Life-span shortening and myeloid-leukemogenicity in C3H mouse after exposure to 10 MeV fast neutrons - Interim report

Abstract

In evaluating cancer risk of neutrons, experimental data on energy dependency of RBE are needed. We started a series of experiments on murine carcinogenicity, especially focusing on leukaemogenesis, of low energy range (0.5MeV- 10MeV) of neutrons. In the first experiment, to evaluate the carcinogenicity of 10MeV neutron, male C3H/nrs mice, susceptible strain to radiation-induced leukemia, were exposed to neutrons generated from cyclotron, using d (25 MeV)-Be reaction at the peak energy of 10 MeV (dose rage: 0.05 - 2Gy ) or to Cs-137 gamma-rays (dose range: 0.2 - 4Gy). The animals were under observation for their life span. Life-shortening effect was significant at more than 1Gy of gamma-rays, and at more than 0.2Gy of neutrons. RBE was calculated to be about 4. The incidence of myeloid leukemia after exposure to neutron- and gamma-rays mice increased linearly in dose dependent manner. RBE was calculated to be about 1.5. RBE of Harderian gland tumor was calculated to be about 8.