The role of epidemiology in the detection of harmful effects of radiation.

Data relating to acute injuries of atomic bomb survivors show that the life span study cohort is biased in favor of exceptionally low levels of radiosensitivity. These data also show that factors influencing the death rates of this cohort include irreversible damage to the immune system. These impressions are still awaiting confirmation. Meanwhile, the Oxford Survey of Childhood Cancers and surveys of nuclear workers show that at low dose levels the cancer risk is much greater than estimates based on atomic bomb survivors; the special association between leukemia and radiation is an exclusively high dose effect, and levels of radiosensitivity are much lower in the middle of the life span than at either extreme.