2-ETHYL-1-HEXANOL
First draft prepared by
Dr K. Ekelman, Additives Evaluation Branch
Division of Health Effects Evaluation
Center for Food Safety and Applied Nutrition
Food and Drug Administration, Washington, DC, USA
1. EXPLANATION
2-Ethyl-1-hexanol (EH; also known as 2-ethylhexyl alcohol and
2-ethylhexanol) has not been reviewed previously by JECFA.
EH is a colorless liquid with a mild floral odor (Furia and
Bellanca, 1975) that occurs naturally in food. EH is prepared by
petrochemical synthesis and is used as a flavoring ingredient in food.
Total annual consumption of EH in the United States from its natural
occurrence in food is reported to be 120 kg (Stofberg and
Grundschober, 1987); total annual production for use as a flavor
additive is estimated to be 209 kg (NRC, 1989). Estimated intake in
the United States from the use of EH as a flavoring ingredient is
approximately 0.65 µg/kg bw/day (FEMA, 1993).
2. BIOLOGICAL DATA
2.1 Biochemical aspects
2.1.1 Absorption, distribution, and excretion
Two adult male CD-strain rats (300 g) were gavaged with
radiolabeled 2-ethyl-1-14C-hexanol (14C-EH; 1 µCi; 8.8 µg) in
cottonseed oil. Two others were given the same amount of 14C-EH and
cottonseed oil, but also were given 0.1 ml (0.64 mmol) of unlabeled
EH. Following administration of the test substance, rats were housed
in metabolism cages with ad libitum access to feed and water;
expired CO2, urine, and faeces were collected every hour for 28 hrs.
Most (99.8%) of the orally administered radioactivity was accounted
for by radioactivity in expired CO2, urine, faeces, an ethanol wash
of the metabolism cage at the end of the experiment, heart, brain,
liver, kidneys, and "residual carcass." EH was efficiently absorbed
following oral administration and rapidly excreted in respired CO2
(6-7%), urine (80-82%), and faeces (8-9%); elimination was essentially
complete by 28 hrs. The major urinary metabolite of EH in the rat was
shown to be 2-ethylhexanoic acid through acid extraction of urine.
This metabolite can undergo partial ß-oxidation and decarboxylation to
produce 14CO2 and 2- and 4-heptanone (in the urine). Other urinary
metabolites of EH were identified as 2-ethyl-5-hydroxyhexanoic acid,
2-ethyl-5-ketohexanoic acid, and 2-ethyl-1,6-hexanedioic acid.
Approximately 3% of the parent compound was excreted unchanged.
Rats and other mammals hydrolyze orally ingested DEHP
(di-[2-ethylhexyl]phthalate, a plasticizer in food-contact materials)
to EH and MEHP (mono-[2-ethylhexyl]phthalate) prior to absorption of
MEHP by the intestine (Albro, 1975).
An in vitro dermal absorption study of EH and seven other
compounds was conducted with full thickness rat skin and human stratum
corneum. The ratio of the rate of absorption of EH through rat and
human skin (rat/human) was reported to be 5.8, indicating that rat
skin is more permeable to EH than is human skin. Damage to skin by
dermal application of EH was defined as the ratio of the permeability
constant for 3H2O after contact with EH to the permeability
constant for 3H20 before application. Ratios for human skin
(1.5±0.4 and 3.7±2.1) and rat skin (31.9±5.1) indicated that dermal
application of EH damages rat skin more than human skin (Barber
et al., 1992).
Excretion balance studies were conducted on female Fischer 344
rats (4 animals/group) following acute oral doses of 50 or 500 mg/kg
bw 14C-EH and repeated oral doses of 50 mg/kg bw/day 14C-EH for 14
days; results of acute gavage doses of 500 mg/kg bw 14C-EH
administered neat and as aqueous suspensions containing 5 mg Polyoxyl
35 castor oil/100 ml were compared. Dermal exposures to 14C-EH
(1 g/kg bw applied dose) for 6 hours and i.v. exposures to 1 mg/kg bw
14C-EH were also studied. Acute oral doses of 50 or 500 mg/kg bw and
repeated oral doses of 50 mg/kg bw/day showed similar excretion
balance profiles of 14C, with some evidence of metabolic saturation
at the high dose. No evidence of metabolic induction was reported
following repeated dosing. All oral doses were rapidly eliminated
during the first 24 hours after dosing, predominantly in the urine.
Approximately 5% of the dermal dose was absorbed. A majority of the
oral and dermal doses were eliminated as glucuronides of oxidized
metabolites of EH, principally glucuronides of 2-ethyladipic acid,
2-ethylhexanoic acid, 5-hydroxy-2-ethylhexanoic acid, and 6-hydroxy-2-
ethylhexanoic acid. Only trace amounts of unchanged EH were
eliminated in the urine. Bioavailability of EH orally administered
with the gavage vehicle was slightly greater than bioavailability of
EH administered alone (Deisinger et al., 1992).
2.1.2 Biotransformation
Knaak and coworkers (1966) studied the metabolism of 8 mg 14C-EH
in rats and 200 mg 14C-EH in rabbits following i.p. injection. The
major urinary metabolite in rats was 2-ethylhexanoyl glucuronide; EH
and 2-ethyl hexanoic acid were also identified in rat urine. In
rabbits, the major urinary metabolite also was 2-ethylhexanoyl
glucuronide; 2-ethyl-2,3-dihydroxyhexanoic acid and EH were also
identified in rabbit urine (Knaak et al., 1966).
The metabolism, distribution and elimination of 14C-DEHP
following oral administration to male and female B6C3F1 mice, Fischer
344 rats, and Cynomolgus monkeys was investigated. Orally
administered DEHP is rapidly hydrolyzed to the monoester (MEHP), then
the alcohol and acid. The GI tract had appreciable amounts of EH, and
absorbed 14-C appeared to be primarily EH. The alcohol was oxidized
by ß-oxidation, omega-, and omega-1-oxidation generating several major
and minor products including acids, ketones, ketoacids, hydroxy acids,
and diacids (such as ethylhexanoic acid [EHA], ethylhexanedioic acid
[DiEHA], and 5-hydroxyethylhexanoic acid [5-OH EHA]). The three
species were able to form glucuronic acid conjugates of the alcohol
oxidation products, but no sulfites were detected. However,
differences between species were noted: metabolism appeared to be less
extensive in the monkey (which excreted largely MEHP and EH as their
glucuronides) than in rodents (which excreted largely products of
faster oxidation, primarily EHA, 5-OH EHA, and diEHA) (Midwest
Research Institute, 1984).
2.1.3 Effects on enzymes and other biochemical parameters
Gavage administration of 1 mmol/kg bw/day EH (approximately
130 mg/kg bw/day) to five male Wistar rats for 14 days was not
associated with liver peroxisome proliferation (Rhodes et al.,
1984).
However, in another study, administration of 2% EH in the diet
(approximately 1 000 mg/kg bw/day) to five male Fischer 344 rats for
three weeks was reported to cause peroxisome proliferation and
significant increases in the activities of liver catalase and
carnitine acetyltransferase (Moody and Reddy, 1978).
When gavage doses of 0, 100, 320, or 950 mg/kg bw/day EH were
administered to male and female Fischer 344 rats (5/sex/group) for 21
days, significant hepatomegaly at 950 mg/kg bw/day, significant
increases in cyanide-insensitive palmitoyl CoA oxidation (a marker for
peroxisome proliferation) in males (dose-related, 320 and 950 mg/kg
bw/day) and females (950 mg/kg bw/day), and significant increases in
lauric acid hydroxylase activity in males and females at 950 mg/kg
bw/day were shown. As well, electron microscopy showed only a slight
increase in the number of peroxisomes in hepatocytes of high-dose rats
(Hodgson, 1987).
Groups of five male and five female Alderley Park rats and mice
were gavaged with 0, 140, 350, 700, 1050, or 1750 mg/kg bw/day EH for
14 days. Rats in the high-dose group exhibited toxic effects (not
specified) and died or were killed during the course of the study.
Dose-related increases in relative liver weights of rats and mice were
observed; the increases were statistically significant in rats at 700
and 1050 mg/kg bw/day, in male mice at 700, 1050, and 1750 mg/kg
bw/day, and in female mice at 1750 mg/kg bw/day. EH administration
resulted in a nearly linear dose-related induction of peroxisomal
ß-oxidation (measured as palmitoyl CoA oxidation activities) in both
rats and mice, although the dose(s) at which this effect was
statistically significant were not stated (Keith et al., 1992).
Activity of succinic dehydrogenase was increased and activity of
lactic dehydrogenase was decreased after 12 daily dermal applications
of 2 ml/kg bw undiluted EH to the shaved skin of the rat. In
addition, EH-treated rats had significantly lower body weights than
control rats 17 days after dermal application of EH was terminated
(Schmidt et al. 1973).
Microsomal P-450 content increased and glucose-6-phosphatase
activity decreased in rat liver microsomal pellets following oral
administration of EH to the intact animal. Administration of EH
increased alcohol dehydrogenase activity demonstrated histochemically
in the centrilobular area of the liver, the number of microbodies, the
dilatation of the smooth endoplasmic reticulum, and the number of
microperoxisomes in the hepatocytes of rats (Lake et al., 1975).
Concentrations of EH ranging from 2.5-15 mM significantly
inhibited the activities of rat liver aminopyrine N-demethylase
(approximately 60% inhibition at 15 mM EH) and aniline hydroxylase
(approximately 50% inhibition at 15 mM EH) in vitro (Seth, 1982).
Rhodes and coworkers (1984) reported that 0.1 or 0.5 mM EH did
not induce palmitoyl CoA oxidase activity (a marker for peroxisome
proliferation) in rat hepatocytes in vitro (Rhodes et al., 1984).
The activity of carnitine acetyltransferase (a peroxisomal
enzyme) in rat liver cells in vitro was significantly induced
(approximately 9X level in untreated cultures) by 1mM EH but not by
0.2 mM EH (Gray et al., (1982).
In an in vitro test system using viable plugs from periportal
or pericentral regions of rat liver, Liang and coworkers (1991)
demonstrated that incubation of these plugs with EH (0.1 to 3 mM)
decreased urea synthesis in a dose-related manner (up to 80%
inhibition at 800 µM 02) and caused extensive cell damage (assessed
by lactate dehydrogenase leakage) Liang et al., 1991).
2.2 Toxicological Studies
2.2.1 Acute toxicity studies
Results of acute toxicity studies with EH are summarized in
Table 1.
Rabbits given 0, 0.2, 0.4, 0.6, 0.8, 1.6 or 3.2 x 10-5 mol/kg EH
(0.26 to 4.16 mg/kg bw i.v.) had dose-related increases in heart rate
and frequency of respiration. However, when EH was administered to
dogs (doses reported as 4.05 and 8.10 mol/kg i.v.), no compound-
related hypotensive effects were seen. Finally, when rabbits and rats
were given acute iv doses of EH (doses not provided), direct toxic
damage to the heart and smooth muscle elements of the blood vessels
was observed (Hollenbach et al., 1972).
2.2.2 Short-term toxicity studies
2.2.2.1 Mice
Doses of 0, 100, 330, 1 000, or 1 500 mg 2-ethyl-1-hexanol/kg
bw/day were administered by gavage for 11 days (9 administrations) to
groups of 10 male and 10 female C3B6F1 mice. Effects clearly related
to administration of the test substance occurred in male and female
mice receiving 330, 1 000, or 1 500 mg/kg bw/day. One male mouse
receiving 330 mg/kg bw/day for 11 days showed ataxic gait and
piloerection following the administration of the 8th dose, but these
symptoms were reported to have disappeared by the next day. Two male
and two female mice receiving 330 mg/kg bw/day were reported to have
acanthosis in the mucous membrane of the forestomach that was usually
associated with hyperkeratosis and was once associated with focal
inflammatory oedema in the submucosa.
Table 1: Summary of Acute Toxicity Studies with EH
Species Route LD50 (mg/kg bw) Reference
Rat Oral 2053 (2.46 mL/kg) Smyth et al., 1969
Rat Oral 37301 Scala and Burtis, 1973
Rat Oral 3 250 Albro, 1975
Rat Oral 3200 - 6400 Treon, 1963
Rat Oral 3200 NIOSH, 1976
Rat I.P. 650 Treon, 1963
Mice I.P. 780 Treon, 1963
Rat I.V. 1670 Mashkina, 1966
Mice I.V. 1670 Mashkina, 1966
Rabbit Dermal 1986 (2.38 mL/kg)2 Smyth et al., 1969
Rabbit Dermal >26003 Scala and Burtis, 1973
Guinea pig Dermal >8300 (>10 mL/kg) Treon, 1963
LC50
Mice Inhal. >227 ppm (6 hr)4 Scala and Burtis, 1973
Table 1 (contd).
Species Route LD50 (mg/kg bw) Reference
Rat Inhal. >227 ppm (6 hr)4 Scala and Burtis, 1973
Guinea pig Inhal. >227 ppm (6 hr)4 Scala and Burtis, 1973
Rat Inhal. saturated vapors (8 hr) Smyth et al., 1969
Rat Inhal. >235 ppm Treon, 1963
(1) Gastrointestinal irritation was reported in rats after oral administration of
EH undiluted or in corn oil.
(2) Mild dermal irritation (3 on a scale of 0 [no irritation] to 10) was reported
when EH was applied to the uncovered rabbit belly and moderate corneal injury
in rabbits when undiluted EH was instilled in the eye (5 on a scale of 0 [no
injury] to 10).
(3) Moderate skin irritation was reported in rabbits following dermal application
of EH and severe eye irritation with persistent, wide-spread corneal opacity
when 0.1 ml undiluted EH was applied to the conjunctival sac.
(4) Mice, rats and guinea pigs (10 each) were exposed for 6 hours to 227 ppm EH,
then observed for 24 hours before necropsy. No deaths occurred during exposure
or observation. All animals exposed to EH exhibited central nervous system
depression and labored breathing and one guinea pig had a clonic convulsion.
During exposure, mucous membranes of the eyes, nose, throat, and respiratory
passages of animals exposed to EH were irritated, but animals recovered within
one hour after exposure was terminated. Gross necropsy revealed areas of slight
haemorrhage in animals exposed to EH.
One female mouse receiving 1 000 mg 2-ethyl-1-hexanol/kg bw/day
showed abdominal position and loss of consciousness; the mouse died
later the same day; microscopic examination revealed tubular
dilatation in the renal cortex and centrilobular fatty infiltration in
the liver of this mouse. Also the following significant effects were
reported to be associated with administration of 1 000 mg/kg bw/day
for 11 days: 1) increased absolute stomach weights in males and
females; 2) increased liver-to-bw ratio for males; 3) increased
stomach-to-bw ratio for females; 4) foci in the forestomach of 3 males
and 2 females; 5) hyperkeratosis and focal or multifocal acanthosis
and inflammatory oedema in the submucosa of the forestomach of males
and females, including focal or multifocal ulceration of the mucous
membrane of a few males and females; and 6) hypertrophy of hepatocytes
in one male and one female.
Males (9/10) and females (6/10) receiving 1 500 mg 2-ethyl-1-
hexanol/kg bw/day for 11 days had clinical signs such as ataxia and
lethargy, some animals also had piloerection, and a few animals showed
abdominal or lateral position and loss of consciousness; one male and
four females died during the study. Microscopic evaluation showed
tubular dilatation and nephrosis in the renal cortices of males and
females that died intercurrently, and centrilobular fatty infiltration
in the liver of females that died intercurrently. The following
statistically significant effects were reported, associated with
administration of 1 500 mg 2-ethyl-1-hexanol/kg bw/day: 1) increased
absolute liver and stomach weights in males and females; 2) increased
organ-to-bw ratios for stomach and liver in males and females; 3)
increased organ-to-brain weight ratios for stomach and liver in males
and females; 4) foci in the forestomach of 7/10 males and 5/10
females; 5) hyperkeratosis and focal or multifocal acanthosis and
inflammatory oedema in the submucosa of the forestomach of most males
and females, including focal or multifocal ulceration of the mucous
membrane in a few males and females; 6) hypertrophy of hepatocytes in
the liver of males and females, including focal necrosis of liver
cells in one male and one female; and 7) bilateral tubular giant cells
in the testicular tubules of two males (BASF, 1992b).
Doses of 0, 25, 125, 250, or 500 mg 2-ethyl-1-hexanol/kg bw/day
were administered by gavage to groups of 10 male and 10 female B6C3F1
mice for 3 months. Animals in the 250 and 500 mg/kg bw/day groups
showed toxic effects related to administration of the test compound.
For male mice receiving 250 mg/kg bw/day, statistically significant
increased stomach-to-bw ratio was observed. Statistically significant
effects observed in animals receiving 500 mg 2-ethyl-1-hexanol/kg
bw/day included: a) increased stomach-to-bw ratio in males and 2)
slight focal or multifocal acanthosis in the mucosa of the forestomach
of 2/10 males and 1/10 female (BASF, 1992b).
2.2.2.2 Rats
Doses of 0, 100, 330, 1 000, or 1 500 mg 2-ethyl-1-hexanol/kg
bw/day were administered by gavage for 11 days (9 applications) to
groups of 10 male and 10 female Fischer 344 rats. Clear toxic effects
occurred in the male and female rats receiving 330, 1 000, or 1 500
mg/kg bw/day.
Female rats receiving 330 mg/kg bw/day for 11 days had increased
kidney-to-bw ratios, but not increased absolute kidney weights or
kidney-to-brain weight ratios. Microscopic findings included
inflammatory oedema in the forestomach of one female rat and decreased
thymus size (microscopic examination) in 1 female and 2 male rats.
Male and female rats receiving 1 000 mg 2-ethyl-1-hexanol/kg
bw/day had reduced feed consumption, body weight, and body weight gain
compared to control rats. Some rats in this dose group showed ataxia
and apathy; a single rat showed piloerection and the genital region of
one rat was smeared with urine. The following statistically
significant effects were also reported to be associated with
administration of 1 000 mg/kg bw/day for 11 days: a) serum cholesterol
and reticulocytes in rats of both sexes were reduced; b) absolute
spleen weights of rats of both sexes were reduced; c) absolute liver
weights of male and female rats were increased; d) organ-to-bw ratios
for stomach, liver and kidneys were increased for male and female
rats; e) brain-to-bw ratio was increased in female rats; f)
spleen-to-bw ratios were reduced in male and female rats; g) liver-to-
brain weight ratios were increased in male and female rats; h) spleen-
to-brain weight ratios were decreased in male and female rats; i) foci
were reported in the forestomachs of 2 males; j) hyperkeratosis and
focal or multifocal acanthosis in the mucous membrane of the
forestomach of most male and female rats, as well as epithelial
degeneration, ulceration and subcutaneous inflammatory oedema; k)
parenchymal involution of lymphoreticular tissue in the spleens of 5
female rats; l) decreased thymus size in 2 males and 5 females
(microscopic evaluation); l) lymphocyte depletion in the thymus of 5
females and lymphocyte necrosis in the thymus of 4 females.
Male and female rats receiving 1 500 mg 2-ethyl-1-hexanol/kg
bw/day showed reduced feed consumption, body weight, and body weight
gain compared to control rats. All animals in the dose group
demonstrated ataxia and lethargy, some animals showed abdominal or
lateral position and appeared to be unconscious, almost all animals
had piloerection, and a few rats had genital regions smeared with
urine. The following statistically significant effects were also
reported to be associated with administration of 1 500 mg 2-ethyl-1-
hexanol/kg bw/day: a) reduced serum cholesterol, glucose, and
reticulocytes in male and female rats; b) increased serum alanine
aminotransferase in male rats; c) decreased absolute spleen, brain,
and adrenal weights and increased absolute liver and stomach weights
in male and female rats; d) increased organ-to-body weight ratios for
stomach, liver, kidney, and brain in male and female rats, decreased
spleen-to-bw ratios for male and female rats, increased adrenal-to-bw
ratio for male rats, and increased lung-to-bw ratio for female rats;
e) increased organ-to-brain weight ratios for liver and stomach in
rats of both sexes, decreased spleen-to-brain weight ratio for male
and female rats, and decreased adrenal-to-brain weight ratio in female
rats.
Foci were reported in the forestomach of 4 male and 7 female rats
dosed with 1 500 mg 2-ethyl-1-hexanol/kg bw/day. Microscopic findings
at this dose level were reported to include: a) hyperkeratosis and
focal or multifocal acanthosis in the mucous membrane of the
forestomach of all male and female rats, as well as epithelial
degeneration, ulceration, and subcutaneous inflammatory oedema in some
animals; b) slight hypertrophy of hepatocytes in the liver of 8 males
and 8 females; c) focal hepatocellular necrosis in 1 female and 2 male
rats; d) parenchymal involution of lymphoreticular tissue in the
spleen of 9 male and 9 female rats; e) decreased thymus size in 10
male and 9 female rats; and f) lymphocyte depletion in the thymus of
9 male and 8 female rats and lymphocyte necrosis in the thymus of 1
male and 6 female rats (BASF, 1992a).
Doses of 0, 25, 125, 250, or 500 mg 2-ethyl-1-hexanol/kg bw/day
were administered by gavage to groups of 10 male and 10 female Fischer
344 rats for 3 months. Animals in the 250 and 500 mg/kg bw/day groups
showed toxic effects. For animals receiving 250 mg/kg bw/day,
statistically significant effects were reported to include: a)
decreased serum alkaline phosphatase and glucose in male rats and
decreased serum alanine aminotransferase in female rats; b) increased
liver-to-bw ratios in male and female rats and increased stomach-to-bw
ratio in female rats; and c) decreased fat deposition of the liver
cells of male rats.
Statistically significant effects observed in animals receiving
500 mg 2-ethyl-1-hexanol/kg bw/day included: a) decreased body weight
and body weight gain in male and female rats; b) decreased serum
alanine aminotransferase, glucose, and cholesterol in male and female
rats, increased reticulocytes in male and female rats, decreased serum
alkaline phosphatase in male rats, and increased serum protein and
albumin in male rats; c) increased absolute liver weights in male and
female rats and increased absolute stomach weights in female rats;
d) increased organ-to-body weight ratios for liver and stomach in male
and female rats; and e) increased organ-to-brain weight ratios for
liver and stomach in male and female rats.
Slightly elevated single or multiple foci were observed in the
mucosa of the forestomach of male and female rats receiving 500 mg/kg
bw/day. Macroscopic findings at this dose level were reported to
include: a) focal or multifocal achanthosis in the mucosa of the
forestomach of 1 male and 5 female rats; b) acanthosis of the whole
mucosa, ballooning degeneration of the epithelia, and inflammatory
oedema in the submucosa of 1 male rat; and c) decreased fat deposition
in the liver and fewer animals with fatty infiltration of the lobular
periphery of the liver compared to vehicle-control rats (BASF, 1992a).
Five male Wistar-derived rats were administered 1 mmol/kg/day
(approximately 130 mg/kg bw/day) EH dissolved in polyethylene glycol
300 (10 ml/kg/day) by gavage for 14 days; 10 control rats were
administered the gavage vehicle alone. At the end of the treatment
period, rats were killed and blood was withdrawn for analysis of
plasma cholesterol and triglyceride levels; livers and testis were
weighed, liver samples were taken for light and electron microscopy,
and the remaining liver was homogenized for determination of total
catalase and CN-insensitive palmitoyl CoA oxidation. No major
pathological signs of hepatotoxicity were observed, although slight
centrilobular hypertrophy (controls: 4/10 rats; EH-treated: 2/5),
slight/moderate glycogen vacuolization (controls: 9/10; EH-treated:
5/5), and slight/moderate centrilobular "fat" vacuolation (controls:
9/10; EH-treated: 1/5) were reported in control and EH-treated rats.
Administration of EH had no significant effect on body weight gain,
liver-to-body-weight ratio, testis-to-body-weight ratio, number of
peroxisomes/504 µm2 liver, serum catalase activity, serum
cholesterol, or serum triglycerides. In addition, 0.1 mM EH had no
effect on acyl CoA oxidase activity after 72 hrs in in vitro culture
with rat hepatocytes (Rhodes et al., 1984).
Gavage administration of 1335 mg/kg bw/day EH in corn oil to 6
male Wistar albino rats for 7 days resulted in significantly increased
liver-to-body-weight ratio (control: 3.5±0.1 g/100 g bw; EH-treated:
4.9±0.1 [p<0.001]), decreased glucose-6-phosphatase activity
(control: 24±2 µg/min/mg microsomal protein; EH-treated: 15±1
[p<0.01]), increased biphenyl 4-hydroxylase activity (control:
1.6±0.1 µmol/hr/g liver; EH-treated: 2.1±0.1 [p<0.01]), and increased
microsomal cytochrome P-450 content (control: 0.07±0.003 delta-E
450-500 nm/mg microsomal protein; EH-treated: 0.1±0.004 [p<0.001])
(Lake et al. 1975).
2.2.3 Long-term toxicity/carcinogenicity studies
2.2.3.1 Mice
2-ethyl-1-hexanol (0, 50, 200, or 750 mg/kg bw/day) was
administered by gavage to groups of 50 male and 50 female B6C3F1 mice
five days per week for a period of 18 months. The purity of the test
substance was reported to be greater than 99.87%. The gavage vehicle
was doubly distilled water containing 5 mg Polyoxyl 35 castor oil per
100 ml. An additional control group of 50 male and 50 female rats was
gavaged with double distilled water only. All rats received 10 ml/kg
bw test substance emulsion, vehicle or double distilled water per
dose.
The method of preparing test substance emulsions was changed
after 6 months of dosing because homogeneity analyses of emulsions
showed considerable variation, ranging from approximately 70% to 140%
of target concentrations. However, variability in dosing during the
early part of the study did not significantly affect the outcome of
the study because of the "clear biological distinction between dose
levels during treatment."
Mice were housed singly and feed and water were available ad
libitum throughout the study. At the initiation of dosing, mice
were 49 days old; mean body weight of males was 23 g (range 21-26 g)
and mean body weight of females was 19 g (range 17-23 g). At the end
of the study, non-fasted mice were decapitated under CO2 anaesthesia.
The general health of the test animals was checked daily, and
test animals were examined and palpated once a week. Mice were
weighed weekly during the first 13 weeks, then every four weeks for
the duration of the study. Feed consumption was determined for a
period of one week every four weeks during the study. Blood samples
were drawn from the tail vein of all surviving animals for
haematological examination at 12 months and at the end of the study.
Animals that survived to the end of the study were necropsied; tissues
and organs were subjected to gross and microscopic pathology
examination.
No EH-related changes were observed in mice administered 50 or
200 mg/kg bw/day EH for 18 months. In mice administered 750 mg/kg
bw/day, the following effects were observed: 1) decreased body weight
gain in males (approximately 26%) and females (24%) that was
associated with a substantial reduction in feed consumption (males:
decreased from about 9% to 20%; females: decreased from about 9% to
30%); 2) increased mortality in males (vehicle controls: 4%;
EH-treated: 30%) and females (vehicle controls: 8%; EH-treated: 30%);
3) treatment-related haematological changes, including slightly
increased polymorphonuclear neutrophils in males and females (males:
controls--19.8±5.9% [12 mo] and 20.5±7.6% [18 mo]; 750 mg/kg
bw/day--26.4±9.1% [12 mo] and 26.9±13.5% [18 mo])(females: controls--
20.6±5.6% [12 mo] and 22.6±10.7% [18 mo]; 750 mg/kg bw/day--24.2±5.4
[12 mo] and 25.1±9% [18 mo]) and slightly decreased lymphocytes in
males and females (males: controls--77±6.9% [12 mo] and 76.6±7.6% [18
mo]; 750 mg/kg bw/day--69.1±9% [12 mo] and 70.6±13.2% [18 mo]); and 4)
treatment-related, but not statistically significant, increased focal
hyperplasia of the epithelium of the forestomach in males (controls--
1/50; 50 mg/kg bw/day--1/50; 200 mg/kg bw/day--1/50; 750 mg/kg
bw/day--5/50) and females (controls--1/50; 50 mg/kg bw/day--1/50; 200
mg/kg bw/day--0/50; 750 mg/kg bw/day--4/50). Also, a slight increase
in the incidence of hepatocellular carcinomas in high-dose females was
statistically significant when compared to the incidence in vehicle
control females but not when compared to the incidence in water-
gavaged control females (vehicle control--0/50; 50 mg/kg bw/day--1/50;
200 mg/kg bw/day--3/50; 750 mg/kg bw/day--5/50). No statistically
significant increase in tumour incidence occurred in male mice. EH is
not oncogenic in the mouse under the conditions of this study (BASF,
1992b).
In a satellite study to the carcinogenicity study in mice cited
above as BASF, 1992b, EH was administered by gavage (vehicle:
distilled water containing 5 mg Polyoxyl 35 castor oil per 100 ml) to
two groups of male and female B6C3F1 mice at 750 mg/kg bw/day. A
control group of 10 males and 10 females was gavaged with the vehicle
only for 13 months; a second (non-recovery) group of 10 males and 10
females was gavaged with EH for 13 months, 5 days/week; a third
(recovery) group of 50 males and 50 females was gavaged with EH for 13
months, 5 days/week, then gavaged with the vehicle only for 5 months,
5 days/week. Mice were killed at the end of the treatment periods--13
months for groups one and two; 18 months for group three--and
subjected to gross pathological assessment. The general health of the
test animals was checked daily, and animals were examined and palpated
once a week. Body weights were determined once a week during the
first 13 weeks of the study, then once every four weeks. Feed
consumption was determined one week in every four weeks throughout the
study. Microscopic examination of tissues and organs was performed
only on mice that died during the study.
Administration of 750 mg/kg bw/day EH to male and female mice for
13 months caused increased mortality in males and females (males:
control--0%, non-recovery--30%, recovery--22% during the first 13
months; females: control--0%, non-recovery--20%, recovery--16% during
the first 13 months). For the non-recovery mice and recovery mice
during treatment with EH, feed consumption was significantly decreased
compared to control mice (at 13 months, males: control--4.7±0.4 g/day,
non-recovery--3.7±0.5 g/day, recovery--4.4±0.6 g/day; females:
control--6.0±1.3 g/day, non-recovery--5.6±1.5 g/day, recovery--5.8±1.0
g/day); following the 5 month recovery period, feed consumption for
mice in the recovery group was in the same range as feed consumption
for control mice (males: control--4.8±0.9 g/day, recovery--4.9±0.8
g/day; females: control--6.3±1.3 g/day, recovery--5.9±1.1 g/day). For
the non-recovery mice and recovery mice during treatment with EH, body
weight gain was significantly decreased (at 13 months, males:
control--40.9±2.7 g, non-recovery--36.7±2.8 g, recovery--38.7±3.2 g;
females: control--38.7±5.4 g, non-recovery--33.8±4.4 g, recovery--
34.9±4.8 g); following the 5 month recovery period, body weight gain
of female mice that had been gavaged with EH for 13 weeks was still
significantly decreased compared to control mice (males: control--
42.7±3.5 g, recovery--42.4±3.6 g; females: control--41.1±5.6 g,
recovery--36.9±5.1 g). Some statistically significant changes in
organ weights and masses or foci in liver and stomach were observed to
be associated with EH administration; these were similar to changes
noted in the results of the carcinogenicity study (BASF, 1992d).
2.2.3.2 Rats
2-ethyl-1-hexanol (0, 50, 100, or 150 mg/kg bw/day) was
administered by gavage to groups of 50 male and 50 female Fischer 344
rats five days/week for a period of 24 months. The purity of the test
substance was reported to be greater than 99.3%. The gavage vehicle
was doubly distilled water containing 5 mg Polyoxyl 35 castor oil per
100 ml. An additional control group of 50 male and 50 female rats was
gavaged with double distilled water only. All rats received 10 ml/kg
bw/day test substance emulsion, vehicle or double distilled water per
dose.
The method of preparing test substance emulsions was changed
after 6 months of dosing because homogeneity analyses of emulsions
showed considerable variation, ranging from approximately 70% to 140%
of target concentrations. However, the report concluded that
variability in dosing during the early part of the study did not
significantly affect the outcome of the study because of the "clear
biological distinction between dose levels during treatment."
Rats were housed singly and food and water were available ad
libitum throughout the study. At the initiation of dosing, rats
were 42 days old; mean body weight of males was 103 g (range 86-128 g)
and mean body weight of females was 81 g (range 64-95 g). At the end
of the study, non-fasted rats were decapitated under CO2 anaesthesia.
The general health of the test animals was checked daily, and
test animals were examined and palpated once a week. Rats were
weighed weekly during the first 13 weeks, then every four weeks for
the duration of the study. Feed consumption was determined for a
period of one week every four weeks during the study. Blood samples
were drawn from a tail vein of all surviving animals for
haematological examination at 12 and 18 months and at the end of the
study. At the end of the study, surviving animals were necropsied;
tissues and organs were subjected to gross and microscopic pathology
examination.
No compound-related changes were associated with administration
of 50 mg/kg bw/day for 24 months; however, body weights and body-
weight gains of rats receiving 50, 150, or 500 mg 2-ethyl-1-hexanol/kg
bw/day were decreased in a statistically significant dose-dependent
manner compared to vehicle control rats. At the end of the study,
body weights were about 5%, 11%, and 23% below control values and body
weight gains were about 8%, 16%, and 33% below control values,
respectively. Feed consumption of male and female rats receiving 500
mg/kg bw/day showed occasional statistically significant decreases
compared to both control groups of rats, but no dose-response
relationship was observed.
An EH-associated increase in mortality was observed for female
mice of the high-dose group only (males: vehicle controls--34%, 50
mg/kg bw/day--46%, 150 mg/kg bw/day--32%, 500 mg/kg bw/day--38%;
females: vehicle controls--28%, 50 mg/kg bw/day--28%, 150 mg/kg
bw/day--26%, 500 mg/kg bw/day--52%).
For rats receiving 100 mg/kg bw/day, the study reported a)
statistically significant reductions in body weight (males: 11%;
females: 9%) and body weight gain (males: 16%; females: 12%) compared
to vehicle control rats and b) slightly increased numbers of animals
with clinical symptoms and incidences of symptoms (frequency/animals)
such as poor general condition (100 mg/kg bw/day: males--69/15;
vehicle control: males--62/12), labored breathing (100 mg/kg bw/day:
males--4/1, females--30/5; vehicle control: males--2/1, females--9/3),
piloerection (100 mg/kg bw/day: males--17/1; vehicle control: males--
0/0), and genital regions smeared with urine (100 mg/kg bw/day:
females--31/4; vehicle controls: females--0/0). Feed consumption of
male and female rats receiving 150 mg/kg bw/day showed occasional
statistically significant decreases compared to both control groups of
rats, but no dose-response relationship was observed.
The following treatment-related changes were observed in rats
dosed with 500 mg/kg bw/day 2-ethyl-1-hexanol for 24 months: a)
statistically significant reductions in body weight gain for males
(33%) and females (31%); b) increased incidences of male and female
rats with clinical symptoms (frequency/animals) such as poor general
condition (500 mg/kg bw/day: males--200/14, females--248/21; vehicle
control: males--62/12, females--34/8), labored breathing (500 mg/kg
bw/day: males--41/4, females--75/12; vehicle control: males--2/1,
females--9/3), piloerection (500 mg/kg bw/day: males--67/2, females--
21/5; vehicle control: males--0/0, females--2/1), and/or genital
region smeared with urine (500 mg/kg bw/day: males--13/1, females--
502/21; vehicle control: males--0/0, females--44/6); and c)
statistically significant increased mortality in dosed females as
reflected in the number of animals that died or were sacrificed in a
moribund condition during the study (52%) compared with vehicle
control females (28%).
Male rats dosed with 500 mg/kg bw/day had slightly increased
anisocytosis, predominantly microcytosis at 12 months, but not at 18
nor 24 months, compared to vehicle control males. No malignant
tumours were detected in high-dose animals that died before scheduled
termination and the sum of primary tumours, benign tumours and
malignant tumours was remarkably lower in the high-dose group compared
to both control groups of rats. Thus, 2-ethyl-1-hexanol was not
oncogenic in the rat under conditions of this assay (BASF, 1992a).
In a satellite study to the BASF carcinogenicity study in rats
cited above as BASF 1992a, EH was administered by gavage (vehicle:
distilled water containing 5 mg Polyoxyl 35 castor oil per 100 ml) to
two groups of male and female Fischer 344 rats at 500 mg/kg bw/day.
A control group of 10 males and 10 females was gavaged with the
vehicle only for 18 months; a second (non-recovery) group of 10 males
and 10 females was gavaged with EH for 18 months, 5 days/week; a third
(recovery) group of 50 males and 50 females was gavaged with EH for 18
months, 5 days/week, then gavaged with the vehicle only for 6 months,
5 days/week. Rats were killed at the end of the treatment periods--18
months for groups one and two; 24 months for group three--and
subjected to gross pathological assessment. The general health of the
test animals was checked daily, and animals were examined and palpated
once a week. Body weights were determined once a week during the
first 13 weeks of the study, then once every four weeks. Feed
consumption was determined one week in every four weeks throughout the
study. Microscopic examination of tissues and organs was performed
only on rats that died during the study.
Administration of 500 mg/kg bw/day EH to male and female rats for
18 months caused slightly increased mortality in females (control--
20%, non-recovery--40%, recovery--34% during the first 18 months) and
decreased feed consumption in males (maximum decrease of approximately
12%). For the non-recovery rats and recovery rats during treatment
with EH, body weight gain was significantly decreased (at 18 months,
males: control--298.7±19.6 g, non-recovery--215.4±21.3 g,
recovery--211.2±22.4 g; females: control--149.9±19.8 g, non-
recovery--128.7±21.7 g, recovery--128.5±18.3 g); following the 6 month
recovery period, body weight gains of males and females that had been
gavaged with EH for 18 weeks had partially recovered but were still
significantly decreased compared to controls (males: control--
266.5±30.7 g, recovery--216.1±23.0 g; females: control--177.5±27.0 g,
recovery--150.6±21.5 g).
The following changes were observed in rats that had been gavaged
with 500 mg/kg bw/day EH for 18 months compared to control rats: 1) a
greater number of animals and/or a higher incidence of clinical
symptoms such as poor general condition, labored breathing, and
genital region smeared with urine in males and females; 2)
statistically significant decreases in the absolute weights of brain
(males and females) and stomach (males); 3) statistically significant
decreases in organ-to-body weight ratios of brain (males and females),
liver (males and females), kidneys (males and females), stomach (males
and females), and testes (BASF, 1992c).
2.2.4 Reproduction studies
The response of mixed cultures of Sertoli and germ cells prepared
from Sprague-Dawley rat testes to model testicular toxicants was
studied. After incubation of the cultures with 2 x 10-4 M EH for 24
hrs, no increase was observed in the normal rate of germ cell
detachment from Sertoli cells into the culture medium (Gray and
Beamand 1984).
Effects of EH on rat testes were examined in vivo and
in vitro. No testicular damage was observed in male Sprague-Dawley
rats given oral doses of 2.7 mmol EH/kg bw/day for 5 days and
incubation with EH (0-1 000 µM for 24 or 48 hours) did not enhance
detachment of germ cells from primary mixed cultures of rat Sertoli
and germ cells (Sjoberg et al., 1986).
EH did not increase lactate and pyruvate concentrations in the
medium of in vitro cultures of rat Sertoli cells. Such increases
are considered to be sensitive indicators of altered Sertoli cells
function associated with Sertoli-cell toxicants (Williams & Foster
1988).
2.2.5 Special studies on developmental toxicity and teratogenicity
2.2.5.1 Mice
Pregnant CD-1 mice were gavaged on gestation days 6-13 with 1525
mg/kg bw/day EH in corn oil; control mice were gavaged with corn oil;
dams were allowed to litter. Administration of EH caused
statistically significant (p<0.05) decreased maternal body weight
gain (control: 7.0±2.5 g; EH: 3.9±3.2 g), decreased number of viable
litters (control: 33/34; EH: 11/20), decreased liveborn per litter
(control: 9.9±2.4; EH: 6.8±3.4), decreased percentage survival of pups
(control: 98.2±8.8; EH: 73.4±32.2), and decreased birth weight
(control: 1.6±0.1 g/pup; EH: 1.4±0.2 g/pup) and weight gain for pups
(control: 0.6±0.1 g/pup; EH: 0.3±0.2 g/pup) (Hardin et al., 1987).
2.2.5.2 Rats
Pregnant Wistar rats were administered undiluted di(2-ethylhexyl)
phthalate (DEHP; 12.5 or 25 mmol/kg bw), EH (6.25 or 12.5 mmol/kg bw,
approximately equivalent to 800 and 1600 mg/kg bw), or 2-ethylhexanoic
acid (EA; 6.25 or 12.5 mmol/kg bw) by gavage on day 12 of gestation.
Control rats were not gavaged (untreated controls). Caffeine (150
mg/kg) was dissolved in water and injected i.p. in some pregnant rats
of each group. Rats were killed on day 20 of gestation; following
Caesarean section, implantation sites were determined in situ and
the number of dead or resorbed fetuses was determined. Live fetuses
were removed and examined; internal and external soft tissue and
skeletal malformations were recorded. At least seven litters for each
experimental condition were analyzed.
Administration of each test compound resulted in statistically
significant, dose-related increases in malformed live fetuses (DEHP:
12.5 mmol/kg bw [7 litters]--4.5±4.5%, 25 mmol/kg bw [7 litters]--
20.8±7.3%; EH: 6.25 mmol/kg bw [7 litters]--2.0±1.3%, 12.5 mmol/kg bw
[7 litters]--22.2±14.7%; EA: 6.25 mmol/kg bw [7 litters]--0.8±0.8%;
12.5 mmol/kg bw [10 litters]--67.8±10.9%) compared to controls (no
malformed live fetuses in 7 litters). Defects in fetuses following
treatment with EH included hydronephrosis (7.8% of live fetuses), tail
defects (4.9% of live fetuses), limb defects (9.7% of live fetuses),
and other defects (1.0% of live fetuses). For each test compound,
caffeine was reported to potentiate (increase) the percent of
malformed live fetuses. However, administration of test compounds did
not significantly affect the percentage of dead and resorbed fetuses
compared to controls. No maternal effects associated with the test
compounds were reported. These results are consistent with the
hypothesis that the proximal teratogen for DEHP is EA, the metabolic
product of EH (Ritter et al., 1986 and 1987).
The developmental toxicity of dermally applied EH was studied in
Fischer 344 rats; results of a dose range-finding study for the
developmental toxicity study were also included. In the dose range-
finding study 0, 420, 840, 1680, or 2520 mg/kg bw/day EH (undiluted)
was applied to the clipped dorsal skin of pregnant F344 rats (8
rats/group); a positive dermal control group (2-methoxyethanol) and a
sham-treated (deionized water) dermal control group were included in
the study. In the developmental toxicity study, 0, 252, 840, or 2520
mg/kg bw/day EH (undiluted) was applied to the clipped dorsal skin of
pregnant F344 rats (25/group); a positive dermal control group
(2-methoxyethanol) and a sham-treated (deionized water) dermal control
group also were included in this study.
Body weights were recorded on gestation days 0, 6, 9, 12, 15, and
21; feed consumption was estimated for 3-day intervals from gestation
days 0-21. Skin irritation was measured before and after each 6-hr
application period. Surviving females were killed on gestation day
21; uterine and liver weights (both studies) and weights of spleen,
adrenals, kidneys, and thymus (developmental toxicity study) were
recorded. Corpora lutea and uterine implantation sites were counted;
ovaries, cervices, vaginas, and abdominal and thoracic cavities were
examined grossly. All live and dead fetuses and resorption sites were
noted. Live fetuses were sexed, weighed, and examined for external,
visceral, and skeletal malformations and variations.
All pregnant females treated with EH survived. Clinical findings
for EH-treated pregnant rats were limited to body weight changes, skin
irritation, and nasal and ocular effects. Decreased body weight gain
was observed in the dose range-finding study for gestation days 6-15
at doses of 1 680 (10.1±7.1 g) and 2 520 mg/kg bw/day EH (10.7±4.8 g)
compared to sham-treated control rats (18.9±6.4 g). In the main
study, weight gain was statistically significantly decreased for
gestation days 6-9 at 2 520 mg/kg bw/day EH (0.1±2.4 g) compared to
sham-treated controls (3.3±1.2 g), and was somewhat, but not
statistically significantly, decreased at 840 mg/kg bw/day EH. No
significant changes in feed consumption were reported at any treatment
level of EH in either study throughout gestation (data not given).
EH-related irritation effects at the treatment site were identified as
mild, and included exfoliation, encrustation and erythema for all
treatment groups in both studies; oedema was not observed.
Gestational effects were observed for neither study at any dose
of EH applied dermally. Also, dermal administration of EH was not
associated with external, visceral, or skeletal malformations.
Dermally applied EH does not produce developmental or teratogenic
effects when administered at doses associated with demonstrable
maternal toxicity (Tyl et al., 1992).
Groups of approximately 15 pregnant Sprague-Dawley rats were
exposed for 7 hrs/day to air saturated with EH vapor (approximately
850 mg/m3 EH) throughout gestation (Nelson et al., 1988). Dams
were weighed daily during the first week of exposure, then weekly.
Dams were killed on gestation day 20; fetuses were removed, sexed,
weighted and examined for external, visceral and skeletal defects. EH
reduced maternal feed intake but did not produce significant maternal
toxicity (data not provided). Inhalation of EH under conditions of
this experiment was not associated with increased malformations
(Nelson et al., 1988).
2.2.6 Special studies on genotoxicity
The results of genotoxicity assays on EH are summarized in Table
2. All reports except Seed (1982) were of negative results for
in vitro assays; results were negative for several in vivo assays,
including a dominant lethal assay, a chromosomal aberration assay, and
a mutagenicity assay on rat urinary metabolites of EH.
2.2.7 Observations in humans
Hollenbach and coworkers (1972) reported that laboratory workers
exposed to EH (among other substances) reported headaches, dizziness,
fatigue and gastrointestinal disorders; also that exposed workers had
slightly decreased blood pressure during the day.
Table 2: Results of genotoxicity assays on EH
Test Test Subject EH Conc. Result Reference
Ames test1 S. typhimurium TA98 0-1.0 µL/plate neg. Kirby et al., 1983
TA100 TA1535
TA1537 TA1538
Ames test1 S. typhimurium TA98 0-220 µg/plate neg. Zeiger et al., 1985
TA100 TA1535 TA1537
Ames test1 S. typhimurium TA98 0-2 000 µg/plate neg.3 Agarwal et al., 1985
TA100 TA1535 TA1537
TA1538 TA2637
Ames test1 S. typhimurium TA98 0-1.8 µl/plate neg. Litton Bionetics Inc., 1982a
TA100 TA1537 TA1535
TA1538
Ames test1 S. typhimurium TA98 urine from rats neg. DiVincenzo et al., 1983
TA100 TA1535 TA1537 gavaged with 1 g/kg
TA1538 bw/day EH for 15 day
In vitro cell BALB/3T3 cells 0-0.162 µg/ml neg.4 Litton Bionetics Inc., 1982b
transformation
assay1
8-Azaguanine S. typhimurium TA100 0-1.5 mM pos.5 Seed, 1982
resistance assay2
Mouse micronucleus B6C3F1 mouse bone 456 mg/kg bw/day neg.6 Litton Bionetics Inc., 1982c
test marrow cells i.p. for 1 or 2 day
Table 2 (contd)
Test Test Subject EH Conc. Result Reference
mouse lymphoma L5178Y/TK+/- mouse 0.01-0.24 µL/mL neg. Kirby et al., 1983
assay1 lymphoma cells
Rec-assay Bacillus subtilis 500 µg/disk neg. Tomita et al., 1982
CHO mutation assay Chinese hamster ovary 1.5-2.8 mM neg. Phillips et al., 1982
(CHO) cells
Unscheduled DNA Primary rat hepatocytes Not given neg. Hodgson et al., 1982
synthesis assay
In vivo dominant ICR/SIM mice 250, 500, 1 000 neg. Rushbrook et al., 1982
lethal assay mg/kg bw/day
for 5 day
In vivo chromosomal F344 rat bone marrow cells .02, .07, .21 g/kg neg. Putnam et al., 1983
aberration assay bw/day for 5 day
(1) Both with and without metabolic activation
(2) Without metabolic activation
(3) Moderate cytotoxicity reported in most cultures
(4) Negative from 0-225 µl/ml without metabolic activation; negative from 0-0.162 µl/ml
with rat hepatocytes for metabolic activation
(5) Small dose-related increase (maximum increase was approximately 3.5 times background)
in mutation frequency accompanied by decreased survival (cytotoxicity)
(6) Negative with and without activation with S9 and with and without
ß-glucuronidase/arylsulfatase
3. COMMENTS
In rats, orally administered 2-ethyl-1-hexanol is absorbed and
rapidly eliminated within 28 hours, mainly in urine and faeces. The
major urinary metabolite is 2-ethylhexanoic acid. In mice, rats and
monkeys, the compound is oxidized by ß-, omega-, and omega-1-oxidation
to various metabolites, including 2-ethylhexanoic acid,
ethylhexanedioic acid, and 5-hydroxyethylhexanoic acid. Glucuronic
acid conjugates are formed in all three species.
The Committee concluded that the available data do not indicate
that 2-ethyl-1-hexanol is genotoxic. With a single exception, in
which a positive result occurred in the presence of significantly
decreased cell survival (cytotoxicity), the results of both in vivo
and in vitro genotoxicity tests were negative.
Although teratogenic effects were reported in the offspring of
mice administered 1 500 mg 2-ethyl-1-hexanol/kg bw/day by gavage on
days 6-13 of gestation, these effects occurred in the presence of
severe maternal toxicity. The body weight gain of treated females
was approximately 40% less than that of untreated controls. In rats,
administration of 1600 mg/kg bw 2-ethyl-1-hexanol by gavage (but not
800 mg/kg bw) on day 12 of gestation was associated with a
statistically significant increase in the number of malformed live
fetuses (malformations included hydronephrosis, tail defects and limb
defects). Maternal toxicity was not reported in this study.
The results of several short-term toxicity studies suggested that
2-ethyl-1-hexanol administered orally to rats and mice at doses
greater than approximately 350 mg/kg bw/day induces liver peroxisome
proliferation and/or marker enzymes for peroxisome proliferation.
However, the results of carcinogenicity studies did not indicate that
long-term oral administration of 2-ethyl-1-hexanol leads to induction
of liver tumours in mice or rats.
The results of long-term oral carcinogenicity studies indicated
that 2-ethyl-1-hexanol is not carcinogenic in rats (24 months) or mice
(18 months). The incidence of hepatocellular carcinomas at 750 mg/kg
bw/day in female mice was slightly higher than in historical controls,
however this effect was considered to be incidental and unrelated to
the administration of 2-ethyl-1-hexanol. The increase was
statistically significant when compared with the incidence in vehicle
control females but not when compared with the incidence in control
females given distilled water by gavage. In these studies, the 750
mg/kg bw/day dose of the compound produced a number of statistically
significant, non-carcinogenic adverse effects, but these effects were
not observed at 50 or 200 mg/kg bw/day in mice or at 50 mg/kg bw/day
in rats.
4. EVALUATION
On the basis of a NOEL of 50 mg/kg bw/day from the long-term
study in rats and using a safety factor of 100, the Committee
established an ADI of 0-0.5 mg/kg bw for 2-ethyl-1-hexanol.
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See Also:
Toxicological Abbreviations