-S.Only the infant dose has been computed. However, dose calculations can easily be extended throughout childhood using the method shown in Table 2 and correcting for the increasing mass of the thyroid with age*. Table 2 _ TOTAL NUMPER OF UTAH INFANTS EXPOSED TO FALLOUT T°? YEAR BIRTHS OF DURING BIRTH 1962 1961 1960 1959 1958 1957 1956 1955 1954 1953 1952 1951 1950 1949 TOTAL = _ _ _ _AV._ THYROID DOSE (RADS)_ | Age YEAR 0.5 to 1.5 26,000 25,000 0.6 - 0.8 24,000 23,000 22,000 22,000 21,000 21,000 20,000 20,000 19,000 0.2 1.3 243,000 0.2 - 20 - 12 - 13 O.04u- 4 Age TOTAL 0.6 - 0.8 0.6 0.6 - 1.5 to 2.5 0.2 1.3 | 0.2 - 20 2 ~ 12 3-18 O.04- 4 AVERAGE DOSE = DOSE 0.2 1.5 1.3 O.20.2 2 5 3 = 0.04- 20 20 12 30 22 4 : 1.3 - 10 Table 2 indicates that about 1/4 million Utah infants were exposed to fallout I°3!, with an indicated average thyroid dose of 1.3 - 10 rads** % The enlargement of the thyroid gland with age reduces its I'3! concentration and the resulting radiation dose from a given intake of P3?. For example, the intake of 1 microcurie (1,000,000 pCi) 23+ gives a 17-rad dose to the e-gram thyroid of a l-year old infant; a 6.8-rad dose to the 8-gram thyroid of an 8-year old child; and a 1.7-rad dose to the 20-gram thyroid of an adult. Furthermore, the weight of evidence indicates that the radiation resistance of the thyroid increases with age ( » although the exact sequence aot changes in sensitivity has not yet been established precisely. “uy earlier crude methods yielded an estimated thyroid dose averaging 4.4 rads to this population ©) , ment. I am pleased (and a little surprised) at the agree-