Safety Measures Proposed for Soil Fumigant Pesticides

Soil fumigants are pesticides that, when injected or incorporated into soil, form a gas that permeates the soil and kills a wide array of soil-borne pests.

Fumigants are used primarily on potatoes, tomatoes, strawberries, carrots, and peppers, among other crops.

To protect human health, EPA is requiring a suite of new mitigation measures for the soil fumigants methyl bromide, chloropicrin, dazomet, metam sodium, and metam potassium.

"The new restrictions protect workers and bystanders against inadvertent exposure to soil fumigants and are practical to implement," said Jim Gulliford, EPA's assistant administrator for the Office of Pesticides, Prevention, and Toxic Substances.

When fumigants dissipate from the soil, workers or bystanders who are exposed to these pesticides may experience eye or respiratory irritation, or more severe and irreversible effects, depending on the fumigant and level of exposure.

Human exposure to high concentrations of methyl bromide, for instance, can result in central nervous system and respiratory system failure, as well as specific and severe adverse effects on the lungs, eyes, and skin.

As part of the new program, users must set up buffer zones around treated fields to reduce the chances of immediate harmful effects to bystanders from fumigant concentrations in air. Buffers can be adjusted based on the use of other good management practices that also reduce risks to bystanders.

Users will be required to post notices at the borders of the fields to be fumigated to inform bystanders and field workers about the location and timing of fumigations and buffer zones so people do not enter these areas.

To ensure emergency preparedness, registrants must provide first responders with fumigant-specific safety information and training. Fumigant applicators must monitor buffer zone perimeters or provide emergency response information directly to neighbors.

Fumigant registrants must conduct outreach programs to educate community members about fumigants, buffer zones, how to recognize early signs of fumigant exposure, and how to respond appropriately in case of an incident.

Fumigant registrants must adopt more stringent worker protection measures, and develop training for fumigation handlers and workers to enhance their knowledge and skills and to promote product stewardship.

EPA is providing 60 days for public comments on implementation of the new mitigation measures and will refine the measures as needed, Gulliford said.

EPA's decision also will halt the use of the fumigant methyl bromide on sites where alternatives are available. Methyl bromide is an odorless, colorless gas that depletes the stratospheric ozone layer, so use of it is governed by the provisions of the Montreal Protocol.

The amount of this chemical produced and imported in the U.S. was reduced incrementally until it was phased out in January 1, 2005 as required by the protocol, except for allowable exemptions agreed to by the governments that are Parties to the Montreal Protocol.

When used as a soil fumigant, methyl bromide gas is injected into the soil at a depth of 12 to 24 inches before a crop is planted. This will sterilize the soil, killing the vast majority of soil organisms.

Immediately after the methyl bromide is injected, the soil is covered with plastic tarps, which slow the movement of methyl bromide from the soil to the atmosphere. Additional methyl bromide is emitted to the atmosphere at the end of the fumigation when the tarps are removed.

When an entire field is fumigated, the tarps are removed 24 to 72 hours later, as can be the case in strawberry production in California.

But with row fumigation, as with tomato production in Florida, the tarps are left on for the entire growing season, as long as 120 days. Up to 95 percent of the methyl bromide injected into the soil can enter the atmosphere.

The newly registered fumigant iodomethane will be reexamined by the EPA later this year to determine what new mitigation or restrictions are necessary.

The EPA says that the soil fumigant 1,3-dichloropropene, which was evaluated previously, may be subject to similar provisions when the soil fumigants are evaluated together again in 2013.

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