Adaptive response by single cell radiation hits--implications for nuclear workers.

Several radiobiology mechanisms show an ability of cells to activate protective mechanisms against the deleterious effects of ionizing radiations. The most interesting with respect to possible health benefits to humans is the phenomenon of adaptive response (AR). Fundamentally AR must be shown to be operative at very low doses and dose rates experienced during human radiation environment activities. A microdosimetric model is presented which, by the use of Poisson cell nucleus hit accumulation, enables examination of the single hit range of radiation exposure where the AR radio-protection is first activated. It is found, with the model, that single charged particle tract specific energy hits to the nucleus can activate AR. Both in vitro and in vivo data reported here indicated that AR may provide a reduction in cancer-causing DNA damage, from both radiation and spontaneous events, for nuclear workers and general public diagnostic treatments.