thyroids was first observed nine years after exposure among these people 1967 fourteen of sixty-eight of the most heavily exposed had develczed n ches wrach were of sufficient concern to require exploretion. Cne carcinema had bedn found. AS a resuit of the survey early in 1969, five more individuals in this pdpulaticn were found to have developed thyroid masses which we felt should be expldred. F were from the more heavily exposed group on Pengelap atoll, l.e. several fhuncred 77 fourteen hundred rads estimated dose to the thyroid; and one on Utirik «affil whe ned probably received 30 rads. These were brought back to the U.S. for s : peck at Brookhaven Wational Laboratory. Because of our interest in and labor of radiated thyroids, the patients were brougnt to our institution in Se for surgical exploration. Three of the five proved to have lesions of tie thyroid which were malicnant (two Rengelap; one Utirik). One of these had externdive regicrsi metastases. A fourth patient possessed several nodules, one of which wag very smail and has prompted serious consideration that this might also be malignant] Autcredicgra: were immediately prepared in addition to a variety of observations commorfly made cn tissues from our animals (not %y-thymidine). Several of these thyroids Had many minut sclid cellular hyperplastic lesions, none of which took up significant ampbunts cf radicicdine. Many of the lesions were papillary in structure and suggested papiliary lesions of multicentric origin. All of these thyroids (except the woman showed the large bizarre nuclear forms repeatedly observed umder this co animais and humans that had received 131y, Mention was made in the past annual report cf a preliminary review thyroid tissues for evidence of radiaticn effect based primarily on the the Marshaltss: Dkzarre muciesr forms and other subtle changes as observed in rats and human thyroid tisshe. study has just been completed in a formal manner. This To test the validity of these criteria as evidence of radiation effet, Dr. Robert Conard of Brookhaven National Laboratory assembled multiple slides] of each ties, Cr thyroid of the Marshallese, of some thyroids of Japanese atomic bomb ca _ thyroids or the Utah-Nevada children who may have been exposed (menticne elsewhere in this report - from Ir. Marvin Rallison) and of miscellaneous unexvosed nodular thyroids collected from elsewhere in Utah. More than 100 individual slid S, completely disguised as to identity, were submitted to this writer for review and ap raisal as to evidence of radiation effect in them. All slides were graded as to posi ve or nezativs evidence of radiation effect, and where positive, the evidence was furthe graded ona basis cf +, ++, or +++; + being the slightest evidence and +++ being pren unced evicence. After individual slides were graded and reported to Dr. Conard, multiple had come from the same thyroid were grouped together (still as unkncwns) reappraised. Although in most cases the ratings on several slides fren individual were similar, it was aopropriate to affix a single rating to e In no case was the rating changed more than one degree to arrive at a coi for a given thyroid. Tha results shew that all of the Marsrallese except identified as having received radiation exposure. Among these was a Mars llese woman who had Leen exposed and several years later had died of other causes cn where a post mortem provided the tissue which was free of gross nedularit of the unexpesed thyroids and a few of the Utah-lievada group were graded or +. Because of the correlation of the observaticns, Dr. Conard subsequ ntly ontainec the individual theoretical records of rad dose delivered to the thyroid ( sed on >ady burden determined scme days after the removal of the Marshallese pecple 7 m Ronge.sp). The degree cf change attributed to radiation effect in the thyroids preveg to corre ats in surprisingly precise fashion with the degree of exposure previously Cajculated. “ost of the Japanese tissues were graded only + or G. Where as sce observers fhave pleced consideral:le weight of evidence for radiation effect upon the presence cf [lymphocyte] Aigl Re on ” ae : . get Bia % : . % , wo “ Sha = Aa