Chemical Fact Sheet

Chemical Abstract Number (CAS #) 74839
CASRN 74-83-9
Methyl bromide
Methane, bromo
Analytical Methods EPA Method 502.2
EPA Method 524.2
EPA Method 601
EPA Method 624
EPA Method 8010
EPA Method 8021
EPA Method 8260
Molecular FormulaCH3Br

Link to the National Library of Medicine's Hazardous Substances
Database for more details on this compound.

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.
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).
Apparent Color COLORLESS GAS
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.
Boiling Point 3.55 deg C
Melting Point -93.66 DEG C
Molecular Weight 94.95
Density 1.730 @ 0 DEG C/4 DEG C (LIQ); 3.974 G/L @ 20 DEG C (GAS)
Odor Threshold Concentration In mg/cu m: odor low 80; odor high 4,000
Sensitivity Data Contact of the skin with high concentrations of vapor or with liquid methyl bromide produces a tingling and burning sensation.
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.
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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