C Fallout is transmitted to children through the food chain. A034 35 THYROID IRRADIATION IN UTAH INFANTS EXPOSED TO IODINE 131 By CHARLES W. MAYS HE INADVERTENT EXPOSURE of about 250 thousand 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 iodine 131 irradiation in children. Iodine 131 is produced in nuclear explosions. If cows eat forage which is contaminated with fresh fallout, iodine 131 appears in their milk. If a child drinks this radioactive milk the iodine 131 concentrates in his thyroid gland and irradiates it. Infants are considered to be the critical members of the population. The transmission of fallout to children is illustrated in the figure. Dr. Robert C. Pendleton (Associate Professor of Molecular and Genetic Biology, University of Utah) was the first to discover that fallout from the Nevada nuclear tests of 1962 would cause significant contamination from radioactive iodine 131 in Utah.’ Both our measurements,’ and those of the U.S. Public Health Service? showed that iodine 131 levels in Utah milk exceeded the radiation protection guide of the Federal August, 1966 Radiation Council. Following Pendleton’s vigorous urging that steps be taken to reduce the exposure, the Utah State Department of Health recommended: transfer of cows from highly contaminated pasture to stored feed; and diversion of highly contaminated milk from the fresh market.‘ This protective action set a precedent: it marked the first official attempt in this coun- try to prevent the intake of fallout-contaminated food. In analyzing the 1962 incident I became deeply concerned about the exposures from the previous years of testing. Unknown to meat the time, this problem was also being investigated through different approaches by Dr. Harold A. Knapp, then with the Atomic Energy Commission (AEC), and by members of the St. Louis Citizens’ Committee for Nuclear Information (C.N.I.). Working independently, we all came to the same conclusion: significant exposures were indicated. For example, thyroid doses to infants in St. George, Utah, from the “Harry” shot of 19 May 1953, were estimated at 120-440 rads* by Knapp; 100-700 rads by C.N.I., and using a less reliable method, 68 rads by myself.5 DOE ARCHIVES