34 tea, it became evéefTifore difficult to extrapolate to body burdenfromfood. It is obvious that further data are required on the transport of low levels of Sr°’ and other products through the ecological cycle in this and other communities to make possible assessment from environmental data alone of the internal radiation hazard to human beingsliving in falloutcontamenated area. More reliable estimates of the Marshallese body burdens can be obtained by whole-body gamma spectrometry and by radiochemical urinalvsis. Radiochemical Analysis of Urine " 0.24 0 'h~ 40 DAYS . iyR ayR RETURNTORONGELAP cea BYR, dg ‘ 3000 a idental inhalation of Sr®°, and were used in esxirapolating back to the one-day Sr*° body burden of the Marshallese.””, The 1958 Rongelap body burdensof Sr*°, Cs'"", and Zn™ are presented in Table 32, and also figures for percent of equilibrium and equilibrium S980 1200 1500 1800 TIM. ON DAYS ~ AFTER MARCH |, 1954 cretion data. These values are subject to some un- ileum from a deceased 35-year-old Rongelap male at this time indicated a level of about 3.7 puCrg 4 Ca, which gives, upon application of the normali- ] zation factor of 2 from vertebra to average skele- ton,°* an average skeletal value of 2 puC/g. Thus the mean body burden of Sr®° for exposed Rongelap people in 1958 was estimated to be 2 muC, or about 9%of the estimated equilibrium value of 1 4 1 4 | 23 myC.°° . The estimated Sr°° body burden increased from 2 mpC in 1958 to 6.0 muC in 1959, or 26% of the estimated equilibrium value. The 1959 Sr?° mean Figure 55. Urinary excretion of Sr°° in exposed Marshallese. urinary value in the exposed Rongelap inhabitants was 6.3 uuC/I] or 10.5 puC/24-hr urine, based Table 32 Estimation®® of Body Burden, in mpC, of Rongelap Population From Urinary Excretion Levels, 1958 Cs Sr’, Exposed Body burden . - Equilibrated body burde Percent of equilibrium Daily intake 2* 23 9 0.015** *3.7 Strontium units (SU) determined by bone biopsy. **15 SU assuming daily calcium intake = g. “ Exposed 900 1300 69 2(?) Zn* Control Exposed Control 1200 1600 73 280 330 85 540 650 83 2.1-4.1 we body burden of Sr°° in March 1958 was 2 puC/g Ca, based on the 24-hr Sr®° output in urine (1 liter per 24 hr), and this appeared to be of the right order of magnitude compared with data from” - certainties, since they are based on a number of assumptions: however, they can be checked by use of other methods. For example, the estimated bone analysis. Two bone samples of vertebra agd ] L 1.0 0.6 half-life of 500 days. These excretion rates cor- respond to those reported by Cowan” in a case of 14 tf ay, March 1957. > 40 days. The smaller fraction is excreted witha a, Sr®° for the 5 years following exposure to fallout are shown in Figure 53. The 4- and 5-yearlevels were muchhigher,after the return of the Marshallese to Rongelap in July 1957, the mean being higher by a factor of 20in March 1958 than in , Sr°? is excreted early, with a biological half-life of value, estimated by Woodward”from urinary ex- The urinary excretion levels of 0 3 vears following exposure. The major fraction of “. Strontium-90. The excretion rate of Sr?” may be expressed as the sum of two exponential functions for the first