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DESIGNATIONS
CAS No.: 74-83-9
Registry name: Methyl bromide
Chemical name: Methyl bromide
Synonyms, Trade names: Bromomethane, Terabol
Chemical name (German): Methylbromid
Chemical name (French): Bromure de méthyle
Appearance: colourless gas, chloroform-like odour
BASIC CHEMICAL AND PHYSICAL DATA
Empirical formula: |
CH3Br |
Rel. molecular mass: |
94.95 g |
Density: |
1.73 g/cm3 liquid at 0°C |
Relative gas density: |
3.3 |
Boiling point: |
4°C |
Melting point: |
-93°C |
Vapour pressure: |
90 x 103 Pa at 20°C |
Ignition temperature: |
535°C |
Explosion limits: |
8.6-20 Vol.% |
Solvolysis/solubility: |
in water: 13.4 g/l readily soluble in common organic solvents |
Conversion factors: |
1 mg/m3 = 0.253 ml/m3 1 ml/m3 = 3.946 mg/m3 |
ORIGIN AND USE
Usage:
Methyl bromide is an insecticide and nematocide with fungicidal, acaricidal,
rodenticidal and herbicidal effects (germinating seed). It is used for the disinfection of
soils, the fumigation of grain, the protection of stocks and the disinfection of
storehouses and mills (especially against grain beetles and flour moths) as a non-blended
gas, or blended with carbon dioxide or ethylidene dibromide.
Origin/derivation:
Methyl bromide is produced from methanol by hydrobromination.
Toxicity
Humans: |
LCLo 60,000 ppm (2h), inhalation |
acc. UBA 1986 |
TCLo 35 ppm (2h), inhalation |
acc. UBA 1986 |
|
Mammals: |
||
Rat |
LC100 0.63 mg/l (6h), inhalation |
acc. UBA 1986 |
LCLo 3120 ppm (15 min), inhalation |
acc UBA 1986 |
|
Guinea pig |
LCLo 300 ppm (9h), inhalation |
acc. UBA 1986 |
Rabbit |
LCLo 2 mg/l (11h), inhalation |
acc. UBA 1986 |
Aquatic organisms: |
||
Fish |
LC50 > 1000 mg/l |
acc. UBA 1986 |
Characteristic effects:
Humans/mammals: Inhalation of high concentrations of methyl bromide that does not immediately cause anesthesia and respiratory shock may cause a lung oedema after several hours of latency, often followed by a serious pneumonia within a few days. Damage to the central nervous system may result from acute as well as from chronic poisoning. The symptoms are headache and nausea, then disturbance comparable to alcohol poisoning, followed by excitation, tremors and epileptic fits usually attached with paralysis of the limbs. The symptoms resulting from a single exposure may last for several weeks. Skin contact with the liquid substance causes blisters. Methyl bromide is readily absorbed through the skin. It is suspected to have carcinogenic potential.
ENVIRONMENTAL BEHAVIOUR
Soil:
In soil and in grain, bromine is found bonded inorganically.
Note:
There is hardly information about the environmental behaviour of methyl bromide.
ENVIRONMENTAL STANDARDS
| Medium/ acceptor |
Sector | Country/organ. | Status | Value | Cat. | Remarks | Source |
| Air: | |||||||
| Workp | D | L |
5 ml/m3 | MAK | carcinogenic III B | acc. AUER TECHNIKUM, 1988 | |
| Workp | D | L |
20 mg/m3 | MAK | acc. AUER TECHNIKUM, 1988 | ||
| Workp | SU | (L) |
0.25 ppm | PDK | acc. AUER TECHNIKUM, 1988 | ||
| Workp | SU | (L) |
1 mg/m3 | PDK | acc. AUER TECHNIKUM, 1988 | ||
| Workp | USA | (L) |
5 ppm | TWA | acc. AUER TECHNIKUM, 1988 | ||
| Workp | USA | (L) |
20 mg/m3 | TWA | acc. AUER TECHNIKUM, 1988 | ||
| Workp | USA | (L) |
15 ppm | STEL | acc. AUER TECHNIKUM, 1988 | ||
| Workp | USA | (L) |
60 mg/m3 | STEL | acc. AUER TECHNIKUM, 1988 | ||
Assessment/comments
Methyl bromide is a very insidious chemical. As the odour threshold is much higher than the toxic concentration, there is no warning effect. Symptoms appear after hours of latency and last for weeks even in cases of a single exposure. It reacts strongly or even explosively with alkali and alkaline earth metals and metal powders.