Health Risks Fail to Deter Proposed Use of Methyl Iodide on California Crops

John R. Balmes

Advocacy groups concerned about occupational and environmental health issues and growers worried about their economic interests have long been at odds when it comes to pesticide regulation in California. A new battle has been waged for the past several years over a potential substitute for methyl bromide, a fumigant that has been widely used by California strawberry growers, who account for 88% of the nation's production of this popular fruit. Methyl bromide is listed as "highly toxic" by the US Environmental Protection Agency (EPA) because inhalational exposure can cause both acute (pulmonary and neurological) and chronic (neurological and reproductive) effects. Many of the readers of this column will remember largely unsuccessful efforts over 20 years ago to restrict its use to protect workers from occupational exposures. As unfortunately is often the case, the economic benefit of this chemical, which is widely used as a gaseous fumigant, trumped occupational health concerns. 

Interestingly, methyl bromide use has been decreasing in recent years, but not because of new-found concerns over the health of largely low-paid, immigrant farm workers. The production and application of methyl bromide has been banned under the Montreal Protocol to prevent depletion of stratospheric ozone. This ban took effect in the United States in 2005, but American farmers were given a reprieve because the use of methyl bromide was deemed "critical" for the economic survival of certain types of agriculture, including strawberry production.

The search for alternatives to the use of methyl bromide has been intense, and the agent that the strawberry industry has been pushing is methyl iodide. Although methyl iodide is considered even more toxic to health than its chemical cousin, it has much lower stratospheric ozone depleting and greenhouse gas properties. Despite protests from scientists and environmental health advocates, the US EPA first registered methyl iodide as a pesticide in October 2007. Tokyo-based Arysta LifeScience, the world's largest producer of methyl iodide, began gearing up to make the product available to the US market under the brand name Midas, but the initial approval was limited, registering use of methyl iodide for only one year.

Of note, Stephen Johnson, EPA Administrator under the Bush administration, hired Elin Miller as Regional Administrator for EPA Region 10 shortly before the limited registration of methyl iodide. Miller had been CEO of Arysta's North American operations. During the final months of the Bush Administration, the US EPA quietly removed the time limits on its decision, effectively giving Arysta a green light to sell methyl iodide in the United States.

A change of wind came with the Obama administration. In September 2009, the US EPA agreed to reopen its decision on methyl iodide, pending results of an evaluation of methyl iodide's toxicity by a special Scientific Review Committee. Three COEH scientists--Paul Blanc, Kathie Hammond and Tom McKone--were members of this committee. Not surprisingly, their final report in February 2010 indicated that "any anticipated scenario for the agricultural... use of this agent... would have a significant adverse impact on the public health." Yet despite this warning, on April 30 the California Department of Pesticide Regulation (DPR) proposed approving the sale and use of the methyl iodide statewide. Final approval, if granted, would not come until sometime after June 14, when the public comment period ends.

To me, the story of methyl iodide's registration by the US EPA and its tentative approval for use in California by the DPR says much about what is wrong with current chemicals policy in our country and state. Hopefully, the US EPA under the present administration will reconsider its registration of this highly toxic chemical.


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