RBE of Tritium Measured in Human Cells Using Cytogenetic Endpoints

Abstract

Radiations differ in the way their energy is deposited in biological material. Because of this, a weighting factor, based in part on the relative biological effectiveness LUBE), is used to normalize doses of different radiation qualities. An evaluation of the RBE for tritium Beta-rays, relative to other radiation qualities, is clearly important to the nuclear industry since tritium exposures contribute to total occupational doses associated with CANDU reactors. However, there is a significant range of published RBE values for tritium relative to both X-rays and gamma-rays in the literature (1). In an effort to sort out some of the ambiguity associated with the effects of tritium, we completed a series of experiments using cultured human diploid fibroblust strains from four different donors. A measurement of the micronucleus induction frequency for both acute and chronic dose delivery resulted in a composite RBE value of approximately one for all strains evaluated. An RBE value of one has also been measured using the induction of this same endpoint in isolated human peripheral blood lymphocytes exposed to 65 Wp X-rays and tritium Beta-rays.