Methyl Iodide Pesticide Controversy in California

Methyl iodide has been approved for use as a pesticide in California's strawberry fields, but the decision has sparked controversy.

Methyl iodide (also known as iodcomethane) has received final approval for use as a fumigant pesticide in California's strawberry fields. Critics of the December 2010 decision to approve the use of methyl iodide say the chemical compound is a known carcinogen and neurotoxin that would threaten public health despite the proposed precautions placed on its use. Read on to learn more about methyl iodide, the possible side effects of methyl iodide exposure, and the history behind California's decision to approve methyl iodide use.

What Is Methyl Iodide?

Methyl iodide, also known as iodomethane, is a chemical compound used in agriculture as a fumigant pesticide. It is typically injected into the soil and then covered by a tarp, or applied by drip irrigation under a tarp before crops are planted. Methyl iodide is a soil sterilizer that effectively kills insects, weed seeds, nematodes (microscopic worms), and disease-causing bacteria and fungi in the ground. Made by Tokyo-based Arysta LifeScience Corp., methyl iodide is sold under the brand name Midas.

Federal Approval of Methyl Iodide

In 2002, Arysta sought federal approval for the use of methyl iodide as a soil fumigant to replace methyl bromide. (At one time a commonly used soil fumigant, methyl bromide is being phased out in both the U.S. and Canada because it harms the ozone layer.)

After first denying registration of methyl iodide in April 2006, the U.S. Environmental Protection Agency (EPA) granted a one-year registration in October 2007. In September 2008, the EPA licensed methyl iodide for sale and use in the U.S. without any time limitation, but with certain restrictions on its application.

Approval of Methyl Iodide in California

After a chemical compound is registered for use by the EPA, some states, including California, require separate state registration. In April 2010, California's Department of Pesticide Regulation (DPR) proposed approving methyl iodide for use within the state. The proposal anticipated the use of methyl iodide in the state's strawberry fields, as well as in the cultivation of tomatoes, peppers, and other plants.

The proposal provided for restrictions on the application of methyl iodide that were more stringent than other states' restrictions and also exceeded those put in place by the EPA. California's proposed restrictions included the following:

  • Workers handling methyl iodide may be exposed to no more than 96 parts per billion averaged over eight hours, half the amount allowed by the EPA.
  • The general public may not be exposed to more than 32 parts per billion averaged over 24 hours, one-fifth the level allowed by the EPA.
  • Methyl iodide will be a restricted material in California, meaning users must receive special training and get certification. Users will also need to obtain a methyl iodide use permit from county agricultural commissioners, who may impose additional restrictions.
  • A half-mile buffer zone is required between fields where methyl iodide is applied and schools, day cares, hospitals, nursing homes, and other sensitive areas.

On December 1, 2010, the California Department of Pesticide Regulation issued a final approval of methyl iodide's use as a pesticide in the state's strawberry fields.

Side Effects of Methyl Iodide Exposure

Critics opposed to the registration of methyl iodide in California say the chemical compound is highly toxic and is a known carcinogen. They point to the fact that methyl iodide is listed on California's Proposition 65 list of "chemicals known to cause cancer" and is used to induce cancer in laboratory animals. Because it is easily dispersed in the air and is extremely water soluble, critics believe methyl iodide would threaten public health despite the California Department of Pesticide Regulation's proposed restrictions on its use.

Alleged side effects that may be suffered by those exposed to methyl iodide include the following:

  • cancer
  • thyroid disease, including thyroid cancer
  • damage to the liver and kidneys
  • nerve and brain damage
  • harm to the fetus and miscarriage
  • irritation of respiratory tract and lungs
  • severe skin irritation
  • permanent eye damage, and
  • neurodevelopmental disorders, including learning disabilities, conduct disorders, autism spectrum disorders, and attention-deficit hyperactivity disorder (ADHD).

Supporters of Methyl Iodide Use in California

In addition to Arysta (the maker of methyl iodide), the list of those who support the Department of Pesticide Regulation's final approval of methyl iodide use in California includes:

  • California's strawberry growers. Strawberries are a $2 billion-per-year industry in California. Almost 90% of the strawberries grown in the U.S. are grown in California. Strawberry growers in California were once among the most intensive users of methyl bromide in the nation, and they claim methyl iodide is needed now that methyl bromide use is being phased out.
  • Author of methyl iodide patent. James Sims helped write the patents for methyl iodide and is a professor emeritus of plant pathology at the University of California, Riverside, which holds the methyl iodide patents. Sims believes methyl iodide can be used safely. He argues that studies showing methyl iodide causes cancer in rats and miscarriages in rabbits do not prove humans will suffer the same side effects.

Opponents of Methyl Iodide Use in California

Over a two-month period, the California Department of Pesticide Regulation accepted comments from the public to the proposed approval of methyl iodide. The DPR received an unprecedented number of comments; the overwhelming majority opposed registration.

Advocacy groups like Pesticide Watch, the Pesticide Action Network North America, and Californians for Pesticide Reform lobbied against final approval of methyl iodide. Other groups who voiced their concerns about methyl iodide included the following:

  • Department of Pesticide Regulation scientists. The DPR's own scientists, who conducted an independent risk assessment of methyl iodide, concluded the chemical posed a potential risk to public health and advised the DPR against registration of methyl iodide. They recommended a maximum exposure of 0.8 parts per billion over eight hours for farm workers and 0.3 parts per billion over 24 hours for the general public. The DPR's provisional approval allowed exposures of over 100 times these amounts.
  • Scientific Review Committee to the Department of Pesticide Regulation. According to an external panel of eight scientists commissioned by the DPR to review the DPR's risk assessment, not enough research had been done on methyl iodide to prove it could be used safely. In particular, the committee pointed to the lack of reliable data showing that methyl iodide -- which quickly dissolves in water -- would not contaminate groundwater.
  • California politicians. Twenty-seven state legislators voiced their opposition to the registration of methyl iodide in a July 2009 letter to the governor of California and the director of the DPR. U.S. Senator Dianne Feinstein (D-Calif.) has asked the EPA to overturn its approval of methyl iodide, which would effectively override the DPR's approval of the fumigant.

Status of Methyl Iodide Registration

Besides California, methyl iodide is currently licensed for use in 47 other states; New York and Washington are the only states that still prohibit its use. According to the EPA, methyl iodide has been used in 12 states. Arysta withdrew its applications to register methyl iodide in New York in January 2009, and withdrew its application for Washington in July 2010. Prior to California's final approval of methyl iodide's use, the EPA publicly stated that the agency may choose to reevaluate methyl iodide based on the outcome of the DPR's external scientific peer review and final risk assessment.

Getting Help

If you believe that you have been harmed by exposure to methyl iodide, you may want to hire a lawyer who specializes in toxic tort or products liability litigation. (To learn more about these kinds of cases, see Nolo's Toxic Torts FAQ and Product Liability FAQ.)

For help in choosing a personal injury attorney who can help you with your case, read Nolo's article Finding a Personal Injury Lawyer, or go to Nolo's Lawyer Directory for a list of personal injury attorneys in your geographical area.

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