ALPHA-METHYLBENZYL ALCOHOL
First draft prepared by
Ms E. Vavasour, Toxicological Evaluation Division
Bureau of Chemical Safety, Food Directorate
Health and Welfare Canada
Ottawa, Ontario, Canada
1 EXPLANATION
alpha-Methylbenzyl alcohol has not previously been evaluated by
the Committee. This substance is used as a flavouring agent in
foods and beverages; it also occurs naturally in a variety of foods
at levels of up to 1.3 ppm (Maarse and Visscher 1991).
2 BIOLOGICAL DATA
2.1 Biochemical aspects
2.1.1 Absorption, distribution, and excretion
Following a single oral dose of 460 mg/kg bw in rabbits,
alpha-methylbenzyl alcohol was rapidly excreted in the urine.
Within 24 hours, 82% of the dose was retrieved as urinary
metabolites (Smith et al. 1954).
2.1.2 Biotransformation
Metabolites in the urine of rabbits following a single oral
dose of 460 mg/kg bw alpha-methylbenzyl alcohol were
alpha-methylbenzyl alcohol glucuronide (50%), hippuric acid (30%)
and mandelic acid (1-2%) (Smith et al. 1954). These results in the
rabbit were cited in a 1959 review, with the observation that both
optical forms of the alcohol behaved similarly with respect to
biotransformation (Williams, 1959).
Hopkins et al. (1972) reported that a small proportion of a
dose of alpha-methylbenzyl alcohol in rats was excreted in the urine
as acetophenone.
Rats displayed substrate stereoselectivity in the metabolism of
racemic mixtures of alpha-methylbenzyl alcohol. The R(+) isomer was
largely excreted as the glucuronide while the S(-) isomer underwent
further oxidative metabolism (Testa and Jenner 1976).
2.2 Toxicological studies
2.2.1 Acute studies
The results of acute toxicity studies with alpha-methylbenzyl
alcohol are summarized in Table 1.
Table 1. Acute toxicity studies with alpha-methylbenzyl alcohol
Animal Route LD50 Reference
(mg/kg bw)
Mouse Oral 1 2501 Dieter 1990
Rat Oral 400 Smyth & Carpenter 1944
Rat Oral 1 2501 Dieter 1990
1Value is a LDlow
2.2.2 Short-term toxicity studies
2.2.2.1 Mice
Groups of male and female B6C3F1 mice (4 or 5/sex/group), 6-8
weeks old, received 0, 125, 250, 500, 1 000, or 2 000 mg/kg bw/dy
alpha-methylbenzyl alcohol in corn oil by gavage, 5 days a week over
16 days (12 doses). The animals were observed twice daily and
weighed on day 1, after one week and at the end of the study. All
animals were necropsied. Histological examinations were performed
on two males and two females in the 500 mg/kg bw/dy dose group and
on one male and one female in the control group. In the 1 000 and
2 000 mg/kg bw/dy groups, 16/18 mice died within 3 days. No
treatment-related histopathological lesions were observed in the
500 mg/kg bw/dy group (Dieter 1990).
In a 13-week study, alpha-methylbenzyl alcohol was administered
by gavage in corn oil to six groups of B6C3F1 mice (10/sex/group)
at dose levels of 0, 47, 94, 188, 375 or 750 mg/kg bw/dy for 5
days/week. Animals were observed twice daily and body weights
recorded once weekly. A necropsy was performed on each animal and
the liver weights were recorded. Histopathological examinations
were performed on all animals in the vehicle control groups, all
animals dying on test and on all male and female mice in the
750 mg/kg bw/dy group. No deaths occurred which were related to the
effects of the test material. At the two top dose levels, mice
exhibited laboured breathing, ataxia and lethargy for up to 30
minutes after dosing. Body weights were not affected by
administration of the test material. Absolute and relative liver
weights were significantly elevated from controls in both male and
female groups receiving 187.5 mg/kg bw, but no dose-response
relationship was evident. No treatment-related histopathological
lesions were observed in the 750 mg/kg bw/dy dose group (Dieter
1990).
2.2.2.2 Rats
Groups of male and female F344/N rats (5/sex/group), 6-7 weeks
old, received 0, 125, 250, 500, 1 000, or 2 000 mg/kg bw/dy
alpha-methylbenzyl alcohol in corn oil by gavage, 5 days a week over
16 days (12 doses). The animals were observed twice daily and
weighed on day 1, after one week and at the end of the study. All
animals were necropsied. Histological examinations were performed
on two males and two females in the 1 000 mg/kg bw/dy dose group and
on one male and one female in the control group. In the 2 000 mg/kg
bw/dy group, 2/5 male and 4/5 female rats died before the end of the
study. Laboured breathing and lethargy were noted in one rat of
each sex immediately after dosing in this group. The body weights
of male and female rats in the top three dose groups were lower than
those of the respective vehicle controls. In the highest dose
group, body weight decrements from controls were 21% and 15%,
respectively, for males and females. Haemorrhage in the
gastrointestinal tract was observed in one female and two male rats
in this group. No treatment-related histopathological lesions were
observed in the two male and two female rats in the 1 000 mg/kg
bw/dy group (Dieter 1990).
alpha-Methylbenzyl alcohol in corn oil was administered by
gavage to six groups of F344/N rats (10/sex/group) at dose levels of
0, 93, 187, 375, 750, or 1 500 mg/kg bw, 5 days/week for 13 weeks.
Animals were observed twice daily and body weights recorded once
weekly. A necropsy was performed on each animal. The livers were
weighed at this time. Histopathological examinations were performed
on all animals in the vehicle control groups, all animals dying on
test and on all male and female rats in the 1 500 mg/kg bw/dy group.
Histopathological examination of the spleen was carried out in male
rats in the 375 mg/kg bw/dy group and in male and female rats in the
750 mg/kg bw/dy group. In the 1 500 mg/kg bw/dy dose group, 1/10
male and 3/10 females died as a result of treatment with the test
material. Body weights of male rats in the 1 500 mg/kg bw/dy groups
were significantly decreased at the end of the study compared with
vehicle controls. Throughout the study, rats receiving 750 or 1 500
mg/kg bw/dy exhibited ataxia, rapid breathing and lethargy for up to
30 minutes after dosing. Relative liver weights were significantly
elevated in all the treated female groups and in the 3 top male dose
groups. The absolute liver weights were also elevated in comparison
with the controls in these groups, with statistical significance in
all but one of the treated female groups (187 mg/kg bw) and none of
the male groups. No pathological changes of the liver were noted
during histopathological examination of the high-dose group. A
minimal-to-mild increase in brown pigment, characteristic of
haemosiderin, was noted in the macrophages of the spleen in 10/10 of
the male rats receiving 750 mg/kg bw, 9/10 receiving 1 500 mg/kg bw.
and in none receiving 375 mg/kg bw. In the female rats, a similar
pigment was seen in 6/10 receiving 1 500 mg/kg bw. and none
receiving 750 mg/kg bw/dy (Dieter 1990).
2.2.3 Long-term toxicity/carcinogenicity studies
2.2.3.1 Mice
A carcinogenicity study was conducted with B6C3F1 mice in
which groups of 49 or 50 mice of each sex were administered 0, 375
or 750 mg/kg bw/dy of alpha-methylbenzyl alcohol in corn oil by
gavage, 5 days/week, for 103 weeks. Mice were observed twice daily.
Body weights were recorded weekly for the first 12 weeks and once a
month for the rest of the study. Necropsy was performed on all
animals at termination and those dying on test. Histopathological
examination of 33 tissues and organs was conducted in all mice from
all groups.
There was a greater than 10% reduction in body weight gain in
the high-dose males and females, but administration of
alpha-methylbenzyl alcohol had no effect on survival. There were no
increases which were attributable to administration of the test
material in neoplastic or nonneoplastic lesions of the kidney or any
of the other tissues. The NOEL for this study was 375 mg/kg bw/day
based on the reduction in body weight gain at the next higher dose
(Dieter 1990).
2.2.3.2 Rats
Male and female F344/N rats, 50/sex/group, received 0, 375 or
750 mg/kg bw/dy alpha-methylbenzyl alcohol in corn oil by gavage 5
days/week for 103 weeks. Rats were observed twice daily. Body
weights were recorded weekly for the first 12 weeks and once a month
for the rest of the study. Necropsy was performed on all animals at
termination and those dying on test. Histopathological examination
of 36 tissues and organs was conducted in all rats from all groups.
There was a greater than 10% reduction in body weight gains in
both treated male groups and the high-dose females. Survival of
rats in these groups was also significantly reduced. At study
termination, male rat survival was 35/50, 8/50 and 1/50 for the
control low-dose and high-dose groups, respectively; for the female
rats, survival was 34/50, 26/50 and 11/50, respectively. A cluster
of accidental deaths in both groups of treated males and in the
high-dose females during weeks 48 to 53 were considered to have been
gavage-related even though the animals had not been handled
differently from the other groups and no other predisposing factors
could be found.
Chronic progressive nephropathy was a common age-related
finding in both male and female rats. Treatment with either dose of
alpha-methylbenzyl alcohol resulted in an increased severity of this
lesion in the male, but not the female rats and also contributed to
lowered survival in these groups. A statistically significant
increase was noted in the combined incidence of adenomas and
adenocarcinomas of the kidney in male rats at both doses (control,
1/49; low-dose, 13/41; high-dose, 14/28 [the denominator represents
the number of animals alive at week 81 when the first kidney tumour
was observed]). In fact, of these neoplasms, only one
adenocarcinoma was detected and it was found in a low-dose animal.
Because renal tubular cell neoplasms are often late-appearing, and
were not visible macroscopically at necropsy, multiple sections of
the kidney were used to evaluate the incidence of these lesions.
The incidence of tubular cell hyperplasia in the male rats was 1/49,
7/41 and 6/28 for the control, low-dose and high-dose animals,
respectively. There was no indication that the renal toxicity was
mediated through alpha2u-globulin, since no compound-related
increases in hyaline droplet formation were observed in the short-
term studies described above (data not presented). [However,
immunohistochemical analysis for detection of alpha2u-globulin is a
more sensitive technique to preclude this as a mechanism for the
genesis of these neoplasms.] Parathyroid hyperplasia, calcification
of the heart and glandular stomach, and fibrous osteodystrophy of
the bone were observed at markedly increased incidences in the low-
dose male rats. These changes were believed to be secondary to a
mineral imbalance caused by renal toxicity. The incidence of
hyperplasia of the transitional epithelium overlying the renal
pelvis also was significantly increased in the low-dose male rats
(control - 3/50; low dose - 20/50; high dose - 4/50; females:
1/50, 0/49, 0/50). Transitional cell papillomas of the urinary
bladder were observed in 1/47 high-dose male rats and 2/48 high-dose
female rats and in none of the other groups. The historical
incidence for this lesion in both sexes of F344/N rats is 0.2%. The
incidences of epithelial hyperplasia of the urinary bladder did not
show an increase in the treated rats (male: control - 3/48; low dose
- 4/46; high dose - 1/47; female: 0/49; 1/47; 0/48).
The incidence of several other lesions was increased in treated
groups compared with controls: in males (centrilobular necrosis of
the liver, inflammation of the forestomach, suppurative inflammation
of the nasal cavity, acute inflammation of the salivary glands); or
in both sexes (congestion of the lung, haemorrhage and foreign
material in the lung). A no-effect level was not observed in this
study since reduced survival and body weight gain and an increased
incidence of kidney adenomas were noted in the male rats at both
doses administered in this study (Dieter 1990).
2.2.4 Reproduction Studies
No information available
2.2.5 Special studies on teratogenicity
alpha-Methylbenzyl alcohol was applied dermally to the skin of
pregnant Sprague-Dawley rats at doses of 0, 0.14, 0.43 and 1.40
ml/kg bw/dy on days 6-15 of gestation. With a specific gravity of
1.01, these doses were equivalent within 1% to the same doses in
g/kg bw. At the high dose, the test material exhibited an increased
incidence of embryolethality, growth retardation and malformations
(anophthalmia, microphthalmia, ventricular septal defects, defects
and irregularities affecting the thorax, kinky tail, defects of the
thoracic ribs and occurrence of cervical ribs) as well as maternal
toxicity. The NOEL in this study was 0.43 g/kg bw/dy. Since only
summary data from this study were available in preparation of this
monograph, it was not possible to determine the independence of the
teratogenic and embryotoxic effects from maternal toxicity (USEPA
1976, cited Dieter, 1990).
2.2.6 Special studies on genotoxicity
The results of genotoxicity studies with alpha-methylbenzyl
alcohol are summarized in Table 2.
2.3 Observations in humans
Contact sensitization tests using 8% alpha-methylbenzyl alcohol
in petrolatum produced no sensitization reactions in 25 volunteers
(Kligman 1966, 1973).
No information was available concerning the effects of
ingestion of this flavouring in humans.
Table 2. Results of genotoxicity assays on alpha-methylbenzyl alcohol
Test System Test Object Concentration of Results Reference
alpha-methylbenzyl
alcohol
Ames test1 S. typhimurium 33-6 666 µg/ml Negative Dieter 1990
TA98, TA100,
TA1535, TA1537
DNA damage/growth E. coli 50 µl/plate Negative Fluck et al. 1976
inhibition
Yeast mutation S. sake 0.20% Positive Kojima et al. 1976
Mammalian cell Mouse L5178Y/TK+/- 62.5-1 200 µg/ml Positive Dieter 1990
mutation lymphoma cells
(trifluorothymidine
resistance)
Chromosomal aberration1 Chinese hamster ovary 1 000-3 000 µg/ml Positive (+S9) Dieter 1990
cells
Sister chromatid Chinese hamster ovary 33.3-1 000 µg/ml Dieter 1990
exchange1 cells
1Both in the presence and absence of metabolic activation.
3 COMMENTS
Following oral administration this compound is rapidly excreted
in the urine. The principal metabolites have been identified as
hippuric acid and the glucuronide conjugate.
The Committee reviewed a series of acute, short-term, and long-
term toxicity studies in which alpha-methylbenzyl alcohol was
administered in corn oil by gavage in rats and mice. In addition,
the Committee evaluated a dermal teratogenicity study in rats and a
battery of in vitro genotoxicity tests, which included bacterial
and mammalian point mutation and mammalian chromosomal aberration
studies.
In the short-term toxicity studies, high rates of mortality
were associated with dose levels of 1 000 mg/kg bw/day and above in
the mouse and 2 000 mg/kg bw/day in the rat.
An increase in haemosiderin deposits in macrophages of the
spleen was noted at 750 mg/kg bw/day in male rats during a 13-week
study. This effect was not, however, noted during a 2-year study.
A dose-related increase in liver weight that was noted in both male
and female rats in the 13-week study could not be assessed in the
2-year study since liver weights were not recorded. However, an
increase in the incidence of centrilobular necrosis was observed in
male rats at both dose levels (375 and 750 mg/kg bw/day) in the
latter study.
In the long-term toxicity studies, the body weight gains were
at least 10% higher in untreated controls in male and female mice
and in female rats at doses of 750 mg/kg bw/day and in male rats at
375 and 750 mg/kg bw/day. Long-term survival of the rats, but not
the mice, was significantly reduced by oral administration of
alpha-methylbenzyl alcohol at 375 or 750 mg/kg bw/day.
Exacerbation of age-related nephropathy was noted at both dose
levels in male rats. The incidence of renal tubular cell
hyperplasia and adenomas was also statistically-significantly
increased in these rats than in untreated controls. A NOEL was not
observed in this study.
A teratogenicity study in rats in which alpha-methylbenzyl
alcohol was administered dermally showed a range of teratogenic and
embryotoxic effects at the highest dose of 1400 mg/kg bw/day.
Maternal toxicity was also demonstrated at this dose. Because
alpha-methylbenzyl alcohol was administered dermally, the extent of
absorption and metabolism were likely to differ from absorption and
metabolism by the oral route, hence comparability of dose levels was
uncertain. The NOEL in this study was 430 mg/kg bw/day.
alpha-Methylbenzyl alcohol was mutagenic in eukaryotic cells
(mammalian and yeast), but not in prokaryotic cells (bacteria) and
induced chromosomal aberrations in mammalian cells in vitro.
The Committee noted that alpha-methylbenzyl alcohol
administered by gavage in corn oil was associated with a higher
incidence of renal tubular cell adenomas in male rats than in
untreated contols, but not in female rats or in mice, at dose levels
at or exceeding the MTD and in the presence of factors that
exacerbated a high incidence of age-related chronic progressive
nephropathy.
4 EVALUATION
The intake of this compound is extremely low. On the basis of
the available evidence, the Committee concluded that the higher
incidence of benign neoplasms in the kidney of male rats is not
relevant to humans. In view of the limited database, the Committee
concluded that the available data could be used to set an ADI by
application of a 1 000-fold safety factor to the minimal-effect
level of 93 mg/kg bw/day with respect to liver weight increase in
the absence of associated pathology in the 13-week study in rats.
On this basis, an ADI of 0-0.1 mg/kg bw/day was allocated for
alpha-methylbenzyl alcohol.
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See Also:
Toxicological Abbreviations
alpha-METHYLBENZYL ALCOHOL (JECFA Evaluation)