~ 8. Table 4 PREDICTED THYROID CANCERS IN THE 565 INFANTS NEAR ST. GEORGE AVERAGE DOSE (120 rad - 440 rad) ASSUMPTION 1) £35 Thyroid Cancers 10®° IN 1953 Infants given 1 rad (Effect of x-rays; Beach & Dolphin) 2) 1/10 of x-ray effect (113+ /x-ray RBE in rats; Doniach) 2 - 9 0.2 - 0.9 3) High Threshold 0 0.01 Wage "NATURAL" INCIDENCE BY 15 YEARS AGE (from Mustacchi & Cutler) DISCUSS ION A number of conclusions follow: 1} Under the assumption of linear dose-response relations, the predict- ed number of induced cancers for the total state is 5-10 times higher than for the high-fallout St. George area where the studies to date have been most emphasized. Therefore, consideration should be given to expanding the studies into additional regions. 2) The advantage of studying the limited population in the St. George area is that the expected number of "natural" thyroid cancers is so low (0.01) that the observation of a single case of thyroid cancer would be high- ly suggestive of radiation damage, while the observation of 2 cases would constitute almost conclusive proof. However, under assumption (B) less than 1 case is predicted. 3} The "epidemic" number of thyroid cancers predicted from assumption (A) have not been observed experimentally”. This indicates that either (1) low doses are less effective rad-for-rad than higher doses, or (2) E** doses are less effective than x-ray doses. Very likely, both of these effects are in operation. * If the additional doses received in later childhood had been included, the predicted number of cancers would have been even higher.