Of this radionuclide are not known. of 657n, 13765 and 905, observed, small (9). 1957. However, based on the levels 556 body burdens were probably ‘he Rongelapese returned to the atoll in mid-July, Whole body counting and urinalysis measurements one year later disclosed significant body burdens of several radionuclides, ‘the most notable being 13765, It is probable that SSHe body burdens increased similarly. The concentrations of 555 in a selected species of fish and in soils are listed in Table 2. Activity in the fish is based on wet weights for comparison with previous work. Pooled Bamples were used in the analyses to reduce the effect of withinSample variation. The 555 values for soil samples collected in 1963 at. both Kabelle Islet and Rongelap Islet are averages — of samples collected at depth increments of O-1.3 cm and 1.3-2.5 cm. Specific activities are not given for soils gince varying amounts of pre-1954 plant detritus could significantly alter the stable iron content but not the 35 re activity. In this instance, activity per unit weight of soil is a better index of changes ‘which occur as a result of input or loss than is specific activity. ; The decrease in o Bp. (goatfish) 5 5 Fe specific activities in Mulloidichthys, . ’ . * ; at Rongelap between 1959-1961 corresponds to an ecological half-life of 11 months, identical to that observed by Jennings (11). Higher specific activities may have occurred