抄録
The discovery of x-rays in 1895 initiated revolutionary advances that joined physics, biology and medicine forever. This was further emphasized with discovery in 1939 of nuclear fission which provided the basis for development of nuclear weapons and, most importantly, many peaceful applications of nuclear technology, including generation of electricity and numerous advances in medicine. Three quarters of a century of research on how external radiation exposure and internally-deposited radionuclides affect biological systems has resulted in extensive knowledge on the health effects of ionizing radiation that greatly exceeds that available on any other toxicant or class of toxicants. The core knowledge on these effects is rooted in human misfortune, detailed studies of the A-Bomb survivors by the Radiation Effects Research Foundation and other human populations that received excessive exposure to external radiation or internally-deposited radionuclides. That knowledge obtained from studying human populations has been complemented and extended by controlled exposure studies with laboratory animals and in vitro cellular and molecular studies. Extensive information has been acquired about how different radionuclides move in the environment from various sources and reach humans. An elaborate science-based system for estimation of human health risks of exposure to ionizing radiation has evolved and serves as the basis of an internationally accepted radiation protection system based on energy deposition in specific organs. This presentation will review from a historical perspective how this body of knowledge on radiation toxicology has been acquired and used to assess accidents such as occurred at the Fukushima nuclear station. Special attention will be given to the critical agricultural pathways for fallout 131I and 134-137Cs to reach humans via consumption of contaminated agricultural products principally milk and meat. The relative importance of external radiation versus irradiation from internally-deposited radionuclides entering the body via ingestion or inhalation for nuclear workers and the general population will be discussed. The nature of the relationship between radiation dose, delivered at different dose rates, and increased excess risk of cancer and other diseases will be discussed in the context of the background incidence of these diseases. The presentation will close by emphasizing the role of scientists in risk communication based on the scientific knowledge acquired over the past three-quarters of a century on the human health hazards of radiation exposure.
