Health and dosimetry considerations in the ICRP 1990 formulation of effective dose

The new recommendations of the International Commission on Radiological Protection contained in Publication 60 supersede those of Publication 26 issued in 1977. The recommendations are intended to assist national authorities in formulation of radiation protection guidance. Sufficient explanatory information is included to clearly note that radiation protection issues cannot be resolved on the basis of scientific considerations alone, but also require value judgments regarding the relative importance of different kinds of risks and the balance between risk and benefit. Ionizing radiation causes both deterministic and stochastic effects in irradiated tissue. It is the aim of radiation protection to avoid deterministic effects by setting dose limits below their thresholds and to control exposure to limit the frequency of stochastic effects, believed to occur (albeit with low frequency) even at the lowest doses. Cancer induction and hereditary effects are the stochastic effects of concern. The Commission has relied largely on studies of the Japanese A-bomb survivors in estimating the probability of a fatal cancer and concluded that the most probable dose-response relationship is linear-quadratic. The linear coefficient at low dose or low dose-rate is obtained from the high dose, high dose-rate estimates of risk by dividing by an effectiveness factor of two. Using the data from the A-bomb survivors, the Commission estimated the distribution the fatal cancer risk among the organs of the body and the length of life lost for cancer in each organ. The Commission further developed the concept of health detriment to represent the combination of the probability of occurrence of a harmful health effect with a judgment of the severity of that effect