WORLD HEALTH ORGANIZATION FOOD AND AGRICULTURE
ORGANIZATION
ORGANISATION MONDIALE DE LA SANTE ORGANISATION POUR L'ALIMENTATION
ET L'AGRICULTURE
VBC/DS/75.5 (Rev.1)
ORIGINAL: ENGLISH
DATA SHEETS ON PESTICIDES No. 5 Rev.1
METHYL BROMIDE
CLASSIFICATION:
Primary use: Insecticidal fumigant
Secondary use: Acaricide, fungicide,
nematocide, rodenticide
Chemical group: Alkyl halide
Data sheet No. 5 (Rev.1) August 1978
It must be noted that the issue of a Data Sheet for a
particular pesticide does not imply endorsement of the pesticide by
WHO or FAO for any particular use, or exclude its use for other
purposes not stated. While the information provided is believed to
be accurate according to data available at the time when the sheet
was compiled, neither WHO nor FAO are responsible for any errors or
omissions, or any consequences therefrom.
The issue of this document does Ce document ne constitue pas une
not constitute formal publication. Il ne doit faire
publication. It should not be l'objet d'aucun compte rendu ou
reviewed, abstracted or quoted résumé ni d'aucune citation sans
without the agreement of the l'autorisation de l'Organisation
Food and Agriculture des Nations Unies pour
Organization of the United l'Alimentation et l'Agriculture
Nations or of the World Health ou de l'Organisation Mondiale de
Organization. la Santé.
1. GENERAL INFORMATION
1.1 COMMON NAME: No common name. Methyl bromide is the chemical
name.
1.1.1 Identity: Methyl bromide
CH3Br
1.1.2 Synonyms: Monobromomethane bromomethane
Local synonyms:
1.2 SYNOPSIS - A powerful fumigant gas which is one of the most toxic
of the common organichalides. In massive dosage, it is narcotic
like a halogenated hydrocarbon solvent. It has a characteristic
delayed neurotoxic action.
1.3 SELECTED PROPERTIES
1.3.1 Physical characteristics - A colourless gas at room temperature
with a slightly sweet odour, b.p. 4.5°C.
1.3.2 Solubility - Water, 3.4 g/l at 25°C. Freely soluble in alcohol.
Soluble in most organic solvents.
1.3.3 Stability - Stable in air; non-inflammable and non-corrosive.
In cold water it forms a dense white precipitate of the hydrate.
It must be noted that the issue of a Data Sheet for a particular
pesticide does not imply endorsement of the pesticide by WHO or FAO for
any particular use, or exclude its use for other purposes not stated.
While the information provided is believed to be accurate according to
data available at the time when the sheet was compiled, neither WHO nor
FAO are responsible for any errors or omissions, or any consequences
therefrom.
R 683 - 1185
The issue of this document does not constitute formal publication.
It should not be reviewed, abstracted or quoted without the
agreement of the Food and Agriculture Organization of the
United Nations or of the World Health Organization.
Ce document ne constitue pas une publication. Il ne doit faire l'objet
d'aucun compte rendu ou résumé ni d'aucune citation sans l'autorisation
de l'Organisation des Nations Unies pour l'Alimentation et
l'Agriculture ou de l'Organisation Mondiale de la Santé.
1.3.4 Vapour pressure (volatility) 2435 kla at 25°C.
1.4 AGRICULTURE, HORTICULTURE AND FORESTRY
1.4.1 Common formulations - Liquid, alone or with 2 g/l chloropicrin as
warning indicator. Sometimes formulated as a mixture with
ethylene dibromide or carbon tetrachloride. There is an FAO
specification for the technical product.
1.4.2 Susceptible pests - A very wide range of pests including most
insects and mites, nematodes, weeds, fungi and rodents.
1.4.3 Use pattern - Used for fumigation of all types of stored dry
foodstuffs, particularly produce in bags and packages, and of
clothing, furniture and timber. Used for treatment of soil
before sowing, especially in glasshouses, to control nematodes,
insects, weeds, and fungi. Used in plant quarantine on seeds and
plants, including fresh fruit and vegetables.
1.4.4 Unintended effects - Phytotoxic, particularly to growing plants,
but safe under normal conditions of use. Its use on seed may
cause phytotoxicity if the recommended application rate is
exceeded.
1.5 PUBLIC HEALTH PROGRAMMES - None.
1.6 HOUSEHOLD USE - Methyl bromide is too dangerous for household use
in the ordinary sense. Specially trained and licensed pest
control operators may fumigate houses after they have been
vacated and sealed and after suitable warning signs have been
posed. On rugs, furniture and clothing at 16-24 g/m3, 12-24
hours exposure at 16-21°C the following may be controlled: carpet
beetles, clothes-moths, silverfish, fleas, roaches. Furs,
feathers, leather and rubber articles should not be fumigated
with methyl bromide.
2. TOXICOLOGY AND RISKS
2.1 TOXICOLOGY - MAMMALS
2.1.1 Absorption route - Absorbed in the lungs or if taken in solution
orally by the gastrointestinal tract. The extent to which it
might be absorbed by the skin under severe conditions of exposure
is unclear. However, under ordinary conditions of exposure, skin
exposure is insignificant, and a suitable respirator or mask is
protective.
2.1.2 Mode of action - A neurotoxic and narcotic agent with a
characteristic delayed action. It acts by combining with the
sulfhydryl group of proteins and enzymes.
2.1.3 Excretion products - Appears to be broken down and excreted as
inorganic bromide in the urine. It is also excreted via the
lungs. After exposure to methyl bromide, volatile bromide,
presumably unchanged methyl bromide, is stored in the tissues,
particularly those tissues which are rich in lipoidal material.
2.1.4 Toxicity, single dose
Oral: LD50 rat: <100 mg/kg
Inhalation: LC50 (15 minutes): rat 21 000 mg/m3
Most susceptible species: Not known
2.1.5 Toxicity, repeated doses:
Oral: No information.
Inhalation: Guinea-pigs tolerated six hour exposures to 780
mg/m3 or 10 hours exposure to 390 mg/m3. Rats, monkeys and
guinea-pigs tolerated seven to eight hour daily exposures to 130
mg/m3 for many months without overt effects. Rabbits showed
lung irritation at this level but were unaffected by 65 mg/m3.
Cumulation of compound: The compound is cumulative upon
repeated exposure. After absorption bromine is widely
distributed in body tissues and is stored in lipoidal tissue.
2.1.6 Dietary studies
Short-term: No information.
Long-term: No information.
2.1.7 Supplementary studies of toxicity: No information.
2.1.8 Modification of toxicity: There are a considerable number of
studies on the toxicity of foodstuffs which have been fumigated
with methyl bromide. Since, in these foodstuffs, the amount of
unchanged methyl bromide is very low the studies are of no use in
assessing the toxicity of methyl bromide per se.
2.2 TOXICOLOGY - MAN
2.2.1 Absorption - See 2.1.1. Inhalation is the important route of
absorption, with this compound.
2.2.2 Dangerous doses
Oral: No information.
Inhalation: Concentrations of about 400 mg/m3 are definitely
toxic and fatalities have occurred from exposures to 1200 mg/m3
and above. Information is lacking on the duration of exposure in
these cases. An exposure level of 31 000 mg/m3 for "a few
hours" proved fatal.
2.2.3 Observations of occupationally exposed workers - Among 90 human
subjects industrially exposed to concentrations up to 140
mg/m3, 33 showed mild intoxication, 22 showed skin lesions.
There is no information on the duration of exposure.
2.2.4 Observations on exposure of the general population - Because of
the rapid breakdown to inorganic bromide after food is fumigated
with methyl bromide it is unlikely that the general population
will be exposed to methyl bromide.
2.2.5 Observations of volunteers - None.
2.2.6 Reported mishaps - In one location in the Americas the absolute
mortality to persons exposed to methyl bromide is reported to be
greater than that associated with any other agricultural
chemical.
Another report states that there are 56 isolated reports of
fatalities due to methyl bromide up to 1964. The majority
resulted from inhalation of leaking fire extinguishers or during
fumigation. There are also 179 reports of non-fatal methyl
bromide poisoning and it has been stated that the actual figure
is probably much higher.
In one mishap there were 34 cases of methyl bromide poisoning at
a date packing plant. The majority had neurological disturbances
involving vision, speech, tremors and numbness of the
extremities. There was a high incidence of mild mental confusion
and some hallucinosis. Depressive states lasted as long as five
months. Two cases, one of apathy and one neurosis were cited as
possibly permanent. No fatalities were reported. The
concentrations in the air were 400-2000 mg/m3. Numerous
similar cases are reported.
2.3 TOXICITY TO NON-MAMMALIAN SPECIES
2.3.1 Fish )
) Toxic to fish and birds but the conditions of use make it
2.3.2 Birds ) non-hazardous.
2.3.3 Other species - Toxic but generally no hazard owing to the
conditions of use. Pre-planting treatment of soil will kill
beneficial as well as harmful soil organisms.
3. FOR REGULATORY AUTHORITIES - RECOMMENDATIONS ON REGULATION OF
COMPOUND
3.1 RECOMMENDED RESTRICTIONS ON AVAILABILITY
(for-definition of categories see introduction)
All formulations, Category 3
3.2 TRANSPORTATION AND STORAGE
United Nations classification 2.0 and 6.1.
Should be transported and stored in conventional gas cylinders in
a cool and dry place protected against excessive heat. The
cylinders should be moved carefully and when not in use they
should be safeguarded by adequate holding Devices. They should
be inspected periodically for leaks by means of a halide detector
lamp. They should be stored under lock and key secure from
access by unauthorized persons and children. No food or drink
should be transported or stored in the same compartment.
3.3 HANDLING - Full protective clothing (see part 4) should be
provided for all handling of the compound. Adequate washing
facilities should be available at all times during handling and
should be close to the site of handling. Eating, drinking and
smoking should be prohibited during handling and before washing
after handling. In discharging the gas, the connecting lines to
the equipment should be strong enough to withstand the maximum
operating pressure and the valves should be opened slowly and
closed promptly after use. Areas in which methyl bromide is
handled routinely should be equipped with adequate exhaust
ventilation. Methyl bromide should not be used to fumigate a
house or part of a house unless the entire structure can be
vacated and marked with suitable warning signs.
3.4 DISPOSAL AND/OR DECONTAMINATION OF CONTAINERS - Not applicable -
empty containers should be re-used with methyl bromide.
3.5 SELECTION, TRAINING AND MEDICAL SUPERVISION OF WORKERS - Pre-
employment medical examination of workers recommended. Persons
suffering from pulmonary diseases, afflictions of the central
nervous system and from cardiovascular disturbances should be
excluded from operations where this material is handled. Special
account should be taken of the workers I mental ability to
comprehend and follow instructions. Training of workers in
techniques to avoid contact essential.
3.6 ADDITIONAL REGULATIONS RECOMMENDED IF DISTRIBUTED BY AIRCRAFT -
Not applicable.
3.7 LABELLING
Minimum cautionary statement
"POISON"
(Skull and crossbones insignia)
"This cylinder contains methyl bromide gas under pressure. The
gas is poisonous if inhaled and may be absorbed through the skin.
Wear protective gloves, clean protective clothing, goggles and a
respirator of the organic vapour type when handling this
material. Avoid any exposure to fumes. Wash hands and exposed
skin after handling and before eating and bathe immediately after
work.
Ensure that the cylinder is tightly sealed and stored and
disposed of in such a way as to prevent accidental contact with
the vapour. Keep the cylinder out of reach of children and well
away from foodstuffs, animal feed and their containers.
In case of contact immediately remove contaminated clothing and
wash the skin thoroughly with soap and water: for eyes flush with
water for 15 minutes. If poisoning occurs call a physician."
3.8 RESIDUES IN FOOD
3.8.1 Maximum residue levels - The Joint FAO/WHO meeting on Pesticide
Residues has recommended maxim= acceptable limits for unchanged
methyl bromide in some stored products at specific periods after
treatment. The Meeting has also recommended levels of inorganic
bromide, arising from the use of bromine-containing fumigants
such as methyl bromide or ethylene dibromide.
The Codex Alimentarius Commission has recommended international
tolerances for inorganic bromide designed to control the use of
bromine-containing fumigants such as methyl bromide and ethylene
dibromide.
4. PREVENTION OF POISONING IN MEN AND EMERGENCY AID
4.1 PRECAUTIONS IN USE
4.1.1 General - Methyl bromide is a powerful fumigant gas and is one of
the most toxic of the common organic halides. In massive dosage,
it is narcotic like a halogenated hydrocarbon solvent. It has a
characteristic delayed neurotoxic action. It should only be
handled by trained personnel wearing protective clothing.
4.1.2 Manufacture and formulation
T.L.V.: ACGIH 60 mg/m3: USSR 1 mg/m3. Closed systems and
forced ventilation are required to reduce as much as possible the
exposure of workers to the chemical. It is recommended that a
small amount of chloropicrin be added to the gas in order to
enable persons to detect leaks and to prevent careless over-
exposure.
4.1.3 Applicators - When discharging the gas, workers should wear high
top safety shoes, woollen outer clothing, suitable gas-tight
goggles and a respirator. Leather or rubber gloves should not be
worn since they are permeable to methyl bromide and will enhance
injury of the skin because they interfere with evaporation and
thus prolong the contact. Particular care is needed when the
equipment is being washed after use. All protective clothing
should be washed immediately after use, and placed outdoors.
Splashes of the liquefied gas should be washed immediately from
the skin or eyes with large quantities of water. Before eating,
drinking or smoking, hands and other exposed skin should be
washed. Until a treated area has been ventilated and found
satisfactory by means of a suitable detector, it must not be
entered, except by trained persons wearing appropriate
respirators or masks.
4.1.4 Other associated workers (including flagmen in aerial operations)
- Not applicable.
4.1.5 Other populations likely to be affected - With good agricultural
and manufacturing practices subject to 4.2 below, other
populations should not be exposed to hazardous levels of
unchanged methyl bromide.
4.2 ENTRY OF PERSON INTO TREATED AREAS - With adequate ventilation
after use unprotected persons should be able to safely enter
treated areas after three days.
4.3 SAFE DISPOSAL OF CONTAINERS AND SPILLAGE - Containers which are
gas cylinders should be emptied during use and returned to the
manufacturer to be refilled with methyl bromide. They should not
be used for any other purpose.
Spills of methyl bromide should be mopped up promptly with an
alkaline solution and the rags used for the purpose should be
placed outdoors.
4.4 EMERGENCY AID
4.4.1 Early symptoms of poisoning - Onset of symptoms is delayed with a
latent period of one half to 48 hours after acute exposure.
Early symptoms are malaise, headache, nausea, vomiting, visual
disturbances and sometimes pulmonary oedema. Later there may be
tremors giving way to violent convulsions.
4.4.2 Treatment before person is seen by a physician, if these symptoms
appear following exposure - The person should stop work and
should move or be moved away from the gas into fresh air. All
soiled garments should be removed at once and placed outdoors.
The skin should be washed with soap and water and if necessary
the eyes should be irrigated with lukewarm water. The person
should be kept at rest until the physician arrives. If the
person stops breathing artificial respiration should be applied.
5. FOR MEDICAL AND LABORATORY PERSONNEL
5.1 MEDICAL DIAGNOSIS AND TREATMENT OF CASES OF POISONING
5.1.1 General information - A powerful fumigant gas which is one of the
most toxic of the common organic halides. In massive dosage, it
is narcotic like a halogenated hydrocarbon solvent. It has a
characteristic delayed neurotoxic effect. It acts by combining
with the sulfhydryl groups of proteins and enzymes. It appears
to be broken down and excreted as inorganic bromine in the urine.
It is also excreted via the lungs. After exposure to methyl
bromide, bromine-containing compounds are stored in the tissues
particularly those tissues which are rich in lipoidal material.
5.1.2 Symptoms and signs - Onset of symptoms is delayed with a latent
period of one half to 48 hours after acute exposure. Early
symptoms are malaise, headache, nausea, vomiting, visual
disturbances and sometimes pulmonary oedema. Late after initial
symptoms tremors occur giving way to violent convulsions
continuing until death which occurs primarily from respiratory
failure because of poor oxygenation of blood due to lung oedema
plus failure of the respiratory centres of the central nervous
system. Chronic intoxication involves visual, speech, gait and
mental process disturbances; complex neurological abnormalities
and syndromes may occur, the abnormalities being persistent and
sometimes permanently incapacitating. Skin lesions may also
appear upon exposure to high concentrations.
5.1.3 Laboratory - Blood levels of bromide following poisoning from
methyl bromide are much lower than that found from poisoning from
inorganic bromide, see 5.2 Surveillance methods.
5.1.4 Treatment - The person should discontinue exposure and be
transferred to fresh air. All soiled garments should be removed
and the skin cleaned with soap and water. Barbiturates
(preferably phenobarbitone or pentobarbitone) should be given
I.M. or I.V. in sufficient dosage to control restlessness or
convulsions. Respiratory assistance with oxygen may be required.
When signs and symptoms of pulmonary oedema develop the oxygen
should be given against a pressure of 3-4 cm of water by
immersing the exhalation tube into water to this extent. In
cases of frank pulmonary oedema venesection may be indicated. If
the liver is enlarged or the patient complains of epigastric pain
glucose solution may be administered intravenously but only if
there is no danger of pulmonary oedema. Epinephrine may also be
used subcutaneously for bronchospasm. If methyl bromide in
liquid form or in high concentrations comes into contact with the
eyes these should be irrigated with lukewarm water for 15
minutes. Skin lesions should be bathed in sodium bicarbonate
solutions and blisters should be treated as second degree thermal
burns.
5.1.5 Prognosis - Even moderate poisoning may lead to prolonged illness
and if more severe, possibly to permanent injury. In one case
neurological abnormalities persisted after one year.
5.1.6 References of previously reported cases - Cases of poisoning and
methods of treatment are documented in: Von Oettingen, W. F. "The
Halogenated Hydrocarbons of Industrial and Toxicological
Importance". Elsevier Monographs on Toxic Agents, Browning, E.,
ed., Chapter 3, Methyl Bromide, pp. 25-55. Elsevier, Amsterdam,
London, New York 1964. Rathus, E. M. & Landy, P. J. (1961)
Brit. J. Industr. Med., 18, 53-57. Hine, C. H. (1969) J.
Occup. Med., 11, 1-10.
5.2 SURVEILLANCE METHODS - There are no readily available techniques
to determine the degree of absorption prior to the appearance of
symptoms. Blood levels of bromide ion are indicative of
absorption but there appears to be no definite relationship
between the bromide level in the blood and the seriousness of the
poisoning. It has been suggested that values of bromide ion in
blood of 50 mg/l and above are indicative of potentially
hazardous exposure. However the presence of bromide ion is non-
specific as to its source and the opportunity for methyl bromide
inhalation must be unquestionable.
5.3 LABORATORY METHODS - References only are given.
5.3.1 Detection and analysis - For levels in air of 200 mg,/m3 or
higher the halide lamp may be used. See Dudley, H. C., Miller,
J. W., Neal, P. A. & Sayers, R. R. (1940) Publ. Hlth Rep.,
55, 2251. For lower levels see Kaye, K., Braid, P. E. &
Doherty, T. H. (1949) Industr. Hyg. Rev., 1, 3, and Berck,
B. (1965) J. Agr. Fd. Chem., 13, 373-377.
Residues of methyl bromide in foodstuffs can be determined by the
gas-chromatographic method of Heuser & Scudamore (1969). A later
modification (Heuser & Scudamore, 1970) allows the determination
of methyl bromide and inorganic bromide separately in the same
sample.
Bromide ion in biological samples can be determined by the method
of Castro (1964), based on that of Mapes & Schrader (1957).
5.3.2 Other tests in cases of poisoning - None.
REFERENCES
Heuser, S. G. & Scudamore, K. A. (1969) Determination of fumigant
residues in cereals and other foodstuffs: a multi-detection
scheme for gas chromatography of solvent extracts, J. Sci. Fd
Agric., 20, 566
Heuser, S. G. & Scudamore, K. A. (1970) Selective determination of
ionised bromide and organic bromides in foodstuffs by gas-liquid
chromatography with special reference to fumigant residues,
Pestic. Sci., 1, 244
Castro, C. E. (1964) In: Zweig, G., ed., Analytical methods for
pesticides, plant growth regulators and food additives, New
York
and London, Academic Press, vol. III, p. 161
Mapes, D. A. & Schrader, S. A. (1957) Determination of total and
inorganic bromide residues in fumigated products, J. Assoc. Off.
Agr. Chem., 40, 189