The problem was complicated enormouslyby the fact only one of the seven years of Nevada testing; doses for the other six years I estimated from measurements of 1952, 1953 and 1955) and, unfortunately, iodine 131 growing season.> New information now permits improved estimates for five of the seven test years, and for the remaining two I have set lower and higher limits. that iodine 131 had not been properly recognized as a fallout hazard during the early years of testing (1951, had not been measured in milk during that time. Therefore, attempts to reconstruct the probable exposures during this period must be indirect because the eightday iodine 131 has long since decayed (but see Appendix). Knapp used the gamma-ray intensity above a contaminated field as an index of its iodine 131 content, while C.N.I. used this and the beta-particle disintegration rate from fallout collection trays.5 ] used the observed beta activity in the air and the fission yield.° Knapp and C.N.I. were concerned chiefly with exposures in Southern Utah near the Nevada Test Site, be- cause that was where the highest individual doses were indicated. My major concern was the North-Central portion of Utah because it contained so many more people. During the 1963 Congressional Fallout Hearings, Dr. Enc Reiss of C.N.I. and I both urged that a study be made of the irradiated Utah children. This study, sup- ported by the U.S. Public Health Service, is now in progress. Originally, the study had two objectives— to search for medical effects, and to estimate the radia- beta-activity in the air or from fission yield during the For 1962, our analysis of milk from Pendleton’s 39 stations scattered throughout Utah indicated that for the daily consumption of one liter (1.06 quarts) of milk, the average yearly iodine 131 intake was 45 thousand picocuries* assuming a three day delay from milking to consumption.’ This agreed closely with the 37 thousand picocuries yearly intake reported by the U.S. Public Health Service for the Salt Lake milk pool.? The corresponding infant thyroid doses** were 0.77 or 0.63 rads respectively. TABLE } ESTIMATED AVERAGE THYROID DOSES TO ALL UTAH INFANTS YEAR DOSE IN RADS tion dosage. The medical] phase is progressing well, but the dose program requires much more work. If the 1962 ,econstruct the exposures may be gone forever. Mem- 1957 HIGHER LOWER OF TESTING LIMIT 0.63 LIMIT — 0.77 ESTIMATION 5.1L. Milk Poo! & Pendleton’s Milk Sta. dosimetry is not completed soon, the best opportunity to 1958 ories fade, records are destroyed, and these children will soon reach adulthood and scatter across the nation. Even 1955 0.2 - 20 Fission Yield 1953 2 - 12 Field Beta Activity After Shot “*Nancy"™ 1952 3 - +8 Field Beta Activity After Shot **Easy*’ 1951 0.04 ~ 4 if no effects appear, the exposures should be evaluated as accurately as possible. If a safe dose exists for iodine 131 in children, proper study of the 250 thousand ir- radiated Utah infants may provide a unique chance to establish it. In this paper I present my estimates of lower and higher limits for the average doses received by Utah infants. I do this for two reasons. First, I hope that the uncertainty of these hmits will stimulate interest in im- proving the dosimetry. Secondly, despite dose uncer- tainties, the indicated exposures are sufficient to justify continued studyof the Utah children. DOSIMETRY Prior to the 1963 Fallout Hearings, I calculated the number of radiation-induced cancers that might be anticipated in the 250 thousand Utah children exposed to fallout iodine 131 as infants. I withheld publication or public discussion of these predictions primarily because I felt that most of my estimates of dose might be somewhat unreliable. Working in isolation at the time, I was aware of milk measurements of iodine 131 for “A rad is the absorption of 100 ergs of energy per gram of tissue. 0.2 METHOD OF DOSE USPHS Salt Loke Milk Pool 1.3 USPHS Salt Lake Milk Pool Fission Yield For 1958 and 1957, USPHSanalysis of the Salt Lake milk poo] indicated average yearly intakes of 11 thousand and 74 thousand picocuries of iodine 131 with associated infant thyroid doses of 0.2 and 1.3 rads respectively.® For 1953 and 1952, the beta activity in fallout col- lection trays at Salt Lake City was 15 million disintegrations per minute per square foot at twelve hours after the detonation of shot “Nancy” on 24 March 1953 and 23 million disintegrations per minute per square foot at twelve hours after the detonation of shot “Easy” on 7 May 1952. Infant thyroid doses have been calculated by C.N.I. as two to twelve rads for this 1953 shot and three to thirteen rads for this 1952 shot (see pages 529-530, ref.5). A number of limitations exist in using these values. First, they are for only one shot during *A picocurie is 2.22 disintegrations per minute. **Assuming 30% uptake in a 2 gram thyroid with a subsequent effective retention half-time of 7.6 days, and the absorption of 0.2 million electron volts of energy per disintegration of iodine 131. DOE ARCHIVES Scientist and Citizen 22