DIETHYLENE GLYCOL MONOETHYL ETHER
First draft prepared by
Dr R. Walker
University of Surrey
United Kingdom
1. EXPLANATION
This substance was previously reviewed at the twentieth meeting
of the Committee (Annex 1, references 41, 42) but no ADI was
allocated because of inadequacies in the toxicological data. In
particular, the lack of metabolic and reproduction/teratogenicity
studies was noted, and the carcinogenicity studies did not meet
current standards. At its present meeting, the Committee reviewed
new data on metabolism and excretion in humans, together with
studies on reproduction and teratogenicity in mice and rats, and a
number of genotoxicity studies that were generally negative. It was
also aware of a number of other studies on pharmacological activity
and irritancy.
Since the last review, additional data have become available
and are summarized and discussed in the following monograph. The
previously published monograph has been expanded and is incorporated
into this monograph.
2. BIOLOGICAL DATA
2.1 Biochemical Aspects
2.1.1 Absorption
In an in vitro system for assessing percutaneous absorption
using human epidermal membranes, the "donor" chambers contained
undiluted diethylene glycol monoethyl ether (> 98% pure) and
diffusion was monitored at 30 min intervals for 8 h using GC. The
absorption rate was 0.21 ± 0.15 mg/cm2/h. Measurement of tritiated
water transfer before and after exposure to the test compound
indicated that there were slight irreversible changes in barrier
function during exposure to the test compound (Dugard et al.,
1984).
2.1.2 Metabolism and pharmacokinetics
Diethylene glycol monoethyl ether administered orally or
subcutaneously in doses of 3-5ml/kg bw to rabbits produced an
increased urinary excretion of glucuronic acid. The increase could
account for only 0.8-2.3% of the dose administered, the major part
of the dose being oxidized (Fellows et al., 1947).
The quantitative urinary excretion of diethylene glycol
monoethyl ether was investigated in the rabbit after oral,
intravenous, subcutaneous and percutaneous administration. After
oral dosing of two animals at a level of 5 ml/kg bw, both animals
died during the first day and total excretion was only 0.8% and
0.33%. After intravenous administration to 15 rabbits at dose levels
of 0.5-3.4 ml/kg most of the dose was excreted during the first day
(for 13/15 rabbits), the percentage excreted tending to increase
with dose.
After a single parenteral dose of 1.0-3.0 ml/kg, urinary
excretion was monitored for up to 4 consecutive days. Excretion was
high in the first 24 h and the total percentage of the dose excreted
in urine increased with dose. After repeated daily parenteral doses
of 0.16, 0.32 or 0.63 ml/kg bw, total urinary excretion increased
with dose and equalled 4.7, 5.0 and 11.6%, respectively.
Groups of 2-3 rabbits received daily applications of 0.08 to
2.5 ml/kg bw to a clipped area of skin for up to 30 days. Total
urinary excretion was small and variable (1.3-9.4%); there was no
correlation between percentage excretion and period of application
over the period 9-30 days.
Blood samples were collected for up to 2.5 h after
administration of diethylene glycol monoethyl ether intravenously to
rabbits at doses of 1.0-3.0 ml/kg bw. Clearance was rapid with less
than half of the dose detectable within 5 min and only small/trace
amounts present in blood after 30 min.
When a single dose of diethylene glycol monoethyl ether
(11.2 mmol) was given to an adult human volunteer (sex and age not
specified) about 68% of the dose was excreted in the urine as
(2-ethoxyethoxy)acetic acid within 12 h (Kamerling et al., 1977;
Miller, 1987).
2.2 Toxicological studies
2.2.1 Acute toxicity
Species Route LD50 Reference
(ml/kg/bw)
Mouse oral 6.6 Laug et al., 1939
oral 12.5 Latven & Molitor, 1939
oral 8.0 Berte et al., 1986
s.c. 2.5-6.0 Hanzlik et al., 1947a
s.c. 5.5 Latven & Molitor, 1939
i.v. .. Latven & Molitor, 1939
4.3 Latven & Molitor, 1939
i.v. 3.9 Stenger et al., 1971
i.p. <2.0 Latven & Molitor, 1939
i.p. 3.9 Karel et al., 1947
i.p. 2.3 Budden et al., 1979
i.p. 5.4 Berte et al., 1986
Rat oral 8.0 Berte et al., 1986
oral 5.5-9.7 Hanzlik et al., 1947a
oral 5.3-5.7 Laug et al., 1939
oral 7.3-10.4 Smyth et al., 1941
oral 6.3 Weil, 1972
s.c. 6.0 Hanzlik et al., 1947a
s.c. 3.4 Stenger et al., 1971
i.v. >4.0-<5.0 Stenger et al., 1971
i.v. 2.2 Budden et al., 1978
i.v. 2.9 Stenger et al., 1971
i.p. 5.4 Berte et al., 1986
i.p. 3.0 Sanderson, 1959
Species Route LD50 Reference
(ml/kg/bw)
Guinea-pig oral 3.7-5.0 Laug et al., 1939
oral 3.1-4.3 Smyth et al., 1941
Rabbit i.v. 2.5 Smyth et al., 1941
i.v. 0.9 Stenger et al., 1971
s.c. 2.0 Stenger et al., 1971
p.c. 8.5 Hanzlik et al., 1947a
p.c. 10.3 Carpenter, 1947
Cat s.c. 1.0-2.0 Lehmann & Flury, 1943
i.v. 4.2 Laug et al., 1939
i.v. 1.0 Budden et al., 1978
Dog i.v. 3.0 Smyth et al., 1941
i.v. 1.0 Budden et al., 1978
No abnormalities were obvious below a dosage level of 1 ml/kg
bw by any route. Ataxia with initially increased and later decreased
respiratory rate occurred with 2-2.5 ml/kg bw while higher dosage
levels led to central nervous depression and coma followed by
recovery or death. Delayed deaths were associated with renal
glomerular and tubular degeneration.
2.2.2 Short-term studies
2.2.2.1 Mice
Groups of 20 male and 20 female mice were fed on diets
containing 0, 0.2, 0.6, 1.8 or 5.4% diethylene glycol monoethyl
ether for 90 days. The test material contained less than 0.4%
ethylene glycol. Six males of the 5.4% group died between the
5th-12th weeks with signs of advanced renal damage (hydropic
degeneration). The growth rate was reduced and anaemia was found in
males at the highest dose level. Serum transaminase and urea levels
were unaffected by treatment. The relative kidney weight was
increased in both sexes receiving the 5.4% diet and in males fed on
the 1.8% diet. In females receiving the highest dosage level, the
relative heart and liver weights were greater than in controls.
Centrilobular hepatocyte enlargement was found at the 5.4 and 1.8%
dietary levels. Renal tubular cell enlargement with nuclear pyknosis
occurred in animals at the 5.4% dietary level. Areas of proximal
tubular degeneration and atrophy were seen in all groups, including
controls, but they appeared with greater frequency at the top
feeding level. No oxalate crystals were seen in the kidneys or
bladder. The no-effect level was 0.6%, equivalent to an intake of
850-1000 mg/kg bw/day (Gaunt et al., 1968).
In a pilot study to determine the MTD for a subsequent
reproduction study, groups of 10 female CD1 mice were given daily
doses of diethylene glycol monoethylether by gavage for 8
consecutive days. No necropsies were performed. The MTD was reported
to be 5500 mg/kg bw (Piccirillo et al., 1983).
In a pilot study to determine the MTD for a subsequent
reproduction study, groups of 8 male and 8 female mice, 8 weeks of
age were given 0.0, 1.0, 2.0, 3.0, 4.0, or 5% diethylene glycol
monoethyl ether (> 99% pure) in drinking water for 14 days. During
the exposure period, one male in the top dose group exhibited
dehydration on days 8-10 and tremors prior to death on day 11. The
weight gain was reduced significantly in the 4.0% and 5.0% dose
groups. No necropsies were performed. The MTD was estimated to be
2.5% in drinking water (NTP 1984).
2.2.2.2 Rats
Groups of 5 male and 5 female rats were given pure diethylene
glycol monoethyl ether in drinking water at doses of 0.21-3.88 g/kg
bw for thirty days. The maximum No Adverse Effect Level was reported
to be 0.49 g/kg bw. In a similar experiment using carbitol solvent
containing ethylene glycol, the NOEL was less than the lowest dose
tested, 0.41 g/kg (Smyth & Carpenter, 1948).
Groups of 12 male and 12 female rats were fed for 90 days on
diets containing 0, 0.25, 1.0 or 5.0% diethylene glycol monoethyl
ether contaminated by 0.64% ethylene glycol. The condition and
health of the animals remained generally good but 1 male on the 5%
diet died after 23 days following a period of weight loss. No
abnormalities were found on haematological examination. Urinary
glutamic oxaloacetic transaminase activity was significantly
increased and the relative kidney weight raised in both sexes and
the relative testes weight raised in males of the 5% group. Renal
tubular dilatation with inflammatory cell infiltration was present
in all groups, including controls, but was accentuated in the 5%
group. Hydropic degeneration was seen in 2 males and 1 female and
slight to moderate fatty infiltration in most animals was also found
in this group. The no-effect level was 1% in the diet, equivalent to
800 mg/kg bw/day (Hall et al., 1966).
Groups of 15 male and 15 female rats were fed on diets
containing 0, 0.5 or 5.0% diethylene glycol monoethylether
(containing less than 0.4% ethylene glycol) for 90 days. No animals
died. The growth rate and food intake were reduced and slight
anaemia was seen in females after 6 weeks and in males at the end of
the study at the highest dosage level. Serum urea and transaminase
levels were unaffected by treatment. The relative weight of kidneys
was increased in the 5% group and cells of the proximal tubular
cells were grossly enlarged with pyknotic nucleii. No oxalate
crystals were found in the kidneys or bladder. The no-effect level
was 0.5% in the diet, equivalent to 250 mg/kg bw/day (Gaunt et al.,
1968).
Groups of male and female rats were given daily s.c. doses of
diethylene glycol monoethyl ether of 100, 200, 400 or 800 µl/kg
bw/day for 4 weeks. No deaths were reported but doses of
200-400 µl/kg bw/day caused dyspnoea, somnolence and mild ataxia,
with some growth retardation in females; 800 µl/kg bw/day also
caused growth retardation in males. Pathological changes in the
liver, kidney and testes were also seen at doses of 200 µl/kg bw/day
(Stenger et al., 1971).
2.2.2.3 Rabbits
Technical diethylene glycol monoethyl ether (containing 30%
ethylene glycol) was applied daily to the clipped abdominal skin of
adult rabbits for up to 30 days. The animals were then observed for
a further 30 days after which they were sacrificed for histological
examination. The mortality varied from 57-65% and histological
examination revealed marked hydropic degeneration of renal tubular
epithelial cells (Hanzlik et al., 1947c)
Tests of renal function (phenol red clearance and blood urea)
were carried out on 18 males and hepatic function (rose Bengal) in 6
males exposed as above to daily doses of 0.02 to 1.5 ml/kg bw. Renal
function was impaired in 83.3% of the animals (15/18) and hepatic
function reduced in 88.3% (5/6) animals. Similar function tests
applied to animals dosed parenterally at daily doses of 0.16 to 0.63
ml/kg bw until death confirmed decreased renal function but hepatic
function was not impaired (Hanzlik et al., 1947d).
2.2.2.4 Ferrets
Groups of 2 or 3 male ferrets were fed on diet providing 0,
0.5, 1.0, 2.0 or 3.0 ml diethylene glycol monoethyl ether/kg bw/day
for 9 months. The sample of solvent contained less than 0.4%
ethylene glycol. The body weights of the two highest dosage levels
tended to be lower than those of controls and their food intake was
also diminished. No abnormal constituents were found in urine. The
water intake of all treatment groups was greater than controls
during the period of measurement (first seven weeks). The
concentrating power of the kidney was decreased consistently at the
two highest dosage levels. However at necropsy organ weights were
not changed by treatment and no abnormal gross or histopathological
abnormalities were detected. The no-effect level was 0.5 ml/kg bw
(Butterworth et al., 1975).
2.2.2.5 Pigs
Groups of 3 male and 3 female pigs were given diethylene glycol
monoethyl ether in their diet for 90 days. Initially the daily
intake was 0, 167, 500 or 1500 mg/kg bw/day but the top dose was
reduced to 1000 mg/kg bw/day after 3 weeks since 2 animals had to be
killed in extremis after 2 and another after 3 weeks. These pigs
became lethargic and comatose and autopsy showed subcutaneous and
pulmonary oedema and pleural and peritoneal effusions. The livers
were of a yellowish colour and they were enlarged, the cut surfaces
showing a pale cortex with petechial and medullary congestion.
Calculi were found in the urinary tract. Proteinuria with casts also
occurred. Serum urea was elevated to above 100 mg% and histological
examination showed hydropic degeneration and tubular desquamation
with glomerular atrophy. Livers showed extensive hydropic
degeneration. There was slight anaemia in males receiving 1000 mg/kg
bw/day for the full 90 days and more severe anaemia in those that
died. Serum urea and transaminase levels were normal in all animals
killed at the end of the investigation. The kidney weight was
elevated in animals receiving the highest dose level. Hepatocytes of
centrilobular and midzonal areas were grossly enlarged with pyknotic
nuclei, and fatty infiltration occurred at the top dosage level and
in one female receiving 500 mg/kg diet. Most of the renal cortex was
affected by extensive areas of tubular hydropic degeneration at the
highest dose level but this was less marked at the 500 mg/kg level.
Other changes at the 1000 mg/kg level were consistent with uraemia
resulting from renal failure. No oxalate crystals were seen in the
kidneys or bladder. The no-effect level was 167 mg/kg bw/day (Gaunt
et al., 1968).
2.2.3 Long-term/carcinogenicity studies
2.2.3.1 Mice
Groups of 10 male and 10 female mice were fed on control diet
or diet containing 5% diethylene glycol monoethyl ether (purity:
less than 0.2% ethylene glycol). This provided males with 7.5 and
females with 6.0 ml/kg bw/day. The body weights were reduced in
males between the 2nd and 6th months but were similar to controls at
other times. Body weight was continuously lower than controls in
females. Approximately 40% of test and control females were alive at
12 months while males survived longer, the last test male at 18
months and control at 21 months approximately. Only one of 30
animals receiving diethylene glycol monoethyl ether (pure or
containing 1% ethylene glycol) showed hydropic degenerative changes
in the kidney (Hanzlik et al., 1947b).
2.2.3.2 Rats
A group of 8 female and 12 male rats was fed on a diet
containing 2.16% diethylene glycol monoethyl ether for up to 2
years. A similar group of litter mates received control diet. Food
and water were offered ad lib. No significant decrease in growth
rate occurred in the test group and the mortality rate was
unaffected; however, the number of animals surviving for 2 years was
not stated. Only animals surviving the longest received full
pathological examination but the number examined was not stated. In
the test group there was an increased incidence of testicular
atrophy with interstitial oedema, centrilobular or diffuse atrophy
of the liver with bile duct proliferation and fatty degeneration,
and an oxalate stone was found in the kidney of one animal (Morris
et al., 1942).
A group of 10 male and 5 female rats were given diethylene
glycol monoethyl ether (purity: less than 0.2% ethylene glycol) as a
1% solution in drinking water. Thirteen male and 8 female control
rats received untreated water; both received diet and drinking fluid
ad libitum. The intake of the diethylene glycol monoethyl ether
was approximately 1.3 ml/kg bw/day in male and 1.5 ml/kg bw/day in
female animals. No significant differences were found in growth rate
or in food or fluid intakes. After approximately 12 months, 8 test
and 4 control animals remained alive. No gross or microscopic
abnormalities were found in the small number of animals examined
(Hanzlik et al., 1947b).
Groups of 8 male and 8 female Wistar rats received drinking
water incorporating diethylene glycol monoethyl ether containing
either 29.5% ethylene glycol or less than 0.2% ethylene glycol.
Groups received the equivalent of 0, 10, 40, 190 or 950 mg of the
purer substance/kg bw/day for up to 757 days. Feed and drinking
fluids were available ad libitum.
Animals were allowed to produce offspring to form a first
generation, and a second generation was produced from these.
However, the length of the period of treatment of the offspring was
not reported.
The lifespan of animals receiving 950 mg of the mixture/kg
bw/day was significantly shortened compared with controls but other
groups were unaffected. Growth was reduced compared with controls in
animals of the parent generation receiving 950 and 190 mg mixture/kg
bw/day or 920 mg purer diethylene glycol monoethyl ether/kg bw/day
but the effect on growth in other groups and other generations was
probably not of significance. No adverse effects were found on
haematological examination, and blood urea and glucose and serum
proteins were unaffected by the treatments. No increase in oxalic or
oxaluric acids were found in the urine of test animals, although the
urine protein concentration was raised in the 950 mg and 920 mg/kg
bw groups.
The tumours found were typical of elderly rats and the overall
incidence (4.4%) was similar to other reported figures for the
strain of rat. However, the report does not allow a full assessment
of the incidence and types of tumours in each group. Bladder calculi
were found only in animals receiving the highest dosage level of the
mixture. Only the liver and kidney were examined microscopically in
all animals but a few more organs were examined in others.
Epithelial necrosis of the renal tubules and cloudy swelling of
hepatic tissue were the only adverse effects which could be
attributed to treatment and these were seen in animals receiving
950, 190 and 40 mg mixture/kg bw/day and 920 mg purer diethylene
glycol monoethyl ether/kg bw/day.
The no adverse effect level for diethylene glycol monoethyl
ether containing less than 0.2% ethylene glycol was 200 mg/kg bw/day
(Smyth et al., 1944, 1964).
2.2.4 Reproduction studies
2.2.4.1 Mice
In a reproduction study, CD1 mice, 11 weeks of age at
commencement, were given diethylene glycol monoethyl ether in
drinking water at concentrations of 0, 0.25, 1.25 or 2.5%. Animals
of each sex (F0 generation) were exposed for a premating period of
7 days, then throughout a 98-day cohabitation period, followed by a
further 21 day segregation. Animals from the last litter produced by
the control and 2.5% groups were weaned and two male and two female
animals selected from each of 10 litters (F1 generation). The F1
animals were caged in groups of two or three by sex and received the
same drinking fluid as the parental groups for 74 ± 10 days. A male
and female from different litters within treatment groups were then
cohabited for one week, the pairs then separated and the females
allowed to produce their litters.
Continuous exposure of the F0 generation to diethylene glycol
monoethyl ether in drinking water from 11 weeks of age had no effect
on the number of pairs able to produce at least one litter, number
of litters per pair, live pups per litter, proportion of pups born
alive nor sex ratios. At the highest (2.5%) concentration, the mean
live pup weights were significantly reduced (P <0.05) relative to
controls. Deaths among the parent groups during the study were not
treatment-related.
In the F1 generation the body weights of males and females
were slightly depressed relative to controls at birth, weaning and
at the start of the mating period. Continuous exposure of this
generation to diethylene glycol monoethyl ether in utero, via
mother's milk, and subsequently at 2.5% in drinking water, had no
significant effects on mating behaviour, fertility rate, number of
live pups per litter, proportion of pups born alive, sex ratio or
live pup weight. At terminal necropsy, sperm assessment indicated no
significant differences in sperm concentration nor percentage of
abnormal sperm in the cauda epididymis between treated and control
males, but the percentage motile sperm was significantly reduced in
treated animals. Body weights were not affected by treatment but the
relative liver weight was significantly increased and relative brain
weight significantly decreased.
The authors concluded that diethylene glycol monoethyl ether
was not a reproductive toxicant under the conditions of this study
in either F0 or F1 breeding pairs (NTP, 1984; Williams et al.,
1990).
Groups of 50 pregnant CD-1 mice were given diethylene glycol
monoethyl ether (>99% pure) by gavage in aqueous solution at the
MTD on days 7-14 of gestation. Maternal body weights were recorded
on days 7 and 18 of gestation and day 3 postpartum. Reproductive
indices reported included pup survival in utero, pup perinatal and
postnatal (2.5d) survival and pup body weights. The dose of
5500 mg/kg bw caused 14% maternal mortality and reduced body weight
in maternal survivors, and slightly reduced mean pup birth weight
but did not affect reproduction indices (97% viable litters and 98%
postnatal survival) (Schuler et al., 1984; Piccirillo et al.,
1983).
2.2.5 Special studies on teratogenicity
2.2.5.1 Drosophila melanogaster
In a teratology screen using Drosophila melanogaster
diethylene glycol monoethyl ether was incorporated into medium at
the MTD. The eggs were deposited on the medium and the insects
exposed throughout incubation, larval stage and pupa formation. The
emergent adult insects were examined for external morphological
anomalies. At a concentration of 7.5 ml/kg medium, developmental
effects were observed in the form of an irregular shaped abdomen in
7.7% of the treated insects; the abnormality was rare in the control
insects (Schuler et al., 1982).
In a similar study, no morphological abnormalities were
observed at the same concentration of 7.5 ml/kg in the medium
(Schuler et al., 1983).
2.2.5.2 Rats
Groups of 15 pregnant Sprague-Dawley rats were exposed to
diethylene glycol monoethyl ether by inhalation of the vapour at an
aerial concentration of 100 ppm for 7 h/day on days 7-15 of
gestation. The dams were sacrificed on day 20 and 2/3 of the fetuses
examined for visceral defects by Wilson's technique and 1/3 for
skeletal defects by Staples technique. At this level of exposure,
diethylene glycol monoethyl ether was not maternally toxic and no
teratogenic or embryotoxic effects were observed (Nelson et al.,
1982, 1984).
Diethylene glycol monoethyl ether was applied to the shaved
interscapular skin of pregnant Sprague-Dawley rats four times daily
on days 7-16 of gestation in doses of 0.35 ml at 2.5 h intervals.
The dams were killed on day 21 and the fetuses weighed and examined
for external malformations. Half of the fetuses were examined for
visceral abnormalities and half for skeletal malformations. There
was no evidence of teratogenicity or fetotoxicity although maternal
body weight was significantly lower than controls (Hardin, 1983;
Hardin et al., 1984).
2.2.6 Special studies on genotoxicity
Test system Test object Concentration Results Reference
of DEGMEE
Ames test S.typhimurium 0-1 ml/plate Negative Berte et al.,
(1) TA97, (1986)
TA100, TA102 Negative
TA1535, TA1537 Weak pos. Berte et al.,
TA1538 Weak pos. (1986)
Yeast gene Saccharomyces 1% & 10% Negative Berte et al.,
mutation cerevisiae D7 (1986)
Micro-nucleus Mice CD-1 2 x 2 ml/kg bw Negative Berte et al.,
test (1986)
(1) With and without beta-naphthoflavone-induced mouse liver S9 fraction.
2.2.7 Special studies on cytotoxicity
In a test to evaluate cytotoxicity against a human hepatoma
cell line in vitro as an alternative to the Draize eye irritation
test, diethylene glycol monoethyl ether was added to the incubation
medium for 24 h at 37 °C. No effects were observed at the maximum
tolerated concentration of 0.2% (15 mM) (Stark et al., 1983). In
similar studies using human hepatoma cell line HepG2, diethylene
glycol monoethyl ether caused an inhibition of 3H-uridine uptake
and the UI50 was estimated to be 191mM (Dierickx & Martens, 1986;
Jacobs et al., 1988).
In further studies of uridine uptake using murine BALB/c 3T3
cells, the UI50 was found to be 129 mM (Shopsis & Sathe, 1984).
2.2.8 Special studies on haematology
Three adult rabbits were given intramuscular doses of
diethylene glycol monoethyl ether of 0.62, 0.82 or 1.6 ml/kg bw
daily for 2 weeks and haematological examinations performed. No
effects were noted on haemoglobin, RBC, total leucocytes, platelets
or reticulocytes. Similarly, no effects on these parameters were
seen in three pigeons dosed i.m. at daily doses of 1 ml/kg bw
(Hanzlik et al., 1947b)
2.2.9 Special studies on irritancy
The inflammatory action of diethylene glycol monoethyl ether
was tested by instillation of one drop of pure material into the
rabbit eye. Slight hyperaemia of the conjunctiva was reported (von
Oettingen & Jirouch, 1931).
In a similar test in the rabbit the degree of irritation was
scored on a three point scale (+,++,+++). The effects were graded as
oedema + and hyperaemia ++ (Latven & Molitor, 1939).
Ocular irritancy was assessed on solutions of commercial
diethylene glycol monoethyl ether containing ethylene glycol at
various concentrations in 0.85% aqueous NaCl solutions. Solutions of
8%, 10% and 12% of the commercial preparation caused inflammation of
the mucous membrane persisting for 5, 10 and 30 mins respectively.
Solutions of 20% caused discomfort (blinking), 25% caused pain
(eye rubbing) and 30% resulted in inflammation that persisted for 60
mins. No other adverse effects on the eye were reported (Cranch
et al., 1942). Ocular effects in similar studies using water,
propylene glycol or Deobase as vehicle were graded maximally at
point 2 on a 10 point scale of injury (Carpenter & Smyth, 1946)
while no evidence of ocular effects was seen when a 10 µl drop of
diethylene glycol monoethyl ether was applied to the cornea of
guinea-pigs (Sanderson, 1959).
The ocular irritation index (OII) was determined in the rabbit
after application of diethylene glycol monoethyl ether, undiluted or
as aqueous solutions, according to official French methods. A 10%
solution was graded as non-irritating (acute OII 1.67) while the
undiluted material caused slight to moderate irritation (acute OII
16.0) (Guillot et al., 1982). Diethylene glycol monoethyl ether
was tested for ocular irritancy in rabbits using objective
quantitative procedures involving determination of dry tissue as an
index of corneal and conjunctival oedema and dye diffusion (Evans
blue) as a measure of vascular leakage in the conjunctivae and
aqueous humour. Diethylene glycol monoethyl ether was applied to the
eye, undiluted or as a solution in distilled water, 1, 3, 6, 7 or 13
times over 2, 4, 7, 26 and 50 h, respectively. A 25% solution
produced significant increases in vascular leakage in the
conjunctivae and aqueous humour while, in addition to these effects,
100% diethylene glycol monoethyl ether caused significant
conjunctival and corneal oedema (Laillier et al., 1976).
Diethylene glycol monoethyl ether was without effect in ocular
irritancy tests in the rabbit conducted according to EEC and OECD
guidelines (Jacobs et al., 1988).
Dermal irritancy was assessed by the trypan blue capillary
permeability method after exposure of depilated rabbit skin to
patches soaked in technical carbitol (ca 30% ethylene glycol) for
2 h daily for 2-6 days. There was no evidence of dermal irritation
using this technique (Hanzlik et al., 1947c). Similarly, the
cutaneous primary irritation index (PII) in patch tests on
diethylene glycol monoethyl ether according to official French
protocols was 0.29 (non-irritant). Determination of the cumulative
cutaneous irritation index by official French methods involving
cutaneous exposure daily for six weeks showed a 10% solution to be
non-irritant (mean maximum irritation index 0.13) while undiluted
material was slightly irritant but well tolerated (MMII 1.13)
(Guillot et al., 1982).
Commercial diethylene glycol monoethyl ether containing
ethylene glycol caused no irritation per se when applied to rabbit
skin for 24 h (Ogiso et al., 1988).
Irritation was assessed after injection of 0.1 ml diethylene
glycol monoethyl ether intradermally into shaved guinea-pig
abdominal skin. The test compound was graded as moderately irritant
in this test. No irritant effects were observed in a 24 h patch test
on shaved, intact abdominal skin of rabbits (Latven & Molitor,
1939). Conversely, in an occluded patch test on abraded rabbit skin,
irritant effects were reported with a primary irritation index of
0.5 (Draize et al., 1944).
Wads of cotton saturated with 50% or 70% aqueous solutions of
commercial grade diethylene glycol monoethyl ether were applied to
depilated skin of rabbits, wounded by crossed cuts into the cutis
and replaced daily until healing was complete. No adverse effects on
healing were reported and scar formation was complete in 4-6 days.
In similar tests in which major wounds were made by excising the
epidermal and dermal layers and laying bare the underlying muscle,
50% carbitol had no significant effect on the healing time relative
to controls (mean 11.5 days); healing was somewhat prolonged with
70% carbitol (19.5 days) (Cranch et al., 1942).
2.2.10 Special studies on pharmacological activity
When 1 ml of a 25% aqueous, solution of diethylene glycol
monoethyl ether was injected into the lymph sac of frogs weighing
about 30 g, moderate central depression resulted. Diethylene glycol
monoethyl ether had no effect on reflex excitability as assessed by
the Turck method in the frog, but muscle response time to a minimal
effective faradic stimulation of the nerve trunk in frog
nerve-muscle preparations was slightly depressed (von Oettingen &
Jirouch, 1931). A lack of effect on reflex reaction time in the frog
by immersion of the leg was reported by Latven & Molitor (1939).
Diethylene glycol monoethyl ether had a slight depressive
action on rabbit ileum smooth muscle contraction using the Magnus
protocol (von Oettingen & Jirouch, 1931) and in later studies the
EC50 was found to be 1.21% ± 0.45% in Ringer's solution (Muir,
1983).
Diethylene glycol monoethyl ether caused a marked depression
and arrest of cardiac activity in perfused frog heart. Dilutions of
1-4% had no effect on peripheral blood vessels in the Trendelenberg
frog perfusion method but i.v. injection of a 50% solution to
lightly anaesthetised rabbits caused a fall in blood pressure
(von Oettingen & Jirouch, 1931).
In a CNS-profile test, 3 NMRI male mice were dosed i.p. with
increasing doses of diethylene glycol monoethyl ether. The minimum
symptomatic dose was 5.0 g/kg bw at which there was ptosis,
piloerection, hypothermia, muscle relaxation, inhibition of Haffner
reflex and cyanosis. The material was classified as a neuroleptic.
The ED50 in the inclined screen test was also found to be 5.0 g/kg
bw (Budden et al., 1979).
In the rotating rod test on four NMRI male mice, diethylene
glycol monoethyl ether was given in increasing doses i.p. and the
time to dropping off measured at intervals after injection. The
minimal effective dose was 300 mg/kg bw. In a balance rod test the
ED50 was found to be 3.1 g/kg bw (Budden et al., 1979).
Diethylene glycol monoethyl ether potentiated the hexobarbitone
sleeping time in female NMR1 mice. The ED50s for a doubling or
quadrupling of the sleeping time were 0.7 (0.43-1.21) g/kg bw and
2.4 (1.37-4.25) g/kg bw respectively (Budden et al., 1979).
2.3 Observations in humans
2.3.1 Acute intoxication
A 44-year old man ingested diethylene glycol monoethyl ether at
doses of about 2 ml/kg bw. Kidney function was affected but there
was no oliguria and only slight uraemia. Effects on nervous and
respiratory functions were also reported (Brennaas, 1960).
2.3.2 Special studies on skin irritation and sensitization
Commercial grade diethylene glycol monoethyl ether was rubbed
on the inner wrist surface for 5 mins daily on 10 consecutive days.
Irritant effects were noted with 3/60 subjects showing congestion or
papules, mainly originating at hair follicles and persisting for
several hours (Cranch et al., 1942). No irritant effects were
evident in 48 h closed patch test on 5 male volunteers diethylene
glycol monoethyl ether was applied at a concentration of 20% in
petrolatum (Kligman, 1972).
Patch tests were conducted on undiluted commercial grade
diethylene glycol monoethyl ether (containing 30% ethylene glycol)
in 99 subjects using 48 h exposure with subsequent examination at
intervals up to 1 month. Slight positive reactions (faint erythema
persisting for 48 h after removal) occurred in 24/99 subjects.
Similar tests on aqueous dilutions of pure diethylene glycol
monoethyl ether (0.2% ethylene glycol) or carbitol solvent were
carried out on 31 subjects. No reactions were seen with 5% solutions
of either material and a concentration-related increasing frequency
of reactions (faint erythema) was seen at higher concentrations.
Undiluted materials led to 14 reactions with the carbitol solvent
and 5 reactions with the pure material (Meininger, 1948).
In 48-h closed patch tests on 50% solutions of diethylene
glycol monoethyl ether, 44% of volunteers showed erythema, oedema or
vesicles, 18% definite erythema and 34% questionable erythema
(Motoyoshi, et al., 1984).
Patch tests were conducted on commercial grade diethylene
glycol monoethyl ether in 98 subjects using an initial contact
period of 7 days, followed by 10 days withdrawal then a further 3
day test period. Definite reactions were reported in 7/98 persons
but a standardized scoring method was not used (Cranch, Smyth &
Carpenter, 1942).
Repeat patch tests using undiluted commercial grade diethylene
glycol monoethyl ether (30% ethylene glycol) were carried out on 45
subjects 4 weeks after initial tests. After a second exposure of
48 h, examinations were carried out at intervals up to 1 month.
Positive reactions (faint erythema restricted to test area) occurred
in 15 subjects (Meininger, 1948).
3. COMMENTS AND EVALUATION
The Committee was informed that the use of diethylene glycol
monoethyl ether as a carrier solvent for flavours could lead to
carry-over levels as high as 1000 mg/kg in foods as consumed, but no
data on potential daily intakes were available. In these
circumstances, the principles previously developed for materials
occurring in foods in small amounts (Annex 1, reference 76) were not
applicable. Although the metabolism, reproduction and
teratogenicity, and genotoxicity studies met some of the
requirements of the Committee, information on chronic
toxicity/carcinogenicity was still inadequate. In view of the
apparent potential for relatively high exposure to this substance,
the Committee was unable to allocate an ADI because of the lack of
such information.
In order to re-evaluate diethylene glycol monoethyl ether the
Committee would require either:
(a) adequate data indicating that human intakes are
sufficiently low for the principles applicable to
materials occurring in foods in small amounts to apply:
or
(b) the results of an adequate carcinogenicity/chronic study
in rats and mice.
The Committee considered that, in the light of the data
reviewed at the present meeting, the 6-month study in pigs requested
at its twentieth meeting would not be needed for a re-evaluation.
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See Also:
Toxicological Abbreviations
Diethylene glycol monoethyl ether (ICSC)
Diethylene glycol monoethyl ether (WHO Food Additives Series 10)
DIETHYLENE GLYCOL MONOETHYL ETHER (JECFA Evaluation)