Methyl Iodide

Methyl iodide is a highly toxic fumigant pesticide that was developed by Arysta LifeScience Corporation, and is marketed as a replacement for methyl bromide, a chemical being phased out under the Montreal Protocol because it depletes stratospheric ozone. On March 20, 2012, following an intense multi-year coalition campaign launched by PAN, Arysta pulled methyl iodide from the U.S. market. It remains in use in other countries, including Mexico.

Methyl iodide is arguably even more toxic for workers and rural communities than methyl bromide, and its use is extremely controversial. Among scientist's greatest concerns is the potential for human exposure to unsafe levels of methyl iodide from drift.

Human Health Harms

Humans exposed to methyl iodide experience dizziness, sleepiness, nausea, diarrhea, slurred speech, lack of coordination, muscle convulsions---and in some cases, pulmonary edema. Listed as an EPA Hazardous Air Pollutant, methyl iodide also affects the the lungs, liver, and kidneys. 

  • Cancer: Known to cause thyroid and lung tumors, methyl iodide is on the California Proposition 65 list of carcinogens. The fumigant's mutagenic properties reaffirm its cancer-causing potential.
  • Developmental & Reproductive Toxicity: In addition to increasing the risk of miscarriage, methyl iodide compromises healthy development of fetal organs including the heart, liver, and brain -- causing permanent damage. (See: CDPR's Assessment)
  • Neurotoxiciy: Methyl iodide is a potent neurotoxin -- four times more toxic than methyl bromide. Both chronic and acute exposure to methyl iodide can cause permanent damage to the central nervous system.
  • Thyroid Toxicity: Methyl iodide is toxic to the thyroid gland and interferes in thyroid hormone levels. Research shows that when methyl iodide compromises these hormones during critical windows of fetal development, exposure can increase risk of miscarriage.

Methyl Iodide: A Mutagenic Agent

Methyl iodide reacts readily with DNA, altering its structure and causing mutations. In a report to the California Department of Pesticide Regulation, the Scientific Review Committee on methyl iodide emphasized the fumigant's "unequivocal status as a mutagenic agent."

Synthetic chemists treat this chemical with great respect, handling it only in a fume hood using specially sealed bottles and syringes for transfer to ensure that none of this highly toxic chemical escapes.

A Drifting Poison

Like all fumigants, methyl iodide is likely to drift away from application sites, putting nearby residents and farmworkers at risk.  Reoccurring accidents with widely used fumigants reveal the inherent danger of methyl iodide fumigation. For example, methyl bromide was involved in 168 incidents reported to Poison Control Centers between 1993 and 2005. Metam sodium was involved in 428 over the same period. As recently as October 2005, at least 300 people, including paramedics, were poisoned by chloropicrin when a strawberry field a quarter-mile away was fumigated in Salinas, California.

Even when accidents do not occur, soil fumigation exposes communities to unsafe levels of toxins. Air monitoring in the rural community of Sisquoc detected chloropicrin — a toxic fumigant known for causing respitory harm — in levels that exceeded the 24-hour level of concern for children, as well as the acceptable cancer risks set by the California Department of Pesticide Regulation. Download the report summary.


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