IPCS
Health and Safety Guide No. 86
METHYL BROMIDE
(BROMOMETHANE)
HEALTH AND SAFETY
GUIDE
This is a companion volume to
Environmental Health Criteria 166: Methyl Bromide (Bromomethane)
Published by the World Health Organization for the International
Programme on Chemical Safety (a collaborative programme of the United
Nations Environment Programme, the International Labour Organisation,
and the World Health Organization)
WORLD HEALTH ORGANIZATION, GENEVA 1994
This report contains the collective views of an international group of
experts and does not necessarily represent the decisions or the stated
policy ofthe United Nations Environment Programme, the International
Labour Organisation, or the World Health Organization
WHO Library Cataloguing in Publication Data
Methyl bromide (bromomethane) : health and safety guide. (Health and
safety guide ; no. 86)
1.Hydrocarbons, Brominated - standards 2.Environmental exposure
I.Series
ISBN 92 4 151086 2 (NLM Classification: WA 240)
ISSN 0259-7268
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© World Health Organization 1994
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The Federal Minister for the Environment, Nature Conservation and
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Printed by Wissenschaftliche Verlagsgesellschaft mbH D-70009 Stuttgart 10
CONTENTS
INTRODUCTION...........................................
1. PRODUCT IDENTITY AND USES...........................
1.1 Identity.........................................
1.2 Physical and chemical properties.................
1.2.1 Chemical properties........................
1.3 Analytical methods...............................
1.4 Production and uses..............................
2. SUMMARY AND EVALUATION..............................
2.1 Human exposure to methyl bromide.................
2.2 Uptake, metabolism, and excretion................
2.3 Effects on organisms in the environment..........
2.4 Effects on experimental animals and
in vitro test systems............................
2.5 Effects on humans................................
3. CONCLUSIONS AND RECOMMENDATIONS.....................
4. HUMAN HEALTH HAZARDS, PREVENTION
AND PROTECTION, EMERGENCY ACTION....................
4.1 Human health hazards, prevention and
protection, first aid............................
4.1.1 Information for physicians.................
4.1.1.1 Symptoms of poisoning................
4.1.1.2 Emergency and first aid procedures...
4.1.1.3 Poisons information..................
4.1.2 Health surveillance advice.................
4.1.3 Protection.................................
4.1.3.1 Protection of workers and fumigators.
4.1.3.2 Protection of the general public.....
4.2 Explosion and fire hazards.......................
4.2.1 Explosion hazards..........................
4.2.2 Fire-fighting procedures...................
4.3 Storage..........................................
4.3.1 Cylinder specifications....................
4.3.2 Reactivity.................................
4.3.3 Precautions for handling and storage.......
4.4 Transport........................................
4.5 Spillage.........................................
4.6 Disposal.........................................
5. HAZARDS FOR THE ENVIRONMENT AND THEIR
PREVENTION..........................................
6. SUMMARY OF CHEMICAL SAFETY INFORMATION..............
7. CURRENT REGULATIONS, GUIDELINES, AND
STANDARDS...........................................
7.1 Previous evaluations by intemational bodies......
7.2 Exposure limits..................................
7.3 Specific restrictions............................
7.3.1 Type of crop, method of fumigation, dosage
restrictions, covering and leaching........
regulations
7.3.2 Restrictions on personnel..................
7.4 Labelling, packaging, and transport..............
7.4.1 Labelling..................................
7.4.2 Packaging..................................
7.4.3 Transport..................................
BIBLIOGRAPHY...........................................
INTRODUCTION
The Environmental Health Criteria (EHC) monographs produced by the
International Programme on Chemical Safety include an assessment of the
effects on the environment and on human health of exposure to a
chemical or combination of chemicals, or physical or biological agents.
They also provide guidelines for setting exposure limits.
The purpose of a Health and Safety Guide is to facilitate the
application of these guidelines in national chemical safety programmes.
The first three sections of a Health and Safety Guide highlight the
relevant technical information in the corresponding EHC. Section 4
includes advice on preventive and protective measures and emergency
action; health workers should be thoroughly familiar with the medical
information to ensure that they can act efficiently in an emergency.
Within the Guide is a Summary of Chemical Safety Information which
should be readily available, and should be clearly explained, to all
who could come into contact with the chemical. The section on
regulatory information has been extracted from the legal file of the
International Register of Potentially Toxic Chemicals (IRPTC) and from
other United Nations sources.
The target readership includes occupational health services, those in
ministries, governmental agencies, industry, and trade unions who are
involved in the safe use of chemicals and the avoidance of
environmental health hazards, and those wanting more information on
this topic. An attempt has been made to use only terms that will be
familiar to the intended user. However, sections 1 and 2 inevitably
contain some technical terms. A bibliography has been included for
readers who require further background information.
Revision of the information in this Guide will take place in due
course, and the eventual aim is to use standardized terminology.
Comments on any difficulties encountered in using the Guide would be
very helpful and should be addressed to:
The Director
International Programme on Chemical Safety
World Health Organization
1211 Geneva 27
Switzerland
THE INFORMATION IN THIS GUIDE
SHOULD BE CONSIDERED AS A
STARTING POINT TO A COMPREHENSIVE
HEALTH AND SAFETY PROGRAMME
1. PRODUCT IDENTITY AND USES
1.1 Identity
Common name: methyl bromide
Chemical formula: CH3Br
Chemical structure:
Figure 1;;;grph86_1.bmp
Relative molecular
mass: 94.94
CAS name: bromomethane
CAS registry No.: 74-83-9
EEC No. 602-002-00-2
EINECS No. 200-813-2
Synonyms: monobromomethane
Methyl bromide is typically available as a liquefied gas. It is
marketed under a variety of trade names with formulations containing
between 30 and 100 % of the compound. Formulations include mixtures
with other fumigants, mostly with chloropicrin or ethylene dibromide,
or hydrocarbons, as inert diluents. Chloropicrin (2 %) or amyl acetate
(0.3 %) is often added to serve as a sensory warning agent.
Chloropicrin is itself a toxic chemical with a noxious odour and
irritating effects at low temperatures. Only 100 % methyl bromide can
be used for commodity fumigation.
1.2 Physical and Chemical Properties
Methyl bromide is a colourless gas at room temperature and pressure.
It is odourless, except in relatively high concentrations when it has a
chloroform-like smell. The gas is heavier than air and has the ability
to penetrate many substances, including usually impermeable materials,
such as concrete, leather, and rubber. Methyl bromide is able to
diffuse through certain plastics; permeation through low density
polyethylene (LDPE) is 8 times higher than through high density
polyethylene (HDPE). However, methyl bromide does not permeate through
PVC. Metal piping is also impervious.
As a liquid, methyl bromide has a solvent action on many plastics and
organic materials. Natural rubber is attacked and acquires a strong,
unpleasant smell.
The physical properties of methyl bromide are summarized in section 6.
1.2.1 Chemical properties
Methyl bromide hydrolyses slowly to form methanol and hydrobromic acid
in aqueous solution but more rapidly in dilute alkali. It is an
effective methylating agent reacting with amines, particularly the more
basic ones, to form methylammonium bromide derivatives. Methyl bromide
also reacts with sulfur compounds under alkaline conditions to give
mercaptans, thioethers, and disulfides. Most structural metals, other
than aluminium, are inert towards pure, dry methyl bromide, but surface
reactions take place on zinc, tin, and magnesium in the presence of
impurities, such as alcohol or moisture. Explosions with aluminium and
with dimethyl sulfoxide have been reported.
Methyl bromide is not considered to be flammable. However, it will
burn in air in the presence of a high energy source of ignition, within
a narrow flammability concentration range (9-20%). Methyl bromide has
no flash point. Thermal decomposition begins above 400 °C. The
products include hydrogen bromide, bromine, carbon oxybromide, carbon
dioxide, and carbon monoxide.
1.3 Analytical Methods
Methyl bromide can be analysed using gas chromatography with electron-
capture detection, and mass spectrophotometry for confirmation
purposes. Purge and trap techniques or headspace sampling methods are
used.
Bromide ion formed from methyl bromide during fumigation can be
detected using X-ray spectroscopy, potientiometry, thiosulfate
titration and gas/liquid chromatography.
1.4 Production and Uses
The world consumption of methyl bromide was over 67 million kg in 1990.
The distribution of principal uses is:
soil (pre-planting) fumigation 77 %
quarantine and commodity fumigation 12 %
structural fumigation 5 %
chemical intermediates 6 %
Since 1960, the major use of methyl bromide has been as a fumigant,
either pre-planting in glasshouses or in the open as a soil fumigant
for the control of nematodes, fungi, insects, weeds, weed seeds, and
soil-borne diseases. It is also used as a post-harvest fumigant to
eradicate pests in mills and warehouses. A wide range of stored
foodstuffs and other products, such as tobacco and to a more limited
extent fresh fruit and vegetables, are fumigated with methyl bromide to
meet quarantine requirements. In some countries, the use of methyl
bromide for quarantine is obligatory.
The use of methyl bromide as a soil fumigant is restricted in some
countries.
Methyl bromide is also used to fumigate buildings, furniture, books,
and archival material.
In the chemical industry, methyl bromide is used primarily as a
methylating agent.
2. SUMMARY AND EVALUATION
2.1 Human Exposure to Methyl Bromide
Human exposure to methyl bromide (through inhalation and skin contact)
is predominantly occupational, particularly during soil or bulk
fumigation, but also during manufacture. However, methyl bromide is a
regulated chemical and there are strict regulations concerning its use
as a fumigant.
Individuals in the vicinity of fumigated fields or buildings may also
be exposed to methyl bromide as well as those who, unaware of the
hazard, enter premises being fumigated. Methyl bromide is odourless at
concentrations usually used. Some formulations contain 2 %
chloropicrin (lacrimation) or 0.3 % amyl acetate (smell) as a warning
agent, but this does not always provide sufficient warning.
Methyl bromide is used extensively for the post-harvest fumigation of
foods, such as cereals, spices, dried fruits, nuts, fresh fruits, and
vegetables. Levels in the food commodities usually decrease rapidly
after aeration, but may be detected for some weeks after the treatment.
Fumigation with methyl bromide or the growing of crops on methyl
bromide-treated soil increases the inorganic bromide content of food
commodities. Adherence to methyl bromide application dosage standards
ensures that the bromide levels do not exceed recommended limits.
Exposure to methyl bromide is also possible through drinking water from
wells contaminated with leaching water.
2.2 Uptake, Metabolism, and Excretion
The results of inhalation studies on rats, beagles, and humans have
shown that methyl bromide is rapidly absorbed through the lungs. It is
also rapidly absorbed in rats following oral administration.
After absorption, methyl bromide or its metabolites are rapidly
distributed to many tissues including the lungs, adrenal glands,
kidneys, liver, nasal turbinates, brain, testes, and adipose tissue.
In a rat inhalation study, the methyl bromide concentration in tissues
reached a maximum 1 h after exposure, but then decreased rapidly with
no traces 48 h later. The metabolism of methyl bromide has not been
elucidated, though glutathione may play a role.
Methylation of proteins and lipids has been observed in tissues from
several species, including humans, exposed via inhalation. Methylated
DNA adducts have also been detected following in vivo and in vitro
exposure of rodents or rodent cells.
In inhalation studies using [14C]-labelled methyl bromide, exhalation
of 14C02 was the major route of elimination of 14C. A lesser amount of
14C was excreted in the urine. Following oral administration of methyl
bromide, urinary excretion was the major route of elimination of 14C.
The central nervous system is an important target for methyl bromide.
Changes in monoamine, amino acid contents and possibly catecholamine
contents may be factors involved in methyl bromide-induced
neurotoxicity.
2.3 Effects on Organisms in the Environment
Methyl bromide is used as a fungicide, partial bactericide, nematocide,
insecticide, herbicide, and rodenticide.
In soil, about 50% of methyl bromide is degraded by hydrolysis and
microbial activity. The remainder eventually dissipates into the
atmosphere. The principal degradation product is inorganic bromide,
which remains as a residue in soil. Some bromide may be leached out
into water or taken up by plants.
Soil fumigation using methyl bromide (with 2% chloropicrin) affects
both target and non-target organisms: various soil microflora and fauna
are adversely affected, at least temporarily, by fumigation. High
mortality of non-target insects bas been noticed following fumigation
under plastic covers. Methyl bromide was detected in different soil
types up to 3 weeks after fumillation, the highest levels being found
in the upper layers (0-40 cm) of the soil.
Although methyl bromide is highly toxic for aquatic organisms, it is
generally of no risk to the aquatic environment. The lowest median
effect concentration (EC50) or median lethal concentration (LC50)
values reported are 2.8 mg/litre for algae, 1.7 mg/litre for daphnids,
and 0.3 mg/litre for fish. No-observed-effect concentrations (NOEC) in
long-term studies were low (0.06 mg/litre) for daphnids and fish.
Toxic concentrations are not expected to be reached under normal
circumstances, because most of the niethyl bromide applied on soil is
degraded or lost through evaporation before it reaches surface water
via run-off. In very special situations (intensive leaching of green-
house soils fumigated with methyl bromide to reduce the organic bromide
content), levels of methly bromide in the mg/litre range can occur in
water; concentrations of up to 9.3 mg methly bromide/litre have been
found in drainage water.
However, relatively high levels of bromide (up to 72 mg/litre) can be
found in the drainage water from greenhouses and could adversely affect
aquatic organisms. An EC50 value of 27 mg bromide/litre for daphnia
and a lowest NOEC for different fish species of 25 mg bromide/litre
were determined with long-term exposure to bromide ion.
Methyl bromide is often used in preference to other insecticides
because of its ability to penetrate quickly and deeply into bulk
materials and soils. Dosages for methyl bromide, as a storage
fumigant, range mostly from 16 to 100 g/m3 for 2-3 days, depending on
temperature. A higher dosage is required to kill eggs and pupae than
adult insects. There is a variation in tolerance between different
species and stages of insect and between different strains of the same
insect.
There are no data on the direct effects of methyl bromide on birds and
wild mammals.
2.4 Effects on Experimental Animals and in vitro Test Systems
Methyl bromide is very toxic for all animal species by all routes of
administration. Deaths from exposure follow a steep dose-response
curve. LC50 (1-h) values for mice and rats are 4680 and 7300 mg/m3,
respectively.
Deaths and neurotoxicity occur within hours or days after single
inhalation exposure to high concentrations. The results of studies on
mice show that more prolonged exposure at low concentrations (6 h/day;
389 mg/m3) may also produce neurotoxicity or deaths appearing after a
delay of several months.
The principal toxic effects associated with death occur in the brain
and kidney. Histopathology of the brain shows necrosis of granular
cells of the cerebellum in mice and rats and neuronal necrosis in the
cerebral cortex, hippocampus, and thalamus in rats. The lowest doses
at which these lesions were observed were 250 mg/m3 for 6 h/day, over 2
years, in mice, and, 622 mg/m3 for 6 h/day, over 5 weeks, in rats. In
the kidney, necrosis of the convoluted tubule epithelium occurred at
doses of 599 mg/m3 for 6 h/day, over 2 weeks, in mice, and 1712 mg/m3
for 6 h/day, over 2 weeks, in rats. Other effects are observed in the
heart (degeneration and focal necrosis), nose (necrosis of olfactory
epithelium), testis (degeneration of seminiferous tubules), and other
organs.
In non-lethal exposure, nasal irritation and neurotoxicity (including
histopathological lesions) are the major toxic effects.
No teratogenic effects have been observed in rats or rabbits. Embryo-
toxicity occurred in rats and rabbits only at doses that were
maternally toxic. In a rat multigeneration study, there were
reductions in the fertility index in the second generation when the
animals were exposed to 117 or 350 mg/m3 for 6 h/day (5 days/week, for
about 8 months), but the effects were not observed following exposure
to 12 mg/m3 for 6 h/day.
Methyl bromide was mutagenic in several in vivo and in vitro assays.
The results of long-term inhalation studies on rats and mice did not
demonstrate any evidence of carcinogenicity. Lesions originally
interpreted as carcinomas of the forestomach in rats following gavage
administration were shown to regress after termination of treatment.
2.5 Effects on Humans
Methyl bromide is well absorbed (50%) by humans via inhalation. It
damages the nervous system, lung, nasal mucosa, kidney, eye, and skin.
Central nervous system effects include blurred vision, mental
confusion, numbness, tremor, speech defects. Topical exposure can
cause skin irritation and burns, and eye injury.
Fatal poisoning results from exposure to relatively high concentrations
of methyl bromide vapour. Non-fatal poisoning has resulted from
exposure to concentrations as low as 389 mg/m3 (100 ppm).
Exposure to high concentrations of methyl bromide causes pulmonary
oedema. Central nervous system depression with respiratory paralysis
and/or circulatory failure are often the immediate cause of death,
which is preceded by convulsions and coma.
Various neuropsychiatric signs and symptoms have been observed during
acute and long-term methyl bromide poisoning. Low-level, short-term
exposure to the vapour has produced a syndrome of polyneuropathy
without overt central nervous system manifestations.
Late sequelae include bronchopneumonia after severe pulmonary lesions,
renal failure with anuria, and severe muscular weakness, sometimes with
paralysis. Generally, these tend to subside over a period varying
between a few weeks and several months, but there have been cases where
sensory disturbances, muscular weakness, disturbances of gait, and
blurred vision have persisted.
Exposure to methyl bromide is accompanied by an increase in the bromide
level in the blood.
The International Agency for Research on Cancer (IARC) concluded that
there was inadequate evidence for the carcinogenicity of methyl bromide
for humans.
3. CONCLUSIONS AND RECOMMENDATIONS
Human exposure to methyl bromide is predominantly occupational, during
manufacture (this is in enclosed processes so the risk of exposure is
small), and its use in soil or bulk fumigation where significant
exposure is possible; members of the general population in the vicinity
of fumigated fields or buildings may also be exposed. The major health
concern is poisoning, sometimes fatal, resulting from acute exposure.
Delayed onset of symptoms may occur.
In most countries, methyl bromide is strictly regulated for application
as a soil, commodities, and structural fumigant. Adherence to good
practices and guidelines should ensure that there are no adverse
effects on persons exposed occupationally. Care should be taken by
manufacturers in the production of methyl bromide, by the suppliers in
its transfer, and by fumigators and other workers in its use. In
fumigation, all necessary precautions must be taken to avoid any
hazards to the general public. Fumigated areas and premises must be
clearly marked and must not be entered until there has been a positive
check for safety.
Methyl bromide residues may be present in food and drinking-water, but,
because of the normally rapid breakdown of methyl bromide, there is no
evidence of any health effects.
Methyl bromide occurs naturally and the oceans are believed to be a
major source. It is manufactured in quantity, primarily as a fumigant,
and enters the environment from its uses in fumigation and to a lesser
extent from the exhaust emissions of motor vehicles using leaded petrol
containing organic bromine additives as lead scavengers. About 50% of
manufactured methyl bromide eventually enters the atmosphere, during or
after use. Some of this methyl bromide is broken down in the lower
atmosphere (troposphere), and some diffuses upwards to the stratosphere
where it decomposes (photolysis) and produces active bromine species
that react with ozone and are partly responsible for the depletion of
the ozone layer. Accordingly, methyl bromide is one of the chemicals
covered by the Montreal Protocol for the protection of the ozone layer.
To protect the environment, emissions of methyl bromide during
manufacture and soil, commodity, and structural fumigation should be
reduced, for example, by improving injection methods for soil
fumigation, better barrier films, or better measurement of the efficacy
of methyl bromide, with the goal of lower dosage rates where possible.
In commodity and structural fumigation, techniques should be developed
to seal fumigation chambers more tightly and to capture and recycle
fumigation gas.
4. HUMAN HEALTH HAZARDS, PREVENTION
AND PROTECTION, EMERGENCY ACTION
4.1 Human Health Hazards, Prevention and Protection, First Aid
Methyl bromide gas can be fatal if inhaled, and harmful if the liquid
is either swallowed or absorbed through the skin.
It is neurotoxic and a severe irritant to the eyes and upper and lower
respiratory tract.
4.1.1 Information for physicians
4.1.1.1 Symptoms of poisoning
Effects of overexposure
Acute effects: Acute poisoning from methyl bromide is characterized by
marked irritation of the respiratory tract, which, in severe cases, may
lead to pulmonary oedema. High concentrations may damage the liver,
kidneys, and central nervous system.
Eye contact: Severe irritant. Contact of liquid or high
concentrations of gas with the eyes may cause
severe, but usually reversible, injury with
temporary blindness.
Skin contact: Liquid in contact with the skin for more than a
few seconds causes irritation and blisters.
Liquid splashed on clothing or leather and/or
high gas concentrations held in contact with
skin, may cause skin burns with large blisters
appearing after several hours. Less severe
exposure may result in an itching skin rash
appearing after several days. Persistent
dermal effects include hyperpigmentation.
Skin absorption: Methyl bromide may be absorbed through the skin
in sufficient quantities to cause systemic
toxicity with signs and symptoms similar to
those following inhalation and can be fatal.
Inhalation: Signs and symptoms of acute poisoning include
headache, dizziness, somnolence, vertigo,
blurred vision, slurred speech, nausea and
vomiting, and possibly convulsions and coma.
The onset of toxic manifestations may be
delayed from 30 min up to two days. Dyspnoea
and pulmonary oedema may also occur, with a
late-onset chemical pneumonitis.
Ingestion: Although ingestion is unlikely, methyl bromide
is highly irritant to mucous membranes and
extremely poisonous if ingested.
Long-term effects: Long-term exposure to low concentrations of methyl
bromide may produce central nervous system effects. Signs include
mental confusion, lethargy, inability to focus the eyes,
incoordination, and muscle weakness.
Repeated skin exposure may cause contact dermatitis. There is no
evidence that methyl bromide induces skin sensitization.
4.1.1.2 Emergency and first aid procedures
Because of the possibility of delayed onset of poisoning, a 24-h
medical surveillance period should be mandatory in all cases where
there is any likelihood of overexposure to methyl bromide.
Eye Holding the eyelids apart, flush eyes at once
contamination: with copious flowing water for at least 15 min.
Get medical attention immediately.
Skin contact: Remove contaminated clothing and shoes and
place in closed containers. Wash skin
thoroughly with mild soap and plenty of water
for at least 15 min. Get medical attention
immediately. All leather items should be
discarded; other contaminated clothing must
preferably be discarded or else thoroughly
ventilated and washed before re-use.
Inhalation: Remove the victim to fresh air. Keep the
victim quiet and warm. Apply artificial
respiration if necessary. Do not give mouth-
to-mouth resuscitation. Get medical attention
immediately.
Ingestion: If methyl bromide is swallowed, wash mouth
thoroughly with plenty of water and give water
or milk to drink. Get medical attention
immediately. If the victim is unconscious, do
not give liquids by mouth and place the patient
in the recovery position.
4.1.1.3 Poisons information
Advice on the diagnosis and treatment of poisoning can be obtained from
Poison Information Centres.
4.1.2 Health surveillance advice
Before employment, a complete history and physical examination should
be carried out, in order to detect pre-employment conditions that might
place an employee at risk, and to establish a base-line for future
health monitoring. A careful history and examination of the nervous
and respiratory systems are important. The skin should be examined for
evidence of chronic disorders.
Medical examination should be repeated on an annual basis.
4.1.3 Protection
4.1.3.1 Protection of workers and fumigators
Ventilation requirements: In production, and formulation, workplace
ventilation must be sufficient to maintain methyl bromide levels below
the prescribed occupational exposure limit. Local exhaust ventilation
at source or vapour extraction may be used.
Protective equipment
Eyes: Splash-proof safety goggles. Contact lenses
should not be worn when working with methyl
bromide because of the danger of it being
trapped behind the contact lens and damaging
the eye.
Gloves: Gloves or rubber boots should not be used as
the liquid or concentrated vapour may be
trapped inside them.
Respirator: Where respiratory protection is required, a
self-contained breathing apparatus (compressed
air) or a full face-piece canister respirator
should be used.
Detection/Monitoring: Use an appropriate monitoring instrument for
methyl bromide in any area where it is being stored or handled: (a)
portable electronic leak detectors are very sensitive and give
continous audible warning, but are non-specific for methyl bromide; (b)
graduated gas detector tubes are more precise, and, when a known amount
of methyl bromide is drawn through a tube, the stain-length is the
indication of the gas concentration in that area.
Other protective equipment: Specially designed protective clothing for
methyl bromide is not available. Do not use rubberized materials; use
cotton overalls. Finger rings or adhesive bandages on hands should not
be worn when handling methyl bromide.
4.1.3.2 Protection of the general public
Areas or buildings being fumigated with methyl bromide must be clearly
identified with warning signs on all entrances showing, at least, the
signal word DANGER and the "Skull and Crossbones" and the words "Area
under fumigation, do not enter until completely aerated", the date and
time of fumigation, the name of the formulation being used, an
emergency telephone number for conlict, and the name and address of the
responsible fumigator. Warning signs should not be removed until the
fumigated area or building is safe for entry, confirmed by a suitable
detector. The safety instructions provided by the producer must be
followed. There may be national specifications for the wording.
4.2 Explosion and Fire Hazards
4.2.1 Explosion hazards
Flash point: None
Flammable Lower flammable limit 8.6 %
(explosive) limits: Upper flammable limit 20 %.
At concentrations used in normal fumigation practices, explosive
levels are not very likely to be reached.
4.2.2 Fire-fighting procedures
Special fire-fighting procedures: If possible, stop methyl bromide flow
immediately. Do not extinguish burning gas, unless flow can be shut
off immediately. Use water spray, fog nozzle or CO2 to keep cylinder
cool. If there is no risk, move cylinder away from fire. Use self-
contained breathing apparatus with a full face-piece, operating in
positive pressure mode, and appropriate protective clothing.
Note: this clothing may trap methyl bromide.
4.3 Storage
4.3.1 Cylinder specifications
Cylinders for methyl bromide must meet specifications laid down by the
authorities in the specific country of use and in particular:
- the thickness of the steel specified must be sufficient to
withstand dropping (the liquid has a high density), and the steel
must be corrosion resistant;
- the cylinders must undergo the required periodic tests;
- the materials of valve components must be compatible and
resistant to corrosion and expansion as a result of exposure to
methyl bromide (joints, packings, membranes);
- valve outlets must be protected by blind nuts and the valves
themselves by caps, during, the storage and transpormation of
cylinders.
4.3.2 Reactivity
Stability: Stable in sealed containers and under normal
conditions.
Conditions to Ignition sources, water contamination and
avoid: heating above 400 °C.
Incompatibility:. Strong oxidizers, aluminium, zinc, and
magnesium metals and their alloys, natural
rubber and certain types of plastics.
Hazardous Hydrogen bromide and carbon monoxide.
decomposition
products:
4.3.3 Precautions for handling and storage
Move and/or transport containers with care; do not use hooks, ropes, or
slings to unload, instead use hand or fork trucks to cradle the
cylinders firmly; do not bump or drag them. Do not dent cans. Store
cylinders and cans upright, secured from tampering and incompatible
material, in cool, well-ventilated, dry areas, away from seeds,
food/animal feed, and human and animal habitations. Test periodically
for leaks using a (hand-held) electronic leak detector. Avoid bodily
contact.
4.4 Transport
Comply with requirements regarding movement of hazardous goods. Check
that containers are sound and the labels undamaged before despatch.
4.5 Spillage
Steps to be taken in case material is released or spilled: Evacuate
area and keep personnel upwind. Use self-contained breathing apparatus
in positive-pressure mode. If practicable, stop flow of vapour. Shut
off all sources of ignition. Ventilate and/or allow to evaporate,
keeping people away from the area until safe re-entry levels are shown
by a (hand-held) electronic leak detector.
4.6 Disposal
Incineration is the recommended waste disposal method for large
quantities. If a suitable designated combustion chamber is not
available, return LABELLED containers to supplier. Crush and bury
empty cans. Incineration is hazardous for the non-specialist;
therefore, only small amounts should be released into the atmosphere,
in a well-ventilated outdoor location. Methyl bromide is a toxic gas
and incineration may be difficult to arrange safely unless an efficient
method of feeding the gas into the incinerator can be arranged.
Incineration requires dilution with additional fuel.
Observe national or local regulations when disposing of methyl bromide.
Contact local and/or national environmental authorities to ensure proper
compliance.
5. HAZARDS FOR THE ENVIRONMENT AND
THEIR PREVENTION
Methyl bromide is present naturally in the atmosphere, and oceans are
believed to be a major source of methyl bromide. Man-made emissions,
mostly from fumigation, but, to a lesser extent, from the exhaust
emissions of motor vehicles using fuel containing bromine compounds,
notably ethylene dibromide, add to the naturally occurring methyl
bromide. Although methyl bromide reacts with the hydroxyl radical in
the troposphere, some is transported to the stratosphere by upward
diffusion. Here, photolysis of methyl bromide becomes of increasing
importance, and is the most dominant loss mechanism in the lower
stratosphere. Active bromine species react with ozone in the
stratosphere contributing to ozone layer depletion.
The solubility of methyl bromide is 16-18 g/litre, at 20 °C; 1013 hPa.
In soil, methyl bromide is partly hydrolysed to bromide ions. After
fumigation using methyl bromide, the soil is sometimes leached with
water to prevent the bromide ions being taken up by plants subsequently
planted on the sterilized soil. This increase in aquatic bromide
levels can be problematical, if surface water is used for leaching.
Methyl bromide can diffuse through plastic drinking-water pipes, if the
surrounding soil has been fumigated with methyl bromide.
In the soil, methyl bromide can diffuse down to a depth of 2 m
depending on the type, conditions, and length of fumigation, the
highest concentration of methyl bromide remaining in the upper soil.
The amount of methyl bromide converted to bromide depends on the
organic matter content of the soil. The bromide produced is largely
water soluble and can be taken up by plants or removed to lower soil
levels by leaching with water.
Methyl bromide is degraded in soil by hydrolysis and microbial
degradation. The rate constant for hydrolysis varies with temperature
and is enhanced by light.
The octanol/water partition coefficient (log Pow) of methyl bromide is
1.19; thus it should not bioaccumulate.
The amount of bromide accumulated in plants depends on various factors,
such as the physical and chenlical properties of the soil, the climatic
trend (temperature and rainfall), the plant species, and on the type of
plant tissue. Leafy vegetables, such as lettuce and spinach, can take
up relatively large amounts of bromide ion without phytotoxic symptoms.
In contrast, other crops, such as carnations, citrus seedlings, cotton,
celery, pepper, and onions, are particularly sensitive to methyl
bromide fumigation.
Methyl bromide is used as a fungicide, bactericide, nematocide,
insecticide, and rodenticide. As a soil fumigant, it eradicates both
target and non-target organisms, destroying most of the soil flora.
6. SUMMARY OF CHEMICAL SAFETY
INFORMATION
This summary should be easily available to all health workers concerned
with, and users of, methyl bromide. It should be displayed at, or
near, entrances to areas where there is potential exposure to methyl
bromide, and on processing equipment and containers. The summary
should be translated into the appropriate language(s). All persons
potentially exposed to the chemical should also have the instructions
in the summary clearly explained.
Space is available for insertion of the National Occupational Exposure
Limit, the address and telephone number of the National Poison Control
Centre, and local trade names.
SUMMARY OF CHEMICAL SAFETY INFORMATION
BROMOMETHANE
CAS chemical name: bromomethane; Common name: methyl bromide; CAS registry number: 74-83-9;
RTECS number: PA 4900000; UN number: 1062; Molecular formula: CH3Br; Relative molecular mass: 94.95
-----------------------------------------------------------------------------------------------------------------------------
PHYSICAL PROPERTIES OTHER CHARACTERISTICS
-----------------------------------------------------------------------------------------------------------------------------
Appearance colourless, odourless gas Methyl bromide is heavier than air;
it decomposes on heating and
Boiling point 4 °C burning producing highly toxic and
Melting point -94 °C irritating fumes (bromides, carbon
Relative density (water = 1) 1.7 oxybromide, carbon dioxide and
monoxide); it reacts withoxidants and
Solubility in water, strong bases and also with oxygen causing
(g/litre at 25 °C) 16-18 a fire hazard; it attacks many metals in the
Solubility in other solvents freely soluble in alcohol presence of water and attacks aluminium
chloroform, ether, carbon with the formation of aluminium alkyls
disulfide, carbon tetra- causing a fire and explosion hazard
chloride, and benzene
Vapour pressure (kPa at 20 °C) 189
Relative vapour density
(air = 1) 3.3
Autoignition temperature 537 °C
Explosive limits, vol% in air 9-20
Octanol/water partition
coefficient an log Pow 1.19
-----------------------------------------------------------------------------------------------------------------------------
HAZARDS/SYSTOMS PREVENTION AND PROTECTION FIRST AID
-----------------------------------------------------------------------------------------------------------------------------
GENERAL: A highly toxic gas or Strictly hygiene In all cases, consult a doctor and seek medical
vapour; can be absorbed into the advice
body by inhalation and through
the skin
-----------------------------------------------------------------------------------------------------------------------------
HAZARDS/SYSTOMS PREVENTION AND PROTECTION FIRST AID
-----------------------------------------------------------------------------------------------------------------------------
SKIN: Tingling, itching; redness, Do not wear gloves; wear Where there is frostbite, do not remove clothes;
burning sensation, blisters protective clothing; rinse with plently of cool water; rinse skin or
(see inhalation); contact with the remember that methly bromide shower whole body; seek medical attention
may produce frostbite readily permeates many materials
Where there is no frostbite, remove clothes
and shoes and place them in a ventilated
container; rinse skin well, washing with
mild soap and running water for 15 min
EYES: Redness, pain blurred Use safety goggles, face shield, Irrigate with plenty of running water for at
vision, temporary or permanent or eye protection in combination least 15 min; if present, remove contact
with breathing protection lenses immediately; refer case for medical
attention
INHALATION: Abdominal pain, Use ventilation, local exhaust Remove to fresh air; if patient conscious, place
dizziness, headache, convulsions, or breathing protection in half-upright position; if unconscious, place
apathy, loss of speech, in the "Recovery" position; where breathing is
incoordination, vomiting laboured, or patient dyspnoeic, use artificial
ventilation; seek medical attention immediately;
if hallucinating, reassure patient and place in
a quiet, but well-ventilated area; if severe,
consider a sedative (e.g., [iv] diazepam) and
seek medical attention immediately; where
patient is convulsing, seek urgent medical care;
meanwhile, check for, and remove, dentures,
restrain patient
INGESTION: Unlikely occupational Do not eat, drink, or smoke
hazard during work; wash hands before
eating, drinking, or smoking
INHALATION RISK: A harmful concentration of this gas in the air will be reached very quickly on loss of containment
EFFECTS OF SHORT-TERM EXPOSURE: The substance irritates the eyes, the skin, and the respiratory tract; inhalation
of the substance may cause lung oedema; the substance may cause effects on the central nervous system, kidneys, and
lungs; exposure to high concentrations may result in death; the effects may be delayed
EFFECTS OF LONG-TERM OR REPEATED EXPOSURE: Repeated or prolonged contact with skin may cause dermatitis. or skin
sensitization; the substance may have effects on the nervous system, kidneys, heart muscle, liver, nose, and lungs;
may cause genetic damage; may impair male fertility
ENVIRONMENT: Toxic for aquatic and terrestrial life
-----------------------------------------------------------------------------------------------------------------------------
HAZARD PREVENTION FIRE FIGHTING
-----------------------------------------------------------------------------------------------------------------------------
FIRE: Combustible under specific Avoid contact with aluminum or Shut off supply; if not possible
conditions. pure oxygen; do not use in the and there is no risk to
vicinity of a fire or hot surface surroundings, let the fire burn
or during welding itself out; in other cases,
extinguish with powder, carbon
dioxide; in case of fire in
surrounding, all extinguishing
agents can be used
-----------------------------------------------------------------------------------------------------------------------------
SPILLAGE DISPOSAL STORAGE PACKING & LABELLING
-----------------------------------------------------------------------------------------------------------------------------
Evaluate danger area, consult an Fireproof if in building; Unbreakable packing; put breakable
expert, never direct water jet separate from strong oxidants, packing into closed unbreakable
on liquid (extra personal protec- bases, cylinders containing container; special insulated cylinder
tion: self-contaminated breathing oxygen and aluminium, cool T symbol
apparatus) ventilation along the floor R: 23-36/37/38
S: 15-27-36/37/39-38-44
UN Haz Class: 2
UN Subsidiary Risks: 6.1
-----------------------------------------------------------------------------------------------------------------------------
TRANSPORT NATIONAL INFORMATION
-----------------------------------------------------------------------------------------------------------------------------
Transport Emergency Card: National Occupational Exposure
TEC (R)-111 Limit:
NFPA Code: H 3; F 0; R 0
National Poison Control Centre:
7. CURRENT REGULATIONS, GUIDELINES,
AND STANDARDS
7.1 Previous Evaluations by International Bodies
The International Agency for Research on Cancer (IARC) evaluated methyl
bromide in 1986 and in 1987, and concluded that there is limited
evidence for the carcinogenicity of methyl bromide for experimental
animals with inadequate evidence for the carcinogenicity of methyl
bromide for humans; the overall evaluation of carcinogenicity for
humans was that it was not classifiable (group 3).
The Joint FAO/WHO Meeting on Pesticide Residues (JMPR) evaluated methyl
bromide and bromide ion in 1965, 1966, 1967, and 1988. The Acceptable
Daily Intake (ADI) is 0-1 mg/kg as bromide ion.
The United Nations Environment Programme has evaluated methyl bromide
as part of activities related to the Montreal Protocol and concluded
that production should be controlled, in order to protect the ozone
layer.
7.2 Exposure Limit
Table 1 gives occupational exposure limits for a number of countries.
Since national regulations and guidelines are subject to change, the
limits legally required should be confirmed.
7.3 Specific Restrictions
7.3.1 Type of crop, method of fumigation, dosage restrictions,
covering and leaching regulations
A number of countries have restrictions on the use of methyl bromide.
Information on possible national restrictions should be obtained.
Table 1. Some national occupational exposure limits for methyl bromidea
-----------------------------------------------------------------------
Concentration Interpretation Notation
(mg/m3)
-----------------------------------------------------------------------
Australia 20 TWA skin
Belgium 19 TWA skin
Bulgaria 10 TWA
Denmark 20 TWA skin
Finland 60 TWA skin
97 STEL
France 20 TWA
Germany 20 TWA skin[C3,ll,i]d
Hungary 10 TWA skin, irritant
20 STEL
Italyc 60 TWA
The Netheriandsce 1 TWA skin
Norwayc 60 TWA
Poland 5
Romaniac 50 TWA
80 ceiling
Sweden 60 TWA skin
80 STEL
Switzerland 20 TWA skin
40 STEL
United Kingdom 20 TWA skin
60 STEL
USA
ACGIH 19 TWA skin
NIOSH/OSHA 20 TWA skin
USSR 1 STEL
-----------------------------------------------------------------------
a From ILO (1991), unless otherwise statedc
b TWA = time-weighted average; STEL, short-term exposure limit
d C3 = suspected of having a carcinogenic potenbal ll, i = systematic
effects (onseth)
e = proposed.
7.3.2 Restictions on personnel
Generally, the use of methyl bromide is restricted to registered
fumigators who may, in some countries, have to undergo a "Fumigation
Operators Examination".
7.4 Labelling, Packaging, and Transport
The regulations regarding labelling, packaging, and transport depend on
the formulation of the methyl bromide fumigation mixture. Formulations
containing only 2 % chloropicrin are classed under the same regulations
as 100% methyl bromide. Formulations containing 67% methyl bromide and
33 % chloropicrin, as well as formulations with ethylene dibromide,
have a different UN Number.
7.4.1 Labelling
The label must indicate the name and address of the producer, supplier,
or distributor, as well as product name, chemical hazard symbols,
authorization numbers, and emergency measures to be taken in the event
of an accident.
The United Nations Committee of Experts on the Transport of Dangerous
Goods classifies methyl bromide as:
------------------------------------------------------
Class Number
------------------------------------------------------
METHYL BROMIDE*
(100 or 98 % methyl bromide) 2 1062
Methyl bromide and 2 1581
chloropicrin mixtures
METHYL BROMIDE AND
ETHYLENE DIBROMIDE
MIXTURES, LIQUID* 6.1 1647
Class 2 - Label: Toxic
------------------------------------------------------
* Proper shipping name
Non-refrigerated pressure (liquefiable) gases shipped in tank-
containers:
max. allowable working pressure: 7 (bar)
filling: 1.51 (kg/litre)
Tankshells should have a pressure-relief device approved by the
competent authority.
The European Community legislation requires methyl bromide to be
labelled as a toxic substance. The following EEC standard phrases are
used:
R 23:Toxic by inhalation
R 36/37/38:Irritating to eyes, respiratory system and skin
S 15:Keep away from heat
S 27:Take off immediately all contaminated clothing
S 36/37/39:Wear suitable protective clothing, gloves and
eye/face protection
S 38:In case of insufficient ventilation, wear suitable
respiratory equipment
S 44:If you fcel unwell, seek medical advice (show the label
where possible)
7.4.2 Packaging
Methyl bromide is marketed as a compressed, liquefied gas in cylinders,
tanks, or cans.
7.4.3 Transport
-----------------------------------------------------------------------
100 or 98% 67% Methyl bromide/
Methyl bromide 33% chloropicrin
-----------------------------------------------------------------------
UN No.: 1062 1581
IMO:
Class: 2: Gases 2: Gases
Label No. 2: POISON GAS + 2: POISON GAS
FLAMMABLE GAS
IMDG CODE page 2158 page 2120
amdt. 25-89 amdt. 25-89
RID/ADR:
Class and Item Nos.: 2,3 (a t) 2,4 (a t)
Hazard/Substance Nos.: 6/1062 26/1581
Danger Label Model Nos,: 6.1 + 13 (RID) 6.1 + 13 (RID)
CEC Regs:
For supply:
Classification: Toxic, symbol
required
Phrases: R: 23-36/37/38 R: 23-36/37/38
S: 15-27-36/37/ S: 15-27-36/37/
39-38-44 39-3 8-44
R: 22-26-36/37/38
+ S: 36/37-38-45
For conveyance:
Classification: Toxic gas Toxic gas
Hazard warning sign: TOXIC GAS TOXIC GAS
US DOT:
Proper shipping name: Methyl bromide Methyl bromide, and
more than 2% chloro-
picrin mixture,
Hazard class: 2 2
Division: 2.3, Poisonous Gas 2.3 Poisonous Gas
Identification No: UN 1062 UN 1581
Label: POISON GAS (2) - INHALATION HAZARD
-----------------------------------------------------------------------
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