Why the concept of hormesis has not been incorporated into mainstream radiation health theory: Radiation perspective

Although adaptive and reparative responses to radiation were recognized in the early decades of this century, mutations and chromosome aberrations were subsequently observed to increase as linear‐nondireshold functions of the dose at low‐to‐intermediate levels of exposure. For certain cancers, likewise, although the dose‐response relationships in humans and laboratory animals have been observed to vary, depending on the type of neoplasm, the dose, dose rate, and LET of the radiation, the age, sex, and genetic background of the exposed population, and other variables, the existing data have been interpreted to suggest that the risks may not depart significantly from linearity at low doses and low dose rates. Hence, although the available data do not exclude alternative dose‐response relationships, the linear‐nonthreshold model has generally come to be used as a basis for assessing the risks of low‐level irradiation for purposes of radiation protection. While the use of this model has generally been considered to be prudent on the basis of the precautionary principle, the possibility that the model may grossly overestimate the risks of low‐level irradiation remains to be excluded. Therefore, especially in the light of the growing evidence that adaptive responses may protect against the effects of small doses of radiation, further research to clarify the relevant dose‐response relationships is strongly indicated.