| Chemical Abstract Number (CAS #) |
74839
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| Synonyms | Bromomethane |
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Methyl bromide | Methane, bromo |
| Analytical Methods |
EPA Method 502.2 |
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EPA Method 524.1 |
EPA Method 524.2 |
EPA Method 601 |
EPA Method 624 |
EPA Method 8010B |
EPA Method 8021A |
EPA Method 8240B |
EPA Method 8260A |
| Molecular Formula | CH3Br |
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| Use | IN IONIZATION CHAMBERS, DEGREASING WOOL, EXTRACTING OILS FROM
NUTS, SEEDS, & FLOWERS.
FUMIGANT USED TO TREAT SOIL, GRAIN & OTHER COMMODITIES;
METHYLATING AGENT.
Has been used as a refrigerant and fire extinguisher.
USED FOR INSECT AND RODENT CONTROL IN SPACE AND COMMODITY
FUMIGATIONS; FOR PREPLANT SOIL FUMIGATION (ONLY WITH CHLOROPICRIN)
TO CONTROL NEMATODES, INSECTS, WEED SEEDS & FUNGI.
Used in food sterilization for pest control in fruits, vegetables, dairy products, nuts, and grain; as
solvent in aniline dyes.
As methylating agent, especially for prepn of antipyrine & other pharmaceuticals.
The first recorded use of methyl bromide occurred in the last part of the 19th century: It was
used as a medicinal agent to destroy malignant tissue and as an anesthetic in dentistry.
Used as a fungicide, nematicide, herbicide (unspecified), herbicide (terrestrial), and an insecticide
and miticide against nematodes and weeds (preemergence) through soil fumigation treatment for
fumigation of storage areas (feed/food-full) and domestic dwellings (indoor).
FOR CONTROL OF TERMITES IN STRUCTURES.
Organic synthesis; extraction solvent for vegetable oils.
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| Consumption Patterns | 65% SOIL FUMIGANT, 15% SPACE FUMIGANT, 10% CHEMICAL PROCESSES,
10% EXPORTS (1985).
CHEMICAL PROFILE: Methyl Bromide. Soil fumigant, 55%; space and structural fumigant,
10%; chemical processes, 10%; grain and commodity fumigant, 5%; exports, 20%.
CHEMICAL PROFILE: Methyl bromide. Demand: 1987: 41 million lb; 1988: 42 million lb; 1992
/projected/: 47 million lb (Includes exports; in addition, 5 million to 7 million lb were imported
from Israel in 1987).
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| Apparent Color | COLORLESS GAS
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| Odor | USUALLY ODORLESS; SWEETISH, CHLOROFORM-LIKE ODOR AT HIGH
CONCN ; Low threshold= 80 mg/cu m, High threshold= 4000 mg/cu m ; Methyl bromide has
practically no odor or irritating effects in low concentration and therefore does not provide any
warning of physiologically dangerous concentrations.
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| Boiling Point | 3.55 deg C
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| Melting Point | -93.66 DEG C
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| Molecular Weight | 94.95
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| Density | 1.730 @ 0 DEG C/4 DEG C (LIQ); 3.974 G/L @ 20 DEG C (GAS)
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| Odor Threshold Concentration | In mg/cu m: odor low 80; odor high 4,000
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| Sensitivity Data | Contact of the skin with high concentrations of vapor or with liquid methyl bromide
produces a tingling and burning sensation.
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| Environmental Impact | The primary source of methyl bromide in the environment is the oceans. Release to the
environment also results from the use of methyl bromide as a soil and space fumigant and its
occurrence in auto exhaust. Methyl bromide released to soil is expected to be primarily lost by
volatilization. Methyl bromide may also leach due to its weak adsorption to soil. Hydrolysis of
methyl bromide to methanol and bromide ions and biodegradation may also occur in soil. Release
of methyl bromide to water is expected to result primarily in volatilization. Hydrolysis to methanol
and bromide ions will occur with a half-life of 20-26.7 days. Bioconcentration is not expected to
be significant. Release of methyl bromide to the atmosphere will result in reaction with
photochemically generated hydroxyl radicals with half-lives ranging from 0.29 years (25 deg C
and 2X10 6 hydroxyl radicals/cc) to 1.6 years (-8 deg C and 5X10 5 hydroxyl radicals/cc).
Direct photolysis is not expected to be important in the troposphere, but is expected to be the
predominant fate of methyl bromide in the stratosphere. Methyl bromide is a major contaminant of
air and a minor contaminant of surface, drinking and groundwater. Human exposure to methyl
bromide is expected to result primarily from inhalation of contaminated ambient or occupational
air.
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| Environmental Fate | Terrestrial Fate: It reacts with soil or organic material to form bromide ion.
Terrestrial Fate: Decomposition of methyl bromide in soil results in production of bromide ion.
The rate of bromide production is influenced by soil type: it is greatest in peaty manure,
intermediate in loam (clay soil), & least in sand. Bromide ion in soil can be absorbed &
concentrated by plants & may be ingested subsequently by humans & animals.
Terrestrial Fate: Retention of bromide ion in soil after fumigation with methyl bromide is related
to the organic content of the soil. The total bromide ion content of soil containing 2.81 & 0.93%
organic carbon was 9 & 5 mg/kg when untreated & 63 & 25 mg/kg following fumigation with
500 mg/kg methyl bromide for 24 hr, respectively.
Aquatic Fate: Monohalomethanes can be hydrolyzed slowly in neutral waters forming methanol
and hydrogen halides. Monohalomethanes
Atmospheric Fate: Monohalomethanes undergo photolysis in the upper atmosphere where
ultraviolet radiation is of sufficient energy to initiate a reaction. Monohalomethanes
TERRESTRIAL FATE: The primary fate of methyl bromide in soil is expected to be
volatilization. Due to its weak adsorption to soil, methyl bromide is expected to leach. Hydrolysis
of methyl bromide may also occur in neutral and alkaline soils yielding methanol and bromide
ions. Biodegradation may also occur.
AQUATIC FATE: The primary fate of methyl bromide in water is expected to be volatilization.
Hydrolysis of methyl bromide to methanol and bromide ion will also occur with half-lives of
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