Toxicological evaluation of some food
additives including anticaking agents,
antimicrobials, antioxidants, emulsifiers
and thickening agents
WHO FOOD ADDITIVES SERIES NO. 5
The evaluations contained in this publication
were prepared by the Joint FAO/WHO Expert
Committee on Food Additives which met in Geneva,
25 June - 4 July 19731
World Health Organization
Geneva
1974
1 Seventeenth Report of the Joint FAO/WHO Expert Committee on
Food Additives, Wld Hlth Org. techn. Rep. Ser., 1974, No. 539;
FAO Nutrition Meetings Report Series, 1974, No. 53.
BUTYLATED HYDROXYTOLUENE
Explanation
Butylated hydroxytoluene has been evaluated for acceptable daily
intake by the Joint FAO/WHO Expert Committee on Food Additives (see
Annex 1, Refs No. 6, No. 8, and No. 13) in 1961, 1964 and 1965.
Since the previous evaluations, additional data have become
available and are summarized and discussed in the following monograph.
The previously published monographs have been expanded and are
reproduced in their entirety below.
BIOLOGICAL DATA
BIOCHEMICAL ASPECTS
Excretion and distribution
The metabolism of butylated hydroxytoluene (BHT) administered
to rabbits orally in single doses of 500 mg/kg bw was studied. The
metabolites 2,6-di-tertbutyl-4-hydroxymethylphenol (BHT-alc),
3,5-di-tert-butyl-4-hydroxybenzoic acid (BHT-acid) and 4,4'-ethylene-
bis-(2,6-di-tert-butylphenol) were identified. The urinary metabolites
of BHT comprised 37.5% as glucuronides, 16.7% as ethereal sulfates
and 6.8% as free phenols; unchanged BHT was present only in the faeces
(Akagi & Aoki, 1962a); 3,5-di-tert-butyl-4-hydroxybenzaldehyde
(BHT-ald) was also isolated from rabbit urine (Aoki, 1962). The main
metabolic pathway was confirmed by administering BHT-alc to rabbits
and isolating BHT-ald, BHT-acid, the ethylene-bis derivative and
unchanged BHT-alc in the urine (Akagi & Aoki, 1962b).
The fate in the body of 14C-labelled BHT has been elucidated.
The relatively slow excretion of BHT is probably attributable to
enterohepatic circulation rather than to tissue retention. Rats were
given single oral doses (1-100 mg/rat) of BHT-14C and approximately
80 to 90% of the dose was recovered in four days in the urine and
faeces. Of the total radioactivity, 40% appeared in the urine of
females and 25% in males. After four days approximately 3.8% of the
dose was retained mainly in the alimentary tract. A substantial
portion of the radioactivity was found in tho bile collected from two
rats (one male, one female) over a period of 40 hours (Daniel & Gage,
1965).
Groups of two rats (one male, one female) were given one to five
oral doses of 44 mg/kg bw BHT on alternate days and each group killed
24 hours after the final dose. The range of the total dose accounted
for was 92 to 103.5% in males and 92.6 to 98.6% in females. There was
an indication of sex difference in the route of excretion, females
excreting 19-43% of the radioactivity in urine and males only 3-15%.
Eight days after administration of five doses 92% of the radioactivity
had been excreted by males and 97% by females. Subcutaneous
administration of graded doses of BHT to female rats revealed
substantial faecal excretion but the rate of excretion decreased with
increasing dose. There was no evidence of accumulation of BHT-14C in
the body under the conditions of repeated oral dosage (Tye et al.,
1965).
The BHT content of fat and liver of rats given diets containing
0.5 and 1.0% BHT for periods up to 35 and 50 days respectively: with
0.5% BHT in the diet, a level of approximately 30 ppm (0.003%) in the
fat was reached in males and 45 ppm (0.0045%) in females, with
approximately 1-3 ppm (0.0001-0.0003%) in the liver, while with 1.0%
BHT the level in the fat was 50 ppm (0.005%) in males and 30 ppm
(0.003%) in females. On cessation of treatment, the level of BHT in
fat fell with a half-life of seven to 10 days (Daniel & Gage, 1965).
The level of BHT in the fat reached a plateau at approximately 100 ppm
(0.01%) after three to four days when daily doses of 500 mg/kg bw were
given by intubation; 200 mg/kg bw per day for one week produced a
level of about 50 ppm (0.005%) (Gilbert & Golberg, 1965).
When feed containing 500 ppm (0.05%) BHT was given to laying
hens, 20 ppm (0.002%) was found in the fat fraction of eggs; 100 ppm
(0.01%) in the feed resulted in residues of less than 5 ppm (0.0005%).
In the broiler chicken, over a period of 21 weeks, the residues in
body fat were 55 ppm (0.0055%) on the 500 ppm (0.05%) diet and less
than 5 ppm (0.0005%) on the 100 ppm (0.01%) diet (Van Stratum & Vos,
1965).
One-day-old chicks were given 14C-BHT at a level of 200 ppm
(0.02%) in the food for 10 weeks. At broiler age, edible portions had
residues amounting to 1-3 ppm (0.0001-0.0003%) of BHT and metabolites.
Similar diets given to laying hens produced residues in eggs of 2 ppm
(0.0002%) after seven days, the level thereafter remaining constant
(Frawley et al., 1965a).
Rabbits were given single or repeated doses of BHT in the range
400-800 mg/kg bw. About 16% of the dose was excreted as ester
glucuronide and 19% as ether glucuronide. Unconjugated phenol (8%)
ethoreal sulfate (8%) and a glycine conjugate (2%) were also excreted.
Excretion of all detectable metabolites was essentially complete three
to four days after administration of the compound and about 54% of the
dose was accounted for as identified metabolites (Dacre, 1961).
Rats were given doses of 100 µg of BHT labelled with 3H
intraperitoneally and the urinary output of radioactivity was measured
for four consecutive days. Four days after the injection 34.5% of the
injected radioactivity was recovered in urine (Ladomery et al., 1963).
The same dose of BHT (100 µg) labelled with 14C was given to
rats and 34% of the radioactivity was excreted in the urine in the
first four days, in close agreement with the previous result using
tritiated BHT (Ladomery et al., 1967a).
The liver and body fat of rats fed a diet containing 0.5% BHT
for 35 days were analysed. The concentration of BHT in the liver never
rose above 5 ppm (0.0005%) in males or 1.5 ppm (0.00015%) in females.
In the body fat the level fluctuated round 30 ppm (0.003%) in males
and 45 ppm (0.0045%) in females. Fat from rats returned to normal diet
showed a progressive fall in the concentration of BHT the half-life
being about seven to 10 days. The daily excretion of radioactivity
in urine and faeces was studied in rats given an oral dose of
14C-labelled BHT (12 mg/kg bw). Excretion became negligible by the
sixth day after administration when about 70% of the injected dose had
been recovered. Less than 1% was excreted as carbon dioxide in the
expired air. About 50% of the radioactivity was excreted in the bile
during the 24-hour period following the oral dose (Daniel & Gage,
1965).
In further work with rats it was found that increased output of
urinary ascorbic acid paralleled liver enlargement induced by BHA or
BHT in onset, degree and duration, being rapid but transient with BHA
and slower in onset but more prolonged with BHT (Gaunt et al., 1965a).
The parallelism between stimulation of processing enzyme activity,
increase in urinary ascorbic acid output, and increase in relative
liver weight brought about by BHT was unaffected by 14 days of dietary
restriction, and all these changes except liver weight were reversible
during 14 days' recovery on normal diet (Gaunt et al., 1965b).
Effects on enzymes and other biochemical parameters
Rats given BHT by daily intubation showed increased activity of
some liver microsomal enzymes. Stimulation of enzyme activity
correlated with an increase in relative liver weight, the threshold
dose for these changes in enzyme activity in female rats being below
25-75 mg BHT/kg bw/day. The storage of BHT in fat appeared to be
influenced by the activity of the processing enzymes. In rats given
500 mg/kg bw daily the level of BHT in fat attained values of 230 ppm
(0.023%) in females and 162 ppm (0.0162%) in males by the second day,
by which time the relative liver weight and processing enzyme
activities had become elevated. Thereafter, liver weight and enzyme
activity continued to rise but the BHT content of fat fell to a
plateau of about 100 ppm (0.01%) in both sexes (Gilbert & Golberg,
1965).
Metabolism
After a single parental dose (100 µg) of -14C BHT, rats excreted
32-35% of the radioactivity in the urine, and 35-37% in the faeces, in
a four day period. The intestinal contents together with the gut wall
contained most of the remaining activity. Biliary excretion was rapid,
and the radioactive material in bile was readily absorbed from the
gut, suggesting a rapid enterohepatic circulation (Ladomery et al.,
1967a). Examination of the biliary metabolites from i.v. and i.p.
doses of small amounts of 14C-BHT, showed the presence of four
principal metabolites. 34 to 53% of the 14C-labelled in the bile was
identified as 3-5-di-t-butyl-4-hydroxy-benzoic acid, which was
probably present as the ester glucuronide. The other metabolites
present were 3,5-di-t-butyl-4-hydroxybenzaldehyde, 3-5-di-t-butyl-4-
hydroxybenzyl alcohol, and 1,2-bis (3,5-di-t-butyl-4-hydroxyphenyl)
ethane (Ladomery et al., 1967b).
Rats were dosed with a single dose of 14C-BHT, and urine and
bile collected for periods ranging from 48 to 96 hours. Faeces were
also collected during this same period. 19 to 58.5% of the
radioactivity appeared in the urine during this period, and 25.7 to
36% in the bile. The major metabolites in the urine were 3,5-di-tert-
butyl-4-hydroxybenzoic acid, both free (9% of the dose), as well as
glucuronide (15%) and S-(3,5-di-tert-butyl-4-hydroxybenzyl)-N-
acetylcysteine. The ester glucuronide and mercaptic acid were also the
major metabolites in rat bile. Free 3,5-di-tert-butyl-4-hydroxybenzoic
acid was the major metabolite in faeces (Daniel et al., 1968).
TOXICOLOGICAL STUDIES
Special studies on liver metabolism
Rats fed stock diets supplemented with 20% lard, and containing
0.2, 0.3, 0.4 or 0.5% (dry weight) BHT for six weeks, showed an
increase in serum cholesterol that was directly related to the level
of dietary BHT. BHT increased the relative weight of the male adrenal
and also caused a significantly greater decrease in growth rate of
male as compared to the female. Increased liver weight in test animals
was paralleled by increased absolute lipid content of the liver
(Johnson & Hewgill, 1961). In another study, rats maintained on diets
containing 0.5% dietary BHT in the presence or absence of a 20% lard
supplement, irrespective of the presence or absence of dietary lard,
BHT increased the basic metabolic rate, the concentration of body
cholesterol and the rate of synthesis of body and liver cholesterol,
and reduced the total fatty acid content of the body. In the animals
fed BHT without lard, BHT increased the rate of synthesis and turnover
of body and liver fatty acids and reduced the growth rate. In the
animals fed BHT with lard, BHT reduced the rate of synthesis of body
and liver fatty acids and reduced the growth rate to a greater extent
than in animals without dietary lard (Johnson & Holdsworth, 1968).
Microsomal preparations from livers of rats, dosed daily with BHT
for up to seven days at a level of 450 mg/kg bw showed an increased
capacity to incorporate labelled amino acids, when compared to
preparations from controls. BHT also stimulated the in vivo
incorporation of amino acids, mainly into the proteins of the
endoplasmic reticulum (Nievel, 1969). Rats fed diets containing BHT at
levels of 0.01 to 0.5% for 12 days, showed liver enlargement, as well
as increased activity of liver microsomal biphenyl-4-hydroxylase, at
all levels except the lowest level of 0.01%. Enzyme activity was not
significantly altered by 0.5% BHT fed for one day (Creaven et al.,
1966).
Special studies on the protective effect in vivo
Groups each of 60 FAF, male mice were maintained on semi-
synthetic diets containing 0, 0.25 or 0.5% BHT. The mean life-span of
the test animals was significantly greater than controls, being
17.0±5.0 and 20.9±4.7 months respectively for the 0.25% or 0.5% BHT,
as compared to 14.5±4.6 months for controls (Harman, 1968). Groups
each of 20 male and 20 female Charles River rats were maintained
on test diets (males 24 weeks, females 36 weeks) containing BHT
and/or carcinogen. (N-2-fluorenylacetamide or N-hydroxy-N-2-
fluorenylacetamide) in the molar ratio of 30:1, equivalent to 6600 ppm
(0.66%) BHT, then continued on control diets for another 12 weeks. The
N-2-fluorenylacetamide alone resulted in hepatomas in 70% of the
male rats, mammary adenocarcinoma in 20% of the females. With
N-hydroxy-N-2-fluorenylacetamide 60% of the males had hepatomas and
70% of the females had mammary adenocarcinoma. BHT reduced the
incidence of hepatomas in males to 20% when the carcinogen was
N-2-fluorenylacetamide, and to 15% (hepatomas in males), when
N-hydroxyl-N-2-fluorenylacetamide was the test compound. Similar
results were obtained with Fischer strain rats. Liver and oesophageal-
tumour production with diethylnitrosamines (55 ppm (0.0055%)) in
drinking water for 24 weeks was not affected by BHT (Ulland et al.,
1973).
Special studies on reproduction
Weanling rats (16 of each sex) were fed a diet containing 20%
lard and 0, 300, 1000 or 3000 ppm (0, 0.03, 0.1 or 0.3%) BHT and mated
at 100 days of age (79 days on test). Ten days after weaning of the
first litter the animals were again mated to produce a second litter.
The offspring (16 females and eight males) were mated at 100 days of
age. Numerous function and clinical tests including serum cholesterols
and lipids were performed on the parents and the first filial
generation up to 28 weeks and gross and microscopical examination at
42 weeks. At the 3000 ppm (0.3%) dietary level a 10-20% reduction in
growth rate of parents and offspring was observed. A 20% elevation of
serum cholesterol levels was observed after 28 weeks, but no
cholesterol elevation after 10 weeks. A 10-20% increase in relative
liver weight was also observed upon killing after 42 weeks on diet.
All other observations at 3000 ppm (0.3%) and all observations at
1000 ppm (0.1%) and 300 ppm (0.03%) were comparable with control. All
criteria of reproduction were normal. No teratogenic effects were
detected (Frawley et al., 1965b). Similar results to those obtained
with the parental and first filial generations were also obtained with
the second filial generation. Examination of two litters obtained from
the latter at 100 days of age revealed no effects except a reduction
of mean body weight at the 3000 ppm (0.3%) level. The offspring were
examined for: litter size, mean body weight, occurrence of stillbirth,
survival rate and gross and microscopic pathology (Frawley, 1967).
Special studies on embryotoxicity
In a study on the embryotoxicity of BHT three dosing schedules
were employed: single doses (1000 mg/kg bw) on a specific day of
gestation, repeated daily doses (750 mg/kg bw) from the time of mating
throughout pregnancy and daily doses (250-500 mg/kg bw for mice and
500 and 700 mg/kg bw for rats) during a seven to 10 week period before
mating, continuing through mating and gestation up to the time the
animals were killed. No significant embryotoxic effects were observed
on examination of the skeletal and soft tissues of the fully developed
fetuses as well as by other criteria. Reproduction and postnatal
development were also unaffected (Clegg, 1965).
Diets containing 0.1 or 0.5% BHT together with two dietary
levels of lard (10 and 20%) were given to mice. The 0.5% level of BHT
produced slight but significant reduction in mean pup weight and total
litter weight at 12 days of age. The 0.1% level of BHT had no such
effect. Out of 7754 mice born, none showed anophthalmia, although 12
out of the 144 mothers were selected from an established anophthalmic
strain (Johnson, 1965).
Acute toxicity
Approximate
LD50 lethal dose
Animal Route (mg/kg bw) (mg/kg bw) Reference
Rat oral 1 700-1 970 - Deichmann et al.,
1955
Cat oral - 940-2 100 Deichmann et al.,
1955
Rabbit oral - 2 100-3 200 Deichmann et al.,
1955
Guinea-pig oral - 10 700 Deichmann et al.,
1955
Rat oral 2 450 Karplyuk, 1959
Mouse oral 2 000 Karplyuk, 1959
Short-term studies
Mouse
BHT was given to pregnant mice in daily doses of 750 mg/kg bw for
18 days. Another group received the same dose for a total of 50 to 64
days including 18 days of pregnancy. No fetal abnormalities were
observed (Clegg, 1965).
In a statistically planned experiment using 144 female mice no
blindness was observed in any of the 1162 litters representing 7765
babies born throughout the reproductive life span of the mothers
(Johnson, 1964).
Rat
Feeding experiments were carried out on 45 pairs of weanling male
rats for five to eight weeks with diets containing 0, 10 and 20% lard
supplements to which 0.001, 0.1 or 0.5% BHT had been added. 0.001%
caused no changes in any of the serum constituents studied. 0.5%
produced increase in the serum cholesterol level within five weeks.
Female rats fed for eight months on a diet containing a 10% lard
supplement with 0.1% BHT showed increased serum cholesterol levels,
but no other significant changes. 0.5% BHT in 10% and 20% lard
supplements fed to female rats for the same period increased serum
cholesterol, phospholipid and mucoprotein levels (Day et al., 1959).
0.3% BHT in the diet of pregnant rats that had been kept for five
weeks on a diet deficient in vitamin E produced no toxic symptoms.
1.55% caused drastic loss of weight and fetal death (Ames et al.,
1956).
BHT fed to rats in groups of 12 for a period of seven weeks at a
dietary level of 0.1% in conjunction with a 20% lard supplement
significantly reduced the initial growth rate and mature weight of
male rats. No effect was noted in female or male rats with a 10% lard
supplement. A paired feeding experiment showed that this inhibition of
growth was a direct toxic effect of BHT and could not be explained by
a reduction in the palatability of the diet. At this level BHT
produced a significant increase in the weight of the liver, both
absolute and relative to body weight. Rats under increased stress
showed significant loss of hair from the top of the head. The toxic
effect of BHT was greater if the fat load in the diet was increased.
Anophthalmia occurred in 10% of the litters (Brown et al., 1959).
Groups of six weanling rats (three male and three female) were
fed BHT at dietary levels of 0, 0.1, 0.2, 0.3, 0.4 and 0.5% in
conjunction with a 20% lard supplement for six weeks. BHT reduced the
growth rate, especially in the males, the effect appearing to become
significant at the 0.3% level. It also increased the absolute liver
weight and the ratio of liver weight to body weight in both sexes, the
latter effect appearing to become significant at the 0.2% level. BHT
increased the ratio of left adrenal weight to body weight in male rats
but had no consistent effect in females. There were no histological
changes attributable to the treatment in the adrenal. All dietary
levels of BHT increased the serum cholesterol and the concentration of
the cholesterol was directly proportional to the BHT level. There was
also a significant increase in the concentration of adrenal
cholesterol. BHT produced no significant changes in the concentration
of total or percent esterified liver cholesterol, total liver lipid or
concentration of total polyunsaturated fatty acids in the liver
(Johnson & Hewgill, 1961).
BHT administered to rats at 250 mg/kg bw for 68 to 82 days caused
reduction in rate of increase in weight and fatty infiltration of the
liver (Karplyuk, 1959).
Feeding experiments conducted for 20 and 90 days respectively
indicated that rats do not find food containing 0.5 or 1% BHT
palatable. However, the animals ingest foods so treated more readily
if these concentrations are attained gradually. Paired feeding
experiments with groups of five or 10 rats for 25 days demonstrated
that diets containing 0.8 and 1% BHT will reduce the daily intake of
food below control values. A level of 1% in the diet retarded weight
gain (Deichmann, 1955).
BHT (2000 ppm (0.2%)) incorporated in a diet containing 19.9%
casein was administered to a group of eight young rats for eight
weeks; a further group of eight rats served as controls. The
experiment was repeated with 16.6% casein in the diet of further
groups for four weeks and again with 9.6% casein (and no added
choline) for seven weeks. In all three instances BHT caused
stimulation of growth and improved protein efficiency. The N content
of the liver was, however, greatly reduced in BHT-treated animals,
except when the level of BHT was reduced to 200 ppm (0.02%). Recovery
of hepatic protein after fasting (details not given) was also impaired
in rats on 2000 ppm (0.2%) BHT. Liver lipid content was increased with
2000 ppm (0.2%) but not with 200 ppm (0.02%) BHT. A dietary level of
2000 ppm (0.2%) BHT also increased the adrenal weight and ascorbic
acid content, although if recalculated on the basis of weight of
gland, there was no significant difference. The increase in adrenal
ascorbic acid is interpreted as indicating a stress imposed on the
organism by BHT (Sporn & Schöbesch, 1961).
Groups of 48 weanling rats (24 of each sex) were given diets
containing 1000 ppm (0.1%) BHT for periods of up to 16 weeks. A group
of 48 rats served as controls. Measurements of growth rate, food
consumption, weight and micropathological examination of organs at
autopsy revealed no difference from untreated rats. However, increase
in relative liver weight and in the weight of the adrenals was
produced without histopathological evidence of damage. Biochemical
measurements and histochemical assessments of liver glucose
phosphatase and glucose 6-phosphate dehydrogenase activities revealed
no difference from the control group (Gaunt et al., 1965a).
Rats were given single doses of 100 mg BHT/kg bw daily for seven
weeks before mating and then throughout pregnancy or were autopsied on
the 20th day of pregnancy. No evidence of fetal abnormality was found
in any of these animals but abnormalities did occur in the progeny of
positive control groups treated with vitamin A (British Industrial
Biological Research Association, 1964).
A three-generation reproduction study was started by another
group in May 1964. They also fed groups of 16 male and 16 female rats
on levels of 0.03, 0.1 and 0.3% BHT in a diet containing 20% fat for
10 weeks. There were two control groups each containing 16 male and 16
female animals. No definite effect on body weight was observed at any
level in the females and there was only a slight depression in the
males at the 0.3% level. There was no significant effect on blood
cholesterol level in either sex after feeding BHT at any of the levels
for 10 weeks. Four of the males at the 0.3% and two at the 0.1% level
died during the experiment. Two deaths occurred among the females at
0.3%. Only one male rat died in both control groups (Frawley et al.,
1965a).
Groups of 20 male and 20 female rats fed 1% BHT in the diet for
10 weeks showed recovery both in liver to body weight ratios and in
morphological appearance of the liver cells within a few weeks after
restoring the animals to a normal diet (ICI, 1964).
Rabbit
Acute effects on electrolyte excretion similar to those described
for large doses of BHA were also obtained following administration of
doses of BHT of 500-700 mg/kg bw (about 2% in the diet). No such
effects were observed at lower dosage levels (Denz & Llaurado, 1957).
Dog
A mild to moderately severe degree of diarrhoea was induced in a
group of four dogs fed doses of 1.4-4.7 g/kg bw every two to four days
over a period of four weeks. Post-mortem examination revealed no
significant gross pathological changes. No signs of intoxication and
no gross or histopathological changes were observed in dogs fed doses
of 0.17-0.94 g/kg bw five days a week for a period of 12 months
(Deichmann et al., 1955).
Fowl
When BHT was fed at a level of 0.125% for 34 weeks to a group of
10 pullets, no differences in fertility, hatchability of eggs or
health Of chicks in comparison with a similar control group were
found. The eggs of the antioxidant-treated birds contained more
carotenoids and vitamin A than those of the controls (Shollenberger et
al., 1957).
Long-term studies
Rat
Groups of 15 male and 15 female rats given diets containing 1%
lard and 0.2, 0.5 or 0.8% BHT for 24 months showed no specific signs
of intoxication, and micropathological studies were negative. For one
group given a diet containing 0.5% BHT, the BHT was dissolved in lard
and then heated for 30 minutes at 150°C before incorporation in the
diet. There were no effects on weight gain or blood constituents and
micropathological studies of the main organs were negative. The
feeding of 1% BHT was followed in both male and female rats by a
subnormal weight gain and by an increase in the weight of the brain
and liver and some other organs in relation to body weight.
Micropathological studies were negative in this group also. BHT in
these concentrations had no specific effect on the number of
erythrocytes and leucocytes, or on the concentration of haemoglobin in
the peripheral blood. A number of rats of both sexes died during this
experiment, but as the fatalities were in no relation to the
concentration of BHT fed, it was believed that the cause of death was
unrelated to the feeding of this substance. Micropathological studies
support this observation (Deichmann et al., 1955).
When fed at the 0.5% level in the diet, BHT had no effect in rats
on the reproductive cycle, the histology of the spleen, kidney, liver
and skin, or on the weight of the heart, spleen or kidney. There was
no significant increase in mortality of rats fed on a diet containing
0.1% BHT and 10% hydrogenated coconut oil for a period of two years.
The effects on weight gain have already been described.
OBSERVATIONS IN MAN
Four human male subjects were administered a single dose of
approximately 40 mg 14C-labelled BHT. About 75% of the administered
radioactivity was excreted in the urine. About 50% of the dose
appeared in the urine in the first 24 hours, followed by a slower
phase which probably represents the release of the compounds or their
metabolites stored in tissues (Daniel et al., 1967). In man, the bulk
of the radioactivity is excreted as the ether insoluble glucuronide of
a metabolite in which the ring methyl group and one tertbutyl methyl
group are oxidized to carboxyl groups, and a methyl group on the other
tert-butyl group is also oxidized, probably to an aldehyde group.
BHT-acid free and conjugated is a minor component of the urine and the
mercapturic acid is virtually absent. The rapidity of the first phase
of the urinary excretion in man suggests that there is no considerable
enterohepatic circulation as has been observed in the rat (Daniel et
al., 1967).
Reported values of BHT in the body fat were 0.23 ± 0.15 ppm
(0.000023% ± 0.000015%) (11 individuals, residents of the United
Kingdom) and 1.30 ± 0.82 ppm (0.000130 ± 0.000082) (12 individuals,
residents of the United States of America (Collings & Sharratt, 1970).
Comments:
Metabolic studies indicate that the prolonger enterohepatic
circulation of BHT metabolites observed in the rat, does not operate
in man. This is directly related to the observed differences in
metabolism between rat and man. No extensive tissue accumulation would
be expected, because of the rapid urinary excretion of BHT metabolites
in man and is supported by the data on BHT residues in human fat.
The effect of BHT on lipid metabolism in the rat is difficult to
interpret. Long-term studies in the rat are adequate but are of
limited significance for extrapolation to man. BHT has been shown to
increase the longevity of mice. BHT is a weak inducer of hepatic
microsomal enzyme systems. Reproduction studies in mice and rats have
failed to confirm earlier observations of anophthalmia.
EVALUATION
Level causing no toxicological effect
Mouse: 5000 ppm (0.5%) in the diet equivalent to 250 mg/kg bw.
Estimate of acceptable daily intake for man
0-0.5* mg/kg bw**
FURTHER WORK OR INFORMATION
Required by 1976.
Studies on the effect on reproduction of mixtures of BHT, BHA and
propyl gallate.
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* As BHA, BHT or the sum of both.
** Temporary.
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See Also:
Toxicological Abbreviations
Butylated hydroxytoluene (ICSC)
Butylated hydroxytoluene (FAO Nutrition Meetings Report Series 38a)
Butylated hydroxytoluene (FAO Nutrition Meetings Report Series 40abc)
Butylated hydroxytoluene (WHO Food Additives Series 10)
Butylated hydroxytoluene (WHO Food Additives Series 21)
Butylated hydroxytoluene (WHO Food Additives Series 35)
BUTYLATED HYDROXYTOLUENE (JECFA Evaluation)