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.
TRICHLORETHYLENE
Biological data
Biochemical aspects
Probably between 71-76% of inhaled trilene is rapidly absorbed through
the lungs. In man most absorption occurs within the first few minutes
of exposure and then decreases to an equilibrium between air/blood
concentrations. Moderate absorption can occur through intact skin and
from the gastrointestinal mucus after ingestion (von Oettingen, 1955).
In the rat, rabbit and dog absorbed trilene is distributed among
all organs and tissues but concentrates mostly in fat and brain and
least in skeletal muscle; lung and liver also retain low levels
(Barrett et al., 1939; Clayton & Parkhouse, 1962; von Oettingen,
1955). Similar organ concentrations are found in guinea-pigs but high
levels were also found in ovaries and adrenals (Fabre & Truhaut,
1952). In the rat trilene and trichloroacetic acid may be selectively
bound to erythrocytes hence giving high spleen levels (Fabre &
Truhaut, 1952) but plasma proteins may also be involved (Soucek &
Vlachová 1960). In man trilene is detectable in the blood within 30
minutes of inhalation (Stewart et al., 1962).
Trilene is metabolized slowly to chloralhydrate (via an epoxide)
and then rapidly to 2,2,2-trichloroacetic acid (CCl3 CHOOH) and
2,2,2-trichlorethanol (CCl3CH2OH), which latter two metabolites are
excreted as urinary glucuronides (e.g. trichlorethanol glucusiduronic
acid) very little unchanged trilene appearing in the urine (Powell,
1945; Butler, 1949; Uhl & Haag, 1958; Williams, 1959; Smith, 1966).
Dogs excrete 5-8% of absorbed trilene as trichloroacetic acid and
15-20% as trichlorethanol up to 4 days after exposure (Barrett et al.,
1939; Barrett & Johnston, 1939; von Oettingen, 1955). The lung and
spleen, less so the liver are probably the main sites of metabolism
(Fabre & Truhaut, 1952; Defalgue, 1961). Rats excrete about 4% of
inhaled trilene as trichloroacetic acid, the lung and spleen being the
main sites of metabolism in vitro and in vivo, the liver being
less important (Fabre & Truhaut, 1952). Rats given oral trilene
excrete 3% as trichloroacetic acid and 15% as trichlorethanol (Daniel,
1957a) trichlorethanol excretion being the better guide to extent of
exposure (Daniel, 1957b). 36Cl labelled trilene was given to rats by
gavage. 10-20% was excreted in the urine as trichloroacetic acid
(1-5%) and trichlorethanol (10-15%), 0-0.5% in the faeces and 72-85%
probably as trilene in the expired air. The metabolites were formed by
intra-molecular rearrangement. Radioactivity was excreted for up to 18
days after single dosing (Daniel, 1963). In vitro studies on rat
liver microsomes showed conversion of trilene to chloral (Byington &
Leibman, 1965). Rabbits excrete 0.5% of absorbed trilene as
trichloroacetic acid (Fabre & Truhaut, 1952; Defalgue, 1961) and after
oral dosing by gavage no significant effects were seen on urobilin,
blood, glucose level or serum cholesterol (Dervilleé et al., 1938).
Guinea-pigs show presence of trichloroacetic acid in their urine after
inhalation (Fabre & Truhaut, 1952). Calves similarly metabolize orally
administered trilene to trichloroacetic acid (1%) and trichlorethanol
(13-25%) appearing in their urine together with a trace of trilene.
The balance is probably exhaled or excreted in the faeces (Seto &
Schultze, 1955).
Man excretes 6-16% of inhaled trilene as trichloroacetic acid
(Ahlmark & Forssman, 1951); others found 7-27% of retained trilene
being excreted as trichloroacetic acid (Powell, 1945; Soucek et al.,
1952) as well as trichlorethanol, monochloracetic acid and chloroform
(Soucek et al., 1952; Defalgue, 1961). Small amounts of
trichloroacetic acid may continue to be excreted in the urine for up
to 12 days after single exposure (von Oettingen, 1955). Five human
subjects exposed for 5 hours to trilene excreted 4% of the retained
dose as monochloracetic acid, 19%. as trichloroacetic acid and 50% as
trichlorethanol over the next 14 day. (Soucek & Vlachová, 1960;
Defalgue, 1961). In another experiment 8 subjects inhaled trilene for
5 hours. 51-64% of the inhaled trilene was retained the rest exhaled
unchanged. Of the retained trilene 38-50% was excreted as urinary
trichlorethanol and 27-36% as urinary trichloroacetic acid. 8.4% of
trichloroacetic acid and trichlorethanol was excreted in the faeces.
Sweat and saliva contained also both metabolites (Bartonicek, 1962).
In all species most of the trichloroacetic and trichlorethanol is
excreted in the first 2 days after exposure but excretion may go on up
to 53 day. Some 2-4 hours elapse after single exposure before
trichloroacetic acid appears in the blood reaching a maximum in 20-50
hours (Ahlmark & Forssman, 1951; Defalgue, 1961). Trichlorethanol
appears to be the main metabolite and is much more toxic (Bartonicek &
Teisinger, 1962). Disulfiram decreases the excretion of
trichloroacetic acid and trichlorethanol by acting either on
converting enzymes or on trilene release from fat depot. (Bartonicek &
Teisinger, 1962) while glucose and insulin increase production (Soucek
& Vlachová, 1960).
Chronic exposure may cause disturbance of protein metabolism by
an increase in the ß-globulin to 16-21% (normal 10-14%) and in fat
metabolism by an increase in unsaturated fatty acids (Guyot-Jeannin &
Van Steenkiste, 1958). Repeated inhalation or oral ingestion by rats
causes transitory elevation of SGOT levels for 24 hours after the last
exposure, the SGPT levels remaining normal. SGOT levels return to
normal within 9 days after exposure. No such transitory effects are
seen in rabbits (Tolot et al,, 1966; Viallier & Casanova, 1965).
Previous ingestion of ethanol potentiates trilene toxicity in rats as
shown by a rise in SGOT, SGPT and SICD) (isocitric dehydrogenase) and
wide-spread degenerative lipid infiltration as well as early
centrilobular necrosis of the liver (Cornish & Adefuin, 1966).
Single exposure of mice to the inhalation LD50 of trilene showed
some hepatotoxicity as evidenced by a rise in SGPT (Gehring, 1968).
Trilene passes readily through the placenta and occurs in foetal
blood in higher concentrations (Helliwell & Hutten, 1950). Orally
administered trilene has no effect on rat liver glutathione levels
(Johnson, 1965).
Trilene exerts a variety of pharmacological effects. It depresses
the CNS with predominant narcotic action but needs relatively high
dosage (Defalgue, 1961). In the CNS there is a variable effect on
blood pressure. Cardiac arrhythmias are frequent with anaesthetic use
(Defalgue, 1961) and bradycardia, ectopic beats and other arrhythmias
have been seen in dogs and rabbits. Possible some vasoconstriction in
the capillary bed may occur (von Oettingen, 1955). In the R.S. the
most common reaction is tachypnoea, especially in young children
(Defalgue, 1961). Little effects occur in the G.I. tract (Defalgue,
1961) nor were any effects seen on basal metabolic rate, liver or
kidney function (von Oettingen, 1955). Trilene absorbed through the
skin appears in the alveolar air (Stewart & Dodd, 1961).
Acute toxicity
Animal Route LD50 LD100 Reference
ml/kg
bodyweight
Mouse inhalation - 7 900 ppm (2 hrs) von Oettingen, 1955
s.c. 11.0 - Plaa et al., 1958
i.p. 2.2 - Klaassen & Plaa, 1966
Rat oral 4.92 - Smyth et al., 1969
inhalation - 20 000 ppm Adams et al., 1951
guinea-pig inhalation - 37 000 ppm (40 min) von Oettingen, 1955
Rabbit s.c. - 1 800 mg/kg Barsoum & Saad, 1934
inhalation - 11 000 ppm Bernardi et al., 1956
percutaneous >20 - Smyth et al., 1969
Dog i.v. - 150 mg/kg Barsoum & Saad, 1934
i.p. 1.9 - Klaassen & Plaa, 1967
Mice, rats, guinea-pigs and rabbits dying acutely from
inhalation, show no toxic effects on the tissues, liver or kidney nor
after s.c. or i.v. administration (Browning, 1965). I.p. injection of
2.5 1/kg trilene into mice had no effect on PSP excretion and produced
no proteinuria or glycosuria, nor histological renal changes (Plaa &
Larson, 1965). Oral doses of 3-4 m/kg bodyweight were fatal to rats,
mice and guinea-pigs with signs of gastro-intestinal irritation (von
Oettingen, 1955). Chronic oral poisoning has caused some liver and
renal damage in dogs and rabbits (von Oettingen, 1955).
Trilene is a local irritant on the skin, causing blisters and
necrosis in man and desquamation with ulceration in rabbits (von
Oettingen, 1955).
Short-term studies
None available.
Long-term studies
None available.
Special studies
Observations in animals exposed for varying periods up to 10
months show disturbed co-ordination and hyperexcitability but no
effects on liver or kidney or blood chemistry. Only the CNS showed
some oedema and ganglion cell degeneration (Browning, 1965). Rats,
guinea-pigs, squirrel monkeys, rabbits and dogs were exposed to 3825
mg/m3 for 6 weeks without significant adverse effects. Exposure to
189 mg/m3 for 90 days also revealed no significant pathological
changes (Prendergast et al., 1967). Groups of 20 mice were exposed for
1-8 weeks to 200 or 1600 ppm daily for 4 hours. Only slight transient
fatty hepatic degeneration and no renal effects were seen (Kylin et
al., 1965).
Guinea-pigs were exposed to vapour of trilene for 2-1/2 to 4
months without adverse effects on bodyweight, haematological findings
or urinalysis results but there was slight evidence of hepatic
parenchymal degeneration and renal glomerular and tubular degeneration
(Lande et al., 1939). Rabbits given for 1-5 months 0.074 g/kg trilene
showed little adverse effect on bodyweight, haematological finding,
urinary analysis but some hepatic and renal lesions were seen (Lande
et al., 1939). Dogs were exposed to 150-750 ppm daily for 2-8 weeks.
Hepatic injury as evidence by BSP excretion, glycogen depletion and
parenchymal degeneration as well as weight loss, lethargy and
diarrhoea occurred but cleared on stopping exposure (Seifter, 1944).
Soyabean meal extracted with trilene but not with hexane or
carbon tetrachloride has caused fatal refractory haemorrhagic aplastic
anaemia in cattle (Stockman, 1916; Picken et al., 1955). The toxic
factor was shown to be associated with the protein fraction (Picken &
Biester, 1957; Seto et al., 1958). Similar effects were produced by
trilene-extracted meat scrap (Rehfeld et al., 1958). However, chicks
fed trilene-extracted meat scraps showed improved growth (Balloun et
al., 1955). The toxic factor has been identified as
S-trans-(dichlorovinyl)-L-cysteine, a reaction product of trilene and
protein which becomes freed on protein hydrolysis (McKinney et al.,
1957). Using radio labelled trilene it has been shown that this
reaction is unlikely to occur when extracting coffee (Brandenberger et
al., 1969).
Groups of 20 male and female rats were fed instant decaffeinated
coffee solid extracted with trilene for 2 years at 0% or 5% of their
diet (equivalent to a residue of 0.5 ppm trilene) without deleterious
effects on survival, behaviour, growth, food consumption, urinalysis,
haematology, organ weights and histopathological findings (Zeitlin,
1963).
Eight males and 16 female rats were fed on a diet containing 0%
or 5% of instant decaffeinated coffee solids extracted with trilene
(equivalent to a residue of 0.5 ppm trilene). Two generations were
studied as regards paternal and filial mortality, conception rate,
resorption, litter size, growth and survival of litter. Organ weights,
blood chemistry, urinalysis and histopathology of the F2 generation
were normal (Zeitlin, 1967).
A teratogenicity study in rats fed 5% of trilene extracted
instant decaffeinated coffee solids (equivalent to 0.5 ppm trilene)
was done for 2 weeks before mating until the 20th day of the 2nd
pregnancy. Foetuses were examined and resorption sites counted. No
significant deformities were noted in the test groups nor was there
any excessive resorption. Alizarin staining revealed no foetal
skeletal abnormalities (Zeitlin, 1966).
Observations in man
There is much experience from safe use of trilene as an
anaesthetic for man and from various other analgesic inhalation
treatments now abandoned e.g. trigeminal neuralgia, migraine, angina
(von Oettingen, 1955). Some authorities recognize a syndrome of
chronic intoxication (Moeschlin, 1956) others admit only to a
transient neurasthenic symptom complex (Anderssen, 1957). Fumes or the
liquid can cause skin burns. No evidence exists of serious
haematological effects. Neurological disturbances are similar to
neurasthenic conditions with rarely apparent cardiac disturbances.
Trigeminal palsies and optic nerve involvement may have been due to
impurities but have not been seen with pure material. Irritation of
the lungs and gastro intestinal symptoms have been reported after
industrial over-exposure. Addiction has been reported (Bardodej &
Vyskocil, 1956; Browning, 1965; Patty, 1958; Defalgue, 1961; Milby,
1968; Mitchell & Parsons-Smith, 1969). Psychomotor performance is not
affected by exposure to 100 ppm but there is a decline in performance
at higher inhalation levels (Stops & McLaughlin, 1967).
Eight males were exposed to 0, 100, 300 or 1000 ppm in air for 2
hours. At 1000 ppm visual perception and motor skills were adversely
affected (Vernon & Ferguson, 1969). In another experiment leucocyte
alkaline phosphatase levels in peripheral leucocytes were elevated
after prolonged exposure. This effect is reversible (Friborská, 1969).
Acute human poisoning cases have recovered without hepatic or
renal sequelae. After ingestion there is some burning of the oral
mucosa, later nausea and vomiting with vertigo, ataxia, somnolence,
confusion, delirium and coma (Browning, 1965). Excessive inhalation
has been blamed for hepato-nephritis but the incidence is very low and
it is possible that liver and renal involvement are the result of
underlying previous disease (Roche et al., 1958). Untoward effects on
the circulation, cardiac irregularities and excessive capillary oozing
with tachypnoea but no adverse hepatic effects have been reported
after anaesthetic use (von Oettingen, 1955). Ingestion of 60 ml
appears to be fatal in man (Pebay-Peyroula et al., 1966). At elevated
temperatures trilene reacts with soda lime to form dichloracetylene
and this reacts further to generate phosgene carbonylchloride And
various acids which are all toxic (Defalgue, 1961). The TLV is 100
ppm, (Amer. Conf. Gov. Ind. Hyg. 1969).
Comments
Ingestion or inhalation of 1,1,2-trichlorethylene produced
metabolites which are more toxic than the parent compound. The use of
1,1,2-trichlorethylene as a solvent is liable to cause formation of
the toxic S-(transdichlorovinyl)-L-cysteine from sulfur-containing
amino acids. There is a large amount of human experience from the use
of 1,1,2-trichlorethylene as an anaesthetic. No formal long-term
studies are available on the solvent per se but 2 year rat feeding
studies, multigeneration studies and teratology studies have been
performed using 1,1,2-trichlorethylene-extracted decaffeinated instant
coffee solids.
Tentative evaluation1
There is a need for care in the choice of food types subjected to
extraction by 1,1,2-trichlorethylene in view of its reactivity with
-SH groups. It should not be used for extracting of protein materials
contributing significantly to the diet. In foods such as coffee
suitable for 1,1,2-trichlorethylene extraction, the use of the solvent
should be restricted to that determined by good manufacturing
practice, which is expected to result in minimal residues unlikely to
have any toxicological significance.
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