Heterocyclic amines (HAs) are formed as pyrolysis products during the cooking of meats/fish. These substances are potent mutagens in the Ames/Salmonella assay and are also carcinogens in laboratory animals. In order to assess the magnitude of the cancer risk posed by their presence in the US diet, we estimated the average intakes of HAs, based on analyses of the concentrations of HAs in cooked foods and data from a dietary survey of the US population and quantified the cancer potencies of the individual compounds using dose-response data from animal bioassays. Measured concentrations of HAs in cooked foods were taken from a major review of the open literature. Only those concentrations that were associated with normal cooking conditions were chosen for use in estimating dietary intakes. The average consumption of HA-bearing foods was determined by analyzing statistically the intakes of 3563 individuals who provided 3 day dietary records in a USDA sponsored random survey of the US population during 1989. Dietary intakes of the five principal HAs in descending order were 2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine (PhIP) > 2-amino-9H-pyrido[2,3-b]indole (A alpha C) > 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) > 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (DiMeIQx) > 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). The carcinogenic potencies, in contrast, were almost the reverse order: IQ > DiMeIQx > MeIQx > PhIP > A alpha C. An upper-bound estimate of the incremental cancer risk is 1.1 x 10(-4), using cancer potencies based on a body surface area basis. Nearly half (46%) of the incremental risk was due to ingestion of PhIP. Consumption of meat and fish products contributed the most (approximately 80%) to total risk.

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Mixtures of amino acids, creatine, and glucose simulating the composition of six different kinds of meats (beef, chicken breast, chicken thigh, turkey breast, pork, and fish) were dry-heated to simulate the formation of heterocyclic amines in meats. The presence of 16 heterocyclic amines was investigated in the model systems and in the six meats and their corresponding meat drippings to determine the importance of meat composition to heterocyclic amine formation. Nine mutagenic amines (IQ, MeIQ, 8-MeIQx, 4,8-DiMeIQx, PhIP, IQx, IFP, DMIP, and TMIP) were found to be present at concentrations >0.1 ng/g in some of the model systems and in some of the meats or pan residues. Heterocyclic amine concentrations clearly are affected by precursor composition in this model system, and the same nine heterocyclic amines formed in the meat and in the model system show that this is a well-controlled surrogate for the reaction conditions that occur in meats during cooking.

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