C. We Meo. - Fagr 16 APPENDIX OTHER POSSIBILITIES OF IODINE 131 DOSE EVALUATION The central problem in this study is one of reconstruction in the absence of complete data. Lacking direct measuretcnts of icdine 131 levels during the 1951-55 tests, cstimates have been based on retrocvective calculations of the available data —gross beta and gamme levels -- end on assumptions on the relation of these levels to the iodine 131 levels. it is fully recognized that at this point serious objections may be raised. Firstly, the yields of various radioactive isotopes have to be assumed in the absence of full information on the major nature of the fissionable material used in each explosion. Secondly, our knowledge of the fractionation process is incomplete. Nevertheless it may be useful to pursue these calculations through as many independent methods as we can find. Not all these methods may prove practicable after detailed examinaticn, but we cannot afford to reject suggesticus too quickly. A new possitility Lins becn pointed out to me by Merril Eics-2bud (Professor of Eavironmental Medicine, New York University lidicel Jnter, Tuxedo, New York). The concept is deseriiv7. br Edvards,?? Both iodine 131 and iodine 129 result from fission. While the iodine 131 Las decayed because of its short eight-day half-life, the iodine 129 with its 16-million year half-life has hardly decayed at all. Thus, the iodine 129 content in the thyroids of people who died soon after an early nuclear test might indicate the iodine 131 dose which was received. It may be possible to obtain sufficient pathological tissue preserved from autopsies performed at that tire, and thus gauge the iodine 129 levels. For exandle, cone micrccsurie of iodine 131 consists I of 3.72 x 107° atorc. a: . : Che Tlesicn rields have been DOE ARCHIVES 33

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