Bromomethane, commonly known as methyl bromide, is an organobromine compound
Organobromine compound
Organobromine compounds are organic compounds that contain carbon bonded to bromine. The most pervasive is the naturally produced bromomethane. One prominent application is the use of polybrominated diphenyl ethers as fire-retardants. A variety of minor organobromine compounds are found in...

 with formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....

Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

Bromine ") is a chemical element with the symbol Br, an atomic number of 35, and an atomic mass of 79.904. It is in the halogen element group. The element was isolated independently by two chemists, Carl Jacob Löwig and Antoine Jerome Balard, in 1825–1826...

. This colorless, odorless, nonflammable gas is produced both industrially and particularly biologically. It has a tetrahedral shape and it is a recognized ozone-depleting
Ozone depletion
Ozone depletion describes two distinct but related phenomena observed since the late 1970s: a steady decline of about 4% per decade in the total volume of ozone in Earth's stratosphere , and a much larger springtime decrease in stratospheric ozone over Earth's polar regions. The latter phenomenon...

 chemical. It was used extensively as a pesticide
Pesticides are substances or mixture of substances intended for preventing, destroying, repelling or mitigating any pest.A pesticide may be a chemical unicycle, biological agent , antimicrobial, disinfectant or device used against any pest...

 until being phased out by most countries in the early 2000s.

Occurrence and manufacture

Bromomethane originates from both natural and human sources. In the ocean
An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...

, marine organisms are estimated to produce 1-2 billion kilograms annually. It is also produced in small quantities by certain terrestrial plants, such as members of the Brassicaceae
Brassicaceae, a medium sized and economically important family of flowering plants , are informally known as the mustards, mustard flowers, the crucifers or the cabbage family....

 family. It is manufactured for agricultural and industrial use by reacting methanol
Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH . It is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, ethanol...

 with hydrogen bromide
Hydrogen bromide
Hydrogen bromide is the diatomic molecule HBr. HBr is a gas at standard conditions. Hydrobromic acid forms upon dissolving HBr in water. Conversely, HBr can be liberated from hydrobromic acid solutions with the addition of a dehydration agent, but not by distillation. Hydrogen bromide and...

CH3OH + HBr → CH3Br + H2O


In 1999, an estimated 71,500 tonnes of synthetic methyl bromide were used annually worldwide. 97% of this estimate is used for fumigation purposes, whilst 3% is used for the manufacture of other products. Moreover 75% of the consumption takes place in developed nations, led by the U.S (43%) and Europe (24%). Asia and the Middle East combine to use 24% whereas Latin America and Africa have the lowest consumption rates at 9%.

Until its production and use were curtailed by the Montreal Protocol
Montreal Protocol
The Montreal Protocol on Substances That Deplete the Ozone Layer is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances believed to be responsible for ozone depletion...

, bromomethane was widely applied as a soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

Sterilization (microbiology)
Sterilization is a term referring to any process that eliminates or kills all forms of microbial life, including transmissible agents present on a surface, contained in a fluid, in medication, or in a compound such as biological culture media...

, mainly for production of seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...

 but also for some crops such as strawberries
Fragaria is a genus of flowering plants in the rose family, Rosaceae, commonly known as strawberries for their edible fruits. Although it is commonly thought that strawberries get their name from straw being used as a mulch in cultivating the plants, the etymology of the word is uncertain. There...

 and almond
The almond , is a species of tree native to the Middle East and South Asia. Almond is also the name of the edible and widely cultivated seed of this tree...

s. In commercial large-scale monoculture
Green Revolution
Green Revolution refers to a series of research, development, and technology transfer initiatives, occurring between the 1940s and the late 1970s, that increased agriculture production around the world, beginning most markedly in the late 1960s....

 seed production, unlike crop production, it is of vital importance to avoid contaminating the crop with off-type seed of the same species. Therefore, selective herbicides cannot be used. Whereas bromomethane is dangerous, it is considerably safer and more effective than some other soil sterilants. Its loss to the seed industry has resulted in changes to cultural practices, with increased reliance on soil steam sterilization
Soil steam sterilization
Soil steam sterilization is a farming technique that sterilizes soil with steam in open fields or greenhouses. Pests of plant cultures such as weeds, bacteria, fungi and viruses are killed through induced hot steam which causes their cell structure to physically degenerate. Biologically, the...

, mechanical rogueing, and fallow seasons. Bromomethane was also used as a general-purpose fumigant to kill a variety of pests including rat
Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...

s and insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

s. Bromomethane has poor fungicidal properties. Bromomethane is the only fumigant allowed (heat treatment is only other option) under ISPM 15
International Standards For Phytosanitary Measures No. 15 is an International Phytosanitary Measure developed by the International Plant Protection Convention that directly addresses the need to treat wood materials of a thickness greater than 6mm, used to ship products between countries...

 regulations when exporting solid wood packaging (forklift pallets, crates, bracing) to ISPM 15 compliant countries. Bromomethane is used to prepare golf courses, particularly to control Bermuda grass. The Montreal Protocol stipulates that bromomethane use be phased out.

Bromomethane is also a precursor in the manufacture of other chemicals as a methylating
In the chemical sciences, methylation denotes the addition of a methyl group to a substrate or the substitution of an atom or group by a methyl group. Methylation is a form of alkylation with, to be specific, a methyl group, rather than a larger carbon chain, replacing a hydrogen atom...

 agent, and has been used as a solvent
A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...

 to extract oil
An oil is any substance that is liquid at ambient temperatures and does not mix with water but may mix with other oils and organic solvents. This general definition includes vegetable oils, volatile essential oils, petrochemical oils, and synthetic oils....

 from seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...

s and wool
Wool is the textile fiber obtained from sheep and certain other animals, including cashmere from goats, mohair from goats, qiviut from muskoxen, vicuña, alpaca, camel from animals in the camel family, and angora from rabbits....


Bromomethane was once used in specialty fire extinguishers, prior to the advent of less toxic halons, as it is electrically non-conductive and leaves no residue. It was used primarily for electrical substations, military aircraft, and other industrial hazards. It was never as popular as other agents due to its high cost and toxicity. Bromomethane was used from the 1920s to the 60s, and continued to be used in aircraft engine fire suppression systems into the late 60s.


Bromomethane is readily photolyzed
Photodissociation, photolysis, or photodecomposition is a chemical reaction in which a chemical compound is broken down by photons. It is defined as the interaction of one or more photons with one target molecule....

 in the atmosphere to release elemental bromine, which is far more destructive to stratospheric ozone than chlorine. As such, it is subject to phase-out requirements of the 1987 Montreal Protocol on Ozone Depleting Substances.

The London Amendment in 1990 added methyl bromide to the list of ODS to be phased out. In 2003 the Global Environment Facility approved funds for a UNEP-UNDP joint project for methyl bromide total sector phase out in seven countries in Central Europe and Central Asia, due for completion in 2007.


In Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, bromomethane (methyl bromide) is the preferred fumigant required by the Australian Quarantine and Inspection Service (AQIS) for most organic goods imported into Australia. AQIS conducts methyl bromide fumigation certification for both domestic and foreign fumigators who can then fumigate containers destined for Australia. A list of alternative fumigants is available for goods imported from Europe (known as the ICON database), where methyl bromide fumigation has been banned. Alternatively, AQIS allows containers from Europe to be fumigated with methyl bromide on arrival to Australia.

New Zealand

In New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

, bromomethane is used as a fumigant for whole logs destined for export. Environmental groups and the Green Party
Green Party of Aotearoa New Zealand
The Green Party of Aotearoa New Zealand is a political party that has seats in the New Zealand parliament. It focuses firstly on environmentalism, arguing that all other aspects of humanity will cease to be of concern if there is no environment to sustain it...

 oppose its use. In May 2011 the Environmental Risk Management Authority
Environmental Risk Management Authority
The Environmental Risk Management Authority is a New Zealand government agency which controls the introduction of hazardous substances and new organisms....

 (ERMA) introduced new rules for its use which restrict the level of public exposure to the fumigant, set minimum buffer zones around fumigation sites, provide for notification to nearby residents and require users to monitor air quality during fumigations and report back to ERMA each year. All methyl bromide fumigations must use recapture technology by 2021.

United States

In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 bromomethane is regulated as a pesticide under the Federal Insecticide, Fungicide, and Rodenticide Act
Federal Insecticide, Fungicide, and Rodenticide Act
The Federal Insecticide, Fungicide, and Rodenticide Act , et seq. is a United States federal law that set up the basic U.S. system of pesticide regulation to protect applicators, consumers, and the environment. It is administered by the Environmental Protection Agency and the appropriate...

 (FIFRA; 7 U.S.C. 136 et seq.) and as a hazardous substance under the Resource Conservation and Recovery Act
Resource Conservation and Recovery Act
The Resource Conservation and Recovery Act , enacted in 1976, is the principal Federal law in the United States governing the disposal of solid waste and hazardous waste.-History and Goals:...

 (RCRA; 42 U.S.C. 6901 et seq.), and is subject to reporting requirements under the Emergency Planning and Community Right-to-Know Act
Emergency Planning and Community Right-to-Know Act
The Emergency Planning and Community Right-to-Know Act of 1986 is a United States federal law passed by the 99th United States Congress located at Title 42, Chapter 116 of the U.S. Code, concerned with emergency response preparedness....

 (EPCRA; 42 U.S.C. 11001 et seq.). The U.S. Clean Air Act
Clean Air Act
A Clean Air Act is one of a number of pieces of legislation relating to the reduction of airborne contaminants, smog and air pollution in general. The use by governments to enforce clean air standards has contributed to an improvement in human health and longer life spans...

 (CAA; 42 U.S.C. 7401 et seq.). A 1998 amendment (P.L. 105-178, Title VI) conformed the Clean Air Act phase out date with that of the Montreal Protocol. Whereas the Montreal Protocol has severely restricted the use of bromomethane internationally, the United States has successfully lobbied for critical-use exemptions. In 2004, over 7 million pounds of bromomethane were applied to California. Applications include tomato, strawberry, and ornamental shrub growers, and fumigation of ham/pork products. Also exempt is the treatment of solid wood packaging (forklift pallets, crates, bracing), and the packaged goods, being exported to ISPM 15 countries(to include Canada in 2012).

Health effects

Brief exposure to high concentrations and prolonged inhalation of lower concentrations are problematic. Exposure levels leading to death vary from 1,600 to 60,000 ppm, depending on the duration of exposure (as a comparison exposure levels of 70 to 400 ppm of carbon monoxide
Carbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...

 cover the same spectrum of illness/death).

"A TLV–TWA of 1 ppm (3.89 mg/m3) is recommended for occupational exposure to methyl bromide"-ACGIH 8 hour time weighted average. Immediately Dangerous To Life or Health Concentration by NIOSH: "The revised IDLH for methyl bromide is 250 ppm based on acute inhalation toxicity data in humans [Clarke et al. 1945]. This may be a conservative value due to the lack of relevant acute toxicity data for workers exposed to concentrations above 220 ppm. [Note: NIOSH recommends as part of its carcinogen policy that the "most protective" respirators be worn for methyl bromide at any detectable concentration.]" Detectable concentration by Drager Tube is 0.5 ppm.

Respiratory, kidney, and neurological effects are of the greatest concern. Scientists have investigated whether bromomethane exposure was linked to the death of four New Zealand port workers who died of neuro-degenerative motor neurone disease between 2002 and 2004 and found no connection.

"Cases of severe methyl bromide poisoning in humans, some of them fatal, were frequently reported. For example, von Oettingen recorded 47 fatal and 174 nonfatal cases of methyl bromide intoxication between 1899 and 1952...Severe poisoning with some fatalities resulted from soil disinfection by injection of methyl bromide into greenhouse soil."-ACGIH

Treatment of wood packaging requires a concentration of up to 16,000 ppm. An Australian Customs officer died of methyl bromide poisioning while inspecting a shipping container that was fumigated in the United States. Canada Border Services Officers avoided the same fate because a Mexican container of granite was fumigated with 98% methyl bromide and 2% chloropicrin
Chloropicrin, also known as PS, is a chemical compound with the structural formula Cl3CNO2. This colourless highly toxic liquid was once used in chemical warfare and is currently used as a fumigant and nematocide.-History:...

 fumigant, the chloropicrin has a tear-gas effect.

NIOSH considers methyl bromide to be a potential occupational carcinogen as defined by the OSHA carcinogen policy [29 CFR 1990]. "methyl bromide showed asignificant dose-response relationship with prostate cancer risk"

Excessive exposure

Expression of toxicity following exposure may involve a latent period of several hours, followed by signs such as nausea
Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...

, abdominal pain, weakness, confusion, pulmonary edema
Pulmonary edema
Pulmonary edema , or oedema , is fluid accumulation in the air spaces and parenchyma of the lungs. It leads to impaired gas exchange and may cause respiratory failure...

, and seizures. Individuals who survive the acute phase often require a prolonged convalescence. Persistent neurological deficits such as asthenia, cognitive impairment, optical atrophy, and paresthesia
Paresthesia , spelled "paraesthesia" in British English, is a sensation of tingling, burning, pricking, or numbness of a person's skin with no apparent long-term physical effect. It is more generally known as the feeling of "pins and needles" or of a limb "falling asleep"...

are frequently present after moderate to severe poisoning. Blood or urine concentrations of inorganic bromide, a bromomethane metabolite, are useful to confirm a diagnosis of poisoning in hospitalized patients or to assist in the forensic investigation of a case of fatal overdosage.

External links

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