Predicting the risk of tumor occurrence under the effect of small doses of carcinogens.

Basic methodological approaches were formulated for determining the permissible levels of carcinogens in man's environment on the basis of current experimental oncological data dealing with the interaction of the organism and carcinogenic compounds. The tumor is proposed as a specific index of the harmfulness criterion of carcinogenic action. Under these conditions, both the frequency and the development time of tumors must be considered. Results are given of an experimental study of the carcinogenic activity of various doses of benz[a]pyrene (0.005, 0.02, 0.1, 0.5, and 2.5 mg) on rats by using a tenfold intratracheal administration. On the basis of mathematical models of the obtained dose-time-effect relationship, the risk of cancer occurrence due to small carcinogen doses is predicted. Small doses were not tested in the experiment. On the basis of the data obtained in the experiment, a maximally permissible concentration of benz a pyrene in the ambient air can be determined. A benz[a]pyrene dose of 0.02 mg is recommended as the basis of the calculation. The effect of this dose is shown at time periods longer than the limits of human life.