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U.S. Department of Health and Human Services

Database of Select Committee on GRAS Substances (SCOGS) Reviews

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Butylated Hydroxyanisole (BHA)

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Report No.:  55
Type of Conclusion:  3
ID Code:  25013-16-5
Year:  1978
CFR Section:  182.3169
SCOGS Opinion:  The absorption and metabolism of BHA by several animal species and by man are well documented. Man excretes a minute quantity of BHA as the free phenol and an ethereal sulfate while the major portion is conjugated with glucoronic acid. In the rat, a larger percentage of administered doses is excreted as the free phenol and an ethereal sulfate. In rats, dogs, monkeys, and man, none of the metabolic products of BHA are antioxidants while in these species, metabolic products of BHT have antioxidant properties. The acute toxicity (LD 5 0) of BHA is about 2g per kg for mice, rats, and rabbits. The no-effect level for short-term effects in the rat has been estimated at 25mg per kg. If this value should be approximately applicable to man, it is 125 to 500 times the estimated daily intake of 0.05 to 0.2mg per kg. Doses of the order of 50 mg per kg or more when fed chronically to animals produced significant liver hypertrophy accompanied by proliferation of endoplasmic reticulum and a nonspecific stimilation of the synthesis of drug-metabolizing systems. Such effects disappeared on cessation of BHA intake but remained as long as the compound continued to be ingested. Two monkeys fed BHA at the 50mg per kg level had marginal proliferation of the endoplasmic reticulum and stimulation of mixed function oxidases. It was noteworthy that at both the 50mg and 500mg per kg level BHA had a more pronounced effect on liver weight in monkeys than BHT. It is not clear that liver hypertrophy per se is a manifestation of microsomal enzyme induction. Liver hypertrophy is a gross measure of enzyme induction, but its absence may not necessarily mean that enzyme induction is absent. In addition, the findings from studies with rats, monkeys, and man suggest that BHA metabolism may vary among animal species. Recent studies show that BHA action on enzyme systems in vitro occurs at very low concentrations. BHA can conceivably affect drug metabolizing enzymes in vivo which are the natural effectors of steroid hydroxylations and prostaglandin synthetases. In addition, there are reports that very low concentrations of BHA interfere with the action of bradykinin and prostaglandin synthesis. It would be desirable to determine whether BHA tissue levels resulting from chronic intake affect metabolic rates of natural substrates such as androgenic, progestational and adrenal steroids, pyridine nucleotides and cytochromes. In addition, the effects on metabolism of common drugs and oral contraceptives should be investigated. In man single doses of BHA requires 10 days for elimination probably due to the solubility and retention of the compound in fat. Thus, with a typical American diet which provides a regular intake of BHA, the chronic tissue level should be determined for man. The evidence indicates that BHA is not mutagenic. While there are teratogenic effects of BHA in the avian embryo test system, several investigations using three mammalian species have failed to establish any teratogenic or embryotoxic potential when BHA is fed to young or adult and pregnant animals at dosages that greatly exceed estimates of human consumption. Data from several studies indicate that BHA is not a carcinogenic substance. There is evidence that BHA may interfere with synthesis of natural carcinogens and suppress or retard growth of tumors induced by known chemical carcinogens. The Select Committee in its report on BHT identified areas of concern regarding the properties of BHT and indicated that additional studies are needed. Although the concentrations at which these responses occur are generally lower with BHA than with BHT, the qualitative effects are comparable. Concern was expressed about the possible enzyme inductive properties of BHT in extrahepatic tissues, particularly the intestine. Questions were also raised regarding the effect of induction of hepatic enzymes on the metabolism of steroids. The long-term effects of continuously maintained liver hypertrophy from multiple stimuli were also raised. This is a part of the general problem of adaptive responses of the liver which develop after the ingestion of many foreign substances including drugs, hormone analogues, insecticides, alkaloids, and carcinogenic polycyclic hydrocarbons. While available data suggest that BHA in food is ingested at levels many times below that which produces short-term effects, several of these questions remain. The Select Committee concludes that studies on the tissue levels of BHA attained in man by chronic ingestion and the contribution of BHA to the general problem of enzyme induction should be assessed. Finally, chronic feeding studies with BHA at dosages equivalent to human exposure and use levels should be conducted in primates to determine the long-term effects of BHA on liver mixed function oxidase systems. The Select Committee regards these questions as less urgent for BHA than for BHT and concludes that: While no evidence in the available information on butylated hydroxyanisole (BHA) demonstrates a hazard to the public when it is used at levels that are now current and in the manner now practiced, uncertaintied exist requiring that additional studies be conducted.