抄録
Space radiations consist of geomagnetic-trapped high LET particles from intensely energetic solar-particle events at a constant low dose and low dose rate. In particular, neutrons, a kind of high LET particles, have a reverse dose-rate effects with relationship on RBE, that is, the exposure at a low dose-rate shows severe effects compared with a high dose-rate. To protect human health, we need to measure the exact total doses of various space radiations over a long-term stay in space. Therefore, we need to know the maximum permissible doses of space radiations. Though physical monitoring of space radiations in recent space experiments indicated about 1 mSv per day, microgravity was reported increase the abnormal development induced by heavy particles in C. morosus and the mutation frequency induced space radiations in D. melanogaster. Our group reported the induction of stress protein (HSP72) in goldfish and a tumor suppressor gene product (p53) in rat. These findings may support that the biological effects of space radiations were enhanced by space environment, especially microgravity. It is quite important to assess the total permissible doses of space radiations from an aspect of space crew's health for long stay in space.
