Tumorigenicity of Small Highly Radioactive Particles

A theoretical approach to tumorigenic risk from exposure of skin and lung to particles of high specific activity is described. Present methods of setting guide lines for skin and lung exposures assume uniform radiation fields and are not applicable for small sources where the dose rate falls off rapidly with radial distance from the particle, exposing cells to a wide variety of doses. The method described herein, based on skin tumor experiments on the rat, is to compute the probability that each cell exposed will form a tumor and to sum for all cells exposed to obtain total tumor probability. Results of the application of this method to beta-, alpha-, and X-ray emitters are presented.