Lethal and Mutagenic Effects of ²⁵²Cf Radiation in Cultured Human Cells

Summary

HeLa MR cells were exposed to radiation emitted from a man-made spontaneously fissioning isotope, californium-252. The neutron to gamma-ray ratio in the radiation dose was measured to be 2·0. The extrapolation number of the dose-survival curve was 1·3 and the Do was 200 cGy. A dose-dependent increase in mutation to 6-TG^r (6-thioguanine resistant) was observed. The relative biological effectiveness (r.b.e.) for cell killing of the neutrons from ²⁵²Cf, calculated relative to high-dose-rate X-rays, was 2·6 at 50 per cent survival. The r.b.e. for mutation induction was 2·7 at a mutation frequency of 5 × 10⁻⁵ per surviving cell.