Frequently linked with accidental mass poisonings, fumigants are inherently dangerous pesticides. Even when accidents do not occur, fumigant application exposes people to unsafe levels of these toxic compounds. Highly volatile, fumigants are used to sterilize soil before planting crops such as strawberries, potatoes and carrots. They are applied intensively — 50-400 pounds per acre compared to 1–5 pounds per acre for other pesticides.

Health Effects & Toxicity

Fumigant pesticides also are among the most toxic chemicals used in agriculture. The U.S. EPA categorizes most fumigants as "highly acutely toxic" — the agency's most extreme toxicity category.

Major Soil Fumigants  

  • Chloropicrin was originally used in chemical warfare during WWI. After the war, chloropicrin's poison gas effects proved useful against soil pests, and chloropicrin remains in wide use as a soil fumigant today.
  • Methyl bromide, a potent neurotoxin also known for its ozone depleting potential, has largely been phased from agricultural use.
  • Methyl iodide, the proposed replacement for methyl bromide, is in fact more toxic than its predecessor.

Acute fumigant poisoning causes eye irritation, sore throat, headaches, nausea, vomiting, breathing difficulties and aggravated asthma, and neurological effects such as convulsions, dizziness, or tremors. Fumigant exposure also has long-lasting effects that include:

  • Cancer: Several fumigants are known carcinogens, including methyl iodide, 1,3-Dichloropropene, and metam sodium; all of which are included in California's Proposition 65 carcinogen list. 
  • Respiratory damage: Exposure to fumigants can cause permanent respiratory damage. In lab animals chronically exposed to chloropicrin, researchers observed permanent damage to the bronchial tree, as well as lung cancer and tumors. (See: CDPR Assessment) The CDC classifies chloropicrin as a "lung damaging agent," noting that poisoning can cause a lethal pulmonary edema.
  • Neurological Effects: Methyl bromide and methyl iodide are both potent neurotoxins. Exposure to methyl bromide adversely affects cognitive function, physical coordination and muscular control (Extension Toxicology Network)
  • Reproductive & developmental effects: Some fumigants are linked to elevated risk of miscarriage. In animal studies, fetal survival rate was significantly reduced from methyl iodide exposure. (See: CDPR Assessment)
  • Immune system effects: Research shows that exposure to metam sodium and its breakdown product, methyl isothiocyanate, can weaken the human immune system.

Poisonings & Drift

The volatility of fumigants makes them inherently dangerous. Communities and farmworkers near agricultural fields face serious risks of acute pesticide poisoning from drifting fumigants.

Fumigant drift has also been measured in air far from application sites, sometimes at levels above those considered “acceptable” for longer-term seasonal exposures by EPA or the California Department of Pesticide Regulation. (See: Second-hand Pesticides: Airborne Pesticide Drift in California) Results from PANNA's Drift Catcher project in Sisquic, California showed that residents were exposed to levels of chloropicrin that exceeded California's acute level of concern for children.

Every few years there is a mass fumigant poisoning:

  • In November 1999, drifting metam sodium poisoned an entire neighborhood in Earlimart, California, resulting in the evacuation of 150 people from their homes. One Earlimart resident recalled that she first noticed something was wrong when her infant son’s eyes began to tear. (See: Second-hand Pesticides for more on metam sodium poisonings)
  • In October 2003, a plume of chloropicrin drifted into the California community of Lamont after being applied to a nearby onion field. 150 residents were poisoned. Despite the widespread illness, application of the pesticide was continued the next day and 100 more people were affected.
  • In 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.

Sometimes I couldn't stand how my eyes were watering and my throat hurt; I couldn't stand the gas. I would run outside the field to get some air. Now I can't breathe well, and my vision is blurry. -Jorge Fernandez, farmworker poisoned by methyl bromide. Salinas, CA

Accidents are unavoidable and, as demonstrated by Drift Catcher results, even typical, accident-free application expose neighbors to amounts of chemicals that exceed levels of concern. Poison Gases in the Field

Fumigants & the Environment

Fumigants dramatically impact soil health and sustainability---eradicating not only weeds and pests, but also beneficial organisms. Several studies cited in the Journal of Pesticide Reform indicate that fumigants can devastate beneficial nematodes, fungi, and bacteria critical to the nitrogen cycle.

Sustainable Alternatives

Economically viable non-chemical alternatives are available and already in use by organic and other sustainable agricultural practitioners. These alternatives include use of resistant cultivars, cultural methods such as crop rotation and use of cover crops as well as physical methods such as soil solarization (download PANNA's Technical Comment letter for more detail on alternatives).


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