Biological effectiveness of neutron irradiation on animals and man

Neutron experiments on a highly radiosensitive in vivo system - oocytes in mice - provide new insight into the nature of the radiosensitive targets of these important cells. With the radiobiological literature as background, neutron data from animals and humans (including studies by the author using reevaluated Hiroshima-Nagasaki dosimetry) are integrated, and the controversial question of radiation protection standards for neutrons is addressed. Oocyte killing in juvenile mice by 0.43-MeV, 252Cf-fission, and 15-MeV neutrons, compared with that by 60Co gamma rays, yields unusually low neutron RBEs (relative biological effectiveness). Study of the neutron literature reveals that factors most important in influencing neutron RBE are dose and biological endpoint. Using various approaches, a value for the neutron Quality Factor much lower than 100 which has been suggested. With the large uncertainty, 17 is not markedly different from the value of 10 presently in general use