De drinking water supplies would be principally in soluble form. The water collected fram a well and a cistern on the Island of Rongelap (Table Three) about 21 months after the March 2, 1954 fallout, was found to have about 80 percent of the activity in the filtrate, but there was an undetermined. amount that settled to the bottom. Other data suggest the material to have been about 10-20 percent soluble in water. In the event contaminated food is ingested it is possible that the total activity--soluble and insoluble--may find its way into the gastrointestinal tract since at times immediately following a fallout most of this activity probably would come from the surface contamination rather than the soil-plant-animal cycle. There may then follow some solubilizing in the acid stomach with subsequent removal from the tract before reaching the lower large intestine. . It is assumed for these calculations that (a) 90% of the fallout material is insoluble when computing doses to the gastrointestinal tract, and (b) that the isotopes of iodine, strontium, and barium are all soluble when computing doses to the thyroid and to the bones. These assumptions are probably conservative, i.e. they may overestimate somewhat the radiation exposures. B. Biological Significance. DOE ARCHIVES After the estimation of radiation doses by any procedure the final step is an evaluation in terms of biological effects both for short and Jong terms. ri