the liquid phase (the lowest estimate reported, Ka66), no activity in the liquid phase from all other nuclides, and the appropriate activity of each iodine isotope in Bikini ash at 50 hours post-detonation, leads us to the same estimate of cistern water content as reported by Sharp and others, about 0.15 n° (Sh57). On the basis of 1) Bikini ash radioiodine activity per unit area estimates given in Table 13, 2) a 20% release of iodine activity from fallout granules to cistern water, and 3) an average cistern water volume of 0.15 m, we estimated the radioiodine activity concentrations for cisterns located at Rongelap Island. A range of cistern water activity at Rongelap Island was estimated to be between 0.2 and 2 times the average values given in Table 14. We based this estimate on the range reported for gross beta-activity measurements (0C68). The instantaneous activity concentrations given in Table 14 were adjusted for the rate of buildup of activity during fallout deposition. The activity concentration in Sifo Island cistern water was assumed by us to be 12% the values given at Rongelap. This was based on a ratio of mean exposure rate at both islands at seven hours post-detonation and the ratio of the fractions of total granule activity on the surface of fallout granules. Kawahara reported that the water removed the iodine near the surface of the fallout granule (Ka66). We assumed that small granules had a greater fraction of total activity near the surface than did large granules, because of the surface-area to volume ratio. We estimated a different portion of iodine activity released from granules sized differently from those at Rongelap by assuming -spherical-shaped granules and a mean granule radius for each island. The cisterns and wells at Utirik Island were observed to be covered as reported by the evacuation team aboard the USS RENSHAW (0C68). Interestingly, ghe range of cistern water activity at Utirik Island was 1.2 x 10° to 5.5 x 10? Bq 2! (0.003 to 0.02 uci ml~!), as computed for 0930 on March 3, 1954, from two different cistern water samples taken on March 9 (0C68). The mean Utirik cistern water activity was about one third the mean cistern water activity reported for Rongelap Island at the same time. The roof over each cistern apparently was not effective in preventing contamination. We assumed that activity in the liquid phase in two cisterns would be directly proportional to the ratio of exposure rates near each cistern as well as to the ratio of the fraction of total activity on the surface of the mean granule size in each cistern. This approach leads us to expect roughly equal radioiodine activity in the liquid phase in cisterns at Rongelap and Utirik Islands at the same point in time. This was largely due to a greater pro- portion of activity on the surface of fallout granules in the Utirik cistern. Thus, on the basis of expected activity vs measured activity, the cistern coverings at Utirik did protect the drinking water to some degree, perhaps reducing its activity by as much as a factor of 3. This reduction was based on the observed average activity ratio between Utirik and Rongelap cistern water. b. Activity Ingested with Drinking Water. Prior to evacuation of Rongelap, many weeks of drought were reported by Sharp (Sh57). In the weeks pre - 42 ~