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Media Contact: Lea Brooks
April 30, 2010 (10-05)
Updated: May 19, 2010

DPR Announces Proposed Decision to Register Methyl Iodide, Using Nation’s Most Stringent Restrictions

Updated May 19, 2010, to announce extension of comment period to June 29, 2010, for a total of 60 days, twice the 30 days required by regulation. The extension was prompted by a high degree of public interest in the proposed decision.

SACRAMENTO – Department of Pesticide Regulation (DPR) Director Mary-Ann Warmerdam today proposed registration of methyl iodide with a comprehensive set of use restrictions that are much more stringent than those required by the federal government.

The U.S. Environmental Protection Agency (U.S. EPA) registered methyl iodide in 2007 as a replacement for methyl bromide, which causes damage to ozone in the upper atmosphere. Methyl iodide does not harm the ozone layer.

"By law, we cannot register a pesticide unless it can be used safely," said DPR Director Mary-Ann Warmerdam. "After extensive reviews, we have determined methyl iodide can be used safely – with the extra, health–protective use restrictions we are proposing that are much stricter than those imposed anywhere else in the U.S. My department considered a wide range of scientific input and followed protocols of both U.S. EPA and the World Health Organization to develop use restrictions to prevent potentially unsafe exposures."

DPR scientists examined more than 175 studies on the potential health and environmental effects of methyl iodide. They paid particular attention to potential exposures of people who live, work or spend time in areas close to fields where methyl iodide might be used.

DPR’s proposed methyl iodide registration takes a much more health–protective stance than U.S. EPA. For example, California’s allowable exposure of 96 parts per billion (ppb) for licensed professionals who apply or handle methyl iodide will be half of what U.S.EPA allows. For others (those not handling or using methyl iodide), DPR will not allow exposures above 32 ppb averaged over 24 hours. This level is five times lower than the U.S. EPA level.

Meeting these stricter exposure standards means that DPR will impose more comprehensive controls on methyl iodide than U.S. EPA or any other state. Examples of these restrictions include:

  • Larger buffer zones around all applications.
  • A minimum of a half–mile buffer around schools, hospitals, nursing homes and similar sites.
  • Reduced application rates and acreage that can be treated.
  • Application limits to protect groundwater.

DPR also will make methyl iodide a California–restricted material, meaning users will be required to have special training and a permit from the county agricultural commissioner, who can impose added use controls tailored to the application site.

DPR’s proposed decision (PDF, 341 kb) to register methyl iodide products is posted on the department Web site,, click on the "Decisions Pending" link. Comments will be accepted until June 29, 2010. DPR will respond to public comments before deciding whether to proceed.

Methyl iodide, also called iodomethane, is licensed for use in 47 other states. Injected into soil before crops are planted, the fumigant spreads through the soil to kill insects, weed seeds, plant diseases and nematodes. It can be applied by drip irrigation under a special protective tarp or injected into the soil using a tractor that automatically places a tarp over the ground after application.

Methyl iodide products are made by Arysta LifeScience Corp. and sold under the brand name, Midas. In 2009, U.S. EPA presented its Stratospheric Ozone Protection Award to Arysta for development of methyl iodide, which U.S. EPA estimated could replace "some 85 percent of the current soil fumigation use of methyl bromide." Under an international treaty, methyl bromide has been phased out in the United States except for certain critical uses for which there are no feasible alternatives.

The major uses of methyl bromide in California are to treat soil where strawberries, nursery plants and nut trees are to be planted. Since U.S. EPA considers methyl iodide a feasible alternative to methyl bromide, the federal agency is expected to approve far fewer exemptions for methyl bromide in California.

Note: An FAQ on the decision (PDF, 63 kb) and a table comparing DPR’s proposed restrictions (PDF, 15 kb) with the less stringent use controls imposed in other states is available on DPR’s Web site,, click on "News and Publications," and then "News Releases."


One of five departments and boards within the California Environmental Protection Agency, DPR regulates the sale and use of pesticides to protect people and the environment.