FAO Nutrition Meetings
Report Series No. 48A
WHO/FOOD ADD/70.39
TOXICOLOGICAL EVALUATION OF SOME
EXTRACTION SOLVENTS AND CERTAIN
OTHER SUBSTANCES
The content of this document is the
result of the deliberations of the Joint
FAO/WHO Expert Committee on Food Additives
which met in Geneva, 24 June -2 July 19701
Food and Agriculture Organization of the United Nations
World Health Organization
1 Fourteenth report of the Joint FAO/WHO Expert Committee on Food
Additives, FAO Nutrition Meetings Report Series in press; Wld Hlth
Org. techn. Rep. Ser., in press.
DICHLOROMETHANE
Biological Data
Biochemical aspects
Dichloromethane (CH2CL2) is rapidly absorbed by the lungs (70-75% of
the inhaled vapour). uniformly distributed in organs and rapidly
excreted via the lungs and in the urine. It is largely excreted
unchanged (von Oettingen et al., 1949; Riley et al., 1966). Because
chlorinated hydrocarbon extraction solvents can react with -SH groups
of protein aminoacids, the reaction of dichloromethane with L-cysteine
was studied. The theoretical reaction product is djenkolic acid
(1-1-di-(1,1-aminocarboxy -2 thioethyl)-methane) which has an acute
oral LD50 of >1O g/kg body weight in mice. Under normal
technological conditions practically none is found in the extracted
material (Klimmer, 1970). Absorbed dichloromethane is probably
hydrolysed in the liver to formaldehyde and HC1. Some of it also
reacts with -SH groups of liver enzymes, e.g. coenzyme A (Heppel &
Porterfield, 1948).
Acute toxicity
Animal Route LDS50 LD100 Reference
Mouse inhalation 56 mg/l air - Svirbely et al., 1947
inhalation - 14 500 ppm Flury & Zernik, 1931
i.p. 1.5 ml/kg - Klaassen & Plaa, 1966
s.c. 76 m moles/kg - Kutob & Plaa, 1962
Rat oral 2 g/kg - Klimmer, 1970
oral 1.6-2 g/kg - Dow Chemical Co., 1968
Guinea-pig inhalation - 50 000 ppm Nuckolls, 1933
Rabbit oral - 1.9 g/kg Spector, 1956
Dog oral - 3g/kg Barsoum & Saad, 1934
i.v. - 200 mg/kg Barsuom & Saad, 1934
i.p. - 0.95 ml/kg Klaassen & Paan, 1967
s.c. - 2.7 g/kg Barsoum & Saad, 1934
This substance is a fairly strong but very volatile narcotic with
an excitement stage, seen especially in rabbits and dogs, and
incoordination in rats (Browning, 1965; Elkins, 1950). Mice were
exposed to the LD50 vapour concentration for 24 hours and their SGPT
elevation was determined to estimate hepatotoxic potential. This was
found to be low (Gehring, 1968). Administration i.p. to mice of 1.5
ml/kg produced albuminuria in 50% of animals with Decreased PSP
excretion (Plaa & Larson, 1965).
Mice injected s.c. with 20 m M/kg exhibited renal tubular
necrosis, but BSP retention and liver histology were unaffected (Kutob
& Plaa, 1962a).
Administration i.p. of the LD50 to mice had no effect on SGPT
retention or SGPT activity. The livers appeared histologically normal
but the kidneys showed occasionally minimal necrosis of convoluted
tubules (K1aassen & Plaa, 1966). Administration s.c. to mice of the
LD50 caused some prolongation of pentobarbital sleeping time, but
little change in BSP retention with normal liver histology (Kutob &
Plaa, 1962).
Oral administration to rats of 11.8 m M/kg by gavage had no
effect on liver glutathione levels (Johnson, 1965). Inhalation of 5000
ppm in air by 95 rats for 7 hours depressed the activity of rats as
measured on activity drums although inspection showed no abnormality
(Heppel & Neal, 1944). Higher levels reduce blood pressure and may
injure the myocardium (von Oettingen, 1955). Administration i.p. to
dogs of the LD50 produced elevation of SGPT in 50% of animals. No
histological liver necrosis was seen but there was moderate neutrophil
infiltration of the sinusoids. Renal histology was normal (Klaassen &
Plaa, 1967).
Short-term studies
Rat
Groups of 30 male and 30 female Wistar II BR46 rats were given
drinking water containing 0, or 125 ppm (i.e. about 2.8 mg/kg) for 91
days, after which 10 male and 10 female rats/group were mated. The
remainder were sacrificed. No effects were observed on body weight
(both sexes), haematology, urinalysis, blood glucose, plasma free
fatty acids (males) or oestrus cycle (females). No pathological
changes were noted in sacrificed animals. Post-exposure reproduction
was normal (Bornmann & Loeser, 1967).
Four groups of 30 male and 30 female rats received either plain
water. 4% alcohol, beer made with natural hops and beer made with a
hop extract containing 2.2% dichloromethane for 13 weeks. However, no
residues of dichloromethane were detectable in the beer. No difference
was noted between test and control groups as regards haematology,
urine analysis, major organ weights, blood chemistry and histology
except for the expected fatty changes in the liver of the three test
groups. The thyroids of the two test groups on beer had significantly
smaller weights than the other two groups. No evidence of toxicity
appeared in beer made with hop extract using dichloromethane (Bornmann
et al., 1968).
2 groups of 60 rats each received for 3 months as drinking fluid
either water, coffee infusion containing 0.000012% or 0.012% of
aqueous dichloromethane. No significant differences were seen between
test and control animals as regards growth or other biological
findings (Klimmer, 1970).
Long-term studies
No adequate information available.
Special studies
Rats, rabbits, dogs and guinea-pigs were exposed to
dichloromethane up to 5000 ppm for varying periods up to 6 months. No
serious adverse effects were seen except for occasional pulmonary
oedema with focal necrosis and fatty degeneration of the liver. Higher
doses produced liver damage in dogs and guinea-pig, but not in rats,
rabbits or monkeys. Reproduction was unaffected (Heppel et al., 1944).
Rabbit skin was treated with 0.5 g/kg for 5 days per week for 90
days without any adverse effects (Dow Chemical Co., 1968),
Observations in man
Use as anaesthetic in man caused prenarcotic excitement but no
other ill effects (Grasset & Gauthier, 1950). Excessive inhalation
(2300 ppm) produces nausea. vomiting, also acute bronchitis and
irritation of the conjunctiva and nose with some anaemia (Moskowitz &
Shapiro, 1952). Most commonly drunkenness is produced (Patty, 1958).
Skin absorption is small but it causes considerable irritation
(Torkelson et al., 1966). The TLV is 500 ppm (Amer. Conf Gov. Ind.
Hyg., 1969).
4 human subjects had the skin of their thumb immersed in
methylenechloride for 30 minutes. The mean peak alveolar concentration
during exposure was 3 ppm. This fell to 0.7 ppm 2 hours after the
exposure (Stewart & Dodd, 1964).
Comments
The solvent is metabolically fairly stable and largely excreted
unchanged. High dosage produces narcosis but a long history of
industrial exposure indicates no major toxicity. There is no evidence
that it produces toxic reaction products with -SH groups when used
according to good manufacturing practice. The long-term data available
were in an abridged form and there was therefore no way of judging the
actual solvent intake in the test animals. However, in short-term
studies food extracted with the solvent appeared to be non-toxic.
Tentative Evaluation
The use of this solvent should be restricted to that determined
by good manufacturing practice, which is expected to result in minimal
residues unlikely to have any significant toxicological effect.
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See Also:
Toxicological Abbreviations
Dichloromethane (ICSC)
Dichloromethane (WHO Food Additives Series 30)
DICHLOROMETHANE (JECFA Evaluation)
Dichloromethane (IARC Summary & Evaluation, Volume 71, 1999)