Somatic and genetic radiation risk estimates from human and laboratory studies: linear and nonlinear models

The harmful effects of radiation have been studied in humans, animals, single cells, and subcellular systems. The data obtained from these studies are presented in the form of a dose response curve in which the effect is measured on the ordinate and the amount of radiation (exposure) or the amount of absorbed energy (dose) is measured on the abscissa. Since a large amount of data has been obtained only at high doses, the measures of risk to humans from low doses must be estimated by extrapolation from these high dose levels using known dose response models. Some of the biological effects most often studied include deaths, cases of disease such as cancer, mutations, transformed cells, and single and double strand DNA breaks. These responses are presented as rates and expressed in such terms as deaths per person per year, cases of disease per million persons per year, number of mutations per surviving cell, number of transformations per surviving cell or the number of DNA single or double strand breaks per cell