tentative value of 3% per year reduction in dietary 239, was estimated from sparse data. The derived quantity, daily activity ingestion rate on day of return to Rongelap (June 29, 1957), was calculated for many individuals for 1375, and was : . : plotted as a function of age in Fig. 4. ous . 137 An example of the variation in Cs values for male and female intake on day of rehabitation is shown in this figure. Differences in the daily ingestion rate of stable elements at the same geo- graphic location have been shown to occur among subgroups of a population C(ICRP74). As an example of the dietary variation at Rongelap, it was observed that coconut sap was used both as a major food supplement for infants, and then again (in a fermented form) in adult life by males as a component of daily fluid intake (Na80). Children and adolescents, however, were observed to receive a large portion of their daily fluid intake from two imported meals per day as part of the school lunch program. Studies indicated that coconuts and coconut tree sap provided the major source of 13765 in the diet (Le80a, Mi80). Thus, the undulating shape of Fig. 4 reflected this variation in the dietary intake of 1376, contaminated foods. Adult average values for activity ingestion rate on day of return were calculated for all nuclides. Results are listed in Table 4. This information, together with the estimate of k for the nuclide of interest, was used in Eq. 2 to estimate adult body-burden histories based on the assumption of declining con- tinuous intake (see Figs. 5 and 6). The declining continuous intake equation (Eq. 3) provided a smooth bodyburden function for Rongelap and Utirik adults. The equation was a tool to pro- vide retroactive body-burden estimates during the early years post return to 15