Methyl Iodide

Why was the authorization of Methyl Iodide being proposed?


Methyl bromide, a pesticide currently used in the United States in fields which grow strawberries, has been phased out internationally and is in the process of being phased out in the United States by the U.S. EPA due to the environmental drawbacks of the pesticide, the most significant of which being its detrimental effects on the earth’s ozone layer.  Since the phasing out of methyl bromide there has been pressure in the agricultural community to develop an alternative and Arysta LifeScience, the largest, privately held agricultural company in the world is making a strong push for methyl iodide to serve as the replacement.  The campaign is currently focused in California because the state is largest market in the country for the pesticide.

Traits of the Chemical

Methyl iodide is a fumigant which is pumped into the soil of a field before a particular crop is planted.  Its purpose is to kill all harmful substances in the ground and prepare the soil for planting.  The pesticide can be used for a variety of crops but will be used mostly in fields which grow strawberries. Studies have shown that the pesticide has an extraordinary ability to react with electron-rich molecules as well with biomolecules, such as DNA, and has been shown to cause mutations by altering the structure of molecules.  The noted benefit of methyl iodide over methyl bromide is that it is not expected to have the same affects on the ozone layer.

However, despite claims that methyl iodide will not have the similar affects of methyl bromide, the pesticide is still known to be a volatile organic compound that can contribute to ground water contamination and is extremely harmful if inhaled.  This poses serious risks due to the fact that it is a drift-prone chemical which reacts with air and water before it is transported into the ozone layer.

Downsides of the Pesticide


Methyl iodide is an acutely toxic chemical which is known to affect the nervous system, lungs, liver and kidneys.  A report by the Scientific Review Committee on methyl iodide to the DPR stated that “there is little doubt that the compound possesses significant toxicity” and the Ventura County Star reports that California state regulators are appalled and “dumbfounded” that the DPR is seeking the use of methyl iodide since it has been known to cause cancer (and has even been used to induce cancer), neurological damage, brain and cervical tumors, and birth defects in laboratory animals.

Other findings by the scientific panel found that the pesticide has such a high level of toxicity that adequate control of human exposure to the chemical would be difficult if not impossible to achieve.  The Pan North America Pesticide Action Network has reported that any anticipated scenario for agricultural use of the pesticide will have significant adverse effects on public health.

Yet this pesticide was approved because the DPR believes proper precautions have been taken to prevent the harmful effects of the pesticide.  The proposed precaution of increased and wider buffer zones would include restrictions more strict than is currently required by the U.S. EPA.  The hope is that stricter regulation will lead to lower exposure levels to the pesticide.  However, Ed Loechler, a biology professor at Boston University, was quoted as saying that the proposed exposure level is still one hundred and twenty times higher than what his own data suggests is safe in order to avoid significant risks.  The DPR asserts that the proposed regulations are health protective and will allow for safe use of the pesticide.  Read the entire report for the Scientific Review Committee here.

Impacts on Water Quality

Methyl iodide’s reactive qualities make it prone to react with groundwater before it dissipates into the air.  One of the more alarming things reported by the Scientific Review Committee was that there was no reliable data on the potential to contaminate groundwater and model calculations performed by the committee indicated that the potential exists for unacceptable high levels of iodide to accumulate in water supplies should the pesticide be used over a long period of time.  Studies done by the Pan North American Pesticide Action Network likewise show that the continued use of methyl iodide in soils will have a cumulative, negative effect.

Are there Viable Alternatives?

On September 1, 2010, the peer-reviewed online journal PLoS ONE published a scientific study comparing organic strawberry farming versus conventional chemical farming in California. The study was conducted by esteemed multidisciplinary team from Washington State University, including agroecologists, soil scientists, microbial ecologists, geneticists, pomologists, statisticians, sensory scientists, and food scientists.  The study, Fruit and Soil Quality of Organic and Conventional Agroecosystems, is the most comprehensive of its kind on the issue of organic versus chemical farming.

The study analyzed 31 chemical and biological properties, nutrition, soil DNA and taste on three varieties of strawberries grown on 13 conventional and 13 organic strawberry fields in California.  California was chosen because ninety percent of the nation’s strawberries come from the state and it has become the epicenter of a raging debate on the use of Methyl Iodide as a commercial fumigant.  Among the study’s findings are:

  • Organic strawberries had a longer shelf life;
  • Organic strawberries were higher in antioxidants, ascorbic acid (i.e., Vitamin C), and phenolic compounds;
  • Independent consumer taste tests found organic “Diamonte” strawberries to have a better taste (sweeter) and appearance than their chemically grown counterpart;
  • Organically farmed soils were richer in carbon and nitrogen, had “greater microbial biomass and activity, and greater functional gene abundance and diversity;” and
  • Organic strawberries were smaller by 13.4%, but had more “dry matter” (less water and more berry).

The study provides strong evidence that organically grown commercial strawberries in California are of a higher nutritional quality, producing berries that last longer, can taste and look better, leaving richer and healthier soil, and paradoxically result in a strawberry plants with “significantly longer survival times than conventional strawberries” for fungal post-harvest rot.

Call to Action

Methyl iodide is a carcinogen so potent it is actually used to induce cancer in animals, so make your opinion known by calling Governor Brown at (916) 445-2841 and urge him to immediately reopen the decision of the Department of Pesticide Regulation and ban methyl iodide use in California. For additional information, please read our California Coastkeeper Alliance comment letter addressed to the U.S. Environmental Protection Agency urging the reconsideration of the approval of methyl iodide.

For further reading on the proposed approval of Methyl Iodide and its overall affects on the environment, visit the following links: