scientific analysis had taken into account their concerns and the agency concluded that its risk assessments "are realistic and demonstrate adequate protection for the most sensitive individuals."
Gulliford said the one-year registration will allow for re-evaluation of methyl iodide after new safety measures are put in place for other agricultural fumigants currently under review by the agency.
EPA scientists spoke this week by telephone with Bergman and two other signers of the letter, who repeated concerns about the lack of specific tests evaluating danger to the developing brains of fetuses and infants.
Conditions the EPA is imposing for use of the product include use of government-approved respirators for workers applying the fumigant, buffer zones around the fields to protect bystanders and five-day restriction on anyone entering the fields after the chemical is applied.
Friday's action came after the government postponed a decision last year and again held off last week after receiving the scientists' letter.
Farmers who grow crops such as strawberries, tomatoes and peppers have been struggling to find alternative products that work as well as the banned methyl bromide.
Critics said use of methyl iodide is complicated by its combination with chloropicrin, another soil fumigant that sickened some 125 farm workers who breathed it last week near Reno, Nev.