24 ee. —~8 (Findlay and LeBlond, 1948; Goldberg et al., 1950). These studies involved the administration of a single large dose of radioflodine. The effects of chronic exposure to radioiodine in sheep were reported by Bustad et al. (19578) and Marks et al. (1957). Exposures ranged from 0.15 to 1800 yC4 1311 per day for periods of a few months to 4 years. Corresponding total doses to the thyroids ranged from 400-800 rads to over 100,000 rads, at dose rates of 3.4 rads/week to 30,000 rads/week. At the lowest level (0.15 pCi/day) thyroids showed no damage, while those at the highest levels were ablated. Exposures at fntermediate levels resulted in slight, moderate, or severe thyroidal effects, depending on the dosage, ang the time of exposure. Although impairment of thyroid function was the effect of interest in this Study, some thyroid adenomas and a fibrosarcoma were also reported (Bustad et a)., 1957b; Marks and Bustad, 1963). Similar effects may be expected in euthyroid people after comparable doses. [Exposures required for ablation of Lhe human thyroid were found to be 32,000-40,000 rads (Goolden and Vavey, 1963). Thyroid Neoplasia Although V3 was being used in the treatment of thyroid cancer in the 1940s, there was apparently no work being done on the role of radiofodine in the production of thyroid cancer at that time. This is not to say that the possibility of the carcinogenic nature of radiolodine was being ignored, however. A 1946 editorial in the Journal of the American Medical Assoctatinn (Anonymous, 1946) stated that The late development of cancer as a result of trradfation (by radiofodine), aithough perhans unlibely, fs certainly within the realm of possibility.