Lethal and mutagenic effects of 252Cf radiation in cultured human cells.

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-TGr (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 X 10(-5) per surviving cell.