Helping Our Peninsula's Environment


Methyl Bromide Pesticide Use

(c) Copyright 2002 David Dilworth


Methyl bromide is a deadly nerve gas which is prohibited for use during wars. Its legal use has killed 19 Californians since 1982 and poisoned 382 other people. TD p 238

Methyl bromide is listed as a hazardous air pollutant under the Clean Air Act amendments of 1990

Methyl bromide's toxicity is CUMULATIVE. Tiny amounts of exposure add up over a week, a season and a lifetime. Any regulation allowing any amount of Methyl bromide pollution which doesn't take this into account is explicitly allowing long term poisoning.

Methyl bromide is a known reproductive toxin. Methyl bromide fumes, which attack the central nervous and respiratory systems, bring on dizziness, vomiting and disorientation, and have been associated with birth defects.

Methyl bromide is listed under California's Proposition 65 as known to cause reproductive toxicity - when it is used as a structural fumigant. Isn't that funny the identical gas when used in agriculture is somehow not known to cause reproductive toxicity. That distinction is merely a political one and is bogus. Scientifically, Methyl Bromide has the identical effects on humans and the environment no matter where it is used.

Agricultural uses of methyl bromide were exempted by law from the Prop 65 listing. This exclusion is scientifically meaningless since the proposition 65 listing is only a finding of whether a chemical is harmful - not a political judgment on where it is used. This is equivalent to asserting that guns can't kill if they are used in agricultural fields. Methyl bromide is equally deadly in agricultural applications as in structural applications.

During a structural fumigation, the 24 hour safe exposure limits to methyl bromide have been set at 21 parts per billion (ppb). The Agency for Toxic Substances and Disease Registry recommends exposure levels of a maximum of 50 ppb. California's Department of Pesticide Regulation sets the 24 hour exposure limit at 210 ppb. This is by far the weakest standard of any agency.

In testimony before the California Assembly in February 1996, Dr. William Pease, a toxicologist at UC Berkeley and the Environmental Defense Fund, illuminated the health effects of methyl bromide as a nerve toxin, a reproductive and developmental toxin, and went on to show that the state has not established methyl bromide air pollution standards to protect humans from chronic exposure to methyl bromide.

He said "nobody is monitoring how much is in the air and the methyl bromide levels that are legally allowed in the air are derived from studies on rats and rabbits, even though primates, including humans, have been shown to be more sensitive."

The one study that attempted to measure the chronic effects of low level exposure ended with six dead beagles after just a few days. It was determined by the researchers that "the cumulative effect for methyl bromide induced neurotoxicity made it difficult to estimate an exposure level which the dogs could tolerate for a 28-day or 1 year exposure study."



In 1991, 18.7 million pounds of methyl bromide were used in California. In 1993 that total dropped to 14.8 million pounds, but in 1995 use rose again to 17.6 million pounds. Measurements for 1996 are not yet available. Some 2 million pounds were used in Monterey County in 1999.

About 96 percent of methyl bromide use in California goes to agricultural uses such as sterilizing soil and killing pests on produce in warehouses, according to a spokesman for the California Farm Bureau. The remaining 4 percent is used for structure fumigations to fumigate homes and buildings to kill termites and other pests.


The most dramatic rise in usage was in Monterey County, the center of the state's booming strawberry industry. The use of methyl bromide soared from 1.4 million pounds to more than 3 million pounds between 1993 and 1995, and some 949 applications per year according to state figures.

In early June 1996, 36 separate detections of methyl bromide were recorded in the air of a suburban residential neighborhood in Castroville, in Monterey County, California, after the fumigant had been applied to a to a nearby strawberry farm field more than 1,300 feet away, far outside the state-approved, 200 foot "buffer" zone - days after it had been applied.


EWG's newest study shows that more than 2.4 million pounds of the acutely toxic pesticide methyl bromide were applied near 758 California schools in 1995.

More important than the heavy use of pesticides is the high potential for human illness from offsite drift of these pesticides. Breathing methyl bromide for example is serious health threat. Methyl bromide is a highly toxic gas that never stays where it is put. According to the latest studies, anywhere from 30-60 percent gets into the air depending on the application method and weather, despite the plastic tarping placed on top. Methyl bromide goes right through plastic. It doesn't take a plastic glue failure, a strong wind or kids ripping off the plastic for there to be methyl bromide in the air around strawberry fields. Applications of methyl bromide to California strawberry fields average around 200 pounds per acre. That means 60 to 120 pounds vaporizes into the surrounding breathing space from each acre of strawberries.

The Department of Pesticide Regulation and the farmers know this. But instead of monitoring how much methyl bromide is in the air, they use computer models to guess where the methyl bromide will go after it leaves

The scientist who developed these computer models while working for the state (now a private consultant on air pollution) compared the DPR buffer zones to more realistic buffer zones using an updated computer model and local, up-to-date weather data. He found that in Salinas for example, DPR buffer zones should be 4 to 10 times larger than currently mandated for various field sizes and pesticide application rates. A DPR buffer zone of 40 feet should be 510 feet, A DPR buffer zone of 140 yards should be more than a quarter mile. This raises serious questions about the safety of people living, working and going to school close to methyl bromide treated fields.


Methyl bromide monitoring at a Central California mobile home park found high levels of methyl bromide escaping the adjacent strawberry field. Methyl bromide was detected at a distance eleven times greater than the state mandated buffer zone.

State testers took air samples around the two 10-acre test plots using dozens of charcoal-filled canisters. During the first fumigation, only one canister detected levels of methyl bromide higher than the allowable 24-hour average of 210 parts per billion, and that result was discarded because the device was located only 25 feet from the edge of the field, instead of the required 30 feet. Eight of the state's canisters registered no pesticide residues.

But the Environmental Working Group, using what they say are more sophisticated silicon-lined canisters, said they detected 24- hour average levels of methyl bromide as high as 350 parts per billion outside the mandatory 30-foot buffer zone -- 67 percent higher than the allowable levels.

The most surprising result was a 24-hour average measurement of 245 parts per billion in a back yard on Revilla Drive, more than 200 feet from the edge of the field. Levels of the fumigant spiked as high as 490 parts per billion in the same back yard, Walker said, apparently pushed there by the area's swirling winds.

EWG air testing near a Watsonville, California elementary school detected levels well above state safety standards. A strawberry field next to the school was fumigated with over 4,000 pounds of the pesticide. The methyl bromide levels measured were the highest found by EWG in an ongoing statewide air monitoring study. EWG calls for ban on methyl bromide use near schools.

In March 1997, the California Dept. of Pesticide Regulation published an internal report showing that when the poison gas is used to fumigate homes, unsafe levels of can drift through empty pipes into neighboring houses. August 19, 1997.


Carbon filters used by the agency to monitor for methyl bromide are considered by a number of experts to be extremely poor instruments for methyl bromide detection under field conditions (Gan et al. 1995a, Gan et al. 1995b). Specifically, the method used by the California DPR may underestimate the amount of methyl bromide in air by 50 to 70 percent (Green et al. 1992).


The California DPR standard for agricultural use of methyl bromide has been repeatedly criticized as too weak (Pease 1996, Wagner 1996). Indeed, some DPR scientists have recommended a much stronger 24 hour exposure standard as low as 1 ppb (CDPR 1995b). The one-day DPR standard of 210 ppb is well above the Minimum Risk Level recommended by the U.S. Public Health Service of 50 ppb exposure on average over 24 hours (ATSDR 1996). Methyl bromide levels in air exceeded the U.S. Public Health Service recommended 24 hour safety standard at three locations - Ventura, Watsonville, and Castroville - in tests conducted by independent technicians under contract to EWG. Those air samples were taken on residential property outside of buffer zones - that is, in supposedly safe areas.

The new rules establish a minimum buffer zone of 100 feet for methyl bromide use on fields of 5 acres or less, 200 feet for more than 5 acres and 300 feet for more than 20 acres. In any location where the field slopes more than 5 degrees, the minimum

buffer zone will be 200 feet. Previous minimum buffer zones ranged from 30 feet to 200 feet.

Organic Growing as an Methyl Bromide Alternative

Organic Strawberry production produces yields as high as 89 percent, eliminates synthetic pesticide and fertilizer use, Increases product price premiums by 50 to 100 percent, reduces environmental stress, premits an increase in soil biodiversity, does

not contribute to pest resistance. US-Environmental Protection Agency "Alternatives to Methyl Bromide, Vol 3"

Telone as a Methyl Bromide Alternative

Telone is just another deadly pesticide.

Ozone as a Methyl Bromide Alternative

SoilZone Inc of Sunnyvale,CA has patented a Methyl Bromide Alternative consisting of using Ozone instead of Methyl Bromide (MB). The method kills pests and then within minutes converts into regular oxygen. It is far safer for humans to handle and for those who live and work in the area it is applied. The costs per acre are roughly equivalent to MB. US-EPA's Bill Thomas said "The preliminary research results with ozone look very promising. I think it is worth pursuing." Mar 8 1998 West Magazine (San Jose Mercury)

For more info: [email protected]; and

This Alternative does not require any non-off-the shelf technology.

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This Page Last Updated 8/16/02