Microdosimetric concepts applied to hormesis.

Abstract

With radiation, unlike chemicals, a small absorbed organ dose can deliver amounts of energy to macromolecular cell targets so great that, if the relevant target is hit, even the best efforts of any repair processes probably cannot prevent cell transformation. Data are shown for both mutagenesis and carcinogenesis, indicating that, in this respect, even the smallest average organ absorbed dose can be effective, particularly for high-LET radiation. Thus while hormesis-enhanced protective processes may render ineffective marginally large amounts of energy deposition per cell target and thus perhaps reduce the incidence of carcinogenesis and mutagenesis, a goal of zero incidence is most likely unrealistic for at least high-LET radiation. The usefulness of the radiation hormesis concept may well be decided on these questions because of the general awareness that even a moderate average life lengthening in the population would not eliminate marked shortening of useful life in the young with induced cancer or serious genetic defects.