Fo» LOW mel) . Telekion ¢ =O “TON 6 anomie tes VNC re fia ‘hy non cliflc folne ee FECRIVG a) WuViGs § 4081 S4 What were the eviecis o this irraciation? BEE The discussion in the following pages of ‘‘Thyroid Irradiation in Utah Infants Exposed to Iodine 131” by Charles Mays, which appeared in our last issue, centers around these two questions and the problems involved in trying to answer them. Obviously, it is desirable to find and treat any malignancies that might develop in any of these children. It is also important to find answers to the questions be- cause of the light this could throw on the more general questions: How much iodine 131 produces thyroid damage of any kind? Thyroid cancer? In what propor- tion of exposed children? These questions are important, not only for past exposure, but for the evalution of possible future exposure from underground testing, atmospheric testing by other nations, Plowshare projects (nuclear explosions for peaceful purposes) or from reactor accidents. w much? A recent paper from the Lawrence Radiation Laboratory (reviewed on page 4 ) presents new estimates of the size of the dose and the number of children exposed; estimates which underscore the need for expanding the search for radiation effects. A procedure for checking these estimates, proposed in the Appendix to Dr. Mays’ article last month, would use the long-lived iodine 129 as an indicator of the amount of iodine 131 originally present. This proposal is discussed further by Dr. Tamplin on page 3. carbon 14—as an indicator of the age of archeological findings. Tissue preserved after autopsies performed on people who died shortly after nuclear tests in the fifties could therefore be tested for iodine 129. This would tell us how much iodine 131 was in the same thyroids prior to death, and the approximate level of iodine 131 exposure to others still living, who were subject to fallout in the same locality in the same year. Autopsy tissue is probably available in Salt Lake City, if not in the smaller towns (CNI has not checked with Salt Lake hospitals, but such tissue would be available in St. Louis, and presumably also in other metropolitan medical centers). Such a study would not have to cover the whole geographical area of high exposure in order to serve as a check on estimates—such as those of Tamplin and Fisher—based on external radiation measurements. 9+ Ika Z Lah >) Whateffects? “70-30. Dr. Conard, who has been studying the Marshall Islanders exposed to fallout from the Bikini test of March 1, 1954, summarizes the thyroid abnormalities found in these people (page 1 ). With one exception, all the abnormalities found have been in the group exposed to 700 or more rads of radiation from iodine 131. The children exposed to the lesser doses, and showing no abnormalities are too few in number, as Conard points out, to establish a threshold dose (a dose The question has been asked: If iodine 129 has a half-life of millions of years, why aren’t we concerned below which no abnormalities would be produced). age than the short-lived iodine 131? Marshall Island experience that are applicable to the Utah-Nevada experience. about its biological effects? Doesn’t it do more dam- The answer is “No.” Because it decays slowly, iodine 129 gives off muchless radioactivity in a given amount of time than does iodine 131. Also, although it takes about seventeen million years for half the radioactivity of iodine 129 to decay (a physical half-life of 17,250,000 years), it is excreted from the body fast enough to make its biologtcal half-life (the time it takes for half of it to disappear from the body) only about three months. In pathological tissue from autopsy, the excretory process would have ceased with death. Because there is a known ratio of iodine 131 to iodine 129 at the time they are created in a nuclear explosion, the iodine 129 still present in the tissue can give a clue to the amount of iodine 131 that was formerly present. This is not unlike the use of another long-lived isotope— They are also too few to draw conclusions from the Six children in the Marshall Islands were exposed to 300-600 rads. On the basis of the assumption used by Mays (35 cancers per million children exposed to one rad of x-rays), one would expect only one case of thyroid cancer per hundred children exposed to 300 rads or one case per 50 children exposed to 600 rads. If iodine 131 is one-tenth as effective as x-rays in producing thyroid damage, one case of thyroid cancer per thou- sand children exposed to 300 rads would be expected or one case in 500 children exposed to 600 rads. It i: therefore not surprising that no cancer has been founc in the six children exposed to doses in this range. Forty children were exposed to 55-125 rads. In thi: exposure range, one would expect a maximum of on« Copyright 1966. Greater St. Louis Citizens’ Committee for Naclear Information i MEET] — ‘7 DOE ARCHIVES bituiuaee, nord li a <