treated cases yield carcinoma; nevertheless, the data suggest that 200 r is a potentially carcinogenic dose to the infant thyroid. While the possi- bility exists that the carcinogenic action may be an indirect, hormonal one, it must still be recognized that this, like leukemia, is an instance of Significant carcinogenesis by less than 1000 rep. It seems likely that the infant thyroid is unduly susceptible, but that the adult thyroid is not.---"28 Table Two indicates the amount of ingested fission product activity to produce one rad dose to the lower Jarge intestine and Graph Five shows the relative doses to the gastrointestinal tract and the thyroid. It may be seen that ingestion of a given activity on the fourth and fifth days may result in nearly two and one-haif times the dose to the thyroid as to the lower large intestine. For a continuous consumption of fallout material from the first hour to the 30th day the ratio of dozes is about 1.7. 3. Bones DOE ARCHIVES It 18 recognized that the intake and deposition of strontium-89 and 90 are intimately associated with the calcium in the diet. Whereas it has been assumed here that a fixed percentage of the strontium intake is deposited in the bones (Reference Five). It is realized that this method involves uncertainties, as would the necessary assumptions to generalize for a wide variety of calcium--strontium ratios and intakes -13- He