RESULTS AND DISCUSSION DAILY ACTI]V1TY INGESTION RATES Daily activity ingestion rates were calculated for dosimetrically significant nuclidis post return. An exponential decline was proposed for the inges- tion rate within a population subgroup and initial reference values are given in figures 16, 11, 12, 13 and 14 (June 1, 1957 was assigned as a return date to Rongelap). Figure 10 demonstrates the difference in ingestion of 1376, for vari- ous population subgroups. This undulating pattern was exhibited by 137¢, | 905, and 6570, 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 ll pug a? for adults to 8.6 ug a? for children. Sr in a western- type diet ruse from 600 Ug at for infants to 690 yg a} for 5 year olds to 3,600 Lg a for 13 year olds and fell to a mean of 1,900 Ug al for adults. Zn in the United Kingdom rose from 2 to 40 mg at, 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 maximums at ages 1 and 20 years. Co is ingested at a rate of 20 ug at for Japanese adults and half this amount for children. The Marshallese population also exhibits dietary changes as a function of age. 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 provided the major source of 13705 on Bikini Atoll (Le80, Mi80), the shape of Figure 10 was in agreement with the observed diet pattern. 12