On the basis of these consideratims, the tissue sections ‘were gradedlas to positive or negative evidence of radiation effect by the following system: 0 + - ++ +++ - Nothing to suggest radiation effect Uncertain category ~- some features suggested there might be radiation effect - cften more samples of tissue would have to a definite decision Definite radiation effect Marked radiation effect; at least some architectural distortio in addition to bizarre nuclear forms After the observations on each individual slide had been recorded and Feported to Dr. Conard, the slides were grouped so that all slides from the same indivifual could be reviewed and a single grade registered for each thyroid. In some cases, there had been considerable variation in the appearance of the tissue from one area tb another. In such cases the evidence for radiation effect was much more convincing inj some areas than in others. Where only a single slide was available a reevaluation andj grading was all that could be done. When the code was broken and the judgement as to radiation changes was] matched against the radiation exposed (so far as was known), it was found that ther was a surprisingly close correlation between exposure and the recognition of radiftion effect in the thyroid. See Fig. 13. Tissues from 7 of the 16 Marshallese who werg thought to have had the greatest radiation to their thyroid had unequivocal evidence in tissues. Most of the Marshallese were singled out as being at least suspicious. Onelfof these that was definitely positive was considered a Marshallese control (thyroid Fissue from post mortem examination from the hospital on Majuro) that later proved to b@ an individual that had been exposed but had developed no gross thyroid pathology (335 rads). Changes in the thyroids from the Japanese bomb casualties showed minor fer only Suspicious change when they were arranged in order depending on their distayee from the epicenter. Those nearest seemed to have the most suggestive change. This {find ing, if Significant, was surprising because the amount of radioiodine in that fallajt was small considering the presence of otherTadloactiveématerials that were in the falldut. Only debatable changes were seen in the tissues from the Utah group, most of which were not thought to have been exposed to significant fallout. considered positive for radiation effect. One case in ]§ was At the present time, it is imposspble to determine for certain just how much radiation exposure these individuals recbived. Certainly the majority had not lived in the fallout area when the largest faflout occurred. Most of these thyroids were adenomatous. ‘Some of those in which suspicion was raised were in glands that contained considerable lymphocytic thyroiditis accompanifd by hyperplasia. - The only gland that was classified as positive had been considfred normal in the pathology report but in this study there seemed to be an occasional ge radiation nucleus. These observations served to illustrate that subtle degrees of radiatiah caused by radioiodine in the thyroid can be identified. . changes