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Risk evaluation of tumor-inducing substances in foods.

Carcinogenic risk assessment of chemicals consists of four phases, namely, 1) hazard identification, 2) exposure assessment, 3) hazard assessment or dose-response assessment, and 4) risk characterization. The third phase of risk assessment is the evaluation of both hazard and exposure information to estimate the mathematical probability that the carcinogenic potential associated with an agent will be realized in the human population under defined conditions of exposure. The estimation of virtually safe dose (VSD) is regarded as a component of the third phase. Carcinogenic risk assessment is still at an embryonal stage of development, and there remains a number of problems to be clarified. With regard to the estimation of VSD, it is an important task to establish the principle for selection of appropriate mathematical models. The intention of this paper is to illustrate the estimation of VSD of two tumor-inducing chemicals, N-ethyl-N-nitrosourea and potassium bromate based on the dose-response data in animals and to discuss the biological implication of the estimated VSD in relation to the risk assessment of the chemicals in humans.