In the following, a linear dose-effect relationship with no threshold -will be assumed in accordance with your suggestion. tion is also made in the BEIR report. evidence for a less conservative, relationship. This conservative assump- There is considerable scientific nonlinear and nonthreshold dose-effect The latter hypothesis assumes some probability of an effect at any dose, however small, but a lesser likelihood of an effect at the low doses under consideration here than would be calculated from the linear hypothesis. Since specific nonlinear relationships have not gained wide acceptance yet, we do not offer calculated risks based on a nonlinear relationship. The following assumption are made here: ~ 1. A linear relationship between radiation dose and effect for genetic and cancer risks. 2. A population of 600 persons at risk. We assume that the age distri- bution is similar to that of the general U. S, population. Some assumption regarding age distribution is necessary because of the effect of age on cancer rates; one. an older population has a greater cancer mortality rate than a younger Also, assuming similarity to the U. S. birth rate, be expected. ever, 12 births per year can This figure is likely to be low. for the Bikini population. How- simple corrections in the calculated risks can be made if the birth rate is higher. 3. An average annual whole-body radiation exposure of 200 millirems. 4. Incidence of natural ly occurring genetic defects and of cancer mortality equal to those of the general U. S. population. — 3009584