Ionizing radiation atomic bomb survivors

Blot, W.J., Akiba, S. and Kato, H. (1984). Ionizing radiation and lung cancer A review including preliminary results from a case-control study among A-bomb survivors, in Atomic Bomb Survivor Data Utilization and Analysis, PRENTICE, R.L. and Thompson, D.J., Eds. (SIAM, Philadelphia). 

Moloney, W.C. and Kastenbaum, M.R. (1955). "Leukemogenic effects of ionizing radiation on atomic bomb survivors in Hiroshima City Science 121,308. 

Figure 3 illustrates rough dose-response model fits with human data for ionizing radiation and leukemia incidence from atomic bomb survivors (24). Data exist down to about the 10-5 lifetime risk per person exposed. This value is close to the region of regulatory interest, and relatively small risk differences are predicted by the three illustrated models in the dose range up to two orders of magnitude below the last observed dose value (ca. 5 rad). 

It is of note that this considerable reliance on laboratory animal data for risk assessment purposes for enviromnental chemicals is in sharp contrast to the situation with ionizing radiation. The cancer risk estimates for ionizing radiation (X rays and y rays) are based to a very great extent on human tumor data obtained from the Life Stage Study (LSS) of the atomic bomb survivors in Hiroshima and Nagasaki, Japan... 

Hazelton, W. D., Moolgavkar, S. H., Curtis, S. B., Zielinski, J. M., Ashmore, J. P, and Krewski, D. (2006). Biologically based analysis of lung cancer incidence in a large Canadian occupational cohort with low-dose ionizing radiation exposure, and comparison with Japanese atomic bomb survivors. J Toxicol Environ Health Part A 69, 1013-1038. 

Radiation is carcinogenic. The frequency of death from cancer of the thyroid, breast, lung, esophagus, stomach, and bladder was higher in Japanese survivors of the atomic bomb than in nonexposed individuals, and carcinogenesis seems to be the primary latent effect of ionizing radiation. The minimal latent period of most cancers was <15 years and depended on an individual s age at exposure and site of cancer. The relation of radiation-induced cancers to low doses and the shape of the dose-response curve (linear or nonlinear), the existence of a threshold, and the influence of dose rate and exposure period have to be determined (Hobbs and McClellan 1986). 

Ionizing radiation is a known environmental cause of female breast cancer. Breast cancer risk is significantly elevated in female survivors of the atomic bombings at Hiroshima and Nagasaki, but varies significantly depending on age at the time of radiation exposure. Relative risk at estimated exposure levels of 1 Sv was approximately 3-4 for women exposed before 10 years of age or between 10 and 20 years of age, but decreased to approximately 2 in women irradiated between 20 and 40 years of age and decreased even further in women exposed after 40 years of age (Boice et al., 1996). 

Environmental chemicals were originally associated with cancer through experimental studies in animals. The classic experiment is to repeatedly paint a test substance on the back of a mouse and look for development of both local and systemic tumors in the animal. Likewise, the ability of ionizing radiation to cause human cancer, especially leukemia, was dramatically shown by the Increased rates of leukemia among survivors of the atomic bombs dropped in World War II, and more recently by the increase in melanoma (skin cancer) in individuals exposed to too much sunlight (UV radiation). 

---