TOXICOLOGICAL EVALUATION OF CERTAIN FOOD ADDITIVES WHO FOOD ADDITIVES SERIES 10 The evaluations contained in this document were prepared by the Joint FAO/WHO Expert Committee on Food Additives* Rome, 21-29 April 1976 Food and Agriculture Organization of the United Nations World Health Organization *Twentieth Report of the Joint FAO/WHO Expert Committee on Food Additives, Geneva, 1976, WHO Technical Report Series No. 599, FAO Food and Nutrition Series No. 1. BUTYLATED HYDROXYANISOLE Explanation Butylated hydroxyanisole was evaluated for acceptable daily intake for man by the Joint FAO/WHO Expert Committee on Food Additives in 1961 and 1973 (see Annex 1, Ref. No. 6, p. 41; No. 33, p. 148). Since the previous evaluation, additional data have become available and are summarized and discussed in the following monograph. The previously published monograph has been expanded and is reproduced in its entirety below. BIOLOGICAL DATA BIOCHEMICAL ASPECTS Absorption, distribution and excretion Butylated hydroxyanisole (BHT) was absorbed from the gastrointestinal tract, and there was some evidence that the feeding of amounts 100-500 times the levels generally permitted in fats for human consumption (in the United States of America 200 mg/kg fat) caused deposition in depot fat, the stability of which was thereby increased (Johnson et al., 1958). However, there was no evidence of cumulation in other tissues (Astill et al., 1960; Bunnell et al., 1955; Hodge et al., 1964). In the rabbit, BHA was conjugated mainly with glucuronic acid or sulfuric acid (Dacre et al., 1956); a small amount of unchanged BHA was excreted in the urine. In rats the 2-tert-butyl isomer was chiefly excreted as glucuronide, while the 3-tert-butyl isomer was excreted mainly as ethereal sulfate (Astill et al., 1960). Thus, these animals effectively detoxicated BHA. The changes described occurred in the liver. No evidence has been found to suggest that BHA produces any adverse biochemical or metabolic effect in the animal body (Dacre, 1960). Dogs excreted 60% of a 350 mg/kg dose unchanged in the faeces within three days. The remainder was excreted in the urine mainly as sulfate conjugates of BHA, tert-butyl-hydroquinone and an unidentified phenol. Only 5.5% of the dose was excreted in urine as the glucuronide (Astill et al., 1962). Rats were injected intra-peritoneally with a single dose of tritium-labelled BHA. Approximately 90% of the radioactivity was recovered in the urine within four days (Golder et al., 1962). Pigs fed 0.1% BHA in the diet for four months, and pullets fed 0.1% BHA in the diet for eight weeks, showed no accumulation in muscle, liver, kidney or the reserve fat (Francois & Pihet, 1960). Effects on enzymes and other biochemical parameters Rats administered 500 mg/kg bw (seven daily doses) of BHA, showed no change in liver glucose-6-phosphatase activity. BHA at dose levels of 100 mg/kg or more (seven daily doses) caused increase in liver weight of male rats, but in females only at doses greater than 200 mg/kg bw (seven daily doses). Liver weight was comparable to control within 14 days of withdrawal of BHA from the diet. No fatty changes were observed (Feuer et al., 1965a), Rats administered BHA (500 mg/kg/day) for two days showed no increased activity of microsomal processing enzymes (aminopyrine demethylase) hexabarbitine oxidase and nitro-anisol demethylase (Gilbert & Golberg, 1965). In another study, rats fed 0.1, 0.25 or 0.5% BHA in the diet for 12 days, showed no increased liver weight, but there was an increase in liver biphenyl-4-hydroxylase activity in the 0.5% group (Creaven et al., 1966). Groups each of eight rats (SPF Carworth strain) equally divided by sex were administered by intubation daily for one week, BHA dissolved in arachis oil, at a dose level equivalent to 0, 50, 100, 200, or 500 mg/kg body weight. BHA had no effect on the growth of the animals. Twenty-four hours after administration of the final dose the animals were sacrificed and liver preparations assayed for glucose-6-phosphatase, glucose-6-phosphate dehydrogenase, hexabarbitone oxidase, nitro-anisol demethylase and aminopyrine demethylase activities. BHA had no effect on these enzyme activities. Histochemical studies showed that BHA caused no fatty changes in liver (Feuer et al., 1965b). Groups each of two to three rhesus monkeys (macaca mulatta) one month old infant or sexually immature juvenile, of both sexes, were administered BHA at a dose level of 500 mg/kg body weight for four weeks. Another group of juveniles received 50 mg BHA/kg body weight for the same period. Controls received equivalent amounts of corn oil. Urine and blood analyses were normal with the exception of serum cholesterol which was elevated at the high dose at week 3 of the study, but which returned to normal at week 4. The livers of all test animals were enlarged. No other organ showed any pathological change. Ultrastructurally, infant and juvenile monkeys treated at the high dose level showed pronounced proliferation of the hepatic smooth endoplasmic reticulum. Infants and juveniles treated with BHA (500 mg/kg) had lower levels of liver lipids than corn oil controls. Nitro-anisol demethylase activity was increased and glucose-6- phosphatase activity was decreased in BHA treated juveniles but unaffected in infant monkeys (Allen & Engblom, 1972). No changes were observed in DNA, RNA and cytochrome P450 levels. Additional biochemical tests were carried out on the liver and plasma of these monkeys. BHA treated animals showed higher plasma triglyceride levels than controls. There was a significant decrease in the level of liver cholesterol, as well as a lowering of the cholesterol/lipid-phosphorus ratio of the liver, in the test animals. Liver succinic dehydrogenase was also lowered in BHT treated animals (Branen et al., 1973). Hepatic microsomal preparations were made from female mice (A/HcJ strain) fed a diet of 0 and 0.5% BHA for 14 days. The aryl hydrocarbon hydroxylase activity (AHH) of the preparations was similar. However, microsomal preparations from the BHA fed mice showed greater sensitivity to in vitro inhibition of AHH activity by alpha- naphthafluorine, and continued increased amounts of cytochrome P450 per unit weight, than preparations from control mice (Speier & Wattenberg, 1975). Rats were maintained on a diet supplemented with 20% lard, and containing 0, 0.1, 0.2, 0.3, 0.4, 0.5% BHA, for a period of six weeks. BHA caused an increase in the total serum cholesterol at the 0.1% level, but no further elevations occurred at higher doses. There was a relatively greater increase in the amount of serum-free cholesterol than of ester-cholesterol. BHA produced enlarged adrenals in males at all levels, but no histological changes were observed. Increased liver weight at the higher dietary BHA levels was accompanied by an increase in the absolute lipid content of the liver. However, BHA had no effect on the concentration in liver of total and esterified cholesterol, or the composition of the polyunsaturated fatty acids (Johnson & Hewgill, 1961). TOXICOLOGICAL STUDIES Special studies on carcinogenicity Groups each of 100 mice (equally divided by sex) were given single s.c. injections (10 mg/mouse) of BHA in trioctanoin and observed for up to 575 days. Another group was given weekly skin applications of 0.1 mg or 10 mg of BHA in acetone, for a period of 309-459 days. Microscopic examination of the skin from the test mice showed no evidence of tumours (Hodge et al., 1966). BHA in lanolin applied to the ears of guinea-pigs once daily for periods of two to six weeks, resulted in a microinvasion of basal cell pseudopods with destruction of the superficial connective tissue and fragmentation of the collagen. BHA alone did not cause these changes (Riley & Seal, 1968). Special studies on mutagenicity (a) Cytogenetics Butylated hydroxyanisole (BHA) was investigated at concentrations of 2.0, 20.0 and 200 µg/ml, in vitro, employing WI-38 human embryonic lung cells for anaphase abnormalities. It was also investigated in vivo by the cytogenetic analysis of metaphase cells from rat bone marrow at dosages of 15, 150 and 1500 mg/kg. BHA did not produce any significant increases in abnormalities above the control values in either assay (Fabrizio, 1974). (b) Host-mediated assay In vitro-Salmonella TA-1530, and G-46, together with Saccharomyces D-3 were employed. A 10% concentration was tested. BHA was non-mutagenic for Salmonella TA-1530 and G-46. Tests with Saccharomyces D-3 demonstrated a biologically significant increase in the frequency of recombinants. This result could not be repeated upon subsequent testing and was therefore thought to be spurious (Fabrizio, 1974). In vivo-BHA was tested at 15, 150 and 1500 mg/kg in ICR Swiss mice employing as indicator organisms Salmonella G-46, and TA-1530, and Saccharomyces D-3. BHA was non-mutagenic for Salmonella but demonstrated a biologically significant increase in the frequency of recombinants. In as much as the host-mediated assay is no longer recommended for routine use, this suggested mutagenic effect was investigated using more sensitive (in terms of detection) procedures. In this study BHA was investigated employing Salmonella typhimurium strains TA-1535, TA-1537 and TA-1538, and Saccharomyces D-4 with and without metabolic activations, in plate and suspension tests. The percent concentrations (w/v) employed were .00375, .0075, .0150 for Salmonella and 0625, 1250 and 02500 for Saccharomyces. Under the conditions of this investigation BHA was non-mutagenic (Fabrizio, 1974). (c) Dominant lethal test Sprague-Dawley C-D strain male rats were used. Dosages of 15, 150 and 1500 mg/kg were employed. Acute study - a single dose was administered with subsequent mating for each of eight weeks. BHA produced random statistical increases in dominant lethality. These were discounted due to the unusually low negative control values (Fabrizio, 1974). Subacute - five daily doses were administered (5 × 15, 5 × 150 and 5 × 1500 mg/kg) and males subsequently mated for each of seven weeks. BHA produced a statistically significant increase in pre-implantation loss in weeks 6 and 7. This effect occurring alone is not demonstrative of mutagenicity (Fabrizio, 1974). Special studies on teratogenicity Groups of rats or mice of various strains were given BHA in accordance with one of three different regimes, viz., daily administration for seven weeks, before pairing continuing until day 18 of pregnancy or daily administration on days 1-20 of pregnancy or single administration on day 9, 11 or 13 of pregnancy. Dosage ranged from 250 to 1000 mg/kg bw. No teratogenic effects were observed at dose levels as high as 300-500 mg/kg bw administered for as long as seven weeks, although under these conditions the mortality was 25%. At a higher dose level (750 mg/kg) mortality was 75% (Clegg, 1965). Pregnant rats receiving a total dose of 0.5 g of BHA in the diet showed less resorptions than rats on control diets (Telford et al., 1962). Other special studies BHA at concentrations as low as 8 × 10-10 mole/litre can inhibit the guinea-pig's smooth muscle contraction caused by bradykinin (Posati & Pallanich, 1970). Groups of mated pairs of Swiss-Webster mice (Mus musulus) were maintained on diets containing 0, or 0.5% BHA. The litters obtained from the mated pairs were weaned at 21 days and then maintained on a diet similar to that of their mother. At six weeks of age the mice were subjected to behavioural tests. The BHA treated offsprings showed increased exploration, decreased sleeping, decreased self-grooming, slower learning and a decreased orientation complex than did the control group (Stokes & Scudder, 1974). Using an in situ method of perfusion for rat intestine, BHA at a level of 2 mg/ml has been shown to reduce the absorption of glucose and methionine, but not butyric acid (Fritsch et al, 1975a). BHA at levels of 400 µg/ml caused an inhibition of the metabolism (as measured by gas evolution) of culture of bacteria isolated from the cecal flora of rats (Fritsch et al, 1975b). Acute toxicity LD50 Animal Route (mg/kg bw) References Mouse oral 2 000 Bunnell et al., 1955; Lehman et al., 1951 Rat oral 2 200-5 000 Bunnell et al., 1955; Lehman et al., 1951 Short-term studies Rat No effect on potassium excretion, as described below for the rabbit was observed in a short-term feeding study in the rat (Dacre, 1960). Groups of seven recently weaned rats were fed for six months on rations containing 0, 0.5, 1, 2 and 3% of BHA. The rats at the 3% level did not eat enough to gain weight and were put on to the 2% diet for a time, then returned to 3%. Even at the 2% level, food consumption was not optimal. Histopathological examination revealed no pathological condition attributable to BHA (Wilder & Kraybill, 1948). Combinations of BHA with other food additives, such as chlorine dioxide, sodium propionate, propyl gallate, or polyoxyethylene-8- stearate, at 50 times the normal levels of use in bread, had no deleterious effects when they were fed in bread to groups of 26 rats for a period of 32 weeks. The treated bread formed 75% of the animals' diet. The daily dosage levels of BHA were from 3.3 to 7.0 mg/kg bw (Graham et al., 1954; Graham & Grice, 1955). Rats were maintained on test diets containing 0, or the equivalent of 500-600 mg/kg bw BHA (1/5 of the LD50), for a period of 10 weeks. The test animals showed decreased growth rate, and reduced activity of the blood enzymes, catalase, peroxidase and cholinesterase. Chemical analysis of livers of test animals showed a decrease in the amount of phospholipid as compared to controls, but there was no lipid accumulation. Histological examination of the tissues and organs did not show any compound-related effects (Karplyuk, 1962). Rabbit In rabbits, a dose of 1 g given daily for five to six days by stomach tube caused a ten-fold increase in sodium excretion and a 20% increase in potassium excretion in the urine. Extracellular fluid volume fell, and this prevented any marked change in the plasma sodium level. The serum potassium fell after five days' treatment and potassium was being replaced by sodium in muscle cells. In heart muscle the changes occurred later than in skeletal muscle and were less marked. The antioxidant may have a direct effect on the kidney; the adrenal cortex showed changes in the zona glomerulosa and there was increased excretion of aldosterone in the urine, associated with the sodium and potassium loss (Denz & Llaurado, 1957). Dog When BHA was fed to dogs at dose levels of 0, 0.3, 30 and 100 mg/kg bw for one year, no ill-effects were observed. Renal function, haematology and histopathology of the main tissues were normal. Organ weights were within normal limits and there was no demonstrable storage of BHA. The urine did not contain a demonstrable increase of reducing substances, even when 100 mg/kg bw of BHA was fed. Groups of three dogs were used at each dose level for these experiments (Hodge et al., 1964). Groups each of four weanling dogs were fed BHA at 0, 5, 50 and 250 mg/kg for 15 months. General health and weight gains of the dogs were within normal range, as were haematologic parameters. Urine from test dogs contained higher ratios of total to inorganic sulfate, and glucuronates than controls. At autopsy, microscopic examination of tissues and organs showed that three/four of the animals at the highest dose level tested had a liver cell degeneration and a diffuse granulocytic infiltration. The lobular structure of the livers of these animals was normal, and there was no excessive connective tissue proliferation (Wilder et al., 1960). Monkeys A group of six adult female rhesus monkeys were maintained on a test diet containing a mixture of BHT and BHA that provide an intake equivalent to 50 mg BHT and 50 mg BHA/kg body weight. Another group of six adult female rhesus monkeys were used as controls. The monkeys were fed the diet for one year prior to breeding and then for an additional year, including a 165 day gestation period. Haematologic studies including haemoglobin, haematocrit, total as well as differential white blood cell count, cholesterol, Na+, K+, total protein, serum glutamic pyruvic transaminase, and serum glutamic oxylacetic transaminase, were carried out at monthly intervals. Body weights were taken at monthly intervals. Records of menstrual cycles were maintained through the test period. After one year the females were bred to rhesus males not receiving test diets. During pregnancy complete blood counts were done on days 40, 80, 120 and 160 of gestation and on days 30 and 60 post- partum. A total of five infants were born to the experiment monkeys and six to the control monkeys. Haematological evaluations were made on infants of the test and control monkeys at days 1, 5, 15, 30 and 60, and observations of the infants were continued through two years of age. Two experimental and two control infants, three months of age, were, removed from their mothers for one month of psychological home cage observations. No clinical abnormalities were observed in parent and offspring during the period of study. The gestation of test animals was free of complications and normal infants were delivered. Adult females continued to have normal infants. Infants born during the exposure period remained healthy, with the exception of one infant that died from unrelated causes. Home cage observations at the third month of life did not reveal any behavioural abnormalities (Allen, 1974). Long-term studies Rat Groups of 15 or more newly weaned rats were placed on diets containing 0, 0.05, 0.5 and 1% BHA in lard (0, 0.003, 0.03 and 0.06% of the total diet) for 22 months. Weight gain was comparable in all groups. Reproduction was normal, and young rats kept on the same ration grew normally. Number, size, weight, weight gain and mortality of the litters were comparable for animals of all groups. After one year on test, the colony suffered from an infectious respiratory disease and many died. There was no significant difference in mortality among the groups. After 22 months, the remaining animals were killed; histopathological examination revealed no changes attributable to the antioxidant (Wilder & Kraybill, 1948). A similar series of tests was undertaken, with an additional group on a diet of 2% BHA in lard (0.12% of the total diet). There were 17 rats in each group. After 21 months, the survivors were killed. Histopathological examination revealed no significant differences compared with the control animals. The rate of gain in weight during the growing period was unchanged, and all rats appeared normal in every respect (Wilder & Kraybill, 1948). In another rat feeding test carried out over a period of two years on groups of 40 rats, there was a small reduction in the mature weight and an increase in relative liver weight in some cases with the highest level of BHA used (0.5% of the diet), but there were no effects on any of the following: the reproductive cycle; histology of the spleen, kidney, liver, or skin; ratio of weight of heart, spleen, or kidneys to total body weight:mortality. The toxicity of BHA was not affected by the dietary fat load (Brown et al., 1959). Rats were maintained on diets containing 0, and the equivalent of 500-600 mg/kg bw BHA (1/5 of the LD50) for a period of one year. During the course of this study, rats were bred to produce three successive generations. Two generations were maintained on the test diet for six months. BHA had no effect on reproductive performance, as measured by litter size, birth weight, date of appearance of incisors, and opening of eyes. Autopsy and histological examination of tissues and organs of parents and offsprings at the termination of the study did not reveal any compound-related effect (Karplyuk, 1962). OBSERVATIONS IN MAN Human volunteers were dosed with 0.5-0.7 mg/kg bw BHA. 22-77% was excreted in the urine as the glucoronide within 24 hours. Less than 1% was excreted in the urine as unchanged BHA, and no dealkylation or hydroxylation products were detected (Astill et al., 1962). In another study, human volunteers were administered a single dose of 14C-labelled BHA (approximately 0.5 mg/kg bw). 60-70% of the radioactivity was excreted in the urine within two days, and by day 11 post-dosing, 80-86.5% of the radioactivity was recovered in the urine (Daniel et al., 1967). Comments Several metabolic studies with orally administered BHA are available in rats, mice and monkeys. In the rat, at the levels tested, there appeared no change in the activity of the liver enzymes studied. In the case of mice, although there appeared no increase in aryl hydrocarbon hydroxylase, there was an increase in cytochrome P450 and the nature of the enzyme appears altered. With monkey, on the other hand, cytochrome P450 levels appeared unaffected whereas some enzyme activities were affected. In this regard, infant monkeys, as opposed to juveniles, did not show these changes. BHA appeared to lower liver cholesterol whereas plasma triglycerides were increased. Female monkeys maintained on a dietary intake of 50 mg/kg body weight for one year prior to breeding, and bred to untreated males, gave birth to normal offspring. BHA had no effect on any of the indices tested. These included haematology and clinical biochemistry as well as behavioural observations on the young. Mutagenic activity of BHA has been tested in several in vitro and in vivo systems. The collective assessment of these tests does not show BHA to be mutagenic. The previously stated requirement that studies on the effect on reproduction of mixtures of BHA, BHT and propyl gallate was considered to be no longer necessary. EVALUATION Level causing no toxicological effect Rat: 5000 ppm (0.5%) in the diet equivalent to 250 mg/kg bw. Estimate of acceptable daily intake for man 0-0.51 mg/kg bw.2 FURTHER WORK OR INFORMATION Required by 1980. A multigeneration reproduction study. REFERENCES Allen, J. R. (1976) Annual Report of the University of Wisconsin Food Research Institute 1974, pp. 308-315 Allen, J. R. & Engblom, J. F. (1972), Fd. Cosmet. Toxicol., 10, 769 Astill, B. D. et al. (1962) J. Ag. & Food Chem., 10, 315 Astill, B. D., Fassett, D. W. & Roudabush, R. L. (1960) Biochem. J., 75, 543 Branen, A. L. et al. (1973) Fd. Cosmet. Toxicol., 11, 797 Brown, W. D., Johnson, A. 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See Also: Toxicological Abbreviations Butylated hydroxyanisole (WHO Food Additives Series 5) Butylated hydroxyanisole (WHO Food Additives Series 21) Butylated hydroxyanisole (WHO Food Additives Series 24) BUTYLATED HYDROXYANISOLE (JECFA Evaluation)