INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY
ENVIRONMENTAL HEALTH CRITERIA 114
DIMETHYLFORMAMIDE
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.
Published under the joint sponsorship of
the United Nations Environment Programme,
the International Labour Organisation,
and the World Health Organization
First draft prepared by Dr. A. Bainova,
Institute of Hygeine and Occupational Health, Sofia, Bulgaria
World Health Orgnization
Geneva, 1991
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WHO Library Cataloguing in Publication Data
Dimethylformamide.
(Environmental health criteria ; 114)
1.Dimethylformamide - adverse effects 2.Dimethylformamide - toxicity
I.Series
ISBN 92 4 157114 4 (NLM Classification: QV 633)
ISSN 0250-863X
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CONTENTS
ENVIRONMENTAL HEALTH CRITERIA FOR DIMETHYLFORMAMIDE
1. SUMMARY AND EVALUATION, CONCLUSIONS, RECOMMENDATIONS
1.1. Summary and evaluation
1.1.1. General properties
1.1.2. Environmental transport, distribution, and transformation
1.1.3. Environmental levels and human exposure
1.1.4. Kinetics and metabolism
1.1.5. Effects on organisms in the environment
1.1.6. Effects on experimental animals and in vitro test systems
1.1.7. Effects on human beings
1.2. Conclusions
1.3. Recommendations
1.3.1. Safe handling
1.3.2. Further research
2. IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, ANALYTICAL METHODS
2.1. Identity
2.2. Physical and chemical properties
2.3. Organoleptic properties
2.4. Analytical methods
2.4.1. Determination of DMF in workplace air
2.4.2. Determination of DMF and metabolites in biological media
2.4.3. Determination of DMF in soil, plants, and food
3. SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE
3.1. Natural occurrence
3.2. Man-made sources
3.2.1. Production and uses
3.2.1.1 Production
3.2.1.2 Uses
4. ENVIRONMENTAL TRANSPORT, DISTRIBUTION, AND TRANSFORMATION
4.1. Transport and distribution between media
4.1.1. Air
4.1.2. Water
4.1.3. Soil
4.1.4. Bioaccumulation
5. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE
5.1. Environmental levels
5.1.1. Air
5.1.2. Water
5.1.3. Soil
5.2. General population exposure
5.3. Occupational exposure
5.3.1. Concentrations in the workplace air
5.3.2. Dermal exposure
6. KINETICS AND METABOLISM
6.1. Animal studies
6.1.1. Absorption
6.1.2. Distribution
6.1.3. Metabolic transformation
6.1.4. Elimination and excretion
6.1.5. Metabolic interaction between DMF and ethanol
6.2. Human studies
6.2.1. Absorption, distribution, metabolism, excretion
6.2.2. The influence of ethanol on DMF
metabolism in human volunteers
6.2.3. Biological monitoring of workers
6.2.3.1 Determination of NMF in the urine
6.2.3.2 N,N-dimethylformamide determination in the
expired air
6.2.3.3 Appraisal
7. EFFECTS ON ORGANISMS IN THE ENVIRONMENT
8. EFFECTS ON EXPERIMENTAL ANIMALS AND IN VITRO TEST SYSTEMS
8.1. Single exposures
8.2. Skin and eye irritation, sensitization
8.2.1. Skin irritation
8.2.2. Eye irritation
8.2.3. Sensitization
8.3. Repeated exposure
8.4. Specific organ toxicity
8.4.1. Liver
8.4.2. Gastrointestinal tract
8.4.3. Cardiovascular system
8.4.4. Kidney
8.4.5. Nervous system
8.4.6. Lungs
8.4.7. Haematopoietic system
8.4.8. Adrenals
8.4.9. Gonads
8.5. Developmental toxicity and reproduction
8.5.1. Developmental toxicity
8.5.1.1 Mouse
8.5.1.2 Rat
8.5.1.3 Rabbit
8.5.1.4 Appraisal
8.6. Mutagenicity and related end-points
8.6.1. In vitro studies
8.6.2. In vivo studies
8.6.3. Appraisal
8.7. Carcinogenicity
8.8. Induction of tumour cell differentiation
8.9. Mechanism of toxicity, mode of action
9. EFFECTS ON HUMAN BEINGS
9.1. General population exposure
9.2. Occupational exposure
9.2.1. Accidental poisoning
9.2.2. Long-term exposure
9.2.3. Epidemiological studies on carcinogenicity
9.2.4. Alcohol intolerance
10. PREVIOUS EVALUATIONS BY INTERNATIONAL BODIES
REFERENCES
RESUME ET EVALUATION, CONCLUSIONS, RECOMMANDATIONS
RESUMEN Y EVALUACION, CONCLUSIONES, RECOMENDACIONES
TASK GROUP MEETING ON ENVIRONMENTAL HEALTH CRITERIA FOR DIMETHYLFORMAMIDE
Members
Dr A. Aitio, International Agency for Research on Cancer, World Health
Organization, Lyon, France (Chairman)
Dr A. Bainova, Institute of Hygiene and Occupational Health, Sofia,
Bulgaria (Co-rapporteur)
Ms J. Favilla, Office of Toxic Substances, US Environmental Protection
Agency, Washington, USA
Dr G.L. Kennedy, Jr, Haskell Laboratory for Toxicology and Industrial
Medicine, EI du Pont de Nemours & Co., Newark, Delaware, USA (Co-
rapporteur)
Professor N.P. Misra, Department of Medicine, Gandhi Medical College,
Bhopal, India
Dr K. Morimoto, Division of Medical Chemistry, National Institute of
Hygienic Sciences, Tokyo, Japan (Vice-Chairman)
Dr C. Sadarangani, Petrochemical Industries Co.KSC., Ahmadi, Kuwait
Dr V. Scailteur, Procter and Gamble GMBH, Frankfurt, Federal
Republic of Germany
Dr Yu Hui Qin, Institute of Environmental Health Monitoring, Chinese
Academy of Preventive Medicine, Beijing, People's Republic of China
Observers
Dr R. Jäckh, European Chemical Industries Ecology and Toxicology
Centre, Brussels, Belgium
Secretariat
Dr R. Hertel, Fraunhofer Institute for Toxicology and Aerosol Research,
Hanover, Federal Republic of Germany
Dr K.W. Jager, International Programme on Chemical Safety, World
Health Organization, Geneva, Switzerland (Secretary)
Dr P.G. Jenkins, International Programme on Chemical Safety, World
Health Organization, Geneva, Switzerland
NOTE TO READERS OF THE CRITERIA DOCUMENTS
Every effort has been made to present information in the criteria
documents as accurately as possible without unduly delaying their
publication. In the interest of all users of the environmental health
criteria documents, readers are kindly requested to communicate any
errors that may have occurred to the Manager of the International
Programme on Chemical Safety, World Health Organization, Geneva,
Switzerland, in order that they may be included in corrigenda, which
will appear in subsequent volumes.
* * *
A detailed data profile and a legal file can be obtained from the
International Register of Potentially Toxic Chemicals, Palais des
Nations, 1211 Geneva 10, Switzerland (Telephone no. 7988400 -
7985850).
ENVIRONMENTAL HEALTH CRITERIA FOR DIMETHYLFORMAMIDE
A WHO Task Group on Environmental Health Criteria for
Dimethylformamide, which met in Wolfsburg from 13 to 17 March 1989,
was organized by the Fraunhofer Institute for Toxicology and Aerosol
Research, Hanover, Federal Republic of Germany. The meeting was
sponsored by the Federal Government. Dr K.W. Jager of the IPCS opened
the meeting and welcomed the participants on behalf of the three
cooperating organizations of the IPCS (UNEP/ILO/WHO). The Task Group
reviewed and revised the draft criteria document and made an
evaluation of the risks for human health and the environment from
exposure to dimethylformamide.
The first and second drafts of this document were prepared by Dr
A. BAINOVA of the Institute of Hygiene and Occupational Health, Sofia,
Bulgaria. Dr K.W. JAGER of the Central Unit, International Programme
on Chemical Safety was responsible for the scientific content of the
document and Mrs M.O. HEAD of Oxford for the editing.
The efforts of all who helped in the preparation and finalization
of the document are gratefully acknowledged.
1. SUMMARY AND EVALUATION, CONCLUSIONS, RECOMMENDATIONS
1.1 Summary and evaluation
1.1.1 General properties
N,N-dimethylformamide (dimethylformamide, DMF, CAS 68-12-2)
is an organic solvent produced in large quantities throughout the
world. It is used in the chemical industry as a solvent, an
intermediate, and an additive. DMF is a colourless liquid with an
unpleasant slight odour that, nevertheless, has poor warning
properties. It is usually stable but, when it comes in contact with
strong oxidizers, halogens, alkylaluminium, or halogenated
hydrocarbons (especially in combination with metals), it may cause
fires and explosions. DMF is completely miscible with water and most
organic solvents. It has a relatively low vapour pressure.
Gas chromatographic procedures for determining DMF are available.
1.1.2 Environmental transport, distribution, and transformation
DMF is stable in ambient air, but may undergo microbial and algal
degradation in water. Adapted microorganisms and activated sludge
efficiently biodegrade DMF. As a result of its complete solubility in
water, DMF moves readily through soils and would not be expected to
accumulate in the food chain.
1.1.3 Environmental levels and human exposure
DMF does not occur naturally. There are few data concerning
environmental levels or the exposure of the general population to DMF.
Concentrations in the air in the range of 0.02-0.12 mg/m3 have been
found in residential areas, near industrial sites. DMF has rarely
been detected in the water of heavily industrialized river basins, and
then only at concentrations below 0.01 mg/litre.
Data are not available on the levels of DMF in soil, plants,
wildlife, and food.
Occupational exposure occurs via skin contact with DMF liquid and
vapour, and through the inhalation of vapour. Concentrations of 3-86
mg/m3 air have been detected, with peaks of up to 600 mg/m3, during
the repair or maintenance of machines. In a few unusual situations,
levels of up to 4500 mg/m3 have been reported.
1.1.4 Kinetics and metabolism
Toxic amounts of DMF may be absorbed by inhalation and through the
skin. Absorbed DMF is distributed uniformly. The metabolic
transformation of DMF takes place mainly in the liver, with the aid of
microsomal enzyme systems. In animals and human beings, the main
product of DMF biotransformation is N-hydroxymethyl- N-methylformamide
(DMF-OH). This metabolite is converted during gas chromatographic
analysis to N-methylformamide, which is itself (together with N-
hydroxy methylformamide and formamide) a minor metabolite. Thus,
metabolic studies and biological monitoring, urinary concentrations of
metabolites are measured and expressed as NMF, though DMF-OH is the
major contributor to this concentration. The determination of NMF/DMF-
OH in the urine may be a suitable biological indicator of total DMF
exposure.
In experimental animals, it has been demonstrated that DMF
metabolism is saturated at high exposure levels and, at very high
levels, DMF inhibits its own metabolism.
Metabolic interaction occurs between DMF and ethanol.
1.1.5 Effects on organisms in the environment
The effects of DMF on the environment have not been well studied.
The toxicity for aquatic organisms appears to be low.
1.1.6 Effects on experimental animals and in vitro test systems
The acute toxicity of DMF in a variety of species is low (in rats,
the oral LD50 is approximately 3000 mg/kg, the dermal LD50,
approximately 5000 mg/kg, and the inhalational LC50, approximately
10 000 mg/m3). It is a slight to moderate skin and eye irritant.
One study on guinea-pigs indicated no sensitization potential. DMF
can facilitate the absorption of other chemical substances through the
skin.
Exposure of experimental animals to DMF via all routes of exposure
may cause dose-related liver injury. Regeneration, after exposure has
ceased, has been demonstrated. In some studies, signs of toxicity in
the myocardium and kidneys have also been described.
DMF has not been shown to be toxic to the testes or ovaries of
rats and effects on fertility have not been demonstrated. DMF has
been found to be embryotoxic and a weak teratogen in rats, mice, and
rabbits. The rabbit was found to be the most sensitive species when
exposed via inhalation: teratogenic effects were observed at 1350
mg/m3 (450 ppm) and above, but not at 450 ppm (150 ppm). After dermal
exposure, a very low incidence of embryotoxic and teratogenic effects
was observed in some studies at dose levels of between 100 and 400
mg/kg per day.
DMF was generally found to be inactive, both in vitro and in
vivo, in an extensive set of short-term tests for genetic and related
effects.
No adequate long-term carcinogenicity studies on experimental
animals have been reported.
1.1.7 Effects on human beings
No adverse effects of DMF on the general population have been
clearly demonstrated.
Skin irritation and conjunctivitis have been reported after direct
contact with DMF.
After accidental exposure to high levels of DMF, abdominal pain,
nausea, vomiting, dizziness, and fatigue occur within 48 h. Liver
function may be disturbed, and blood pressure changes, tachycardia,
and ECG abnormalities have been reported. Recovery is usually
complete.
Following long-term repeated exposure, symptoms include headache,
loss of appetite, and fatigue. Biochemical signs of liver dysfunction
may be observed. Liver damage seems to occur only when the DMF
exposure level exceeds 30 mg/m3, in the absence of skin contact. This
airborne level corresponds to approximately 40 mg NMF/DMF-OH/g
creatinine in a post-shift urine sample.
Exposure to DMF, even at concentrations below 30 mg/m3, may cause
alcohol intolerance. Symptoms may include a sudden facial flush,
tightness in the chest, and dizziness, sometimes accompanied by nausea
and dyspnoea. They last from 2 to 4 h and disappear without
treatment.
There is limited evidence that DMF is carcinogenic for human
beings. An increased incidence of testicular tumours was reported in
one study, whereas another study showed an increased incidence of
tumours of the buccal cavity and pharynx, but not of the testes.
In two studies, which provide few details, an increased frequency
of miscarriages was reported in women exposed to DMF, among other
chemicals.
1.2 Conclusions
1. In view of the present uses of DMF, general population
exposure is probably very low.
2. DMF is readily absorbed through the skin as well as via
inhalation. Determination of urinary NMF/DMF-OH is a useful
means of estimating the total amount of DMF absorbed.
3. The risk of liver damage is low, when the level of DMF in
ambient air is kept below 30 mg/m3 and there is no skin
contact. A tentative value for the corresponding urinary
NMF/DMF-OH level in a post-shift sample is 40 mg/g creatinine.
4. DMF is embryotoxic and a weak teratogen in rats, mice, and
rabbits.
5. There is limited evidence of carcinogenicity of DMF for human
beings.
6. Available data indicate low environmental toxicity. It is
unlikely that bioaccumulation takes place.
1.3 Recommendations
1.3.1 Safe handling
1. Airborne concentrations should be maintained below 30 mg/m3
and skin contact should be prevented.
2. Urinary NMF/DMF-OH, as an index of total exposure, should be
monitored and maintained below 40 mg NMF/g creatinine in post-
shift samples. If this level is exceeded, action should be
taken to reduce exposure.
1.3.2 Further research
1. The possible carcinogenic effects of DMF in human beings
should be investigated by means of studies on experimental
animals and human populations.
2. More information is needed on the extrapolation of the
embryotoxicity and teratogenicity of DMF from animal studies
to human beings. Comparison of the kinetics of DMF in human
beings and animals would be valuable.
3. There is a need for more information on the mechanisms of
action and the relative potency of the metabolites of DMF in
both animals and human beings.
4. The relationships should be refined between: (a) urinary
metabolite concentrations and atmospheric exposure levels (in
the absence of skin contact), and (b) total dose via all
routes (as indicated by post-shift urinary NMF levels) and the
absence of hepatotoxicity.
2. IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, ANALYTICAL METHODS
2.1 Identity
Chemical structure: H3C O
\ //
N -- C
/ \
H3C H
Chemical formula: C3H7NO
Common name: dimethylformamide
Common synonyms: N,N-dimethylformamide,
DMF, DMFA, formdimethylamide
CAS registry number: 68-12-2
Relative molecular mass 73.1
Conversion factors: 1 ppm = 3 mg/m3
(at 20 °C) 1 mg/m3 = 0.33 ppm
2.2 Physical and chemical properties
Some physical properties of DMF (Eberling, 1980) are given in
Table 1. DMF is a colourless, organic solvent, free from suspended
matter. Technical DMF may contain impurities, depending on the
manufacturing and purification processes.
DMF is stable. It is hygroscopic and easily absorbs water from a
humid atmosphere and should therefore be kept under dry nitrogen. High
purity DMF, required for acrylic fibres, is best stored in aluminium
tanks. DMF does not change under light or oxygen and does not
polymerize spontaneously. Temperatures > 350 °C may cause
decomposition to form dimethylamine and carbon dioxide, with pressure
developing in closed containers (Farhi et al., 1968; US NIOSH, 1978).
In a fire involving DMF, or at temperatures > 350 °C, the toxic gases
and vapours consist primarily of dimethylamine and carbon monoxide.
DMF reacts readily with alkylaluminiums. Contact with carbon
tetrachloride and other halogenated hydrocarbons, particularly when in
contact with iron, as well as contact with strong oxidizing agents
(e.g., methylene diisocyanate, halogens, and permanganates) may cause
fires and explosions. In acidic solution (pH 3.8), DMF can be
nitrosated by sodium nitrate yielding small amounts of N-nitroso-
dimethylamine (0.04% at 37 °C and 1% at 90 °C).
Table 1. Physical properties of DMF
----------------------------------------------------------------------------
Property Value
----------------------------------------------------------------------------
Melting point (°C) - 60.5
Boiling point (°C) 153
Flash point (°C) 58 (closed cup)
67 (open cup)
Auto-ignition temperature (°C) 445
Density at 25 °C (specific gravity) (g/ml) 0.9445
Relative vapour density 2.51
Vapour pressure (mmHg/kPa)
at 20 °C 2.65/0.35
at 25 °C 3.7/0.48
at 60 °C 26/3.46
Vapour concentration in saturated air at
25 °C (mg/m3) 14 800
Explosive limits in air at 20 °C
(101 kPa/1 atm./%vol.)
lower limit 2.2 (70g/m3)
upper limit 16 (500 g/m3)
n- Octanol/water partitition coefficient 0.13
Solubility in water Miscible in all proportions
Solubility in organic solvents Miscible with ether, ketones,
aromatic hydrocarbons,
ethanol, but not with
aliphatic hydrocarbons
Dielectric constant at 20 °C 36.7
----------------------------------------------------------------------------
2.3 Organoleptic properties
DMF is a colourless liquid with an unpleasant taste and an
ammonia-like, specific odour that has poor warning properties (US
NIOSH, 1978). The odour threshold for the most sensitive people
ranges from 0.12 to 0.15 mg/m3 (Odoshashvili, 1963; Lazarev & Levina,
1976; Amster et al., 1983; Clay & Spittler, 1983). For some people,
the odour threshold has been reported to be as high as 60 mg/m3
(Leonardous et al., 1965).
2.4 Analytical methods
2.4.1 Determination of DMF in workplace air
Colorimetric methods, based on the development of a red colour
after the addition of hydroxylamine chloride as alkaline solution, are
not specific (Farhi et al., 1968). Lauwerys et al. (1980) described a
simple spectrophotometric method for measuring DMF vapour
concentrations. Gas-liquid chromatography is now the method of choice
(Kimmerle & Eben, 1975a; US NIOSH, 1977; Muravieva & Anvaer, 1979;
Brugnone et al., 1980a; Muravieva, 1983; Stransky, 1986). Detector
tubes, certified by US NIOSH, or other direct-reading devices
calibrated to measure DMF (Krivanek et al., 1978; US NIOSH, 1978) can
be used. High-performance liquid chroma tographic analysis (Lipski,
1982) can also be used. Mass spectrometric analysis for DMF in
expired air has been described by Wilson & Ottley (1981), with a lower
limit of detection of 0.5 mg/m3.
2.4.2 Determination of DMF and metabolites in biological media
Barnes & Henry (1974) developed a method for the gas
chromatographic determination of NMF ( N-methylformamide) (thought to
be the principal metabolite of DMF) in urine at concentrations of
between 5 and 500 µg/litre by either direct injection of the urine or
of urine extracts. Methods for simultaneous gas chromatographic
determination of DMF and NMF in the same blood sample (0.2 ml) and of
DMF, NMF, and formamide in 1 ml 24-h urine have been published by
Kimmerle & Eben (1975a) and Muravieva & Anvaer (1979). Similar
techniques were reported by Krivanek et al. (1978), Sanotsky et al.
(1978), and Lauwerys et al. (1980), involving primarily the
determination of NMF in the urine (Table 2).
2.4.3 Determination of DMF in soil, plants, and food
Analytical methods for the determination of DMF in these media
have not been described.
Table 2. Analytical methods for the determination of DMF, NMF (DMF-OH),
and formamide (NMF-OH) in urine, blood, and other biological tissues
-------------------------------------------------------------------------------------------------------------------
Biological Analytical method Detection limits Reference
tissue DMF NMF (DMF-OH) Formamide
(NMF-OH)
-------------------------------------------------------------------------------------------------------------------
Urine gas chromatography 0.5 mg/litre Barnes & Henry (1974)
gas chromatography 1.5 mg/litre 1 mg/litre 3.5 mg/litre Kimmerle & Eben (1975a)
gas chromatography 0.1 mg/litre Krivanek et al. (1978)
gas chromatography 1.5 mg/litre 3 mg/litre 10 mg/litre Muravieva & Anvaer (1979)
gas chromatography 0.8 mg/litre Mráz et al. (1987)
gas chromatography Lauwerys et al. (1980)
Blood gas chromatography 1 mg/litre 1.5 mg/litre Kimmerle & Eben (1975a)
gas chromatography 0.03 mg/litre 0.3 mg/litre 10 mg/litre Sanotsky et al. (1978)
gas chromatography 1.5 mg/litre 3 mg/litre Muravieva & Anvaer (1979)
gas chromatography 0.4 mmol/litre Lundberg et al. (1983)
Livera gas chromatography 0.2 mmol/kg Lundberg et al. (1983)
Kidney 0.6 mmol/kg
Brain 0.3 mmol/kg
Adrenals 0.9 mmol/kg
-------------------------------------------------------------------------------------------------------------------
a Tissue homogenate.
3. SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE
3.1 Natural occurrence
DMF does not occur naturally.
3.2 Man-made sources
3.2.1 Production and uses
3.2.1.1 Production
DMF was first synthesized in 1893 from carbon monoxide and
dimethylamine (Kennedy, 1986). It is usually manufactured by a one-
stage reaction of carbon monoxide with dimethylamine:
catalyst
CO + (CH3)2NH ----> (CH3)2
or by a two-stage reaction with methylformate and dimethylamine
(Eberling, 1980):
catalyst
CO + CH3OH ----> HCOOCH3
HCOOCH3 + (CH3)2NH ----> HCON(CH3)2 + CH3OH
DMF can also be manufactured from carbon dioxide, hydrogen, and
dimethylamine, in the presence of halogen-containing transition metal
compounds.
DMF is shipped in tank trucks and tank containers, and is also
marketed in 200-kg steel drums. The materials for DMF handling and
storage are usually (carbon) steels, austenitic steels, and aluminium.
Seals and pipelines should be made of polytetrafluoro-ethylene,
polyethylene, or polypropylene of high relative molecular mass.
Ethylene-propylene rubber can also be used.
The world production capacity of DMF is about 225 x 103
tonnes/year (Eberling, 1980). Production in the USA in 1979 was
15 000 tonnes. In 1980, NIOSH estimated that 69 000 US workers, in
various occupations in 25 major industries, were exposed to DMF.
Data are not available on losses of DMF into the environment and
into the ambient air during its production and use.
DMF can be recovered from the air by scrubbing with water and from
aqueous solution by distillation.
3.2.1.2 Uses
DMF is a universal industrial solvent, because of its water
solubility, organic nature, and high dielectric constant. The main
use (65-75%) of DMF is as solvent for acrylic fibres and
polyurethanes; 15-20% is used in the production of pharmaceutical
products (Eberling, 1980).
DMF is used as:
- a spinning solvent for synthetic textiles, based on
polyacrylonitrile or cellulose triacetate;
- a resin, rubber, and polymer solvent;
- a solvent for dyes and pigments for use with textiles, wood,
leather, films, paper, and plastics;
- a solvent in pesticide formulations;
- a booster solvent in coating, printing, and adhesive
formulations;
- a chemical intermediate, catalyst, and reaction medium in
chemical manufacturing and the pharmaceutical industry;
- a solvent in the production of polyurethane and other synthetic
leathers, or synthetic rubber;
- a selective absorption and extraction solvent for recovery,
purification, absorption, separation, and desulfurization of
non-paraffinic compounds from paraffin hydrocarbons;
- in the manufacture of paint stripper components for the removal
of vinyl films, epoxy coatings, and varnish finishes; in the
production of wire enamels, based on polyamides, polyurethanes,
and other polymers;
- in the pigment and dye industry to improve dyeing properties;
- a crystallization solvent in the pharmaceutical industry;
- a solvent for carbonaceous deposit cleaning applications for
high-voltage capacitors;
- an oil sludge dispersing agent;
- an anti-stall gasoline additive;
- a laboratory solvent and as a solvent for the extraction of
biological material in chemical analysis.
DMF (itself, or as a component in consumer products) is not
generally available to the general population (Farhi et al., 1968;
Bainova, 1980; Lundberg, 1982; Tanaka & Utsunomiya, 1982; Barral-
Chamaillard & Rouzioux, 1983; Kennedy, 1986; US EPA, 1986).
Because of its hepatotoxicity, DMF is not used as a solvent in
pharmaceutical or cosmetic products.
DMF has been approved by the US FDA as a component of adhesives,
for use in the packaging, transport, or storage of food.
DMF is present in some registered pesticides as an inert solvent.
4. ENVIRONMENTAL TRANSPORT, DISTRIBUTION, AND TRANSFORMATION
4.1 Transport and distribution between media
4.1.1 Air
DMF is stable in air. Concentrations in ambient air are related
to its industrial use. No data have been found on the rates of
reaction of DMF with hydroxyl radicals, ozone, or other atmospheric
pollutants. Darnall et al. (1976) reported DMF to have a half-life of
9.9 days in a polluted atmosphere. In oxidizing smog-chamber studies
(Laity et al., 1973; Farley, 1977; Sickles et al., 1980), no
photochemical oxidation of DMF occurred. The ultraviolet (UV)
absorption spectrum for DMF indicated no absorption > 290 nm
(Grasselli, 1973), showing that no photodegradation should be expected
in the environment. The water solubility of DMF suggests that it
should be easily removed from air by rainfall.
The DMF levels in the air of working environments depend on the
rate of usage, technology, and industrial hygiene practices (Aldyreva
& Gafurov, 1980; Brugnone et al., 1980a; Lauwerys et al., 1980;
Yonemoto & Suzuki, 1980; Koudela & Spazier, 1981; Taccola et al.,
1981; Paoletti & Iannaccone, 1982; Tomasini et al., 1983; Sala et al.,
1984; Kennedy, 1986; US EPA, 1986).
4.1.2 Water
According to Eberling (1980), aqueous solutions of DMF undergo
slight hydrolysis at neutral pH. After 120 h of refluxing, only 0.17%
of a 50% solution was hydrolysed. The hydrolysis of DMF is
accelerated by acids and alkalis. No data about the oxidation or
photodegradation of DMF are available.
DMF is susceptible to biodegradation by activated sludges, though
an acclimation period is usually required. Water from the Vistula
River was reported to biodegrade DMF, as was an unspecified bacterial
culture isolated from soil exposed to petroleum + petroleum products
(Chromek et al., 1983). Dojlido (1979) reported that, in an activated
sludge system, 100% of the 70 mg DMF/litre was degraded in 38 days.
In a river die-away test, under light aeration conditions, 28 mg
DMF/litre were degraded in the water with a lag time of 2 days. The
lag time decreased when acclimatized microorganisms were used in the
test.
Chromek et al. (1983) determined the changes in respiration rate
in algal cultures of Scenedesmus quadricauda, after treatment with
1000 mg DMF/litre. DMF degradation via dimethylamine to ammonia
occurred within 3 days. The rate of DMF degradation to ammonia
depended on the degree of adaptation of the heterotrophic mixed
cultures (activated sludge) and varied between 35 and 70 mg/g per h.
The dimethylamine decomposition rate was about 25 mg/g per h.
Gubser (1969) reported that, in a continuous-flow activated sludge
system, DMF was reduced by 90-100% within 10 days at concentrations of
20 and 50 mg/litre, and within 28 days at a concentration of 81
mg/litre. Chromek et al. (1983) found that the alga Scenedesmus
quadricauda in cultures was able to degrade DMF to dimethylamine and
ammonia in 3 days. The DMF concentration tested was about 1000
mg/litre; this corresponds to values seen in industrial effluents.
After the formation of an adaptive enzymatic system, the DMF
concentration decreased at a constant rate of about 40 mg/g per h.
Adaptation of the culture resulted in an enhanced rate of degradation.
Pseudomonas sp., Pseudomonas sp.II, and Vibrio aeromonas, isolated
from sewage effluents, degraded DMF (US EPA, 1986). Begert (1975)
proposed several series of aerobic bacterial systems, which eliminated
more than 90% of the DMF in the sewage from a chemical textile plant.
The complete water solubility and low n-octanol/water partition
coefficient (Table 1) of DMF suggest that adsorption on sediments in
water is not an important environmental process. DMF is not expected
to evaporate from the aquatic environment to any significant rate
because of its volatility and high water solubility (US EPA, 1986).
4.1.3 Soil
Contamination of soil with DMF may occur through spillage or
leakage during its production, transport, storage, or use. DMF's high
solubility in water and its low n-octanol/water partition coefficient
show that it can seep down into soil and potentially into ground
water. DMF was completely biodegraded by a bacterial culture,
isolated from soil that had been in contact with low levels of
petroleum and petroleum products for several years. This culture was
used for the purification of waste waters containing 250 mg DMF/litre
in an aerated tank; the addition of activated sludge for 18 h resulted
in the biodegradation of 94% of the DMF (Romadina, 1975).
4.1.4 Bioaccumulation
Sasaki (1978) found that DMF did not bioaccumulate in the carp;
the low partition coefficient was considered to be the explanation.
5. ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE
5.1 Environmental levels
5.1.1 Air
Air-monitoring for DMF was conducted at distances ranging from 25
to 300 m from an artificial fibre plant in the USSR. Odoshashvili
(1963) found that DMF levels were only below the proposed allowable
limit of 0.03 mg/m3 at 300 m from the plant.
Residents of private homes within a 0.5 mile radius of a chemical
waste recycling site complained of unpleasant odours. DMF was found
to be the major atmopheric contaminant in concentrations of up to 0.12
mg/m3, but it originated primarily from the industrial sites nearby
and not from the soil or the waste site (Clay & Spittler, 1983).
Amster et al. (1983) studied another abandoned chemical waste facility
in the USA, in response to complaints from nearby residents about
odour, with similar results, i.e., air levels of 0.024-0.15 mg DMF/m3
originated from a neighbouring industry.
5.1.2 Water
Very low concentrations of DMF were found in effluent waters from
sewage-treatment plants or municipal sewage-treatment systems (US EPA,
1986). A concentration of 2 µg/litre was measured in a sample taken
from a sewage-treatment plant on the western shore of Lake Michigan.
Ewing et al. (1977) examined 204 water samples from 14 heavily
industrialized river basins in the USA. DMF was found in only one
sample, at a concentration of 2 µg/litre. Samples of 63 effluent and
22 intake waters from various chemical manufacturers were collected in
areas throughout the USA (Perry et al., 1979) and analysed for organic
pollutants. Over 570 compounds were tentatively identified, of which
33 were important pollutants. DMF was detected once at a concentration
< 10 µg/litre.
Chromek et al. (1983) reported that DMF concentrations of
approximately 1000 mg/litre were found in effluents from the
production of synthetic leather.
5.1.3 Soil
No data are available on DMF levels in soil and plants.
5.2 General population exposure
No data are available on exposure of the general population to
DMF.
However, DMF may be a component of coatings, adhesives, engine
degreasing agents, and photographic developers for consumer use.
Exposure through the use of DMF in food processing, food
packaging, and pesticides may occur, but data are not available.
5.3 Occupational exposure
5.3.1 Concentrations in the workplace air
DMF is not highly volatile and is manufactured in closed systems.
Data on DMF concentrations in plants manufacturing DMF are not
available.
Concentrations of DMF in the workplace air in various industrial
applications, are listed in Table 3. In most cases, the mean
concentrations are less than 30 mg/m3, but certain jobs, particularly
those involving mixing operations, result in higher concentrations.
The cleaning of equipment or tanks that have contained DMF can involve
exposure to levels of up to 147 mg/m3. Kang-de & Hui-lan (1981)
reported an unusually high DMF concentration of 4525 mg/m3 during
repairs following an accident. The ranges of concentration reported
vary considerably, but the time of sampling is not generally
specified. The highest values have been found during repair or
maintenance work, in accidents, and where batch sampling (opening the
reactor system) was being conducted.
5.3.2 Dermal exposure
The relative importance of dermal exposure to liquid or vapour DMF
(versus inhalation of vapour) was studied by Aldyreva & Gafurov
(1980), Lauwerys et al. (1980), Bortsevich (1984), and Sala et al.
(1984).
Lauwerys et al. (1980) studied 7 workers from a spinning mill in a
polyacrylic fibre factory. During the first week, the workers wore
gloves and during the second week, a barrier cream was applied twice
each day to the hands and forearms. On the first day of the third
week, the skin was not protected, but the workers were equipped with
self-contained breathing equipment. The average N-methylformamide
(NMF) concentration in the urine at the end of the day, when there was
no dermal protection, was about 3 times higher than that during the
first week. Eight hours after the start of exposure without skin
protection, one worker reported abdominal pains; a second worker had
to stop working 48 h later because of severe gastric pain. Hence,
from the second day, the workers were requested to resume wearing
their impermeable gloves. Urinary NMF concentrations returned to the
values found during the first week. This convinced the workers of the
need to avoid all contact with the DMF solution and to use protective
gloves correctly. The study also showed that gloves were more
effective than silicone or glycerol barrier creams in preventing skin
absorption of DMF.
In a new plant producing artificial leather, Aldyreva et al. (1980)
found DMF in nearly all washings from the operators' hands.
According to Bortsevich (1984), the quantity of DMF absorbed
through the skin might be twice the quantity taken up through
inhalation. The author reported significant DMF concentrations in the
skin washings from the palms of hands, shoulders, back, thighs, and
abdomen. Part of the dermal uptake of DMF may result from its
presence in the air and part from contaminated clothing.
Table 3. DMF concentrations in air in various industrial applications
----------------------------------------------------------------------------------------------------------------------------
Factory product Job description Mean DMF Range of DMF Reference
concentrations concentrations
(mg/m3) (mg/m3)
----------------------------------------------------------------------------------------------------------------------------
Polyacrylic fibres spinning line - maintenance - 1-46.6 Lauwerys et al. (1980)
Artificial leather various (pre-improvement) - 0-60 Aldyreva & Gafurov (1980)
various (post-improvement) 1/3 samples below
detection
production 5.3 1.9-8.3 Brugnone et al. (1980a)
production (highest in mixing) > 30 < 150 Taccola et al. (1981)
production - normal 4.2-66 Paoletti & Iannaccone
opening reactor - < 549 (1982)
maintenance of rollers < 120
production - mixing > 34 Tomasini et al. (1983)
soaking and drying 12.1 (± 40.2) - Bortsevich (1984)
coating and colouring 32.3 (± 98.7) -
mixing resins 22.7 and 85.2 2-117 Sala et al. (1984)
spreading "transfer" system 33.8 8-72
spreading "coagulate" system 14 2-49
tank cleaning 86.3 9-147
machine cleaning 24.1 12-35
Surface-treating handlers 0-15.4 - Yonemoto & Suzuki (1980)
agents
Solvents - often > 30 peak 105-600 Lyle et al. (1979)
Synthetic rubber repairing, accidents, - 9.5-4525 Kang-de & Hui-lan (1981)
sampling with system opened,
extracting < 10 -
Unspecified chemicals unspecified - 50-250 Koudela & Spazier (1981)
----------------------------------------------------------------------------------------------------------------------------
Sala et al. (1984) reported that the total daily excretion of NMF
(DMF-OHa and NMF) in the 24-h urine samples of a worker who usually
cleaned the tanks in a factory where artificial polyurethane leathers
were produced, was 95-725 mg or 35-390 mg NMF/litre. This is higher
than would have been expected in a subject with a mean airborne
exposure of 100 mg DMF/m3. The worker usually operated without using
any personal protection.
Penetration through various glove materials has been studied.
Breakthrough time was > 480 min for butyl rubber, 6-66 min for
neoprene, and 5-22 min for polyvinylchloride and polyvinyl alcohol
(Henry & Schlatter, 1981).
Similarly, Sansone & Tewari (1978) showed that < 0.1% DMF passed
through neoprene gloves, 0.1-1% through natural rubber gloves, 1-10%
through nitrile gloves, and > 10% through poly-vinylchloride gloves,
in half an hour.
---------------------------------------------------------------------------
a DMF-OH = N-hydroxymethyl- N-methylformamide.
6. KINETICS AND METABOLISM
6.1 Animal studies
6.1.1 Absorption
Sanotsky et al. (1978) determined DMF concentrations in the blood
of rats, 24 h after the oral administration of 200-4000 mg DMF/kg body
weight and found mean blood levels ranging from 40 to 1870 mg/litre.
DMF is readily absorbed via inhalation and dermally. Maximal blood
and tissue concentrations were observed in rats up to 3 h after
exposure to 438 and 6015 mg DMF/m3 (Kimmerle & Eben, 1975a) or to 1690
and 6700 mg DMF/m3 (Lundberg et al., 1983). According to Massmann
(1956), at least 0.8 ml of 100% DMF was absorbed through 14 cm2 of
exposed skin of the tails of rats in the course of 8 h, which is
equivalent to an absorption rate of about 57 mg/cm2 per 8 h.
6.1.2 Distribution
Twenty-four hours after an ip dose of 14C-DMF in male rats, about
4% of the radioactivity was recovered in the blood, less than 1% in
the brain, heart, lungs, stomach, intestines, spleen, and kidneys, and
1-3% in the liver, adipose tissue, and muscles (Scailteur & Lauwerys,
1984).
Kimmerle & Eben (1975a) studied DMF and NMF (DMF-OH)a
concentrations in the blood of rats and dogs after single and repeated
respiratory exposure. At the highest airborne concentration (6015
mg/m3), DMF was still detectable in the blood of male rats up to 2
days after the end of a 3-h exposure. At lower concentrations, DMF
levels in the blood decreased rapidly (Table 4). After 3 h exposure
to 63 mg/m3 or 6 h exposure to 87 mg/m3, similar levels of NMF were
found in the blood at the end of the periods of exposure, but no NMF
was detectable 3 h after the end of exposure. Only after a 3-h
exposure to a very high concentration (6015 mg/m3) did NMF levels in
blood continue to increase for the 2 days following exposure (Table 4).
Blood concentrations of DMF in male dogs also decreased rapidly
following a 6-h single exposure. However, NMF could be detected in
the blood at higher concentrations and for a longer period of time
after exposure (Table 5).
---------------------------------------------------------------------------
a DMF = dimethylformamide;
DMF-OH= N-hydroxymethyl- N-methylformamide;
NMF = N-methylformamide;
NMF-OH = N-hydroxymethylformamide;
F = formamide.
Table 4. Concentrations of DMF and NMF in the blood of male rats after
a single inhalation exposure
---------------------------------------------------------------------
Hours after Inhalation exposure to DMF (3 h)
end of 6015 mg/m3 438 mg/m3 63mg/m3
exposure --------------------------------------------------------
DMF NMF DMF NMF DMF NMF
(mg/litre) (mg/litre) (mg/litre)
---------------------------------------------------------------------
0 1190 11.5 25.7 7.3 NDa 2.5
0.5 1166 12.1 21.7 6.9 1.9
1 1329 15.8 20.7 10.2 1.2
2.5 1275 20.9 10.5 11.8 0.5
4.5 1322 25.9 1.8 10.6 ND
21 824 50.3
45 46 84.3
-----------------------------------------------------------------------
a ND = not detectable.
When male rats were exposed to 1050 ± 126 mg/m3, 6 h/day, for 5
days, the levels of DMF and NMF in the blood returned to ND levels
before each consecutive exposure. However, when male dogs were
exposed to 177 ± 36 mg NFM/m3, 6 h/day, for 5 days, NMF accumulated in
the blood (10 mg/litre, 2 h after the first exposure; 30 mg/litre, 3 h
after the fifth exposure). In contrast, in female dogs, exposed to 69
± 12 mg/m3, 6 h/day, for 5 days, the daily NMF concentration in the
blood remained almost constant, returning to a low level of about 1-
1.5 mg/ml, before each new exposure.
Table 5. Concentrations of DMF and NMF in the blood of male dogs
after a single inhalation exposure
------------------------------------------------------------------------
Hours after Inhalation exposure to DMF (6 h)
end of 513 ± 114 mg/m3 60 ± 9 mg/m3
exposure ------------------------------------------------------------
DMF NMF DMF NMF
(mg/litre) (mg/litre) (mg/litre) (mg/litre)
------------------------------------------------------------------------
0 51.6 9.7 7.4 10.5
0.5 54.9 13.7 5.6 11.9
1 47.7 14.9 4.1 12.1
2 39.4 17.4 0.7 13.3
3 38.7 23.6 NDa 13.3
27 3.1
------------------------------------------------------------------------
a ND = not detectable.
Finally, in male and female dogs exposed to 63 ± 9 mg/m3, 6 h/day,
for 5 days a week over 4 weeks, DMF levels went back to ND before each
new exposure. There was no accumulation of NMF. The weekly average
concentrations of NMF were slightly higher in males than in females.
Lundberg et al. (1983) measured DMF and NMF concentrations in
various organs of the rat after a single 4-h inhalation exposure to
1690 or 6700 DMF mg/m3; DMF and NMF were distributed uniformly
throughout the tissues (Tables 6 and 7). Blood levels of NMF (DMF-OH)
for the first 3 h following exposure were lower after exposure to 6700
mg/m3 than after exposure to 1690 mg/m3 (Table 6 and 7). The authors
suggested that high DMF doses inhibit DMF biotransformation. This
interpretation is supported by the results of Kimmerle & Eben (1975a),
who reported that NMF concentrations in the blood (11-21 mg/litre)
during the first 3 h following a 3-h exposure to 6015 mg DMF/m3 were
lower than those following a 6-h exposure to 513 mg/m3.
6.1.3 Metabolic transformation
After iv injection of DMF in cats, Massman (1956) found that only
a small amount of the compound was excreted unchanged in the urine.
He could not detect any hydrolysis of the amide to dimethylamine and
formic acid. Barnes & Ranta (1972) identified a urinary metabolite,
NMF, in the urine of rats treated with sc injections of DMF.
After single or repeated respiratory exposure to DMF, Kimmerle &
Eben (1975a) identified NMF and formamide in the urine of rats and
dogs. The authors proposed a model of successive N-demethylations of
DMF.
In in vitro studies, Barnes & Ranta (1972) measured a low level
of formaldehyde, when rat liver homogenates were incubated with DMF in
the presence of an NADPH-generating system. They concluded that DMF
was N-demethylated in the liver with the help of microsomal enzymes.
This was in agreement with previous in vivo findings.
Later on, however, it was shown that the incubation of various rat
tissues with DMF did not release formaldehyde in vitro. Furthermore,
neither formaldehyde nor any other monocarbon derivative (CO, CH3OH,
CH4, HCOOH) was detected, when DMF was incubated with fortified liver
microsomes. However, a metabolite determined by gas chromatography
(GC) was identified as NMF. This led to speculation that DMF-OH was a
probable metabolite of DMF that was broken down (demethylated) to form
NMF during gas chromatographic analysis (Scailteur et al., 1984).
Brindley et al. (1983) indicated that a stable precursor of
formaldehyde was present in the urine of mice treated with DMF.
Direct evidence that DMF-OH is a metabolite of DMF was only
obtained by investigating urine samples of animals treated with DMF.
DMF-OH was identified in rat urine using HPLC combined with chemical
ionization mass spectrometry (Scailteur et al., 1984) and in mouse
urine high-field H-NMR spectroscopy and radio thin layer
chromatography (Kestell et al., 1986).
Table 6. Concentrations of DMF and NMF in rat tissues after a 4-h exposure to 6700 mg DMF/m3
------------------------------------------------------------------------------------------------------------------------
Hours after Blood Liver Kidney Brain Adrenals
end of (mg/litre) (mmol/kg)
exposure DMF NMF DMF NMF DMF NMF DMF NMF DMF NMF
------------------------------------------------------------------------------------------------------------------------
0 965 < 24 9.8 < 0.3 11.0 0.8 11.4 0.4 8.6 < 1.0
3 1089 < 24 11.7 0.5 12.8 < 0.6 2.7 < 0.3 8.8 < 1.0
6 950 71 10.1 0.7 11.5 1.3 10.1 0.5 9.0 1.2
20 263 295 2.6 1.9 3.1 2.3 1.5 2.1 1.9 1.9
48 < 29 < 24 < 0.2 < 0.3 < 0.6 < 0.6 < 0.3 < 0.3 < 0.9 < 1.0
------------------------------------------------------------------------------------------------------------------------
Table 7. Concentrations of DMF and NMF in rat tissues after a 4-h exposure to 1690 mg DMF/m3
------------------------------------------------------------------------------------------------------------------------
Hours after Blood Liver Kidney Brain Adrenals
end of (mg/litre) (mmol/kg)
exposure DMF NMF DMF NMF DMF NMF DMF NMF DMF NMF
------------------------------------------------------------------------------------------------------------------------
0 373 41 2.8 0.5 3.1 0.9 3.1 0.52 .1 < 1.0
3 205 47 1.8 0.5 2.8 0.9 2.0 0.6 1.6 < 1.0
6 197 47 1.8 0.6 2.0 1.2 1.9 0.7 1.5 1.0
20 < 29 < 24 < 0.5 < 0.3 < 0.6 0.6 < 0.3 < 0.3 < 0.9 < 1.0
------------------------------------------------------------------------------------------------------------------------
Using GC combined with mass spectrometry, Scailteur & Lauwerys
(1984a,b) showed that besides the major metabolite, DMF-OH, a small
amount of NMF could also be identified in the urine of DMF-treated
rats. This was confirmed by Kestell et al. (1986) using H-NMR
spectroscopy. Thus when urine samples are analysed after DMF
administration, using gas chromatography, the combination of DMF-OH +
NMF is determined as NMF and the combination of hydroxymethylformamide
(NMF-OH) + formamide, as formamide (Scailteur et al., 1984). Using
GC/MS, Scailteur & Lauwerys (1984a,b) could not identify NMF in the
urine of DMF-OH-treated rats. The authors therefore suggested that
NMF is not a product of DMF-OH biotransformation, but is directly
formed from DMF.
Hepatectomy markedly reduced the in vivo transformation of DMF
into DMF-OH, confirming that the liver is the main site of metabolic
degradation (Scailteur et al., 1984).
In parallel with the hypothesis of Lundberg et al. (1983) that
high doses of DMF could inhibit its biotransformation, Scailteur et
al. (1984) showed that the urinary excretion of metabolites (DMF-OH +
NMF, NMF-OH + F) was the same, following 2 daily ip injections of 0.5
mg/kg body weight or 2 daily ip injections of 1 ml/kg.
Scailteur & Lauwerys (1984a) studied the mechanism of the in vitro
and in vivo oxidative biotransformation of DMF. Addition of catalase
or superoxide dismutase to liver microsomes, incubated with DMF,
decreased the level of DMF-OH production. in vitro and in vivo, DMF
transformation was also diminished in the presence of radical
scavengers, such as dimethylsulfoxide, tert-butyl alcohol,
hydroquinone, and trichloroacetonitrile. Addition of IRON/EDTAa to
microsomes, incubated with DMF in vitro, stimulated DMF oxidation.
The authors concluded that the metabolic transformation of DMF to DMF-
OH involved hydroxyl radicals.
Metabolites, other than DMF-OH (NMF) and NMF-OH (F), appear to be
formed from DMF. Indeed, about 20% of an ip dose was recovered in the
urine of mice (Brindley et al., 1983) and rats (Scailteur & Lauwerys,
1984a,b), as unidentified chemicals.
Kestell et al. (1986, 1987) identified low levels of methylamine
and dimethylamine in the urine of DMF-treated mice (about 4%).
A metabolic transformation scheme is presented in Fig. 1, based on
the above data.
---------------------------------------------------------------------------
a EDTA = ethylene diamine tetra acetate.
6.1.4 Elimination and excretion
The transformation and excretion of DMF in rodents is rapid. When
14C-labelled DMF in 0.1 ml saline was injected ip at 6.8 mmol/kg body
weight in mice, about 83% of the radioactivity was recovered in the
urine within 24 h following injection. Of this amount, only 5% was
unchanged DMF and 56% was C-hydroxylated or N-demethylated
derivatives. About 18% of the dose was excreted in the form of
unknown chemicals (Brindley et al., 1983).
Similarly, 24 h after ip injection of 400 mg DMF/kg body weight in
0.2 ml saline in mice, about 56% of the dose was excreted in the urine
as DMF-OH and only 5% as unchanged DMF (Kestell et al., 1986).
Within 72 h of an ip administration of 1 ml 14C-DMF/kg to male
or female rats, 70% of the injected radioactivity was recovered in the
urine. Approximately 15% was excreted as unchanged DMF, 50% as DMF-OH
(NMF), and 5% as NMF-OH (F). About 20% was excreted as unidentified
metabolite(s) (Scailteur & Lauwerys, 1984a,b).
After oral exposure to DMF (40-2000 mg/kg), Sanotsky et al. (1978)
determined that about 6% of the dose was excreted in 24 h.
The elimination of DMF, NMF (DMF-OH), and formamide (NMF-OH) was
measured after single or repeated inhalation exposure in rats and dogs
(Kimmerle & Eben, 1975a). Twenty-four hours after a single exposure to
63 mg NMF/m3 for 3 h, or 87 mg/m3 for 6 h, no NMF was found in the
urine of male rats. Under the same conditions, exposure to 513 mg/m3
for 6 h or to 6015 mg/m3 for 3 h led to excretion of 4 mg and 14 mg
NMF (DMF-OH), respectively, during the 24 h following the start of
exposure. Only in the last case was DMF also measured in the urine.
After repeated exposure of male rats to DMF (1050 mg/m3, 6 h/day, for
5 days), urinary levels of NMF (DMF-OH) remained practically constant
for the first 3 days, then slightly decreased from the fourth day of
exposure. Excretion of F (NMF-OH) was much lower than excretion of NMF
(DMF-OH).
While no accumulation of urinary NMF (DMF-OH) was observed in male
rats, male dogs exposed to 177 mg DMF/m3 (6 h/day for 5 days) excreted
increasing concentrations of NMF (DMF-OH) (36 mg/24 h after the first
inhalation; 87 mg/24 h after the 4th inhalation). Urinary excretion
of formamide (NMF-OH) varied between 10 and 20 mg/24 h. Excretion of
unchanged DMF was very low (< 2 mg/24 h). However, in female dogs
exposed to 69 mg/m3 (6 h/day for 5 days), no urinary accumulation of
NMF or F was observed. When male or female rats were exposed for 4
weeks to 63 mg/m3 (6 h/day, 5 days per week), NMF and F concentrations
in the urine remained practically constant during the exposure period.
Male dogs generally excreted slightly higher levels of metabolites
than female dogs (Kimmerle & Eben, 1975a).
In rats treated with repeated, high, ip doses of DMF (4 daily
injections of 1 ml/kg body weight), Scailteur et al. (1984) showed
that females excreted higher amounts of unchanged DMF than males. The
pattern of metabolite (NMF, F) excretion was similar in both sexes
after single or repeated ip administration.
6.1.5 Metabolic interaction between DMF and ethanol
DMF and ethanol appear to interact metabolically.
The alterations in blood metabolites depend on the dose of DMF,
the time interval between DMF and ethanol administration, and the
respective routes of administration.
The various studies performed are summarized in Table 8. Blood
concentrations of DMF and NMF, ethanol, and acetaldehyde were measured
using GC methods.
The influence of DMF on ethanol oxidation might be explained, at
least partially, by its inhibitory effect on the activity of alcohol
dehydrogenase in vitro and in vivo (Sharkawi, 1979) and aldehyde
dehydrogenase in vivo (Elovaara et al., 1983).
Table 8. Metabolic interaction between DMF and ethanol
-----------------------------------------------------------------------------------------------------------------------------------------
Species Ethanol Time of DMF Effects on blood concentrations of: Reference
dose administration dose
(route) (route) DMF and Ethanol and
NMF acetaldehyde
-----------------------------------------------------------------------------------------------------------------------------------------
Rat .2 g/kg immediately before 312 mg/m3 No effects on not measured Eben & Kimmerle (1976)
(oral) DMF exposure 2 h (inhalation) DMF and NMF
Rat 2 g/kg immediately before 261 or 627 mg/m3 DMF increased not measured Eben & Kimmerle (1976)
(oral) DMF exposure 2 h (inhalation) NMF formation
Rat 2 g/kg per day daily immediately about 600 mg/m3 DMF increased ethanol increased Eben & Kimmerle (1976)
for 5 days before DMF 2 h/day 5 days NMF formation
(oral) exposure (inhalation)
Dog 2 g/kg immediately before about 630 mg/m3 DMF increased not measured Eben & Kimmerle (1976)
(oral) DMF exposure 2 h (inhalation) NMF decreased
Dog 2 g/kg immediately after 630 mg/m3 DMF increased not measured Eben & Kimmerle (1976)
(oral) DMF exposure 2 h (inhalation) NMF decreased
Rat 2 g/kg 1 h after last 3000 mg/m3 not measured acetaldehyde Hanasono et al. (1977)
(oral) DMF exposure 4 h/day 3 days increased
(inhalation)
Rat 2 g/kg 1 h after last 6000 mg/m3 not measured ethanol increased Hanasono et al. (1977)
(oral) DMF exposure 4 h/day 3 days acetaldehyde
(inhalation) decreased
Mouse 1 g/kg 2 h after DMF 1.2 ml/kg not measured ethanol increased Sharkawi (1980)
(ip) exposure (ip)
Rat 2 g/kg 3 h after DMF 0.15 g/kg not measured ethanol increased Hanasono et al. (1977)
(oral) exposure (oral) acetaldehyde
decreased
Rat 2 g/kg 18 h after DMF 0.15 g/kg not measured acetaldehydea Hanasono et al. (1977)
(oral) exposure (oral) increased
Table 8. (continued)
-----------------------------------------------------------------------------------------------------------------------------------------
Species Ethanol Time of DMF Effects on blood concentrations of: Reference
dose administration dose
(route) (route) DMF and Ethanol and
NMF acetaldehyde
-----------------------------------------------------------------------------------------------------------------------------------------
Rat 2 g/kg 18 h after DMF 1.5 g/kg not measured ethanol increased Hanasono et al. (1977)
(oral) exposure (oral)
Rat 2 g/kg 24 h after last 3000 mg/m3 not measured acetaldehyde Hanasono et al. (1977)
(oral) DMF exposure 4 h/day 3 days increased
(inhalation)
Rat 2 g/kg 24 h after last 12 000 mg/m3 not measured acetaldehyde Hanasono et al. (1977)
(oral) DMF exposure 4 h/day 3 days increased
(inhalation)
-----------------------------------------------------------------------------------------------------------------------------------------
a Increased acetaldehyde level observed after this dose of DMF was equivalent to that produced by an equimolar dose of disulfiram (antabuse).
6.2 Human studies
6.2.1 Absorption, distribution, metabolism, excretion
In vitro studies on excised human skin (Bortsevich, 1984) showed
a relationship between the amount of DMF absorbed through the dermal
barrier and the DMF concentrations in water, as well as the exposure
time. DMF enhances its own penetration. Some of the results are
given in Table 9. They are of practical value, because such solutions
are used in synthetic fibre production.
After respiratory exposure to DMF, lung retention in workers in an
artificial leather factory was 72% (Brugnone, 1980a,b).
Table 9. Quantities of DMF absorbed in in vitro studies on
excised human skin
--------------------------------------------------------------
Exposure period DMF solutions in water
(h) 100% 60% 30% 15%
% DMF absorbed through the skin (mg/cm2)
--------------------------------------------------------------
0.5 0.046 NDa NDa NDa
1-1.5 7.400 0.035 0.013 0.006
2-2.5 20.550 0.087 0.048 0.009
3-3.5 40.810 0.222 0.097 0.017
4-4.5 51.730 0.300 0.160 0.069
--------------------------------------------------------------
a ND = Not detectable.
The relative importance of skin versus inhalation for DMF
absorption was studied in volunteers by Maxfield et al. (1975),
Kimmerle & Eben (1975a), and Krivanek et al. (1978) (section 6.2.3.1).
As in animals, the major human metabolite of DMF has been reported
to be DMF-OH and not NMF. However, it is measured as NMF when using
gas chromatography including the small amount of NMF excreted in the
urine (Scailteur & Lauwerys, 1987).
When a male volunteer inhaled the DMF vapours that were produced
over liquid DMF in a beaker for 6 h, Mraz & Turecek (1987) identified
the metabolite N-acetyl- S-( N-methylcarbamoyl) cysteine in the urine.
Malonova & Bardodej (1983) reported a possible increase in the
urinary excretion of mercapturates in workers exposed to unknown
concentrations of DMF (approximately twice the excretion in controls
(smokers)).
6.2.2 The influence of ethanol on DMF metabolism in human volunteers
Eben & Kimmerle (1976) exposed 4 subjects via inhalation to DMF
(159 mg/m3) for 2 h with, and without, ingestion of 19 g ethanol (50
ml 38% gin), 10 min before they inhaled the DMF. No changes in DMF
concentrations in blood were found. The comparatively lower NMF
concentrations in the blood of subjects with combined exposure to
ethanol and DMF indicated that the ethanol decreased the
biotransformation of DMF. No significant differences in the blood
levels of ethanol and acetaldehyde were detected in subjects with, or
without, ethanol exposure, which differed from the effects observed in
animal studies. The authors suggested that this was because of the
relatively low concentrations of DMF used in the human studies.
6.2.3 Biological monitoring of workers
N-Hydroxymethyl- N-methylformamide (DMF-OH) has been identified as
the main urinary metabolite of DMF. It is measured, using gas
chromatography, as NMF together with the small proportion of NMF
excreted in the urine. Some results of studies on the correlation
between exposure levels to DMF and NMF excretion in workers and human
volunteers are given in Table 10.
6.2.3.1 Determination of NMF in the urine
NMF (DMF-OH) in the urine is a sensitive biological parameter of
human DMF exposure. NMF levels in the urine are usually greater at
the end of the shift than on the morning after the exposure. Lauwerys
et al. (1980) compared a group of 22 male workers from the spinning
mill in a polyacrylic fibre plant with 28 controls. The workers in the
spinning department wore gloves and long sleeves, but did not have any
respiratory protection. Spot urine samples were collected before, and
after, the work shift for 5 consecutive days, to determine NMF and
creatinine concentrations. NMF was notdetected in the urine of
control workers, who were not exposed to DMF. There was a poor
correlation, on an individual basis, between the integrated DMF
exposure and the NMF concentration in the urine collected at the end
of the shift, or in that collected before resuming work the following
day. However, on a group basis, there was a good correlation between
the intensity of exposure and NMF levels in the urine collected at the
end of the shift.
In a second study in the polyacrylic fibre plant, Lauwerys et al.
(1980) studied the NMF levels in the urine of 7 workers for 3 weeks,
when different types of personal protective devices were used.
Absorption of DMF vapours through the skin was more important than
through inhalation. In the absence of skin contact, a concentration
of 40-50 mg NMF/g creatinine, in post-shift samples, corresponded to
an average concentration of DMF vapour of 13 mg/m3 (45 ppm) during a
6-h exposure period.
Table 10. NMF levels in urine as a test for DMF exposure
------------------------------------------------------------------------------------------------------------------
Subjects DMF concentrations NMF concentrations Time of sampling Reference
in the air in the urine
------------------------------------------------------------------------------------------------------------------
4 volunteers 78 ± 24 mg/m3a 24 mg/24 h Kimmerle & Eben (1975a)
261 ± 75 mg/m3a 97.4 mg/24 h
63 ± 12 mg/m3b 30 mg/24 h
4 volunteers 159 ± 96 mg/m3a 44.8 mg/24 h Eben & Kimmerle (1976)
4 volunteers 32.4 ± 2.1 mg/m3a,c 5 mg/24 h Maxfield et al. (1975)
8 volunteers 26.4 ± 0.9 mg/m3b 2.5 mg/24 h Krivanek et al. (1978)
22 workers 13 mg/m3b 20-40 mg/g post-shift samples Lauwerys et al. (1980)
creatinine
9 workers 15.4 mg/m3b 0.4-19.6 mg/24 h Yonemoto & Suzuki (1980)
85 workers 30-150 mg/m3b,c 0.104-0.224 mg/ml Aldyreva et al. (1980)
23 workers above 30 mg/m3b 20-40 mg/24 h Taccola et al. (1981)
2 volunteers 30 mg/m3b 102.6 µmol/8 h Wicarova & Dadak (1981)
39 workers 217.5 µmol/24 h
30 workers 14-86.3 mg/m3b 12-188.3 mg/g 4 h after the work shift Sala et al. (1984)
creatinine different work areas
------------------------------------------------------------------------------------------------------------------
a Single inhalation exposure to DMF (2, 4, or 6 h/day).
b Repeated inhalation exposure to DMF (6, 7, 7.5 h/day).
c Dermal absorption.
Yonemoto & Suzuki (1980) studied the relationship between the
individual occupational exposure to DMF and the amount of NMF in the
urine of 9 male workers who handled polyurethane surface-treating
agents for synthetic leather. The time-weighted average individual
exposures ranged from 0 to 15.4 mg DMF/m3. The amount of NMF excreted
daily ranged from 0.4 to 19.56 mg/24 h. The excretion rate of NMF
(mg/h) increased from the beginning of exposure and reached a maximum
in the urine samples collected in the evening. The relationship
between the total daily NMF excretion in the urine and the level of
exposure was represented as a linear regression, indicating that the
best biological index of DMF exposure is the determination of NMF in
the 24-h urine (Fig. 2). At an 8-h integrated DMF exposure of 15
mg/m3, the NMF level in the urine of the workers was less than 20
mg/24 h. This value is higher than those obtained for volunteers
(Kimmerle & Eben, 1975b; Krivanek et al., 1978) or for workers
(Lauwerys et al., 1980). Yonemoto & Suzuki (1980) stated that the
difference might be due to dermal absorption of DMF, because the
workers did not use protective gloves or special working overalls.
Wicarova & Dadak (1981) studied the relationship between the
amount of NMF in the shift urine (8 h) or the all-day urine (24 h) of
workers and DMF concentrations in the air (0-100 mg/m3) in an
artificial leather plant . The relationship was linear for the shift
urine samples. For the 24-h urine samples, the relationship was
linear only in the range of 0-80 mg DMF/m3 (see also Table 10).
When Dixon et al. (1983) studied the urinary NMF excretion in a
group of 32-37 workers who were exposed to similar air levels of DMF
for either 8 h per shift (5 days/week) or 12 h per shift (4
days/week), they found higher concentrations of NMF in the urine when
the workers were working 8-h shifts. A possible explanation was that
a 13% reduction in urine volume was seen in workers on 8-h shifts
during the summer months compared with higher urine outputs seen in
the same workers on 12-h shifts during the winter months.
Sala et al. (1984) found a correlation between urinary NMF levels,
4 h after workplace exposure, and the workers' exposure levels to DMF
in 5 job categories relating to artificial leather production. They
reported airborne DMF concentrations of 4.5-14 mg/m3 for spreading
"coagulate" system workers, with a mean NMF in urine of 16 mg/g
creatinine, 9.4 mg DMF/m3 for finishing workers, with a mean NMF
urinary value of 12 mg/g creatinine (low exposures), and 86.3 mg
DMF/m3 in tank cleaning workers with a corresponding urinary value of
188.3 mg NMF/g creatinine (highest exposure).
6.2.3.2 N,N-Dimethylformamide determination in the expired air
Airborne DMF concentrations change considerably during the work
shift and from one workplace to another. Brugnone et al. (1980a)
measured the DMF concentrations in the alveolar air every hour during
the 8-h shift of 8 workers employed in an artificial leather plant.
The alveolar DMF concentration in 6 workers was correlated with the
DMF concentration in the air of the respective workplaces.
In a second study, Brugnone et al. (1984) studied 8 exposed
workers by determining the DMF concentrations in the environmental
air, alveolar air, blood, and urine. Air samples were collected at
hourly intervals during an 8-h work shift, blood samples, at 2-h
intervals, and urine samples, at 4-h intervals. No DMF was found in
the blood or urine. A good correlation between the alveolar and
environmental DMF concentrations was found in 6 out of the 8 workers,
and at all subsequent hours, except for the fourth hour.
In practice, the alveolar air test is more difficult to perform
and use for routine examination than measurement of NMF levels in
urine samples, and is not recommended for biological monitoring.
6.2.3.3 Appraisal
The level of NMF in a post-shift urine sample is the most
appropriate biological parameter for total DMF exposure (inhalation
plus dermal) during the shift.
7. EFFECTS ON ORGANISMS IN THE ENVIRONMENT
The effects of DMF on organisms in the environment have been
reviewed by Kennedy (1986) and by US EPA (1986).
The LC50s of DMF for various aquatic species, given in Table 11,
indicate a low toxicity for the species tested.
DMF is commonly used to facilitate the solution of lipophilic
compounds in water during aquatic toxicity tests.
Cardwell et al. (1978) studied the long-term toxicity of DMF for
fathead minnow (Pimephales promelas), brown trout (Salvelinus
fontinalis), and bluegill (Lepomis macrochirus), and found threshold
limits of between 43 and 98 mg DMF/litre for the brook trout and
between 5 and 10 mg/litre for the fathead minnow. LeBlanc &
Surprenant (1983) showed that a level of 0.1 ml DMF/litre was
acceptable for long-term aquatic toxicity tests. In a study by
Tonogai et al. (1982), the 24-h and 48-h static median tolerance
limits for the Himedaka (Oryzias latipes) were > 1000 mg DMF/litre.
A no-observed-effect level (NOEL) of 7700 mg/litre was reported
for the rainbow trout by Shubat et al. (1982).
Solutions of DMF of 25 g/litre (2.5%) were shown to be lethal
within 0.5 h for eggs of sea urchins (Lythechinus variegatus, Arbacia
punctulata, Lythechinus pictus), the surf clam (Spisule solidissima),
and the annelid (Pectinaria) (Rebhun & Sawada, 1969).
Hughes & Vilkas (1983) determined that the highest concentration
that had no significant effect on the green alga Selenastrum
capricornatum, was 1 ml/litre and the no-effect level was 0.5
ml/litre.
Concentrations ranging from 0.085-0.340% DMF had an inhibitory
effect on cultures of Streptomyces aureofaciens (Welward & Halama,
1978).
Table 11. Medial lethal (LC50) concentrations (mg/litre) for aquatic
organisms exposed to dimethylformamide (DMF)
----------------------------------------------------------------------------------------------------
Species LC50 Reference
---------------------------------------
24-h 48-h 96-h
----------------------------------------------------------------------------------------------------
Guppy 1300 Dojlido (1979)
(Paecilia reticulata)
Rainbow trout 9800 Poirier et al. (1986)
(Salmo gairdneri) 9860 Shubat et al. (1982)
Fathead minnow 10 600 Poirier et al. (1986)
(Pimephales promelas)
Bluegill 7100 Poirier et al. (1986)
(Lepomis macrochirus)
Midge (Paratanytarsus 36 200 Poirier et al. (1986)
parthenogeneticus)
Daphnid (Daphnia magna) 14 500 Poirier et al. (1986)
12 300 LeBlanc & Surprenant
(approx.) (1983)
Larvae (Aedes aegypti) 68 000 Kramer et al. (1983)
(approx.)
----------------------------------------------------------------------------------------------------
8. EFFECTS ON EXPERIMENTAL ANIMALS AND IN VITRO TEST SYSTEMS
8.1 Single exposures
Data on the acute toxicity of DMF in different laboratory animals,
when administered by different routes, have been reviewed by Kennedy
(1986). The acute toxicity in a number of species, following oral,
dermal, inhalation (Table 12), or parenteral (Table 13) administration
of DMF is relatively low, with lethal doses generally in the g/kg
range for the oral, dermal, and parenteral routes and in the g/m3 for
inhalation exposures. Animals given large single doses of DMF or
exposed to high air levels showed general depression, anaesthesia,
loss of appetite, loss of body weight, tremors, laboured breathing,
convulsions, haemorrage of the nose and mouth, liver injury, and coma
immediately preceding death.
In mice and rats, exposed to DMF via inhalation, signs of mucous
membrane irritation were seen (Lobanova, 1958; Lundberg et al., 1986),
and lung damage was detected histologically (Clayton et al., 1963).
Where tissue pathology was included in the study, the prominent
organ showing damage was the liver (Massmann, 1956; Sanotsky et al.,
1978; Mathew et al., 1980; Lundberg et al., 1981). No obvious species
differences were observed with regard to acute lethality, but young
rats appeared more sensitive to DMF-induced lethality than older rats
(Kimura et al., 1971).
8.2 Skin and eye irritation, sensitization
DMF was reported to be irritating to the eyes, mucous membranes,
and the skin (Hamilton & Hardy, 1974; Aldyreva & Gafurov, 1980).
8.2.1 Skin irritation
Rat tails dipped in DMF at 40 °C for 8 h became mummified in a few
days (Massmann, 1956).
A single application of 500 mg DMF/kg resulted in transient
irritation within 2-3 h in mice, but no irritation in rats (Wiles &
Narcisse, 1971). DMF was slightly irritating for mice at doses of
2500 and 5000 mg/kg. No skin irritation was detected in rabbits with
applications of 100, 200, or 500 mg DMF/kg. Single applications of
DMF on the skin of rats and guinea-pigs did not cause irritation
(Kiss, 1979; Bainova, 1985). Repeated 28-day treatments with 960 or
1920 mg/kg did not induce marked local dermal effects in rats (Bainova
et al., 1985).
Table 12. LD50 and LC50 values of DMF after oral, dermal, or
inhalation exposure in various animal species
----------------------------------------------------------------------------------------------------
Species Oral LD50 Dermal LD50 Inhalation LC50 Reference
(mg/kg) (mg/kg) (mg/m3)
----------------------------------------------------------------------------------------------------
Rat 3000 Thiersch (1962)
5000 9432 US NIOSH (1977)
3920 Massmann (1956)
11 140 12 000 Schottek (1970, 1972)
4000 Sanotsky et al. (1978)
> 11 520 Bainova & Antov (1980)
15 000 Clayton et al. (1963)
4320 Lazarev & Levina (1976)
11 000a Stula & Krauss (1977)
> 13 440 Lundberg et al. (1986)
3200 Qin & Gue (1976)
14 000 Cai & Huang (1979)
7170 Bartsch et al. (1976)
Mouse 3950 Lazarev & Levina (1976)
5550 Lazarev & Levina (1976)
> 5000 Wiles & Narcisse (1971)
6420 Bartsch et al. (1976)
3700 6000-9400 Lobanova (1958)
5400, 6200 Qin & Gue (1976)
18 300 Cai & Huang (1979)
Rabbit > 5000 > 500 Wiles & Narcisse (1971)
1500a Stula & Krauss (1977)
Mongolian gerbil 3929 Llewellyn et al. (1974)
----------------------------------------------------------------------------------------------------
a Pregnant females.
Table 13. LD50s (mg/kg body weight) of DMF after parenteral administration
in various animal species
----------------------------------------------------------------------------------------------------------
Species Intraperitoneal Intravenous Intramuscular Subcutaneous Reference
----------------------------------------------------------------------------------------------------------
Rat 1480 4030 Massmann (1956)
2500 Thiersch (1962)
4440 2830 Bartsch et al. (1976)
4600 Pham Huu Chanh et al. (1971)
5470 Shottek (1970, 1972)
Mouse 300 Massmann (1956)
3500 3800 4500 US NIOSH (1977)
650 Barral-Chamaillard
& Rouzioux (1983)
1454 Burgun et al. (1975)
2000 Antoine et al. (1983)
3150 2800 Wiles & Narcisse (1971)
5200 Pham Huu Chanh et al. (1971)
5850 3490 Bartsch et al. (1976)
Rabbit 945 1800 Massmann (1956)
1000 Wiles & Narcisse (1971)
5000 US NIOSH (1977)
Guinea-pig 1300 Wahlberg & Boman (1979)
1030 US NIOSH (1977)
4000 Ungar et al. (1976)
Dog 470 Barral-Chamaillard
& Rouzioux (1983)
Cat 500 Massmann (1956)
----------------------------------------------------------------------------------------------------------
After repeated application of DMF to the skin of guinea-pigs for
21 days (Bainova, 1985), the mean irritative dose was 31% DMF (range
17-56%).
Dermal irritation was not seen in rabbits treated dermally with 2
g DMF/kg for 6 h, daily 15 times during a 4-week period (Kennedy,
1986).
8.2.2 Eye irritation
A 25% (25 g/litre) solution of DMF in water, injected into the
conjunctival sac of the rabbit, did not produce any effects; 50% was
slightly irritating, and 75-100% produced more severe irritation
(Massmann, 1956). Single dose DMF instillation (0.1 ml) produced
moderate corneal damage and conjunctival redness that was most
pronounced at 2-3 days. By day 14, a mild degree of conjunctival
redness, moderate corneal damage with an area of severe injury, slight
surface distortion, and subsurface vascularization were observed
(Kennedy & Sherman, 1986). In another study, the same authors
reported that, after a single DMF instillation, the eye inflammation
subsided and disappeared by the 8th day.
8.2.3 Sensitization
DMF was tested, using a maximization technique, on guinea-pigs to
determine skin sensitization; it did not induce any response (Bainova,
1985).
8.3 Repeated exposure
The effects of repeated oral, dermal, or inhalation exposure to
DMF in various animal species have been reviewed by Kennedy (1986) and
these data, together with other new information are summarized in
Table 14. In all species tested, except the dog, liver damage was
produced, the degree of damage generally being proportional to the
dose administered. In the two reported studies on the dog (Clayton et
al., 1963; Kimmerle & Eben, 1975a), the inhalation exposure conditions
appeared to be too low (60 mg/m3) to produce damage, though 1 out of
the 4 dogs tested by Clayton did have altered liver function tests.
Higher levels were not tested. Some evidence of recovery from the
hepatotoxic effects of DMF was found in rats (Kennedy & Sherman,
1986).
Higher, intermittent doses of DMF appeared to produce more
pronounced effects in male rats than continuous dosing (Bainova et
al., 1981a; Bainova, 1985). Tanaka (1971) found more pronounced liver
damage in rats following one rather than three weeks of exposure and
considered that the high regenerative capacity of liver tissue was
responsible for the observation.
Other tissues and organs that are affected, particularly by high
doses of DMF, will be discussed in section 8.4.
8.4 Specific organ toxicity
8.4.1 Liver
The potency of DMF as a hepatotoxic agent has been reviewed by
Kennedy (1986) and by Scailteur & Lauwerys (1987). The effects of DMF
on the liver were studied after single or repeated inhalation, dermal,
or oral treatment of rats, mice, and rabbits (Massmann, 1956; Clayton
et al., 1963; Shottek, 1970; Tanaka, 1971; Kimmerle & Eben, 1975a;
Medyankin, 1975; Sanotsky et al., 1978; Germanova et al., 1979; Mathew
et al., 1980; Bainova et al., 1981a; Lundberg et al., 1981; Lundberg,
1982; Brondeau et al., 1983; Bainova, 1985; Kennedy & Sherman, 1986;
Scailteur & Lauwerys, 1987). Single oral administrations of 2250-5000
mg DMF/kg in rats (Kennedy & Sherman, 1986) caused clay-coloured
liver, congestion, and centrilobular necrosis of hepatocytes. Lower
doses resulted in deviations in liver function, such as decreased
excretion of cholic acid in the bile, bromosulfthalein retention,
increased serum activities of GOT, GPT, LAP, OCT, AlcP, ChE, LDH, and
gamma-GT, and significant enhancement of cholesterol, triglyceride,
and bilirubin contents in the serum and liver homogenates. In rats,
following both intraperitoneal (ip) and inhalation exposure, there
were no increases in SDH levels at 420 and 840 mg/m3 but a lower level
(210 mg/m3) raised the serum activity of SDH (Lundberg et al., 1986).
Pathomorphological investigation demonstrated lipid degeneration and
cloudy swelling of hepatocytes in the central zones of the lobules
followed by signs of regeneration.
DMF at 0.6 ml/kg, administered intraperitoneally, caused mild
changes in rat liver lobules. Marked centrilobular necrosis and
central phlebitis were found in the rats treated with single ip doses
of 0.9 and 1.2 ml DMF/kg (Mathew et al., 1980). A single ip dose of
0.5 ml DMF/kg to hamsters caused centrilobular necrosis accompanied by
haemosiderosis (Ungar et al., 1976). Morphological changes were
reported in the liver by Clayton et al. (1963), Shottek (1970), Tanaka
(1971), and Santa Cruz & Corpino (1978) after repeated DMF exposure of
young animals, with periodic peaks (Table 14).
Table 14. Effects of repeated oral, dermal, or inhalation exposure to DMF in various animal species
________________________________________________________________________________________________________
Species Route of Dose Duration Effects Reference
exposure
________________________________________________________________________________________________________
Mongolian oral 10 000 mg/kg 30 days no changes in body weight, liver, Llewellyn
gerbil drinking-water or kidney et al. (1974)
10 000 mg/kg 200 days mortality in 25% of animals;
drinking-water liver necrosis
17 000 mg/kg 80 days mortality with liver necrosis;
drinking-water LD50 cumulative 90 206 mg/kg
body weight
34 000 mg/kg 6 days mortality with liver necrosis;
drinking-water LD50 cumulative 3846 mg/kg body
weight
Mouse oral 620 or 1240 30 days anorexia, loss of body weight Qin & Gue
mg/kg diet (1976)
160, 540, 119 days dose-related increase in relative Becci et al.
1850 mg/kg diet and absolute liver weights; no (1983)
other histological or biochemical
changes; NOEL, 246-326 mg/kg
diet per day
Rat oral 320 or 640 30 days anorexia, loss of body weight Qin & Gue
mg/kg diet (1976)
50, 500, 5000 100 days body weight decrease; liver Qin & Gue
mg/litre damage at 5000 mg/litre; (1976)
drinking-water increase in liver to body weight
ratio at 500 and 5000 mg/litre;
structural liver changes and
regeneration at 5000 mg/litre;
NOEL, 50 mg/litre
Table 14 (continued)
________________________________________________________________________________________________________
Species Route of Dose Duration Effects Reference
exposure
________________________________________________________________________________________________________
Rat oral 102, 497, 1000 14 days no behavioural changes at 102 or Savolainen
mg/litre 49 days 497 mg/litre for 49 days; dose- (1981)
drinking-water related deviations in cerebral
and glial cell enzyme activities
215, 750, 2500 104 days dose-related increase in relative Becci et al.
mg/kg diet and absolute liver weights, (1983)
considered to be physiological
adaptation; NOEL, 210-235 mg/kg
diet per day
200, 1000, 5000 90 days slight anaemia and leukocytosis, Kennedy &
mg/kg diet hypercholesterolaemia at 1000 and Sherman (1986)
(equivalent to 5000 mg/kg diet; NOEL, 200 mg/kg
12, 60, 300 mg/ diet
kg/body weight
per day)
0.1, 0.5, 1.0 14 days dose-related increase in liver/ Elovaara
g/litre in 49 days body weight ratios; in liver et al.
drinking-water and kidneys, increased values of (1983)
reduced glutathione, microsomal
UDP glucuronosyl transferase,
and ethoxycoumarin O-demethylase
activities; no changes in liver
microsomal cytochrome P-450 or
ADPH-cytochrome reductase
activity
Rat dermal 470 mg/kg per 30 days continuous dosing caused Schottek
day for 29 days hepatoxicity and did not protect (1970)
and 11 140 mg/kg against lethality; pretreatment
on the 30th day did not enhance toxic reactions
after application of the LD50
in 30-day pretreated rats
Table 14 (continued).
________________________________________________________________________________________________________
Species Route of Dose Duration Effects Reference
exposure
________________________________________________________________________________________________________
215, 430, 960, 30 days dose-related changes in GOT, Bainova &
or 4800 mg/kg GPT, AlcP, ChE, gamma-GT, lipid Antov (1980)
per day fractions in serum and liver
homogenates; NOEL, 215 mg/kg
Rat dermal 215, 320, 960, 30 days dose-related changes (at doses Bainova (1985)
or 4800 mg/kg > 320 mg/kg) in enzyme
activities per day in liver,
myocardium, and kidney
homogenates; NOEL, 215 mg/kg
Rat dermal 960 mg/kg daily 28 days functional, biochemical, and Bainova et al.
or 1920 mg/kg pathomorphological changes in (1981a)
applied liver; and lipid metabolism Bainova (1985)
intermittentlya on the 4th, 8th, 14th, and 28th
day of the tests; changes more
pronounced after intermittent
exposure
4-h dipping of 60 days concentration-related changes Medyankin
tails in 60, 65, in liver and nervous system; (1975)
70, or 80% DMF NOEL, 60% DMF in water
in water
4-h dipping of 120 days no changes at 30% DMF contact and Medyankin
tails in 5 mg DMF/m3 inhalation; adverse (1975)
30 or 60% DMF effects at other concentrations
and inhalation of
5 or 10 mg DMF/m3,
6 h daily
Table 14 (continued).
________________________________________________________________________________________________________
Species Route of Dose Duration Effects Reference
exposure
________________________________________________________________________________________________________
Rabbit dermal 50, 100% water 7 days died at 5-8 day of application Huang et al.
solution, 3 at 100% DMF; liver biochemical (1981)
times/day, 2 ml/ and histological changes
application
2000 mg/kg per 9 days anorexia, cyanosis, and mortality Kennedy &
day with liver necrosis Sherman (1986)
Guinea dermal 50, 75, 100% 7 days died 2-4 days after application of Huang et al.
-pig solution, 75 or 100% and 4-9 days after 50%; (1981)
3 times/day, loss of body weight; liver damage
2 ml/application
Rat inhalation 1800 mg/m3 for 6 days concentration-related mortality; Schottek
6 h daily cumulation of hepatoxic effect (1970)
750 and 1500 6 days
mg/m3, 6 h daily
30 mg/m3 for 8 days no changes in the function of Sanotsky &
6 h daily the thyroid or adrenal glands Ulanova (1975)
aerosol for 3 or liver and kidney necrosis, lung Santa Cruz &
0.5 h daily 30 days changes, arterial changes in Corpino (1978);
(concentration myocardium Santa Cruz &
unknown) Maccioni (1978)
22 ± 1.6 mg/m3 18 weeks liver changes, no other responses Cai & Huang
for 6 h daily, (1979)
6 days a week
Table 14 (continued).
________________________________________________________________________________________________________
Species Route of Dose Duration Effects Reference
exposure
________________________________________________________________________________________________________
Rat inhalation 130 mg/m3 for 27 days functional changes in kidneys Germanova et al.
4 h daily and liver; arterial blood pressure (1979)
more pronounced after additional
300 mg/m3 in 27 days single administration of 500 mg
5 peaks of DMF/kg on the 1st, 8th, and
15 min at 27th days of the studies, and
40-min intervals after intermittent exposure
7569 mg/m3 5 days weakness, weight loss, Kennedy &
for 6 h daily dehydration, liver necrosis Sherman (1986)
Young rat inhalation 600 mg/m3 for 28 days increased serum GOT and GPT; Tanaka (1971)
(3-12 8 h daily morphological liver changes,
weeks old) mainly in 3-week-old rats;
no histological abnormalities
in other organs
Young rat inhalation 600 mg/m3 for 28 days liver changes at the 1st, 2nd, Tanaka (1971)
(3 weeks 8 h daily and 3rd, and 4th week of test more
old) 600 mg/m3 for intense in the group exposed
1 h daily for 8 h daily; no cumulation of
hepatoxic effect
Table 14 (continued).
________________________________________________________________________________________________________
Species Route of Dose Duration Effects Reference
exposure
________________________________________________________________________________________________________
Rat, inhalation 450, 900, 1800, 60 days increased serum GOT, GPT, AlcP, Craig et al.
mouse 3600 mg/m3 cholesterol, anaemia and (1984)
for 6 h daily histological liver changes at
900 mg/m3 or more; liver weight
increase at 450 mg/m3; NOEL
below 450 mg/m3 in both species
Rat, cat inhalation 300, 690, 1350 120 days anorexia, weight loss, liver Massmann
mg/m3, 8 h daily degeneration, and necrosis; (1956)
changes in brain, myocardium,
and kidneys; no abnormalities
in blood tests or ECG
Rabbit inhalation 22 ± 1.6 mg/m3 18 weeks no changes in ECG or liver Cai & Huang
for 6 h daily, parameters (1979)