ASA 78 ESTIMATED THYROID DOSES & PREDICTED THYROID CANCERS IN UTAH INFANTS EXPOSED TO FALLOUT I3? Charles W. Mays _ Physics Group Leader, Radiobiology Div., Anatomy Dept., U. of Utah Salt Lake City, Utah ABSTRACT: The inadvertent exposure of about 250,000 Utah infants to average thyroid doses estimated at 1.3-10 rads may provide a unique opportunity to establish the effects of low doses of IP3? irradiation in children. INTRODUCT ION Iodine~131 is produced in nuclear explosions. If cows eat forage which is contaminated with fresh fallout, °°! appears in their milk. If a child drinks this radioactive milk, I'3!? concentrates in his thyroid gland and irradiates it. Infants are considered to be the critical members of the population. Dr. Robert C. Pendleton* was the first to discover that fallout from the Nevada nuclear-tests of 1962 would cause significant contamination from radioactive 32 in utah. Following his vigorous urging that steps be taken to reduce the exposure, the Utah State Department of Health recommended: (1) transfer of cows from highly contaminated pasture to stored feed, and (2) diversion of highly contaminated milk from the fresh market (2) , protective action set a precedent: This it marked the first official attempt in this country to prevent the intake of fallout-contaminated food. In analyzing the 1962 incident I became fascinated with the implications of exposures from the previous years of testing. Unknown to me at the time, this problemwas also being investigated through different approaches by Dr. Harold A. Knapp then with the AEC, and by members of the St. Louis Committee on Nuclear Information. same conclusion: Working independently, we all came to the significant exposures were indicated. The problem was complicated enormously by the fact that I23? was not properly recognized as a fallout hazard during the early years of testing (1951, 1952, 1953 & 1955), and, unfortunately, I°?! was not measured in milk “associate Professor of Genetic and Molecular Biology and Head, Department of Radiological Health, University of Utah.