MUTAGENICITY AND CYTOTOXICITY OF 4.4-MEV ALPHA-PARTICLES EMITTED BY PU-238

The induction of mutation by α particles emitted by plutonium-238 (LET at the cell surface 100 keV/μm) and 250-kVp X rays has been measured utilizing the hypoxanthine-guanine phosphoribosyl transferase (HGPRT) locus in mammalian cells (CHO). Dose-response relationships for mutagenicity and survival of Chinese hamster cell line CHO are presented. Linear plots of mutations to 6-thioguanine resistance describe cumulative curves which reveal nonthreshold responses for both radiations. Although neither of these curves is linear over the entire range of doses shown, the initial portions of both curves are linear with non-zero slopes. The linear slopes for α- and X-ray-induced mutations are 4.79 ± 0.50 and 1.30 ± 0.23 x 10-7 mutations per viable cell per rad, respectively. However, plots of mutation frequency against survival show that for a given level of survival, α radiation is relatively less mutagenic than is X radiation.