RESULTS AND DISCUSSION Daily Activity Ingestion Rates Daily activity ingestion rates were calculated for dosimetrically significant nuclides post return. An exponential decline was proposed for the inges- tion rate within a population subgroup and initial reference values are given in Figures 10 through 14 (June 1, 1957, was assigned as a return date to Rongelap). Figure 10 demonstrates the differences in ingestion of 1376, for various popula- tion subgroups. This undulating pattern was exhibited by 1376, 995, and 620, nuclides for which sufficient data existed for analysis. Differences in ingestion rates of the stable element at the same geographic location have been shown to occur among members of a population (ICRP 23). Age dependent diet studies for ingestion of Cs for urban Japan have values varying from 11 pug at for adults to 8.6 Ug at for children. Sr in a western type diet rose from 600 yg at for infants to 690 pg at for 5 year olds to 3,600 pg a for 13 year olds and fell to a mean of 1,900 ug at for adults. Zn in the United Kingdom rose from 2 to 40 mg al, the higher value of Zn being observed in adult tea drinkers. Fe ingestion in a western type diet has a mini~ mum at age 3 and maxima at ages 1 and 20 years. ue al Co is ingested at a rate of 20 for Japanese adults and half this amount for children. population also exhibits dietary changes as a function of age. The Marshallese The authors of the Marshall Islands Diet and Living Pattern Study (Na80) observed coconut sap being used as a major food supplement for infants, and later in adult life as a major source of daily fluid intake. Since coconuts and coconut tree sap pro- vided the major source of 13766 on Bikini Atoll (Le80, Mi80), the shape of Figure 10 was in agreement with the observed diet pattern. 22