-S5Only 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”. TOTAL NUMBER OF UTAH INFANTS EXPOSED TO FALLOUT I??? YEAR OF BIRTH 1962 1961 1960 1959 1958 1957 1956 1955 1954 1953 1952 1951 1950 1949 TOTAL = BIRTHS DURING YEAR — — . AV-_ THYROID _DOSE _(RADS) _ Age Age TOTAL 0.5 to 1.5 1.5 to 2.5 DOSE 26,000 25,000 0.6 - 0.8 24,000 23,000 22,000 22,000 21,000 21,000 20,000 20,000 19,000 243,000 0.6 - 0.8 0.2 1.3 0.2 1.3 0.2 - 20 0.2 - 20 2 - 12 3 -18 O.04- 4 2 - 22 3 - 18 0.04- 4 AVERAGE DOSE = 0.6 - 0.8 0.6 ~ 0.8 0.2 1.5 1.3 0.2 0.2 2 5 3 = Q.04- 20 20 12 30 22 4 1.3 - 10 Table 2 indicates that about 1/4 million Utah infants were exposed to fallout 31, with an indicated average thyroid dose of 1.3 - 10 rads**. “The enlargement of the thyroid gland with age reduces its I??? concentration and the resulting radiation dose from a given intake of I?°4. For example, the intake of 1 microcurie (1,000,000 pCi) E31 gives a 17-rad dose to the 2-gram thyroid of a 1-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 of changes in sensitivity has not yet been established precisely. “My 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- DOE ARCHIVES )?