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CHEMINFO Record Number: 379
CCOHS Chemical Name: Methyl bromide

Bromure de méthyle

Chemical Name French: Bromométhane
Chemical Name Spanish: Bromometano

Trade Name(s):

CAS Registry Number: 74-83-9
UN/NA Number(s): 1062
RTECS Number(s): PA4900000
EU EINECS/ELINCS Number: 200-813-2
Chemical Family: Halogenated aliphatic hydrocarbon / saturated halogenated hydrocarbon / halogenated alkane / haloalkane / monohaloalkane / alkyl halide / alkyl bromide
Molecular Formula: C-H3-Br
Structural Formula: CH3-Br


Appearance and Odour:
Colourless gas at room temperature or colourless liquid under pressure; chloroform-like odour at high concentration.

Odour Threshold:
65 mg/m3 (17 ppm) (2); 80-4000 mg/m3 (20-1000 ppm) (7)

Warning Properties:
POOR - Odour threshold exceeds the TLV. Odourants such as chloropicrin may be added as a warning agent.

Methyl bromide is commerically available as a liquefied gas in pressure cylinders or as a gas in solution in diethyl ether or t-butyl methyl ether. Some mixtures used for fumigation also contain chloropicrin as an active ingredient (32-33%) or as a warning agent (2%). There are specific hazards associated with these solvents. See CHEMINFO 597 for additional information on diethyl ether and CHEMINFO 606 for additional information on tert-butyl methyl ether. Some mixtures used for fumigation also contain chloropicrin as an active ingredient (32-33%) or as a warning agent (2%).

Uses and Occurrences:
Insecticide and fumigant for use in grain elevators, mills, ships, greenhouses and food-processing facilities; soil fumigant; methylating agent in chemical manufacture.


Colourless gas with a chloroform-like odour at high concentrations. Also available in solution. Will not burn, unless in the presence of a high energy source of ignition. Can decompose at high temperatures forming toxic gases. COMPRESSED GAS. VERY TOXIC. May be fatal if inhaled or absorbed through the skin. CORROSIVE to the eyes, skin and respiratory tract. May cause lung injury - effects may be delayed. Central nervous system depressant. Vapour may cause headache, nausea, dizziness, drowsiness, incoordination, confusion, unconsciousness and death. Severe exposure may result in lung, liver, kidney and nervous system damage. POSSIBLE MUTAGEN - May cause genetic damage, based on animal data.


Effects of Short-Term (Acute) Exposure

Hundreds of cases of methyl bromide poisoning have occurred, including many fatalities. Methyl bromide is a central nervous system depressant. Vapour can initially cause headache, dizziness, abdominal pain, nausea, vomiting, chest pain, difficulty breathing, visual disturbances (blurred or double vision, transient blindness), muscular pain and numbness.

A characteristic delay of more than 1 hr, up to 48 hrs, in the onset of symptoms, was noted in several cases (11).

Severe exposures may cause tremors, convulsions, unconsciousness, permanent brain damage and damage to lungs (edema, congestion and bleeding), liver and kidney. Exposure to more than 10000 ppm methyl bromide for more than a few minutes may cause death (2).

Skin Contact:
Methyl bromide can cause severe irritation or corrosive skin injury (blisters and vesicles like a second-degree burn) (2,7,9).
In particular, severe injury can occur if gas or liquid is trapped in gloves, boots or other clothing (5).

Methyl bromide can be absorbed through the skin. In severe cases, symptoms like those described for inhalation may occur. Some fatalities have occurred (2).

Eye Contact:
Vapour can cause irritation and tearing (lachrymation). Blurred vision, double vision, temporary blindness and retinal bleeding have been reported, but may in part be due to inhalation (2). The liquid can cause severe burns to the cornea (4).

No specific data is available. Methyl bromide solutions might cause effects like those described for inhalation.

Effects of Long-Term (Chronic) Exposure

SKIN: Prolonged or repeated contact with liquid may cause skin burns and lesions.

NERVOUS SYSTEM: Chronic methyl bromide exposure mainly causes injury to the central nervous system. Injury is characterized by lethargy, muscular pains, visual, speech and sensory disturbances, and mental confusion (7). More severe effects include tremors, hallucinations, fainting spells and seizures (convulsions) (17).

Kidney damage, liver damage and permanent brain damage may result from prolonged or repeated exposure (5,7).


The available human information is limited and inconclusive. One human population study examined mortality in 3579 employees of three chemical manufacturing plants and a research establishment. There were numerous potentially harmful exposures. One sub-group, which had two deaths from testicular cancer, had potential exposure to methyl bromide.(24) No firm conclusions can be drawn from this study due to limitations such as the combined exposures and poor exposure information. The International Agency for Research on Cancer (IARC) has determined that there is inadequate evidence for the carcinogenicity of methyl bromide in humans. There is limited evidence for the carcinogenicity of methyl bromide to experimental animals.
The US National Institute for Occupational Safety and Health (NIOSH) has recommended that methyl bromide be considered as a potential occupational carcinogen.(8)

The International Agency for Research on Cancer (IARC) has concluded that this chemical is not classifiable as to its carcinogenicity to humans (Group 3).

The American Conference of Governmental Industrial Hygienists (ACGIH) has designated this chemical as not classifiable as a human carcinogen (A4).

The US National Toxicology Program (NTP) has not listed this chemical in its report on carcinogens.

Teratogenicity and Embryotoxicity:
No human information. In limited animal tests, it was not teratogenic or embryotoxic.

Reproductive Toxicity:
No information available

Methyl bromide is considered mutagenic based on positive results obtained in tests using live animals. There is no human information available. Positive results have been obtained in tests using cultured human white blood cells.(24,25)

Toxicologically Synergistic Materials:
No information available

Potential for Accumulation:
Probably does not accumulate. Some methyl bromide is removed from the body unchanged in exhaled air. The remainder is broken down in the body (17). Bromide ion is a breakdown product and is excreted over several weeks (20).


Take proper precautions to ensure your own safety before attempting rescue; e.g., wear appropriate protective equipment, use the "buddy" system. Remove source of contamination or move victim to fresh air. If breathing has stopped, trained personnel should begin artificial respiration (AR) or, if the heart has stopped, cardiopulmonary resuscitation (CPR) immediately. If breathing is difficult, oxygen may be beneficial if administered by a person trained in its use, preferably on a doctor's advice. Obtain medical attention immediately. NOTE: Potentially fatal injury to the lungs and nervous system may occur. Symptoms may only appear after a delay of several hours.

Skin Contact:
Avoid direct contact with this chemical. Wear chemical protective gloves, if necessary. GAS OR SOLUTION: Flush contaminated area with lukewarm, gently flowing water for at least 20-30 minutes, by the clock. If irritation persists, repeat flushing. DO NOT INTERRUPT FLUSHING. If necessary, keep emergency vehicle waiting. Under running water, remove contaminated clothing, shoes and leather goods (e.g. watchbands, belts). Transport victim to an emergency care facility immediately. Discard contaminated clothing, shoes and leather goods.

Eye Contact:
Avoid direct contact. Wear chemical protective gloves, if necessary. GAS OR SOLUTION: Immediately flush the contaminated eye(s) with lukewarm, gently flowing water for at least 20-30 minutes, by the clock, while holding the eyelid(s) open. Neutral saline solution may be used as soon as it is available. DO NOT INTERRUPT FLUSHING. If necessary, keep emergency vehicle waiting. Take care not to rinse contaminated water into the unaffected eye or onto the face. If irritation persists, repeat flushing. Quickly transport victim to an emergency care facility.

SOLUTIONS: Never give anything by mouth if victim is rapidly losing consciousness, is unconscious or convulsing. Have victim rinse mouth thoroughly with water. DO NOT INDUCE VOMITING. Have victim drink 240 to 300 mL (8 to 10 oz.) of water. If vomiting occurs naturally, rinse mouth and repeat administration of water. If breathing has stopped, trained personnel should begin artificial respiration (AR) or, if the heart has stopped, cardiopulmonary resuscitation (CPR) immediately (avoid mouth-to-mouth contact). Obtain medical attention immediately. GAS: Ingestion is not an applicable route of exposure for gases.

First Aid Comments:
Provide general supportive measures (comfort, warmth, rest).
Consult a doctor and/or the nearest Poison Control Centre for all exposures except minor instances of inhalation or skin contact.
Some recommendations in the above sections may be considered medical acts in some jurisdictions. These recommendations should be reviewed with a doctor and appropriate delegation obtained, as required.
All first aid procedures should be periodically reviewed by a doctor familiar with the material and its conditions of use in the workplace.


Flash Point:
None. Practically non-flammable.(22)

Lower Flammable (Explosive) Limit (LFL/LEL):
10% (with high energy ignition source) (22)

Upper Flammable (Explosive) Limit (UFL/UEL):
16% (with high energy ignition source) (22)

Autoignition (Ignition) Temperature:
537 deg C (999 deg F) (22)

Sensitivity to Mechanical Impact:
Probably not sensitive. Stable material.

Sensitivity to Static Charge:
Information not available

Combustion and Thermal Decomposition Products:
When heated to decomposition, it emits highly toxic bromides including hydrogen bromide. Carbon dioxide, carbon monoxide and hydrogen bromide may be released in a fire.

Fire Hazard Summary:
Not ordinarily considered to be combustible; however, it will burn in air in the presence of a high energy source of ignition and within a narrow flammability range. During a fire, irritating/toxic hydrogen bromide gas may be generated.

Extinguishing Media:
Use flooding quantities of water as fog.

Fire Fighting Instructions:
Do not enter without wearing specialized protective equipment suitable for the situation. Firefighter's normal protective clothing (Bunker Gear) will not provide adequate protection. A full-body encapsulating chemical resistant suit with positive pressure self-contained breathing apparatus (MSHA/NIOSH approved or equivalent) may be necessary.
Evacuate area. Firefighters may enter the area only if they are protected from all contact with the material. Full protective clothing and self-contained breathing apparatus should be worn. No skin surface should be exposed. Approach fire from upwind to avoid hazardous vapours and toxic decomposition products. Extinguish fire using extinguishing agent suitable for surrounding fire. Isolate materials not yet involved in fire and protect personnel. Move containers from fire area if it can be done without risk. Use flooding quantities of water as a fog. Use water spray to keep fire-exposed containers cool.
Do not enter without wearing specialized protective equipment suitable for the situation. Firefighter's normal protective clothing (Bunker Gear) will not provide adequate protection. Chemical resistant clothing (e.g. chemical splash suit) and positive pressure self-contained breathing apparatus (MSHA/NIOSH approved or equivalent) may be necessary.


NFPA - Health: 3 - Short exposure could cause serious temporary or residual injury.
NFPA - Flammability: 1 - Must be preheated before ignition can occur.
NFPA - Instability: 0 - Normally stable, even under fire conditions, and not reactive with water.


Molecular Weight: 94.95

Conversion Factor:
1 ppm = 3.88 mg/m3; 1 mg/m3 = 0.258 ppm at 25 deg C

Physical State: Gas
Melting Point: -93.6 deg C (-136.5 deg F)
Boiling Point: 3.56 deg C (38.4 deg F)
Relative Density (Specific Gravity): Not applicable (gas)
Solubility in Water: Slightly soluble (0.9 g/L at 20 deg C; 13.4 g/L at 25 deg C)
Solubility in Other Liquids: Soluble in ethanol, benzene, carbon disulfide, carbon tetrachloride, chloroform and diethyl ether.
Coefficient of Oil/Water Distribution (Partition Coefficient): Log P (oct) = 1.19; also reported 1.09 and 1.69
pH Value: Aqueous solutions are acidic.
Vapour Density: 3.3 (air = 1)
Vapour Pressure: 1520 mm Hg (202.6 kPa) at 23.3 deg C; 1420 mm Hg (189.3 kPa) at 20 deg C
Saturation Vapour Concentration: Not applicable
Evaporation Rate: Not applicable
Critical Temperature: 194 deg C (381 deg F)

Other Physical Properties:
VISCOSITY-DYNAMIC: 0.397 centipoise (0.397 mPa.s) at 0 deg C



Hazardous Polymerization:
Does not occur.

Incompatibility - Materials to Avoid:

NOTE: Chemical reactions that could result in a hazardous situation (e.g. generation of flammable or toxic chemicals, fire or detonation) are listed here. Many of these reactions can be done safely if specific control measures (e.g. cooling of the reaction) are in place. Although not intended to be complete, an overview of important reactions involving common chemicals is provided to assist in the development of safe work practices.

ALUMINUM - Can react violently, forming spontaneously combustible aluminum alkyls.
DIMETHYL SULFOXIDE - Can react violently.
MINERAL ACIDS - Can react violently.
AMINES - Can react violently.
STRONG OXIDIZING AGENTS (eg. organic peroxides) - Can react violently.
CAUSTICS - Can react violently.
NITRIDES - Can react violently.
ALKALI OR ALKALINE EARTH METALS (eg. magnesium) - Can react violently.
METALS - Can react violently.
STRONG REDUCING AGENTS (eg. hydrazines) - Can react violently.
AZO AND DIAZO COMPOUNDS - Can react violently.

Hazardous Decomposition Products:
Bromides, hydrogen bromide

Conditions to Avoid:
High energy source of ignition, high heat.(22)

Corrosivity to Metals:
Corrosive to aluminum, magnesium and most metals

Stability and Reactivity Comments:
Burns in oxygen


LC50 (rat): 11000 mg/m3 (about 2800 ppm) (30-min exposure) (2,8,17)
LC50 (rat): 302 ppm (8-hr exposure) (2,10)
LC50 (rat): 50 mg/m3 (about 13 ppm) (24-hr exposure) (2)
LC50 (mouse): 4.68 mg/L (about 1170 ppm) (1-hr exposure) (1,11,17)
LC50 (mouse): 1540 mg/m3 (393 ppm) (2-hr exposure) (17)
LD50 (oral, rat): 214 mg/kg (2,17)

SHORT-TERM INHALATION STUDIES: Male and female mice were exposed by inhalation for 6 hours per day, 5 days per week to methyl bromide at doses of 0-200 ppm for 2 weeks. Only 4 female mice and 1 male survived 10exposures at 200 ppm. No deaths occurred at lower doses. Neurobehavioural effects including trembling and paralysis, occurred in all groups, but were most pronounced at doses of 50, 100 and 200 ppm. Red urine was observed in the mice exposed to 200 ppm.(21)
Groups of male and female mice were exposed for 6 hours per day, 5 days per week to doses of methyl bromide up to 120 ppm for 13 weeks. The mean body weight of mice exposed to 120 ppm was significantly reduced.(21)

LONG-TERM INHALATION: Groups of rats and mice were exposed to methyl bromide for 6 hours per day, 5 days per week for 6 weeks at a dose of 160 ppm. Mortality rates exceeded 50% in the male mice after 8 exposures, in female mice after 6 exposures and male rats after 14 exposures. Only female rats survived 30 exposures with less than 50% mortality. Lesions occurred in the kidney, brain, testes, heart, nasal cavity, adrenal glands, liver, spleen or thymus of rats and/or mice. Nephrosis (kidney damage) was probably the major cause of death of mice, whereas neuronal necrosis (destruction of nerve cells) may have been the principal cause of early death of some rats.(21)
Rats, rabbits and guinea pigs were exposed for 7.5-8 hours/day, 5 days/week for up to 6 months to methyl bromide at 65, 130, 250, 420 and 850 mg/m3.
Increased mortality occurred early in the study at concentrations of 130 mg/m3 (34 ppm) (rabbits) and 420 mg/m3 (108 ppm) (rats and guinea pigs).
Surviving animals exhibited signs of severe injury to the nervous system such as paralysis of the legs, hyperexcitability and convulsions. These signs were also seen in monkeys exposed at 250 mg/m3. Lung, liver and kidney damage were observed in high-dose animals (2).
Groups of male and female mice were exposed to methyl bromide at doses of 0, 10, 33 or 100 ppm for 6 hours per day, 5 days per week for up to 103 weeks. 27 males and 7 females exposed to 100 ppm died by 20 weeks.
Exposure was discontinued in this dose group. Clinical signs of neurotoxicity including tremours, abnormal posture, tachypnea and hind leg paralysis persisted in this high dose group. Neurobehavioural changes occurred in this dose group. These animals were less active and exhibited a heightened sensitivity in the startle response. Mean body weight of survivors of the 100 ppm group was markedly lower. Methyl bromide was not carcinogenic under these conditions. However there was an increase in the incidence of several non-neoplastic lesions in the brain, heart, bone (sternum) and nose, in the group exposed to 100 ppm.(21)

CARCINOGENICITY: The International Agency for Research on Cancer (IARC)has determined there is limited evidence for the carcinogenicity of methyl bromide to experimental animals.(24)
In one 13-week study, oral administration of 50 mg/kg methyl bromide in oil produced forestomach cancer. In a follow-up study, 50 mg/kg was administered in oil for 13, 17, 21 or 25 weeks. Other groups were administered methyl bromide for 13, 17 or 21 weeks and then observed for up to 25 weeks. An oil control group was used. Increased cell growth was observed in the forestomachs in all treated groups, but this effect regressed by 25 weeks in the groups that were followed-up.(24)
No significant increase in tumours was observed in two inhalation studies with mice (exposures of up to 100 ppm for up to 103 weeks or up to 64 ppm for 104 weeks). In one inhalation study with rats, an increase in the incidence of pituitary gland tumours was observed in the high dose group (100 ppm for 104 weeks). In another rat inhalation study, no increase in tumour incidence was observed at concentrations up to 90 ppm for 29 months.(21,24)

TERATOGENICITY AND EMBRYOTOXICITY: Methyl bromide did not cause birth defects or fetotoxicity in rats or rabbits which were exposed daily by inhalation at 20 or 70 ppm during gestation or prior to breeding (rats only). High-dose rats and rabbits showed maternal toxicity (2).

MUTAGENICITY: Methyl bromide is considered mutagenic based on positive results observed in rats and mice exposed by inhalation.
Positive results (micronuclei induction and sister chromatid exchanges in bone marrow and red blood cells) have been obtained in studies using rats and mice exposed by inhalation for 14 days. Negative results were obtained following exposure for 4, 8 or 12 weeks.(21) Another poorly reported study has also shown positive results in the somatic cells of live animals.(21,24) Negative results were obtained in studies examining the reproductive cells (sperm abnormalities and a dominant lethal test) of rats exposed by inhalation.(21,25)
Positive and negative results have also been obtained in studies using bacteria, cultured mammalian cells and fruit flies.(21,24,25)


Selected Bibliography:
(1) Documentation of the threshold limit values and biological exposure indices. 6th ed. Vol. II. ACGIH, 1991. p. 945-948
(2) IARC Monographs on the evaluation of the carcinogenic risk of chemicals to humans. Vol. 41. IARC, 1986. p. 187-212
(3) NIOSH pocket guide to chemical hazards. NIOSH, June 1994. p. 200-201
(4) Patty's industrial hygiene and toxicology. 3rd rev. ed. Vol. 2B. John Wiley & Sons, 1982. p. 3433-3436, 3442-3446, 3586-3601
(5) Gosselin, R.E., et al. Clinical toxicology of commercial products. 5th ed. Williams & Wilkins, 1984. p. III-280 - III-284, II-158
(6) Merck Index. 10th ed. 1983. p. 865
(7) Sittig, M. Handbook of toxic and hazardous chemicals and carcinogens. 2nd ed. Noyes Publications, 1985. p. 587-588
(8) NIOSH Current intelligence bulletin 43 : monohalomethanes : methyl chloride, methyl bromide, methyl iodide. National Institute for Occupational Safety and Health, Sept. 27, 1984
(9) Zwaveling, J.H., et al. Exposure of the skin to methyl bromide : a study of six cases occupationally exposed to high concentrations during fumigation. Human Toxicol. Vol. 6 (1987). p. 491-495
(10) Honma, T., et al. Neurotoxicity and metabolism of methyl bromide in rats. Toxicology and Applied Pharmacology. Vol. 81 (1985). p. 183-191
(11) Alexeeff, G.V., et al. Determination of acute toxic effects in mice following exposure to methyl bromide. Journal of Toxicology and Environmental Health. Vol. 15 (1985). p. 109-123
(12) Moriya, M., et al. Further mutagenicity studies on pesticides in bacterial reversion assay systems. Mutation Research. Vol. 116 (1983). p. 185-216
(13) Kramers, P.G.N., et al. Mutagenicity of methyl bromide in a series of short-term tests. Mutation Research. Vol. 155 (1985). p. 41-47
(14) Voogd, C.E., et al. Genotoxicity of methylbromide in short-term assay systems. Mutation Research. Vol. 97, no. 3 (June 1982). p. 233
(15) NACE Basic corrosion course. National Association of Corrosion Engineers, Dec. 1974. p. 122-123
(16) Forsberg, K., et al. Quick selection guide to chemical protective clothing. 4th ed. Van Nostrand Reinhold, 2002
(17) Methyl bromide : chemical hazard information profile (draft report). U.S. Environmental Protection Agency, Feb. 20, 1985
(18) Fumigation using methyl bromide (bromomethane) : guidance note GS 1. Health and Safety Executive, Sept. 1977
(19) Braker, W., et al. Matheson gas data book. 6th ed. Matheson, 1980. p. 456-460
(20) Neurotoxicity of industrial and commercial chemicals. Vol. II. CRC Press, 1985. p. 99, 102-107
(21) NTP technical report on the toxicology and carcinogenesis of methyl bromide (CAS no. 74-83-9) in B6C3F1 mice (inhalation studies). (NIH publication no. 92-2840). US Department of Health and Human Services, March, 1992
(22) Fire protection guide to hazardous materials. 13th ed. Edited by A.B. Spencer, et al. National Fire Protection Association, 2002. NFPA 325; NFPA 49; NFPA 491
(23) European Economic Community. Commission Directive 94/69/EC. December 19, 1994
(24) International Agency for Research on Cancer (IARC). IARC monographs on the evaluation of carcinogenic risks to humans. Vol. 71. Re-evaluation of some organic chemicals, hydrazine and hydrogen peroxide. Parts 1-3. World Health Organization, 1999
(25) International Programme on Chemical Safety (IPCS). Methyl bromide. Environmental Health Criteria 166. World Health Organization, 1995
(26) European Communities (EC). Commission Directive 2001/59/EC. Aug. 6, 2001

Information on chemicals reviewed in the CHEMINFO database is drawn from a number of publicly available sources. A list of general references used to compile CHEMINFO records is available in the database Help.

Review/Preparation Date: 1992-11-30

Revision Indicators:
Trans PEL-C 1993-04-01
Trans PEL comments 1993-04-01
Sampling 1996-01-01
EU safety 1996-01-01
EU number 1996-01-01
Respiratory guidelines 1996-01-01
TLV-TWA 1997-09-01
US transport 1998-03-01
TLV comments 1998-08-01
Carcinogenicity 2000-03-01
Mutagenicity 2000-03-01
Toxicological ifno 2000-03-01
WHMIS (detailed class) 2000-03-01
ERPG 2001-03-01
EU risks 2002-03-13
TDG 2002-05-22
Extinguishing media 2003-03-08
Bibliography 2003-03-08
Personal hygiene 2003-05-05
TLV basis 2003-08-01
PEL transitional comments 2003-10-14
PEL-C transitional 2003-10-14
Resistance of materials for PPE 2004-03-15
EU classification 2005-10-24
EU risks 2005-10-24
Relative density 2006-09-28

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