rivatives (Be69). To estimate the error, partial cross derivatives and partial derivatives were determined for k and P° with respect to the fifty-year cumulative intake. Since only one measurement for adult average 5556 body burden was avail- able, the relative standard deviation of the adult average P° was assumed to equal the relative standard deviation of individual adult P°'s which were determined from the 1970 individual adult 37 Fe body burdens. Only two values for the set of adult average 600, and 23954 body burdens were available and therefore the same method was employed to obtain adult average standard deviations for k and P°, External Radiation Exposure The external radiation exposure rate data were measured by many individuals and an explanation of their methods can be found in their reports (Ché60, He65, Gr77b, JCAES7, Ti81, USPHS5S9). A value of 2.8x10° Gy in tissue of interest per nC kg (0.73 rad per R) measured in air at one meter above the surface was used to convert their data to absorbed dose in tissue. based on several considerations. This factor was First, the planar source represented by the flat atoll was assumed to be an exponential distribution of 13764 activity with depth in soil, typical of aged fallout (Be70). The nature of this source caused minimal variation of absorbed dose with depth of organ; however, the difference in the number of electrons per gram of air and per gram of tissue necessitated a correction. Secondly, since the atolls presented a varying exposure rate envi- ronment, absorbed dose was adjusted for living pattern variations. Both of these considerations combine to give the above factor used to convert external exposure to absorbed dose in tissue. Specific details on the adjustment for liv- ing pattern variation were given by Miltenberger and Greenhouse (Gr77b). ll