“Ionizing radiation has always been with us and will be for all foreseeable time. Our genetic system is probably well adjusted by natural selection to normal background radiation. Added radiation will increase the frequency of mutations; most of these will be harmful. Exposure to radiation in large amounts will increase malignant disease; small amounts may possibly do the same. In view of these potentially harmful effects every reasonable effort should be made to reduce the levels of ionizing radiation to which man is exposed to to the lowest levels that can reasonably be attained.”