INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY
ENVIRONMENTAL HEALTH CRITERIA 177
1,2-Dibromoethame
This report contains the collective views of an international group of
experts and does not necessarily represent the decisions or the stated
policy of the United Nations Environment Programme, the International
Labour Organisation, or the World Health Organization.
First draft prepared by Dr J. Sekizawa,
National Institute of Health Science, Japan
Published under the joint sponsorship of the United Nations
Environment Programme, the International Labour Organisation, and the
World Health Organization
World Health Organization
Geneva, 1996
The International Programme on Chemical Safety (IPCS) is a joint
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carried out by the IPCS include the development of know-how for coping
with chemical accidents, coordination of laboratory testing and
epidemiological studies, and promotion of research on the mechanisms
of the biological action of chemicals.
WHO Library Cataloguing in Publication Data
1,2-Dibromoethame.
(Environmental health criteria ; 177)
1.Ethylene dibromide - adverse effects 2.Solvents
3.Environmental exposure I.Series
ISBN 92 4 157177 2 (NLM Classification: QV 633)
ISSN 0250-863X
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CONTENTS
ENVIRONMENTAL HEALTH CRITERIA FOR 1,2-DIBROMOETHANE
Preamble
1. SUMMARY
1.1. Identity, physical and chemical properties, and analytical
methods
1.2. Sources of human and environmental exposure
1.3. Environmental levels and degradation
1.4. Kinetics and metabolism in laboratory animals
1.5. Effects on laboratory mammals and in vitro test systems
1.6. Effects on humans
1.7. Effects on organisms in the environment
2. IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, ANALYTICAL METHODS
2.1. Identity
2.2. Physical and chemical properties
2.3. Conversion factors
2.4. Analytical methods
2.4.1. Air
2.4.2. Water
2.4.3. Soils and sediment
2.4.4. Food
3. SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE
3.1. Natural occurrence
3.2. Anthropogenic sources
3.2.1. Production levels and processes
3.2.1.1 World production figures
3.2.1.2 Manufacturing processes
3.2.2. Uses
3.2.2.1 Petrol additive
3.2.2.2 Fumigant
4. ENVIRONMENTAL TRANSPORT, DISTRIBUTION AND TRANSFORMATION
4.1. Transport and distribution between media
4.1.1. Air
4.1.2. Soil
5. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE
5.1. Environmental levels
5.1.1. Air
5.1.2. Water
5.1.3. Food
5.2. Occupational exposure
6. KINETICS AND METABOLISM
6.1. Absorption
6.2. Distribution
6.3. Metabolic transformation
6.4. Elimination and excretion in expired air, faeces and urine
6.5. Retention and turnover
6.6. Reaction with body components
7. EFFECTS ON EXPERIMENTAL ANIMALS AND IN VITRO TEST SYSTEMS
7.1. Single exposure
7.1.1. Oral
7.1.1.1 Rat
7.1.1.2 Chicken
7.1.2. Inhalation
7.1.2.1 Rat
7.1.2.2 Guinea-pig
7.1.3. Intraperitoneal injection
7.1.3.1 Mouse
7.1.3.2 Rat
7.2. Short-term exposure
7.2.1. Oral
7.2.1.1 Chicken
7.2.2. Inhalation
7.2.2.1 Mouse
7.2.2.2 Rat
7.2.2.3 Guinea-pig
7.2.2.4 Rabbit
7.2.2.5 Monkey
7.3. Eye and skin irritation
7.3.1. Rabbit
7.4. Long-term exposure
7.4.1. Oral
7.4.1.1 Mouse
7.4.1.2 Rat
7.4.2. Inhalation
7.4.2.1 Mouse
7.4.2.2 Rat
7.5. Developmental toxicity
7.5.1. Reproduction
7.5.1.1 Effects on sperm
7.5.1.2 Effects on ova
7.5.2. Teratogenicity
7.5.2.1 Effects on neonatal behaviour
7.6. Mutagenicity and related end-points
7.6.1. In vitro assays
7.6.2. In vivo assays
7.6.3. Other studies
7.7. Carcinogenicity
7.7.1. Administration by gavage
7.7.1.1 Mouse
7.7.1.2 Rat
7.7.2. Administration in drinking-water
7.7.2.1 Mouse
7.7.3. Inhalation
7.7.3.1 Mouse
7.7.3.2 Rat
7.7.4. Dermal application
7.7.4.1 Mouse
7.7.5. Cell transformation
7.8. Biochemical studies and species specificity
8. EFFECTS ON HUMANS
8.1. Acute toxicity
8.2. Occupational exposure
8.2.1. Cancer incidence
8.2.2. Reproductive effects
9. EFFECTS ON ORGANISMS IN THE ENVIRONMENT
9.1. Aquatic organisms
9.1.1. Invertebrates
9.1.2. Fish
9.2. Terrestrial biota
9.3. Microorganisms
9.4. Plants
10. EVALUATION OF HUMAN HEALTH RISKS AND EFFECTS ON THE ENVIRONMENT
10.1. Evaluation of human health risks
10.2. Evaluation of effects on the environment
11. CONCLUSIONS AND RECOMMENDATIONS
12. FURTHER RESEARCH
13. PREVIOUS EVALUATIONS BY INTERNATIONAL BODIES
REFERENCES
RESUME
RESUMEN
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This publication was made possible by grant number 5 U01
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WHO TASK GROUP ON ENVIRONMENTAL HEALTH CRITERIA FOR 1,2-DIBROMOETHANE
Members
Dr T. Bailey, US Environmental Protection Agency, Washington DC, USA
Dr A.L. Black, Department of Human Services and Health, Canberra,
Australia
Mr D.J. Clegg, Carp, Ontario, Canada
Dr S. Dobson, Institute of Terrestrial Ecology, Monks Wood, Abbots
Ripton, Huntingdon, Cambridgeshire, United Kingdom
(Vice-Chairman)
Dr P.E.T. Douben, Her Majesty's Inspectorate of Pollution, London,
United Kingdom (EHC Joint Rapporteur)
Dr P. Fenner-Crisp, US Environmental Protection Agency, Washington DC,
USA
Dr R. Hailey, National Institute of Environmental Health Sciences,
National Institutes of Health, Research Triangle Park, USA
Ms K. Hughes, Environmental Health Directorate, Health Canada, Ottawa,
Ontario, Canada (EHC Joint Rapporteur)
Dr D. Kanungo, Central Insecticides Laboratory, Government of India,
Ministry of Agriculture & Cooperation, Directorate of Plant
Protection, Quarantine & Storage, Faridabad, Haryana, India
Dr L. Landner, MFG, European Environmental Research Group Ltd,
Stockholm, Sweden
Dr M.H. Litchfield, Melrose Consultancy, Denmans Lane, Fontwell,
Arundel, West Sussex, United Kingdom (CAG Joint Rapporteur)
Professor M. Lotti, Institute of Occupational Medicine, University of
Padua, Padua, Italy (Chairman)
Professor D.R. Mattison, University of Pittsburgh, Graduate School of
Public Health, Pittsburgh, Pennsylvania, USA
Dr J. Sekizawa, National Institute of Health Sciences, Tokyo, Japan
Dr P. Sinhaseni, Chulalongkorn University, Bangkok, Thailand
Dr S.A. Soliman, King Saud University, Bureidah, Saudi Arabia
Dr M. Tasheva, National Centre of Hygiene, Medical Ecology and
Nutrition, Sofia, Bulgaria (CAG Joint Rapporteur)
Mr J.R. Taylor, Pesticides Safety Directorate, Ministry of
Agriculture, Fisheries and Food, York, United Kingdom
Dr H.M. Temmink, Wageningen Agricultural University, Wageningen, The
Netherlands
Dr M.I. Willems, TNO Nutrition and Food Research Institute, Zeist, The
Netherlands
Secretariat
Ms A. Sundén Byléhn, International Register of Potentially Toxic
Chemicals, United Nations Environment Programme, Châtelaine,
Switzerland
Dr P. Chamberlain, International Programme on Chemical Safety, World
Health Organization, Geneva, Switzerland
Dr J. Herrman, International Programme on Chemical Safety, World
Health Organization, Geneva, Switzerland
Dr K. Jager, International Programme on Chemical Safety, World Health
Organization, Geneva, Switzerland
Dr P. Jenkins, International Programme on Chemical Safety, World
Health Organization, Geneva, Switzerland
Dr W. Kreisel, World Health Organization, Geneva, Switzerland
Dr M. Mercier, International Programme on Chemical Safety, World
Health Organization, Geneva, Switzerland
Dr M.I. Mikheev, Occupational Health, World Health Organization,
Geneva, Switzerland
Dr G. Moy, Food Safety, World Health Organization, Geneva, Switzerland
Mr I. Obadia, International Labour Organisation, Geneva,
Switzerland
Dr R. Plestina, International Programme on Chemical Safety, World
Health Organization, Geneva, Switzerland
Dr E. Smith, International Programme on Chemical Safety, World Health
Organization, Geneva, Switzerland (EHC Secretary)
Mr J. Wilbourn, International Agency for Research on Cancer, Lyon,
France
ENVIRONMENTAL HEALTH CRITERIA FOR 1,2-DIBROMOETHANE
The Core Assessment Group (CAG) of the Joint Meeting on
Pesticides (JMP) met at the World Health Organization, Geneva from
25 October to 3 November 1994. Dr W. Kreisel, Executive Director,
welcomed the participants on behalf of WHO, and Dr M. Mercier,
Director, IPCS, on behalf of the IPCS and its cooperating
organizations (UNEP/ILO/WHO). The Core Assessment Group reviewed and
revised the draft monograph and made an evaluation of the risks for
human health and the environment from exposure to 1,2-dibromoethane
(ethylene dibromide).
The preparation of the first draft of the monograph was
coordinated by Dr J. Sekizawa, National Institute of Health Sciences,
Japan. The second draft, revised in the light of international
comment, was prepared under the coordination of Dr Sekizawa.
Dr E. Smith and Dr P.G. Jenkins, both members of the IPCS Central
Unit, were responsible for the scientific content and technical
editing, respectively.
The efforts of all who helped in the preparation and finalization
of the monograph are gratefully acknowledged.
The authors who contributed to the first draft were:
Dr C. Hashida The Jikei University School of Medicine, Japan
Dr Y. Hayashi National Institute of Health Sciences, Japan
Dr E. Kamata National Institute of Health Sciences, Japan
Dr Y. Kurokawa National Institute of Health Sciences, Japan
Dr A. Matsuoka National Institute of Health Sciences, Japan
Dr T. Matsushima The Japan Industrial Safety and Health
Association
Dr K. Morimoto National Institute of Health Sciences, Japan
Dr M. Nakadate National Institute of Health Sciences, Japan
Dr G. Ohmori The Jikei University School of Medicine, Japan
Dr Y. Saito National Institute of Health Sciences, Japan
Dr J. Sekizawa National Institute of Health Sciences, Japan
Dr T. Sohuni National Institute of Health Sciences, Japan
Dr M. Takeda National Institute of Health Sciences, Japan
Dr M. Takemura Ashiya University, Japan
Dr Y. Takenaka National Institute of Health Sciences, Japan
Dr S. Tanaka National Institute of Health Sciences, Japan
ABBREVIATIONS
BCF bioconcentration factor
BUN blood urea nitrogen
ECD electron capture detector
EDB 1,2-dibromoethane (ethylene dibromide)
FID flame ionization detector
GC gas chromatography
GSH glutathione
gamma-GT gamma-glutamyltranspeptidase
HECD Hall electron capture detector
LOEL lowest-observed-effect level
MS mass spectrometry
NADPH reduced nicotinamide adenine dinucleotide phosphate
NOEL no-observed-effect level
PIB piperonyl butoxide
SGOT serum glutamic-oxalic transaminase
SGPT serum glutamic-pyruvic transaminase
TEAM total exposure assessment methodology
TWA time-weighted average
UDS unscheduled DNA synthesis
VHH volatile halogenated hydrocarbon
VOC volatile organic carbon compound
1. Summary
1.1 Identity, physical and chemical properties, and analytical
methods
1,2-Dibromoethane (ethylene dibromide) is a colourless liquid
(melting point 9.9°C, boiling point 131.4°C) with a chloroform-like
odour. It is quite volatile, with a vapour pressure of 1.47 kPa
(11 mmHg) at 25°C and a vapour density compared to air of 6.1.
1,2-Dibromoethane is miscible with most organic solvents. Its
solubility in water is 4.3 g/litre at 30°C.
1,2-Dibromoethane in ambient air is analysed by GC after
absorption to porous polymers followed by rapid thermal desorption. A
purge-trap method is used for water samples. 1,2-Dibromoethane
residues in foods and other media can either be extracted by solvents
or be subjected to automated headspace analysis under cryogenic
conditions followed by analysis by GC and HPLC after derivatization.
1.2 Sources of human and environmental exposure
1,2-Dibromoethane is used as a scavenger of lead antiknock agents
in gasoline. It is also used as a soil fumigant and for fumigation of
grains and fruits. Reduced use of leaded gasoline in some countries
and cancellations of registrations for the use of 1,2-dibromoethane
for agricultural applications has reduced human exposure to
1,2-dibromoethane. However, it is still used as a lead scavenger in
gasoline in some countries, as a fumigant, for quarantine purposes, as
a solvent and as an intermediate for industrial chemicals.
1.3 Environmental levels and degradation
Concentrations of 1,2-dibromoethane measured in air range from
undetectable to the order of ng/m3 in urban areas. 1,2-Dibromoethane
has been found in ground water at up to 0.2 µg/litre and in surface
water at up to 50 µg/litre in areas of extensive agricultural use.
Although 1,2-dibromoethane leaches through soil, some is retained in
the soil matrix and may later contaminate irrigation wells. There is
a lack of information on microbial breakdown in soils.
The high volatility of 1,2-dibromoethane means that the major
environmental sink is the atmosphere. Stratospheric photolysis may
lead to the formation of breakdown products with ozone-depleting
potential.
1.4 Kinetics and metabolism in laboratory animals
1,2-Dibromoethane is rapidly absorbed orally, dermally and by
inhalation. Metabolites are thought to play an important role in
1,2-dibromoethane toxicity for humans. It can be metabolized by an
oxidative pathway (cytochrome P-450 system) and a conjugation pathway
(glutathione S-transferase system). Two reactive metabolites,
bromacetaldehyde formed via the oxidation pathway and thiiranium ion
formed via the conjugation pathway, are thought to interact with
cellular macromolecules (proteins, DNA) to form covalently bound
products.
1.5 Effects on laboratory mammals and in vitro test systems
1,2-Dibromoethane is acutely toxic to animals (oral LD50 for
rats of 146-417 mg/kg body weight, inhalation LC50 for rats of
3080 mg/m3 after a 2-h exposure, mortality observed following dermal
application of 210 mg/kg to rabbits). Toxic effects of
1,2-dibromoethane were mainly observed in the liver and kidneys.
Inhaled 1,2-dibromoethane vapour produced nasal irritation and
depression of the central nervous system. In rats exposed to
concentrations between 1540 and 77 000 mg/m3 (200-10 000 ppm) for
exposure durations between 0.1 and 16.0 h, deaths occurred in all
groups and were related to concentration and time. 1,2-Dibromoethane
(1.0% solution) caused irritation of shaved abdominal skin and eye
irritation in rabbits.
After oral subchronic exposure, mortality and decreases in weight
gain were observed in rats and mice at 100 mg/kg body weight per day.
Decreases in weight gain and nasal pathological effects were noted in
rats exposed to 1,2-dibromoethane at 115 mg/m3 (578 ppm) for
6 h/day, 5 days/week, for 13 weeks. The NOEL for histopathological
alterations of the nasal cavity was 23 mg/m3 (3 ppm) in this study.
In a similar study in mice, the same pathological changes were
observed, also with a NOEL of 23 mg/m3 (3 ppm).
After mice or rats were administered 1,2-dibromoethane by gavage
at 37-107 mg/kg body weight per day (TWA) for 49-90 weeks or mice were
administered 103-117 mg/kg body weight per day in drinking-water for
15-17 months, non-carcinogenic changes such as liver degeneration,
testicular atrophy, and forestomach acanthosis and hyperkeratosis in
addition to mortality were observed. After inhalation exposure (mice
or rats exposed to 77-388 mg/m3 for 6-18 months), inflammation of
the trachea and nasal cavity, testicular degeneration and hepatic
necrosis were observed.
1,2-Dibromoethane was not teratogenic in rats or mice following
inhalational exposure. Developmental toxicity (impairment of
development of motor coordination) was observed in the offspring of
male rats treated intraperitoneally with 1.25 mg/kg body weight per
day and in the offspring of female rats treated by inhalation
509 mg/m3, 4 h/day, 3 days/week from day 3 to day 20 of gestation.
1,2-Dibromoethane affected the reproductive performance of rats (in
males at the exposure level of 684 mg/m3, 7 h/day, 5 days/week, for
10 weeks, and in females at the exposure level of 614 mg/m3,
7 h/day, 7 days/week, for 3 weeks). The NOEL for this parameter was
300 mg/m3 in both sexes. The NOEL for reproductive performance of
male rats in a feeding study was 50 mg/kg per day after a 90-day
exposure. Spermatogenesis was affected in bulls following oral dosing
with 2 mg/kg per day for less than 21 days and in rabbits following
subcutaneous injection of 15 mg/kg for 5 days. Feeding of
1,2-dibromoethane caused diminution of egg size in hens after exposure
to 12.5 mg/kg per day for 12 weeks.
1,2-Dibromoethane did not induce dominant lethal mutations in
mice or rats, and did not produce chromosomal aberrations or
micronuclei in the bone-marrow cells of mice treated in vivo.
However, it was mutagenic in bacterial assays and caused single-strand
DNA breaks. Metabolites of 1,2-dibromoethane were covalently bound to
DNA, in vivo and in vitro. Sister chromatid exchange, mutations
and unscheduled DNA synthesis were observed in human cells in vitro.
Carcinogenicity studies involving oral administration (mice and
rats exposed by gavage to 37-107 mg/kg body weight per day (TWA) for
49-90 weeks; mice given 1,2-dibromoethane in drinking-water at
103-117 mg/kg body weight per day for 15-17 months), inhalational
exposure (mice and rats exposed at 10-40 ppm for 6-18 months) or skin
administration (25-50 mg/mice, 3 times/week for 400-594 days) showed
that 1,2-dibromoethane is carcinogenic to rats and mice, causing
tumours in a variety of organs (both at the application site and
distant sites, including the nasal cavity, lung, stomach, liver, skin,
circulatory system and mammary glands). In many cases it reduced the
latency period in developing tumours.
1.6 Effects on humans
1,2-Dibromoethane may produce adverse effects on the respiratory,
nervous and renal systems.
Acute (single) inhalation exposure to 1,2-dibromoethane at
215 mg/m3 (28 ppm) for 30 min or more has been shown to be fatal for
humans. Ingestion of 140 mg/kg body weight was fatal. Long-term
exposure to 1,2-dibromoethane (5 y) at a concentration of 0.68 mg/m3
in the breathing zone significantly decreased sperm counts and
fertility in occupationally exposed workers.
1.7 Effects on organisms in the environment
Few aquatic ecotoxicity studies have been performed with
1,2-dibromoethane. The LC50s for aquatic organisms are greater than
5 mg/litre. No information is available on terrestrial organisms.
2. IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, ANALYTICAL METHODS
2.1 Identity
Chemical name 1,2-dibromoethane
(IUPAC):
Chemical structure: Br - CH2 - CH2 - Br
Molecular formula: C2H4Br2
Relative molecular 187.9
mass:
CAS chemical name: ethylene dibromide
CAS registry number: 106-93-4
Synonyms: sym-dibromothane, DBE, dibromo, bromure
d'ethylene, 1,2-ethylene dibromide, ethylene
bromide
Major trade names: Nematron, Nemafume, Bromofume, Dowfume W-85,
Aadibrom, Iscobrome D
Formulations: kerosene (30 and 97%),
emulsifiable concentrate (40 and 48%)
in combination with other pesticides
2.2 Physical and chemical properties
Appearance: colourless liquid with chloroform-like odour
Melting point: 9.9°C (Stenger, 1983)
Boiling point: 131.4°C (Stenger, 1983)
Vapour pressure: 1.47 kPa (11.0 mmHg)
(at 25°C) (Verschueren, 1983)
Vapour density: 6.1
Specific gravity: 2.172 (Stenger, 1983)
(at 25°C)
Refractive index (n20): 1.5379
Solubility in water: 4.3 g/litre at 30°C (Verschueren, 1983)
soluble in ether, etanol, benzene, acetone
(Weast et al., 1988)
Saturating concentration 113 g/m3 (at 20°C), 168 g/m3 (at 30°C)
in air:
Log Pow 1.76 or 1.93
Stability: decomposes gradually when exposed to light
1,2-Dibromoethane is flammable. Chemically, 1,2-dibromoethane is
a bifunctional alkylating agent.
2.3 Conversion factors
1 ppm = 7.68 mg/m3 (at 25°C);
1 mg/m3 = 0.13 ppm
2.4 Analytical methods
Analytical methods for volatile halogenated hydrocarbons (VHH)
are applicable to 1,2-dibromoethane. Determination of
1,2-dibromoethane is usually carried out by gas chromatography with
electron capture detection (GC-ECD). High resolution GC capillary
columns can be used for multiple analysis in high-resolution gas
chromatography (HR-GC) or high-resolution gas chromatography - mass
spectrometry (HR-GC-MS). A sensitive photoionization detector (Dumas
& Bond, 1982; Collins & Barker, 1983), a Hall electroconductivity
detector (Cairns et al., 1984) or mass spectrometry can also be used
for determination and confirmation of 1,2-dibromoethane. GC-ECD is
the most sensitive method.
The preconcentration of trace 1,2-dibromoethane in samples is
usually carried out through collection by cryogenic trapping or by
absorption on solid absorbents. The former is the preferred
preconcentration technique. Ice formation in the trap-tube during
sampling can be a problem, especially with ambient water and
homogenized food samples. Co-collected water can alter sample or
column flow rates in separation techniques that require subfreezing at
initial GC oven temperature (Pleil et al., 1987).
2.4.1 Air
A convenient analytical method for trace levels of
1,2-dibromoethane in ambient air is a combination of preconcentration
by absorption on porous polymers, such as Tenax, Porapack, Florisil,
silica-gel or charcoal, followed by rapid thermal desorption and
direct application for GC. Tenax GC resin is widely used for
1,2-dibromoethane sampling in ambient air (Barkley et al., 1980; Clark
et al., 1982, 1984a,b; Krost et al., 1982; Harkov et al., 1984),
although Porapack, Chromosorb, silica gel and charcoal have also been
used extensively (Kojima & Seo, 1976; Jagielski et al., 1978; Mann et
al., 1980). 1,2-Dibromoethane is absorbed by passing air samples
through the columns followed by thermal desorption and direct
application to GC. Alternatively, 1,2-dibromoethane in air is
collected by cryogenic cooling in capillary trap-tubes and then
thermally desorbed for GC analysis using trap-ovens with carrier gases
(Barkley et al., 1980; Harkov et al., 1984; McClenny et al., 1984;
Ballschmiter et al., 1986).
The relatively high concentrations of 1,2-dibromoethane in or
near fumigation chambers for foods and in automobile exhaust gases can
be directly determined by sampling with a gas-tight syringe followed
by GC analysis (Hasanen et al., 1979; Dumas & Bond, 1982; Morris et
al., 1982; Collins & Barker, 1983).
Analytical methods for measuring 1,2-dibromoethane in ambient air
are summarized in Table 1.
2.4.2 Water
A purge-trap method using absorbents such as Tenax GC and
Amberlite XAD-4 resin is the most effective concentration technique
for recovering 1,2-dibromoethane from water samples before GC
analysis. The GC test solution is prepared by eluting the absorbent
columns with a small volume of hexane (Spingarn et al., 1982;
Stottmeister et al., 1986). Another method for 1,2-dibromoethane
concentration is direct absorption on organic resins like Amberlite
XAD-1, 2, 4, 7 and 8, and XE-340 (Libbey, 1986). Direct absorption of
water samples on, for example, Amberlite XAD resins can be used for
the concentration of 1,2-dibromoethane in aquatic media (Libbey, 1986;
Woodrow et al., 1986).
Solvent extraction and headspace collection are simple methods
for recovering 1,2-dibromoethane from water samples (Saito et al.,
1978; Keough et al., 1984; Koida et al., 1986).
Analytical methods for measuring 1,2-dibromoethane in water are
summarized in Table 2.
2.4.3 Soils and sediment
1,2-Dibromoethane in sediments can be concentrated by a purge-
trap procedure, either after dilution of sediment samples with water
or after vacuum extraction from sediment samples into a cryogenically
cooled trap (Amin & Narang, 1985).
Analytical methods for measuring 1,2-dibromoethane in soils are
summarized in Table 3.
Table 1. Analytical methods for 1,2-dibromoethane in air
Collection from air Preparation for GC GC conditions Minimum detection Detectora Reference
limit (amount)
Collected on Chromosorb extracted with hexane 1.5% OV-17+1.95% OV-210; 100 pg ECD Mann et al.
101 cartridge (20 ml); extracted with column temp: 75°C; in 70% FSRD (1980)
(10 mm i.d. × 10 cm) 1% MeOH in benzene, gas flow: N2
(ambient air) extract kept in a 70 ml/min
screw-capped test tube
and injected into GC
Collected directly with a applied directly with 5.5% DC-200+11% GF-1/Ga 0.1 ng ECD Morris et al.
gas-tight syringe gas-tight syringe Chrim Q (0.3 mm o.d. × 150 cm, (1982); Morris
stainless steel); column temp: & Rippon (1985)
90°C; gas flow: 40 ml/min
Collected directly with a applied directly with 5% Carbowax 20M/Chromosorb 2 µg PID Dumas &
gas-tight syringe gas-tight syringe W (3 mm i.d. × 200 cm, stainless FSRD Bond (1982)
steel); column temp: 120°C;
gas flow: N2 30 ml/min (portable
gas chromatograph)
Collected with a gas-tight applied by direct CPS-20 M (1/8- × 4 tefron tube); 1 ppb PID Cairns et al.
syringe (ambient air) injection column temp: ambient temp; (1984)
Collected on Tenax GC applied by rapidly Fused silica SP-2000 FSOT not given ECD Harkov et al.
cartridge at a flow rate of raising trap oven GC/MS (1984)
approx.300-1000 ml/min for temperature to 140°C
24 h; desorbed from the with purge of high
cartridge by heating purity N2 (50 ml/min)
rapidly at 250°C and
collected in an evacuated
stainless steel cylinder
under cryogenic conditions
using vacuum distillation
for 30 min (ambient air)
Table 1 (cont'd)
Collection from air Preparation for GC GC conditions Minimum detection Detectora Reference
limit (amount)
Collected on a double applied by rapidly OV-1 fused silica capillary 1 ppb ECD McClenny et
loop of 0.32 mm (o.d.) heating the tube (-150 column (0.32 mm i.d. × 50 m); al. (1984)
nickel tubing packed with to 100°C in 55 sec) and column temp: -50°C (3 min)
60-80 mesh Pyrex beads cooling quickly (120 8°C/min 150°C (7 min)
under cryogenic conditions to -150°C in 225 sec) -50°C (10 min); gas flow:
(-150°C) (ambient air) H2 4 ml/min
a ECD = electron caputure detector; PID = photoionization detector; GC = gas chromatography; MS = mass spectrometry;
FSRD = full-scale recorder deflection
Table 2. Analytical methods for 1,2-dibromoethane in water
Collection Preparation for GC GC conditions Minimum detection Detectora Reference
limit (amount)
Headspace method applied on a fused 1.J & W FSOT (0.326 mm i.d. × 30 m); 1.8 pg GC/MS Keough et al.
silica line Temp: column 70°C, ion source 299°C; (1984)
(0.25 mm i.d. × 100 cm) split ratio: 1:10; gas flow:
at 250-275°C with a 1.5 ml/min; ion dwell time:
gas-tight syringe 100 msec;
2.OV-1 FSOT (0.32 mm i.d. × 50 m); not given ECD
column temp: 60-90°C; split ratio:
1:1; gas flow: He 10 ml/min
N2 100 ml/min
Extracted with applied directly with a 1.5% OV-17 on Chromosorb W 0.05 mg/litre GC/MS Koida et al.
hexane micro-syringe (3 mm i.d. × 150 cm); temp: column (CI-NID) (1986)
200°C; separator 120°C; ion source
200°C; reaction gas: isotutane;
gas flow: H2 20 ml/min
Collected by purging applied by rapidly 0.2% Carbowax 1500 on Carbopack C 0.3 mg/litre FID Stottmeister et
into purge-trap thermal desorption (3 mm i.d. × 200 cm); column temp: al. (1986)
tubing (Tenax GC (200°C) 35°C (4 min), (8°C/min) 170°C
155 mg) at flow (20 min); gas flow: N2 4 ml/min
rate of 50 ml/min
for 30 min
Table 2 (cont'd)
Collection Preparation for GC GC conditions Minimum detection Detectora Reference
limit (amount)
Collected by absorption extracted with ether 1.DB-1701 FSOT(0.25 mm i.d. × 30 m); 1 ppt ECD Woodrow et
on Amberlite and concentrated in column temp: 230°C; split ratio: al. (1986)
XAD-4 cartridge Kudernadanish 1:10; gas flow: H2 19 ml/sec at
column ball concentrator with 3 230°C; make-up gas Ar/CH4 20 ml/sec;
(4.7 mm o.d. × 12 cm) at Snyder column; applied 2.SE-54 FSOT (0.25 mm i.d. × 30 m);
flow rate of 10 ml/min with a microsyringe column temp: 100°C (5°C/min)
for 18-24 h 250°C (other conditions described
above)
a ECD = electron capture detector; GC = gas chromatography; MS = mass spectrometry; FID = flame ionization detector;
CI = chemical ionization; NID = negative ion detector
Table 3. Analytical methods for 1,2-dibromoethane in soil
Collection Preparation for GC GC conditions Minimum detection Detectora Reference
limit (amount)
Collected by steam fortify 50 ml of the not given ECD Abdel-Kader
distillation of an extract to folder paper et al. (1979)
aqueous slurry of soil and then measure with
into dry-ice-cooled molecular emission cavity
solvent (acetone: analyser; 4 mm × 4 mm
isooctane = 1:1) deep stainless steel
under N2 stream at cavity; gas flow:
60°C and drying H2 2.5 litre/min;
over Na2SO4 N2 4.0 litre/min;
wave length: 376 nm;
split: 1.4 nm
Collected on Prapack apply by thermal 4% OV-11 & 6% SP 2100 Supelcopor 7 ppb PID Amin &
N by purge of desorption of the (2.0 mm × 2.7 m); column temp: 40°C Narang (1985)
an aqueous slurry absorbent spiked with (5 min), (3°C/min) 70°C; gas flow:
of soil for 30 min fluorobenzene as an N2 30 ml/min, 15% SF-95 & 6% OV-225 1 ppb ECD
internal standard on Chromosorb W (2 mm i.d. × 3.6 m);
column temp: 60°C (10 min),
(3°C/min) 80°C (10 min) 65°C-75°C
(isothermal)
DB-5 FSOT(0.25 mm i.d. × 60 m) PID
column temp: 50°C (15 min) (4°C/min) ECD
170°C (14 min); gas flow:
He 60 cm/sec make-up gas He 8 ml/min
a ECD = electron caputure detector; PID = photoionization detector; GC = gas chromatography; FID = flame ionization detector
2.4.4 Food
Continuous extraction with hexane in a Dean-Stark apparatus for
one hour or soaking in a solvent solution of ethanol or acetone and
water (1 : 5) for 2 or 3 days is used for the analysis of
1,2-dibromoethane in agricultural crops and their products. A highly
sensitive method for the analysis of 1,2-dibromoethane in flour and
biscuits was developed by Rains & Holder (1981). Continuous
extraction with hexane is used for fruit, vegetables and grains
(Sekita et al., 1981, 1983; Kato et al., 1982; Iwata et al., 1983;
Konishi et al., 1985; De Vries et al., 1985; Alleman et al., 1986;
Nakamura, 1986).
Soaking in aqueous ethanol or acetone and water solution is used
for grains and their products (Clower, 1980; Daft, 1983, 1985, 1987;
Cairns et al., 1984; Barry & Petzinger, 1985; Sawyer & Walters, 1986;
Clower et al., 1986). For fruit (papaya and lemon), hexane, hexane-
water and acetonitrile are used. In the case of grain, intermediate
products, ready-to-eat products, corn bread mix, baby cereal and
bread, 1,2-dibromoethane can be extracted with an acetone-water (5+1)
solution, 0.1N HCl or light petroleum. Where necessary, Florisil
cleanup is useful for the removal of materials interfering with GC
analysis.
The purge-trap method on layers of Tenax TA (Heikes, 1985a,b),
Tenax resins (GC and TA) or Amberlite XAD-4 (Heikes & Hopper, 1986;
Daft, 1988) under a nitrogen gas stream is also used for the
collection of 1,2-dibromoethane from grains and their products. The
resins are eluted with hexane.
Automated headspace analysis is employed for measurement of
1,2-dibromoethane in fumigated crops in combination with GC-ECD and
GC-MS (Mestres et al., 1980; Entz & Hollifield, 1982; Gilbert et al.,
1985; Pranoto-Soetardhi et al., 1986). Equilibrium partitioning
between the samples and the gaseous headspace can be accelerated by
warming the vials. For detection, the gas chromatographic method with
an electron capture detector is used in all the above-mentioned
methods. Gas chromatography-mass spectrometry is also used. The
detection limit ranges from 0.1 µg/kg to a few µg/kg according to the
method used and the food being tested.
1,2-Dibromoethane can be analysed in animal feed by continuous
extraction with hexane in a Dean-Stark apparatus, followed by cleanup
on a Florisil column (Ishikuro, 1986).
3. SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE
3.1 Natural occurrence
1,2-Dibromoethane is not a naturally occurring substance.
3.2 Anthropogenic sources
3.2.1 Production levels and processes
3.2.1.1 World production figures
In 1975, 1400 tonnes was produced in Japan. Production in
Belgium, France, Italy, the Netherlands, Spain, Switzerland and the
United Kingdom, was estimated to be between 3000 and 30 000 tonnes
(IARC, 1977).
3.2.1.2 Manufacturing processes
1,2-Dibromoethane is made by direct bromination of ethylene or
reacting hydrobromic acid with acetylene (Roskill, 1992).
3.2.2 Uses
Major uses of 1,2-dibromoethane are as a lead scavenger in
tetraalkyllead petrol and antiknock preparations, as a soil and grain
fumigant, as an intermediate in the synthesis of dyes and
pharmaceuticals, and as a solvent for resins, gums and waxes (IARC,
1977).
Reduction in the use of leaded gasoline from the late-1970s in
developed countries and of 1,2-dibromoethane for agricultural
applications in the 1980s, owing to its carcinogenicity in animals,
reduced human exposure to 1,2-dibromoethane. However, it is still used
in large amounts for many industrial purposes in developed countries,
and as a petrol additive in developing countries.
3.2.2.1 Petrol additive
1,2-Dibromoethane has been added to scavenge the inorganic lead
compounds (e.g., lead oxide and sulfate) remaining after fuel
combustion. Lead accumulation is prevented by the reaction of
1,2-dibromoethane with lead oxide to form volatile lead bromide, which
can pass from the combustion chamber to the atmosphere (IARC, 1977).
In 1981, use as a lead scavenger represented 83% of the
1,2-dibromoethane consumed (SRI International, 1982).
In 1972, 122 000 tonnes 1,2-dibromoethane was added to petrol
formulations in the USA; this figure declined to 73 000 tonnes in 1980
and to 24 000 tonnes in 1992 (Roskill, 1992). In 1992, sales of
unleaded petrol accounted for more than 90% of petrol in the USA. In
the European Community, all new vehicles must be fitted with
three-way convertors that can only use unleaded petrol by the
mid-1990s. This is also true of Japan, where almost all cars run on
unleaded petrol (Roskill, 1992).
In 1992, demand for 1,2-dibromoethane as a gasoline additive in
the USA was 24 000 tonnes and consumption outside the USA, principally
in Europe, was 25 000 to 30 000 tonnes, giving an estimated world
demand of 49 000 to 54 000 tonnes. The amount of 1,2-dibromoethane
used in Germany in 1989 was 980 tonnes, calculated on the basis of the
petrol consumed in the Federal Republic of Germany in 1989 (BUA,
1991). Legislation banning the use of lead in gasoline and controlling
the agricultural use of 1,2-dibromoethane has reduced world demand for
1,2-dibromoethane by at least 75% (Roskill, 1992).
3.2.2.2 Fumigant
The volatility of 1,2-dibromoethane allows it to be distributed
as a gas through substances such as soil in sufficiently high
concentrations to kill target pests. Its chemical and biocidal
properties allowed it to be effectively utilized in a wide range of
applications. Its primary pesticidal use has been as a soil
nematocide (Pignatello & Cohen, 1989).
1,2-Dibromoethane has been used in the spot fumigation of grain
milling machinery, post-harvest fumigation of grain, and in the
control and prevention of infestations in produce. Additional minor
uses have been the control of bark beetles in felled logs, moths in
stored furniture and clothing, termites under concrete slab
foundations and porches, Japanese beetles in balled ornamental trees
and grass sod, and wax moths in stored honeycombs and beehive
superstructures.
In post-harvest grain fumigation of barley, maize, oats, rice,
rye, sorghum and wheat, 1,2-dibromoethane has often been used in
conjunction with 1,2-dichloroethane (ethylene dichloride) or carbon
tetrachloride.
Residues of 1,2-dibromoethane in tropical fruits, imported wheat
and beans have been prohibited in Japan (MHW, 1985, 1987, 1988). Use
of 1,2-dibromoethane for agricultural purposes has been prohibited in
Egypt, Kenya, the Netherlands, Sweden, the United Kingdom and the USA
(BUA, 1991; IRPTC, 1993). However, it is still used for quarantine
purpose in some countries.
4. ENVIRONMENTAL TRANSPORT, DISTRIBUTION AND TRANSFORMATION
4.1 Transport and distribution between media
The use of 1,2-dibromoethane on a field contaminated both the
field and crops for 2 years (Yuita, 1984). About 10% of bromine-
containing pesticides was retained, in the form of bromine, in the
soil and crops. The remaining 90% seemed to have moved to underground
water and rivers.
4.1.1 Air
The atmospheric chemistry of bromine compounds has received
attention because of the role that they play in the depletion of the
stratospheric ozone layer. Wofsy et al. (1975) suggested that bromine
atoms can be more effective than chlorine atoms in the catalytic
destruction of ozone. A major uncertainty is the absolute
concentration of bromine compounds in both the troposphere and the
stratosphere.
4.1.2 Soil
Injection of 1,2-dibromoethane as a soil fumigant at 70 kg/ha
into fine sandy loam resulted in a concentration of 130 µg/kg nearly
one year later (Steinberg et al., 1987).
The disappearance with time of 1,2-dibromoethane was measured in
a sediment-water mixture (ratio 0.075) and a half-life of 55 h was
calculated (Jafvert & Wolfe, 1987).
Important factors influencing the movement of soil fumigants
include their physical and chemical characteristics, temperature,
moisture, presence of organic matter, soil texture and soil profile
variability (Munnecke & Van Gundy, 1979).
1,2-Dibromoethane is moderately hydrophillic, having a calculated
octanol-water partition coefficient of 58 (Lyman, 1982). At
environmental levels (10-1000 ppb), 1,2-dibromoethane has a soil
organic carbon partition coefficient of 66 ml/g (Rogers & McFarlane,
1981).
1,2-Dibromoethane has a low vapour pressure and moves slowly in
the vapour phase. Little, if any, mass flow occurs except in
extremely warm soil or when water is applied. Soil temperature is
important and may affect 1,2-dibromoethane movement in several ways.
A rise in temperature increases the vapour pressure and decreases the
solubility. This alters the phase distribution and results in an
increase in the rate of diffusion of 1,2-dibromoethane through soils.
Fumigation of warm soils (25°C) results in a faster rate and greater
distance of nematicide diffusion. In colder soils (5°C), the rate of
diffusion is slower and the persistence of the chemical is longer, but
the total distance of diffusion of an effective dosage is decreased.
The approximate movement and fate of 1,2-dibromoethane in two soils
were predicted using extrapolations from laboratory experiments and
soil-vapour phase concentrations obtained from simulated field
experiments. The most far-reaching diffusion patterns in mineral
soils are those obtained in soils whose moisture content is nearest
the wilting point of plants (15 bars moisture tension). As the
moisture content of the soil is increased, the diffusion pattern
gradually becomes more limited. The soil texture and type determine
to a large extent the amount of soil moisture present and the size of
the connecting air spaces. Soil air space and the size of pores are
important because these chemicals move primarily in the vapour phase
and smaller pores are most easily blocked when water is present. A
material balance for 1,2-dibromoethane was surveyed when
1,2-dibromoethane (equivalent to 47 litres/ha) was applied under
various conditions to several soils using a soil fumigation technique
in both field and laboratory experiments. Most of the
1,2-dibromoethane was accounted for; the remainder was mostly
irreversibly adsorbed or lost during sampling. The 1,2-dibromoethane
not accounted for represented between 10 and 40%. After 3 days at
15°C, about 40% of the 1,2-dibromoethane was absorbed in the
soil-particle phase, 25% was in the soil-water phase, and 20% remained
in the liquid state (McKenry & Thomason, 1974).
1,2-Dibromoethane soil fumigation is used for the control of
plant parasitic nematodes on high value crops. In Ontario, Canada,
soil types fumigated varied from loamy sand to muck. Three soils
differing in texture (Fox loam sand, Vineland silt loam and Lincoln
clay) were studied for penetration of 1,2-dibromoethane (Townshend et
al., 1980). Fox loam sand (highest content of sand and lowest of
organic matter) showed the most rapid penetration; moisture level,
temperature and their interactions had the greatest effects on
movement of 1,2-dibromoethane. On Vineland silt loam (medium-textured
soil) the degree of penetration was dependent on moisture, temperature
and bulk density, and there were relatively small interaction effects.
On Lincoln clay (high content of organic matter and fine-textured
soil) 1,2-dibromoethane did not move in the soil, regardless of
edaphic factors, thus explaining the difficulty of using
1,2-dibromoethane fumigation to control nematodes in clay.
1,2-Dibromoethane persists in top soil at µg/kg levels for at
least 20 years, despite its predicted lability in the environment
(high water solubility and low soil-water partition coefficient).
Misleading results were obtained when studies of microbial
degradation, sorption, desorption and analytical recovery were
conducted with freshly spiked soils or sediments (Pignatello, 1986).
1,2-Dibromoethane can serve as a C1 unit and energy source for some
soil aerobic or anaerobic microorganisms. However, residual
1,2-dibromoethane is strongly bound to soils and can only be extracted
from them by warming with polar solvents. Surfactants showed no
enhanced extraction ability. Thermal desorption at temperatures as
high as 200°C in an N2 stream resulted in more decomposition than
desorption, while a fresh spike of 14C-labelled 1,2-dibromoethane
was recovered quantitatively.
Diffusion of residual 1,2-dibromoethane from soil to water is
very slow and highly temperature-dependent (diffusion coefficient:
10-16 cm2/sec) (Pignatello et al., 1987). 1,2-Dibromoethane, when
present as a groundwater contaminant in areas where it had been used
as a soil fumigant, was degraded anaerobically by microorganisms in
two types of soils from 1,2-dibromoethane-contaminated groundwater
discharge areas. At initial concentrations of 6 to 8 µg/litre,
1,2-dibromoethane was degraded in a few days to near or below the
detection limit (0.02 µg/litre). At 15 to 18 µg/litre degradation was
slow. Bromide ion released at the higher concentration was 1.4 ± 0.3
and 23.1 ± 0.2 molar equivalents for the two soil types. A study
using 14C-1,2-dibromoethane showed that 1,2-dibromoethane was
converted to approximately equal amounts of CO2 and cellular carbon;
only small amounts of 14C were not attributable to these products.
However, 1,2-dibromoethane was not degraded in autoclaved soil water
samples. The results suggested that, initially, microbial degradation
of 1,2-dibromoethane in the topsoil was too slow to prevent leaching
of large quantities to groundwater. With continued application the
microbial community may have adapted to the higher levels and
degradation rates increased; this has been observed with other
agricultural chemicals. The results of acetate incorporation studies
suggested that the highest application rates of 1,2-dibromoethane are
definitely toxic to topsoil microbial communities.
5. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE
5.1 Environmental levels
5.1.1 Air
1,2-Dibromoethane enters the atmosphere from its use as a petrol
additive to scavenge the lead oxide resulting from the combustion of
alkyllead antiknock additive, and from its use in agriculture as an
insecticidal and fungicidal fumigant.
Nilsson et al. (1987) reported that the exhaust gas of chain saws
fuelled with petrol contained a mean 1,2-dibromoethane level of
0.0008 (0.0001-0.001) mg/m3 under snow-free conditions and
0.002 (0.0001-0.005) mg/m3 with snow on the ground during the
winter. 1,2-Dibromoethane levels are around 45% higher in cold start
than in hot start conditions and have a tendency to decrease with
increasing vehicle speed (see Tables 4 and 5). Concentrations of
1,2-dibromoethane in raw, undiluted exhaust from vehicles using leaded
petrol are in the range of 55-146 µg/m3 (7.2-19 ppb), 46-122 µg/m3
(6.0-16 ppb) and 38-115 mg/m3 (5.0-15 ppb) under the conditions of
USA Federal test driving, idle, and a steady speed of 30 mph,
respectively (Jacobs, 1980). Based on these levels, 1,2-dibromoethane
concentrations in air alongside roads due to vehicle exhaust emissions
may range from 0.04 to 122 µg/m3 (0.005-0.19 ppb). These results
are similar to the observations of Leinster et al. (1978).
Table 4. 1,2-Dibromoethane produced by motor vehicles (petrol engine)
under constant speed test conditions
Vehicle speed km/h Concentration (µg/m3)
Engine not Vehicle with Vehicle with
defineda 3 litre engineb 0.85 litre engineb
Cold start (idle) 70 878 332
10 78
30 62-70 618 165
40 61
50 2 669 155
64 180 139
80 98 135
a Leinster et al. (1978)
b Tsani-Bazaca et al. (1981)
Table 5. 1,2-Dibromoethane in the exhaust emission of motor vehicles
(petrol engine) (µg/m3)a
Conditions 3 litre engine 0.85 letre engine
ECEb
cold start 292-560 733-538
hot start 200-234 533-538
ECD/CVSc 14-25 26-34
USA Federald
cold start 48 29
hot start 22
a From: Tsani-Bazaca et al. (1981)
b standard European driving cycle
c ECE driving cycle under constant volume sampling condition
d 1973 driving cycle
1,2-Dibromoethane levels in air have been measured at several
sites around the world (Table 6). Leinster et al. (1978) concluded
that the lower levels during the autumn were the result of a reduction
in evaporative loss particularly from parked vehicles (the calculated
evaporation rate for 1,2-dibromoethane at 5°C is less than one third
of that at 30°C). An indication of the magnitude of evaporative loss
from parked vehicles was provided by levels of 0.02-0.05 µg/m3
measured in a car park. It was also probable that an opposite trend
would be produced by a change in driving conditions. For example,
cold starts and driving speeds of vehicles have a marked influence on
the 1,2-dibromoethane content of exhaust emissions.
The 1,2-dibromoethane added to leaded petrol contributes to a
large amount of methyl bromide in urban atmospheres. IPCS (1995)
estimated that per annum between 7000 and 18 000 tonnes of methyl
bromide could be emitted from car exhausts. Reactions in the lower
troposphere with hydroxyl radicals and other chemical species are the
most important of the possible removal mechanisms within the
atmosphere (UNEP, 1992). The end-products of both photodissociation
of methyl bromide and reactions with hydroxyl radicals in the
atmosphere include bromide species (BUA, 1987). Active bromine
species react with ozone mainly in the lower stratosphere and are
thought to be partly responsible for the destruction of the ozone
layer. However, 1,2-dibromoethane was not included as a controlled
substance in the "Montreal Protocol on Substances that Deplete the
Ozone Layer".
Table 6. Environmental concentrations of 1,2-dibromoethane
Location Measuring period Concentration (µg/m3) Reference
London August 1976a 0.08-0.09 µg/m3 Leinster et al. (1978)
December 1976b 0.001-0.01 µg/m3
12 Canadian cities 1989-1992 mean 0.05 ± 0.05 µg/m3 Environment Canada
range n.d.-1.73 µg/m3 (1994)
Busy streets at 2 m height 0.07-1.26 µg/m3 Tsani-Bazaca et al.
and 5 m from kerbside (1981)
Los Angeles, California, USA 9-21 April 1979 0.25 ± 0.20 ng/m3 (33.2 ± 26.2 ppt) Singh et al. (1981)
range 0.041-1.4 ng/m3 (5.4-187.2 ppt)
Oakland, California, USA 28 June-10 July 1979 0.12 ± 0.10 ng/m3 (15.8 ± 12.5 ppt) Singh et al. (1981)
range 0.018-0.65 ng/m3 (2.4-84.5 ppt)
Phoenix, Arizona, USA 23 April-6 May 1979 0.31 ± 0.29 ng/m3 (40.3 ± 38.3 ppt) Singh et al. (1981)
range 0.018-1.6 ng/m3 (2.4-204.4 ppt)
Background 38 ng/m3
Various cities (7) 1-2 weeks in 1980 0.122-0.453 ng/m3 (0.016-0.059 ppt)c Singh et al. (1982)
2.826 ng/m3 (0.368 ppt)d
Denver, Colorado, USA 1-2 weeks n.d.-2.304 µg/m3 (0.3 ppb) Going & Spigarelli (1976);
Leinster et al. (1978)
Sites in New Jersey, USA late 1983-Spring 1984 0.077-5.4 µg/m3 Harkov et al. (1985)
Summer 1981 < 0.038 µg/m3 Harkov et al. (1983)
Winter 1982 < 0.038 µg/m3 Harkov et al. (1983)
Table 6 (cont'd)
Location Measuring period Concentration (µg/m3) Reference
Central London Summer 1982 0.23 µg/m3 (0.03 ppb)e,f Clark et al. (1984a,b)
Exhibition Road May-August 1983 0.23 µg/m3 (0.03 ppb)e
Rural site Summer 1982 0.12 µg/m3 (0.015 ppb)e,g Clark et al. (1984a,b)
Silwood Park, United Kingdom May-August 1983 0.15 µg/m3 (0.019 ppb)e
Motorway outside London, Summer 1982 0.39 µg/m3 (0.05 ppb)e,h Clark et al. (1984a,b)
Toddington May-August 1983 0.31 µg/m3 (0.04 ppb)e
Central London Summer 1982 1.0 µg/m3 (0.13 ppb)i Clark et al. (1984a,b)
May-August 1983 0.62 µg/m3 (0.08 ppb)i
Motorway site Summer 1982 2.0 µg/m3 (0.26 ppb)i Clark et al. (1984a,b)
May-August 1983 1.2 µg/m3 (0.15 ppb)i
Anchorage (Alaska) March 1983 31-177 ng/m3 (4-23 ppt) Berg et al. (1984)
Barrow (Alaska) March 1983 n.d.-177 ng/m3 (n.d.-28 ppt) Berg et al. (1984)
Mould Bay Coast (Alaska) March 1983 38-284 ng/m3 (5-37 ppt) Berg et al. (1984)
Thule (Greenland) March 1983 15-246 ng/m3 (2-32 ppt) Berg et al. (1984)
North Pole March 1983 92.2 ng/m3 (12 ppt) Berg et al. (1984)
Ny-Alesund (Norway) March-April 1983 31-150 ng/m3 (4-20 ppt) Berg et al. (1984)
Table 6 (cont'd)
Location Measuring period Concentration (µg/m3) Reference
Bear Island (Norway) March-April 1983 23-100 ng/m3 (3-13 ppt) Berg et al. (1984)
Bodo (Norway) March-April 1983 38-110 ng/m3 (5-14 ppt) Berg et al. (1984)
a temperature range 28-30°C
b temperature range 4-8°C
c average level for each city
d maximum concentration found in Houston, Texas, USA
e mean hourly concentrations
f range 0.078-1 µg/m3 (0.01-0.13 ppb)
g range ND-0.78 µg/m3 (ND-0.01 ppb)
h range 0.07-2.0 µg/m3 (0.009-0.26 ppb)
i maximum hourly concentrations
1,2-Dibromoethane levels of 0.07-1.26 µg/m3 have been found in
busy streets. Higher levels were found in a road tunnel and were
associated with poor ventilation (Tsani-Bazaca et al., 1981). Three
field studies on the measurement of selected potentially hazardous
organic compounds in urban environments were conducted in the USA in
1979 (Los Angeles, California, 9-21 April; Oakland, California,
28 June-10 July; and Phoenix, Arizona, 23 April-6 May). These studies
were performed to characterize the atmospheric abundance, fate and
human exposure to these compounds (Table 6). The background
concentration of 1,2-dibromoethane was 38 ng/m3 (5 ppt). Assuming
an average respiratory volume of 23 m3 at 25°C and 1 atm for a 70-kg
male, the average daily dose (µg/day) of 1,2-dibromoethane at these
locations can be calculated as 6.0 ± 2.7 for Los Angeles, 2.9 ± 0.8
for Oakland and 7.0 ± 2.7 for Phoenix. The ratios of
1,2-dibromoethane to total haloethane and VHH (volatile halogenated
hydrocarbons) in the average daily doses were 2.7% and 0.57%, 5.6% and
1.14%, and 2.8% and 1.03%, respectively. The chemical loss rate of
1,2-dibromoethane was 2.8% per day (sunlight = 12 h). There was
diurnal variation in 1,2-dibromoethane levels at the three locations.
The afternoon minimum at Phoenix was attributed to deep vertical
mixing associated with hot and dry weather. The afternoon maximum at
Oakland was most likely a result of transport from upwind sources
(Singh et al., 1981).
Other studies measuring 1,2-dibromoethane in the ambient
atmosphere of urban and rural areas have been performed (Going & Long,
1975; Going & Spigarelli, 1976). Sources of 1,2-dibromoethane in air
were considered to be emissions from stations dispensing leaded petrol
and evaporative emissions from motor vehicles using leaded petrol.
Atmospheric levels of 1,2-dibromoethane were low (0.046 to
3.5 µg/m3) (0.006 to 0.45 ppb) in worst case conditions near petrol
stations and with heavy traffic in cities. These levels are 10 to
10 000 times less than the occupational exposure level of 1 mg/m3
(0.13 ppm) for 15 min recommended by the US National Institute of
Occupational Safety and Health (Jacobs, 1980).
Tsani-Bazaca et al. (1981) monitored the concentrations of VHH
collected in 1979 at several locations and utilizing vehicles
operating under various conditions on a busy road in central London
(2000 vehicles/h), a poorly ventilated tunnel (1600 vehicles/h at peak
traffic flow), and a semi-rural industrialized area. The
concentration of 1,2-dibromoethane varied between 0.07 and
1.26 µg/m3. There was a good correlation between 1,2-dibromoethane
and benzene concentrations (correlation coefficient : 0.93) at the
three locations and a higher correlation between 1,2-dibromoethane and
1,2-dichloroethane (correlation coefficient : 0.94).
In 1983, 54 air samples at 6 urban sites and 54 air samples at
6 mountainous sites were collected in Japan and were analysed for the
presence of 1,2-dibromoethane. A total of 35 samples from 5 urban
sites contained 1,2-dibromoethane at concentrations of
0.008-0.322 µg/m3 (0.001-0.042 ppb). The detection limit was
0.005-0.008 µg/m3 (0.0007-0.001 ppb). A total of 36 samples from
5 mountainous sites contained 1,2-dibromoethane at concentrations of
0.008-0.515 µg/m3 (0.001-0.067 ppb). The detection limit was
0.002-0.008 µg/m3 (0.0003-0.001 ppb) (Environment Agency Japan,
1985).
Urban 1,2-dibromoethane levels at seven sites in selected cities
in the USA in 1980, using on-site and real-time measurement instrument
following a 24-h measurement schedule for a period of 1-2 weeks, were
0.12-0.45 µg/m3 (16-59 ppt) (Singh et al., 1982). The average
concentration of 1,2-dibromoethane did not exceed 0.015-0.46 µg/m3
(0.06 ppb) (average range 0.002-0.06 ppb) at any study site and
average levels ranged from 0.122 µg/m3 (0.016 ppb) at St. Louis,
Missouri, to 0.46 µg/m3 (0.059 ppb) at Houston, Texas. The maximum
concentration of 2.83 µg/m3 (0.368 ppb) was found at Houston. In
general, the highest average levels were found during the night and
early morning. In the case of Denver, Colorado, typical ambient
concentration data suggested a range of not detectable to 2.3 µg/m3
(0.300 ppb) (Going & Spigarelli, 1976; Leinster et al., 1978).
The Office of Science and Research (USA) monitored VHH in ambient
air at listed abandoned hazardous waste sites and sanitary landfills
in New Jersey (Harkov et al., 1985). 1,2-Dibromoethane was found at
mean levels of 2.1 µg/m3 (0.27 ppb), 2.2 µg/m3 (0.288 ppb),
3.6 µg/m3 (0.47 ppb), 5.4 µg/m3 (0.7 ppb), 0.38 µg/m3
(0.05 ppb), 0.077 µg/m3 (0.01 ppb) and 0.15 µg/m3 (0.02 ppb) at
different sites during late 1983 and early 1984. It was below the
detection limit 0.038 µg/m3 (0.005 ppb) at three sites during the
summer of 1981 (Harkov et al., 1983) and the winter of 1982 (Harkov et
al., 1984).
Ambient air monitoring survey of VHH at a busy road in central
London, a rural site and a motorway location near London showed mean
hourly 1,2-dibromoethane concentrations of 0.23, 1.2 and 0.39 µg/m3
(0.03, 0.15 and 0.05 ppb), respectively, in summer 1982 and 0.23, 0.15
and 0.31 µg/m3 (0.03, 0.019 and 0.04 ppb) between May and August
1983 (Clark et al., 1984a,b). The maximum hourly concentrations of
1,2-dibromoethane at the urban and motorway sites were 1.0 and
2.0 µg/m3 (0.13 and 0.26 ppb) in 1982, and 0.61 and 1.2 µg/m3
(0.08 and 0.15 ppb) in 1983, respectively. 1,2-Dibromoethane
concentrations at the urban site were in the same ranges
0.07-0.31 ng/m3 (0.01-0.04 ppt) as those measured by other workers
(Leinster et al., 1978; Tsani-Bazaca et al., 1981; Singh et al.,
1982). The low concentrations found at the rural site were primarily
related to the low incidence of vehicular pollutant sources in the
area. However, the site was near the urban fringe of London and near
several small towns and this may explain occasional elevated
concentrations.
1,2-Dibromoethane concentrations were measured at Point Arena,
California between 1979 and 1981; the background level of
1,2-dibromoethane in the troposphere was found to be less than
0.023 µg/m3 (3 ppt) (Singh et al., 1983).
Berg et al. (1984) measured atmospheric 1,2-dibromoethane
concentrations at eight arctic sites in 1983. Concentrations at three
sites in Alaska (Anchorage, Barrow, Mould Bay Coast) in March were
0.031-0.177 µg/m3 (4-23 ppt), not detectable to 0.22 µg/m3
(29 ppt) and 0.038-0.284 µg/m3 (5-37 ppt), respectively.
1,2-Dibromoethane levels in Greenland (Thule) and at the North Pole in
March were 0.015-0.246 µg/m3 (2-32 ppt) and 0.096 µg/m3 (12 ppt),
respectively. Those at Norwegian sites (Ny-Alesund, Bear Island,
Bodo) during March-April were 0.031-0.15 µg/m3 (4-20 ppt),
0.023-0.10 µg/m3 (3-13 ppt) and 0.038-0.11 µg/m3 (5-14 ppt),
respectively. The mean concentration ± standard deviation was
0.084-0.77 µg/m3 (11 ± 10 ppt). Other organobromine compounds, such
as methyl bromide, methylene dibromide and bromoform, were detected at
similar concentrations.
Monthly monitoring of the atmosphere of Barrow, Alaska (72 °N),
showed that the 1,2-dibromoethane concentration was higher in winter
than in other seasons, although the monthly average concentrations did
not differ greatly (7.68-10.7 ng/m3) (1.0-1.4 ppt) except in
January. From the results of atmospheric VHH monitoring, Rasmussen &
Khalil (1984) suggested that VHH in arctic air might be an indicator
of polluted air transported from industrial mid-latitude sources.
5.1.2 Water
Widespread use of 1,2-dibromoethane as a soil fumigant in the USA
resulted in its detection in both groundwater and surface water in
California, Florida, Georgia, and Hawaii (Sun, 1984), Connecticut
(Isaacson et al., 1984) and New Jersey (Page, 1981), and in wells used
for irrigation in Georgia (Martl et al., 1984). 1,2-Dibromoethane
was reported in groundwater in Georgia, California, Florida, and
Hawaii by US EPA (1986).
Laboratory studies have shown that 1,2-dibromoethane
photohydrolyses rapidly in aqueous solutions when irradiated. The
degradation is a two-stage process in which 1,2-dibromoethane is
converted to bromoethanol (half-life, 7.6 min) and then to ethylene
oxide (half-life, 64 min). Further degradation to ethylene glycol was
less influenced by light, as shown by a half-life of 10 days (Castro &
Belser, 1978). While the above study provides some understanding of
aqueous degradation, Logan (1988) cautions that the efficiency of the
photo-reactions were not reported in terms of quantum yield.
1,2-Dibromoethane was found in ground- and surface water in New
Jersey (over 1000 different wells and 600 different sites) during
1977-1979; the highest levels were 0.2 µg/litre in surface water and
48.8 µg/litre in groundwater (Page, 1981).
Analyses of 350 well water samples from Connecticut in 1984
revealed concentrations of up to 2 µg/litre. 1,2-Dibromoethane was
rapidly lost from water samples exposed to the atmosphere or boiled
for few minutes. It could not be detected in water samples purged
with nitrogen for 10 min (Isaacson et al., 1984).
In southwest Georgia, USA, agricultural practices involve
intensive use of groundwater for irrigation and pesticides for control
of plant and insect pests. 1,2-Dibromoethane was found at levels of
between 1 and 90 µg/litre in water samples from three irrigation wells
collected between 1981 and 1983. Application at ratios of
14-19 litres/ha) near wells showed that 1,2-dibromoethane
concentrations in the aquifer did not appear to be directly related to
the application rate of the compound to the surface. The
concentrations in the wells may reflect application of the compound at
sites some distance from the wells (Martl et al., 1984).
In 1982, 27 water samples and 27 bottom sediment samples were
collected at nine sites in Japan and were analysed for the presence of
1,2-dibromoethane. None of the water or bottom sediment samples
contained 1,2-dibromoethane. The detection limit was 0.3-2 µg/litre
for water and 0.0016-0.01 µg/kg for bottom sediment (Environment
Agency Japan, 1985).
In 1983, 1,2-dibromoethane surveillance of the water of six rural
wells in Ibaraki prefecture, Japan, where 1,2-dibromoethane was used
for soil fumigation or as a pesticide on pine tree, showed no
1,2-dibromoethane contamination (detection limit, 5 µg/litre) (Nemoto
et al., 1984).
Groundwater samples from nine sites in and around vegetable-
growing areas in Gifu Prefecture, Japan, were collected twelve times
between July 1983 and December 1984. 1,2-Dibromoethane levels ranged
from 0.06 to 0.55 µg/litre at seven sites and the mean values of
1,2-dibromoethane at each site varied between 0.15 and 0.28 µg/litre.
1,2-Dibromoethane levels in groundwater around the vegetable-growing
areas did not differ from those within the areas, where
1,2-dibromoethane application was limited to once a year in the first
two weeks of July. Sites where 1,2-dibromoethane were detected around
these areas overlapped completely the stream of groundwater coming
from these areas (Terao et al., 1985). The annual variation of
concentrations in the groundwater was small. 1,2-Dibromoethane
concentration showed good correlation with bromine ion concentration
and bromine ion/chlorine ion ratio at each site (Terao et al., 1984).
Mayer et al. (1991) studied 1,2-dibromoethane concentrations in
detail in water from a domestic well, approximately 10 m deep, in a
fruit growing area of Whatcom County, Washington, USA where
1,2-dibromoethane had been used extensively prior to its 1983 ban.
Additional wells (n = 107) were also sampled over a 4-year period; no
details of well depths were given. Correlation analysis showed no
relationship between 1,2-dibromoethane concentration in water and
temperature but significant negative correlation between precipitation
and 1,2-dibromoethane. The analysis allowed lag times of between
0 and 12 months; a 3-month lag was found to give the best relationship
between precipitation and 1,2-dibromoethane in the water. The
dilution effect of precipitation was followed by slow
1,2-dibromoethane infiltration from overlying soils which tended to
re-establish prior concentrations over about 3 months. The authors
stated that water contamination can result from such continuing
infiltration of soil-matrix-derived 1,2-dibromoethane long after
agricultural use has ceased.
5.1.3 Food
Beckman et al. (1967) reported that part of the inorganic bromine
in foods and raw agricultural commodities comes from the soil.
1,2-Dibromoethane was applied annually at 54 kg/ha and samples from
40 crops grown in soil treated with 1,2-dibromoethane were analysed
over a 3-year period. In general, leafy portions of plants contained
the highest levels of bromide on the basis of weight. Residue levels
were calculated as inorganic bromide ion present in the crop after
harvest. Levels in crop samples from untreated soil were less than
1.6 mg/m3 (0.2 ppm), and the highest level in crops from treated
soil was 137 mg/kg (17.8 ppm) in sugar beet tops. Most of the crops
were harvested about 100 days after soil treatment but time from
treatment to harvest ranged from 55 days for strawberries to 10 years
for walnuts.
1,2-Dibromoethane was absorbed strongly by cereal, grains, cereal
products and other produce during the fumigation period. Even when
normal ventilation procedures were followed, residues of
1,2-dibromoethane disappeared very slowly. Nearly all the
1,2-dibromoethane was physically sorbed and at normal temperatures
there was little formation of inorganic bromide. However,
occasionally in produce at higher temperatures and moisture content
there was rapid breakdown to inorganic bromide (Heuser & Scudamore,
1967).
Levels of 1,2-dibromoethane in wheat were between 10 and
20 mg/kg, and, for its products, between 2 and 4 mg/kg in flour,
0.002-0.04 in white bread and 0.006-0.16 in wholemeal bread. When
flour was treated directly with 1,2-dibromoethane, ventilated
thoroughly, and then baked into loaves, there were residues of
20-24 mg/kg in the flour and 0.33-0.47 mg/kg in the bread (FAO/WHO,
1972). Desorption of 1,2-dibromoethane occurred at low (14-17°C)
rather than high (30-37°C) temperatures, and was abolished by grinding
the grain (Bielorai & Alumot, 1975).
Rappaport et al. (1984) reported that the decay of the outgassing
rate over time from fumigated oranges was approximately first order.
Outgassing was significantly slowed by reducing either the temperature
or the ventilation rate. In laboratory trials, ventilation at
0.6 air changes/h removed 1,2-dibromoethane vapours from the surface
of oranges, and prevented reabsorption onto the fruits.
A pesticide formulation, consisting of carbon tetrachloride (CT),
1,2-dichloroethane (EDC), 1,2-dibromoethane in 63 : 30 : 7 w/w
proportions, was applied to 27.3 tonnes of wheat stored in a paper
laminate bin (Berck, 1974). The CT-EDC-1,2-dibromoethane distribution-
persistence patterns were monitored at 16 bin locations over a 14-day
period by GC. Fumigant residues in the wheat, in flour, bran, and
middlings derived from the wheat, and in bread baked from the flour
were determined over a 7-week period. 1,2-Dibromoethane residues in
the wheat varied, depending on the bin location and contact time, and
ranged from 0 to 3.3 mg/kg. Residues in bran and middlings were
greater than those in flour, and ranged from 0 to 0.4 mg/kg. No
1,2-dibromoethane residues were found in any of the bread tested
(detection limit, 10 ng/kg).
1,2-Dibromoethane levels were studied in biscuits (22 samples)
and flour (22 samples), the biscuits being baked from each of the
flour samples for 12 min at 268°C. After baking, the samples were
sealed in plastic bags and frozen to prevent any further loss of
1,2-dibromoethane. Flour samples were also sealed in plastic bags and
frozen. Levels of 1,2-dibromoethane in flour and biscuits ranged from
non-detectable to 4.2 mg/kg and to 0.26 mg/kg, respectively. There
was poor correlation between the levels of 1,2-dibromoethane in flour
and biscuits.
5.2 Occupational exposure
Air concentrations of 1,2-dibromoethane in ventilated containers
dropped from several ppm immediately after fumigation to a few ppb
after 5-10 days; levels remained between 15 and 23 mg/kg (2 and 3 ppm)
for 15-20 days during unventilated, refrigerated storage. Results of
experiments on a laboratory scale (0.25 carton) and a large scale
(400 cartons) suggested that workers transporting and distributing
fumigated citrus fruit could routinely be exposed to airborne
1,2-dibromoethane at concen trations greater than 998 µg/kg (130 ppb)
(OSHA, 1983).
The US National Institute for Occupational Safety and Health
(NIOSH) estimated that approximately 108 000 workers in the USA were
potentially exposed to 1,2-dibromoethane in their workplaces (Table 7)
and that another 875 000 workers handling leaded petrol were exposed
to very low levels (NIOSH, 1981). There is no estimate of the number
of motorists exposed to 1,2-dibromoethane during self-service
operations at filling stations.
Table 7. Occupations with potenial exposure to 1,2-dibromoethanea
Antiknock compound makers Motor fuel workers
Cabbage growers Oil processors
Corn growers Organic chemical synthesizers
1,2-Dibromoethane workers Petrol blenders
Drug makers Resin makers
Fat processors Seed corn maggot controllers
Fire-extinguisher makers Soil fumigators
Fruit fumigators Termite controllers
Fumigant workers Tetraethyllead makers
Grain elevator workers Waterproofing makers
Grain fumigators Waxmakers
Gum processors Wood insect controllers
Lead scavenger makers Wool reclaimers
a From: NIOSH (1977)
In the 1970s, US EPA examined the exposure of professional
pesticide applicators involved with 1,2-dibromoethane soil fumigation.
It was estimated that applicators applying 1,2-dibromoethane for
30-40 days/year would receive a total annual inhalation dose of
3-40 mg/kg and farmer-applicators applying 1,2-dibromoethane for
7-10 days/year would receive a total annual inhalation dose of
0.7-10 mg/kg (US EPA, 1977).
1,2-Dibromoethane exposures were measured in a plant where lead
antiknock blends for petrol were prepared (Jacobs, 1980). The
antiknock blend constituents were mixed in tanks under enclosed-system
conditions and the only manual operations were connecting and
disconnecting hoses while loading and unloading tank cars, taking
quality control samples, and processing and loading drums. The levels
of worker exposure to 1,2-dibromoethane in antiknock blending and
storage areas were 0.77 µg/m3 (0.1 ppb) (laboratory technician) to
6.3 µg/m3 (0.82 ppb) (raw maternal blender). In addition to
long-term personal sampling, some short-term monitoring of specific
tasks was conducted. The results are shown in Table 8.
Table 8. Short-term air levels of 1,2-dibromoethane in antiknock
blending plant tank cars (Jacobs, 1980)
Taska Sampling time Concentration
mg/m3 ppm
Quality control sample 13 min, 10 sec 5.38 0.7
Loading tank car 7 min 1.07 0.14
a Respirator worn during these tasks
Personal air monitoring during vehicle refuelling at a petroleum
laboratory 10 m downwind of the fuel pump and fuel-handling facilities
was performed at a USA plant in July, 1975 (Table 9). The average
exposure of filling station attendants to 1,2-dibromoethane during
refuelling was 1.8 µg/m3 (0.24 ppb). Measurements at the car fuel
tank filler pipe showed maximum instantaneous 1,2-dibromoethane
concentrations of 105 µg/m3 (13.7 ppb), with an average for four
samples of 10.0 µg/m3 (1.3 ppb). This represented the maximum for a
short-term exposure. The concentration of 1,2-dibromoethane in air at
the fuel pump island was similar to values measured at upwind and
downwind sites. Overall, the very low 1,2-dibromoethane air levels
measured in this study indicated that the potential for filling
station attendant exposure to 1,2-dibromoethane while refuelling cars
was low and less than the current or proposed USA occupational air
standard for 1,2-dibromoethane exposure (Jacobs, 1980).
Exhaust emissions from various types of internal combustion
engines, including four-stroke Otto engines and diesel engines, are a
major source of environmental and occupational exposure to
1,2-dibromoethane (Hasanen et al., 1981). There are few data on the
composition of and exposure to exhaust emissions from two-stroke
engines.
Table 9. Petrol station attendant exposure to 1,2-dibromoethane
during vehicle refuelling (Jacobs, 1980)
Sample Concentration
mg/m3 ppb
Upwind background < 0.77 < 0.1
Downwind background < 0.77 < 0.1
Fuel pump island 0.99 0.13
Near vehicle fuel pipe 9.98 1.3a
during refueling 105.2 13.7b
Personal air sampler 2.15 0.28
a Average
b Maximum
Seven chain saws fuelled with 93-octane standard petrol-
containing tetramethyllead (lead content 0.15 g/litre) and
1,2-dibromoethane as a scavenger were tested on a test-bench
permitting a variable load to be applied by an electric power brake
(Nilsson et al., 1987). 1,2-Dibromoethane emissions were low
(2.5 mg/m3). Exposure to chain saw exhaust during logging was
studied under snowy and snow-free conditions. The time-weighted
average exposure to 1,2-dibromoethane was lower in the snow-free
conditions (0.0008 (0.0004-0.001) mg/m3) than in the snowy
conditions (0.002 (0.0001-0.005) mg/m3).
1,2-Dibromoethane is mainly used as a scavenger in tetraalkyllead
petrol and antiknock preparations, as a soil and grain fumigant, as
an intermediate in the synthesis of dyes and pharmaceuticals and as a
solvent for resins, gums and waxes (Alexeeff et al., 1990).
Rumsey & Tanita (1978) performed an industrial hygiene survey of
two manufacturing and two user facilities involving 1,2-dibromoethane.
Samples were taken from more than 69 potentially-exposed workers in
17 job classifications. Median 1,2-dibromoethane exposure (by similar
job types) in the manufacturing process ranged from 0.076 to
3.8 mg/m3 (0.010 to 0.5 ppm) (35 TWA personal samples). General
area samples collected at breathing zone heights had median TWA levels
of 1.5 mg/m3 (0.2 ppm) for 10 samples at process sites, and
3.8 mg/m3 (0.5 ppm) for 3 samples at laboratory sites.
Papaya workers in Hawaii were exposed to a geometric mean of
676 mg/m3 (88 ppb), and peaks up to 2.01 mg/m3 (262 ppb) were
measured (Steenland et al., 1986).
6. KINETICS AND METABOLISM
6.1 Absorption
1,2-Dibromoethane was found in the blood of rodents almost
immediately after dermal and oral exposure. Jakobson et al. (1982)
reported that during a 6-h dermal exposure of guinea-pigs of both
sexes (weighing between 600 and 1000 g) with undiluted
1,2-dibromoethane applied to 3.1 cm2 of shaved skin on the back
(1.0 ml/animal), the blood concentration of 1,2-dibromoethane
increased rapidly during 1 h to a level of 2 mg/litre and then slowly
decreased. The influx of 1,2-dibromoethane into the blood after 1 h
was largely in equilibrium with its disappearance.
In male Sprague-Dawley rats given 15 mg/kg body weight of
[14C-1,2] 1,2-dibromoethane in corn oil by gavage, the blood levels
at 24 h and 48 h were 0.90 and 0.64 mg/litre, respectively (Plotnick
et al., 1979). The excretion of radioactivity in faeces within 24 h
was 1.7% of the dose. The remainder was recovered either in the urine
(72%) or in the tissues (2.8%) (Table 10). The results indicated
rapid 1,2-dibromoethane absorption from the gastrointestinal tract.
No absorption information regarding inhalation exposure exists.
Table 10. The distribution of 14C in selected tissues and body
fluids of male rats 24 h after a single oral dose of
14C-1,2-dibromoethane (15 mg/kg)a
Tissue Tissue concentrationsb Percentage of dose
(mg equivalent/kg or mg/litre) (%)
Liver 4.78 ± 0.24 1.7 ± 0.07
Kidneys 3.32 ± 0.42 0.21 ± 0.02
Spleen 1.00 ± 0.03 0.22 ± < 0.01
Testes 0.49 ± 0.05 0.04 ± < 0.01
Brain 0.41 ± 0.04 0.02 ± < 0.01
Fat 0.35 ± 0.04 0.15 ± 0.02
Blood 0.90 ± 0.05 0.59 ± 0.03
Plasma 0.46 ± 0.04
Urinec 72.38 ± 0.98
Faecesc 1.65 ± 0.28
a From: Plotnick et al. (1979)
b Values represent mean concentrations (expressed as parent
compound) ± S.E.M. of duplicate determinations for six animals.
c n = 12
6.2 Distribution
Plotnick et al. (1979) compared levels of 14C in selected
tissues of male Sprague-Dawley rats following oral administration of
14C-1,2-dibromoethane. One day after the administration, the
highest levels of radioactivity were found in the liver and kidneys
(Table 10).
Distribution of 14C-1,2-dibromoethane (30 mg/kg body weight)
after intraperitoneal administration to male guinea-pigs was studied
by Plotnick & Conner (1976). The liver and kidneys contained the
highest levels of radioactivity followed by the adrenal glands
(Table 11).
Table 11. Distribution of 14C-1,2-dibromoethane in selected tissues
of male guinea-pigs at various time intervals following
intraperitoneal administrationa
Tissues/organs 4 h 8 h 24 h 72 h
Liver 129.0 104.9 38.0 15.6
Kidneys 286.6b 236.5 3.5 10.5
Adrenals 60.7 60.8 28.6 10.4
Pancreas 35.0 36.8 18.7 6.0
Spleen 15.8 14.0 14.9 7.0
Heart 14.0 15.6 9.5 3.3
Lungs 20.9 19.0 15.4 5.8
Testes 10.7 10.7 8.3 4.0
Brain 6.2 7.6 6.5 2.5
Fatc 21.4 7.9 3.2 2.1
Muscle 5.5 5.0 4.2 2.2
Blood 10.0 3.4 5.0 2.8
a From: Plotnick & Conner (1976)
b Values represent mean levels in mg equivalent/kg of tissue or
litre of fluid for three animals at each time interval
c Suprarenal fat
Kowalski et al. (1985) reported epithelial binding of
1,2-dibromoethane in the respiratory and upper alimentary tracts of
C57BL mice, Sprague-Dawley rats and Fischer-344 rats after intravenous
and intraperitoneal injection of 14C-1,2-dibromoethane. In C57BL
mice, there was a high level of radioactivity in the nasal and
bronchial mucosa and liver 5 min after intravenous injection of
14C-1,2-dibromoethane. In the nose, the highest labelling was
present in a spotty band beneath the epithelium of the
ethmoturbinates. The radioactive labelling of the mucosa of the
respiratory tract was persistent, and 10 days after injection a
selectively bound radioactivity remained. High labelling was also
present in the mucosa of the forestomach, whereas there was no
selective uptake of radioactivity in the glandular stomach or
intestine. Similar distribution patterns were observed in the
intraperitoneally injected mice killed after 30 min or subsequently.
6.3 Metabolic transformation
The metabolism of 1,2-dibromoethane has been extensively studied
and metabolites have been identified in in vivo and in vitro
studies (Table 12, Fig. 1).
Table 12. Metabolites of 1,2-dibromoethane
(a) In vivo
Metabolite Animal; route; substrate Reference
Bromide Swiss-Webster mice; White et al.
intraperitoneal; plasma (1983)
N-acetyl-S-(2-hydroxy male Wistar rat; oral; Van Bladeren et
ethyl)-L-cysteine urine al. (1981b)
GS-CH2-CH2SG female white rat; oral; Nachtomi (1970)
liver
GSCH2CH2OH sulfoxide liver Nachtomi (1970)
GSCH2CH2OH liver and kidney Nachtomi (1970)
S-(2-hydroxyethyl) kidney Nachtomi (1970)
mercapturic acid
(b) In vitro
Metabolite Tissue Reference
GSCH2CH2SG rat liver and kidney extract Nachtomi (1970)
GSCH2CH2OH rat liver and kidney extract Nachtomi (1970)
Bromide (1984) rat liver cytosols White et al.
Bromide (1983) mouse liver cytosols White et al.
Inorganic bromide may be formed as a consequence of attack by GSH
or oxidative catabolism. In the first case, the expected intermediate
would be S-(2-bromoethyl)-GSH, which can be converted to bis-GSH or
S-(2-hydroxyethyl)-GSH. Sulfoxidation of S-(2-hydroxyethyl)-GSH
would yield S-(2-hydroxyethyl)-GSH- S-oxide or further metabolism
would produce S-(2-hydroxyethyl)-cysteine, which in turn may undergo
sulfoxidation to yield N-acetyl- S-(2-hydroxyethyl)-cysteine-
S-oxide. The oxidative metabolism of 1,2-dibromoethane by
cytochrome P-450-dependent mixed function oxidases would be expected
to yield 2-bromoacetaldehyde as the initial product. This may be
converted by dehydrogenase to 2-bromoacetic acid or undergo attack by
GSH and subsequent dehydrogenase activity to give rise to
S-carboxymethyl-GSH. S-carboxymethyl-cysteine may be further
metabolized to thioglycolic acid. A reactive intermediate binds
mainly to DNA guanyl remnants and may be responsible for the
genotoxicity.
White et al. (1983) reported a deuterium isotope effect on the
metabolism of 1,2-dibromoethane. The metabolism of 1,2-dibromoethane
and tetradeutero-1,2-dibromoethane (d4-1,2-dibromoethane) was compared
in male Swiss-Webster mice. Three hours after intraperitoneal
administration of 1,2-dibromoethane or d4-1,2-dibromoethane
(50 mg/kg), there was 42% less bromide in the plasma of
d4-1,2-dibromoethane-treated mice than in the plasma of
1,2-dibromoethane-treated mice. This difference demonstrated a
significant deuterium isotope effect on the metabolism of
1,2-dibromoethane in vivo. In in vitro studies, which measured
bromide ion released from the substrate to monitor the rate of
metabolism, hepatic glutathione- S-transferase was unaffected. Since
the decreased metabolism of d4-1,2-dibromoethane was apparently due to
a reduced rate of microsomal oxidation, these data supported the
hypothesis that conjugation with GSH is responsible for the genotoxic
effect of 1,2-dibromoethane.
White et al. (1984) studied metabolism in isolated rat
hepatocytes. Cytosolic metabolism of 1,2-dibromoethane was not
affected by deuterium substitution. Both compounds caused DNA
single-strand breaks, as measured by the alkaline elution technique,
when incubated at a concentration of 0.1 mM with hepatocytes. No
difference in the degree of DNA damage was demonstrated between
hepatocytes incubated with 1,2-dibromoethane and those incubated with
d4-1,2-dibromoethane.
1,2-Dibromoethane can be metabolized by freshly isolated rat
hepatocytes to S-(2-hydroxyethyl)glutathione, S-(carboxymethyl)
glutathione and S,S'-(1,2-ethanediyl)bis(glutathione). These three
metabolites account for 84% of the total intracellular glutathione
depletion (Jean & Reed, 1992). These reactions were negligible in the
presence of rat glutathione- S-transferase, but conjugation was
catalysed by the rat alpha class enzyme 2-2 and, to a lesser extent,
the rat µ class enzyme 3-3. Of the three classes of human cytosolic
glutathione- S-transferases, 1,2-dibromoethane conjugation was
catalysed by the alpha class enzymes (Cmarik et al., 1990).
Human fetal liver appears to be especially active (several times
higher specific activity of glutathione- S-transferase, compared to
adult liver, as reported by Wiesma et al., 1986) in metabolizing
1,2-dibromoethane in vitro (Kulkarni et al., 1992).
1,2-Dibromoethane-induced lipid peroxidation and cytotoxicity
were increased upon concomitant exposure to carbon tetrachloride.
Similarly, the amount of 1,2-dibromoethane metabolites bound
covalently to proteins was enhanced. The effect of carbon
tetrachloride has been related to a shift in the 1,2-dibromoethane
metabolism from GSH-dependent to P-450-dependent (Chiarpotto et al.,
1993).
Oral administration of large doses of 1,2-dibromoethane
(37.6 mg/animal) to male Wistar rats (weighing around 200 g),
following a single dose of disulfiram (12 mg/kg), led to decreased
excretion of the mercapturic acid metabolite, a phenomenon associated
with a decrease in cytochrome P-450 levels (van Bladeren et al.,
1981a). In an additional reaction, 1,2-dibromoethane is debrominated
by an oxidative process catalysed by an enzyme in hepatic microsomes.
This system requires NADPH and oxygen and is inducible by
phenobarbital but not by methyl-cholanthrene (Hill et al., 1978).
Simula et al. (1993) reported an increased mutagenicity of
1,2-dibromoethane in the Salmonella typhimurium strain TA100
expressing human glutathione- S-transferase A1-1, indicating that
human glutathione- S-transferases are able to metabolize
1,2-dibromoethane to reactive intermediates.
In a study with isolated human hepatocytes (Cmarik et al., 1990),
it was found that concurrent treatment with diethylmaleate reduced the
intracellular glutathione level and inhibited 1,2-dibromoethane
concentratio