49
to that of the phantom, which was countedfor 30
min (Figure 52).
In future whole-body counting of these people,
it will be possible, by counting for longer periods
and using an 8-in. Nal crystal, to improve the
absolute measurement of trace amountsofother
radionuclides that may be present.
Since a total of 227 Marshallese persons were
surveyed with the whole-body counter, in addition
to numerouscontrols, the spectral analyses were
performed with the aid of a 704 IBM computer.
Radiochemical Procedures
Twenty-four-hour urine specimens were collected in plastic bottles and sent to BNL for radio-
chemical analysis. A modification of the method
of Farabee*® was used for the analysis of Sr®*°. Sr
wasprecipitated as the alkaline phosphate, ashed
with HNO, and H,QO,, and dissolved in dilute
HNO.,,. After the solution was brought up toa
volume of 800 cc, the alkaline earths were com-
plexed with EDTA, and the pH wasadjusted to
5.5. The solution was then passed throughan ion
exchange column (Dowex-50 in the Na form),
and the column wasrinsed with 300 cc of a solution of 1% citric acid and 0.75% EDTAat a pH of
5.0. The combined effluents contained >95% of
the total Ca. The column was then rinsed with 6
NV HNO, to remove the Sr®°. Carrier Sr was added
to the Sr®*° fraction and precipitated with 70%
fuming HNO,,. Yttrium-90 was milked and counted
by the method of the AEC Health and Safety
Laboratory.*'
The supernatant from the alkaline phosphate
precipitation was measured and divided into two
portions. One portion was scavanged for cesium
with added carrier by meansof a double precipitation of the aluminum sulfate and the chloro-.
platinate.** The second portion was analyzed for
K by flame spectrophotometry.
Food samples were weighed and dry-ashed in a
mu fle furnace at 800°C. The ash was weighed,
and a small portion was counted for gross beta
activity. The ash wasdissolved in dilute HNO,
and processed by the method described abovefor
urine analysis.
All counting was done in a low-level beta anticoincidence type of counter, designed andbuilt at
BNL. Samples were mounted on glass fiber filter
discs with nylon rings and discs and Mylarfilm.
Samples were counted against NBS standards
processed and counted underidentical geometry.*!
RESULTS AND DISCUSSION
All three of the above methods wereused for
estimating the body burdens of gamma- and betaemitting radionuclides in the Marshallese people.
Individual values for all the people examined in
1959 may be found in Appendix 7 for gamma
spectrographic analyses and in Appendix 8 for
radiochemicalanalyses.
Environmental Estimate
One methodused (the least quantitative) was
the environmental estimate of body burden. The
environmental estimate of internally-deposited
Sr®° was made in two ways. In the first method,
animals subsisting on diets similar to humandiets
were sacrificed and their tissues were analyzed
radiochemically. A number ofrats were collected
on Rongelap Island at 2, 4, and 5 years after the
1954 accident. If the diet of these rats, primarily
land plants, was sufficiently similar to the diet of
human beings inhabiting this area, the rat analyses might serve as indicators of the humaninternal
radiation contamination. The Sr®°/Ca ratios of
varioustissues of these rats were measured directly and comparedto the ratios of the food andsoil
on Rongelapcollected at the sametime; thatis, the
environmental contamination was compared with
the directly measured contamination in animal
tissue. Extrapolation of the environmental data
gives the equilibrium value which can be expected, whereas the direct measurement gives the
value at the time of measurement (and thus the
percent of the equilibrium valuefor the individual
radionuclides).
The Sr*°/Ca ratios for different plant foods on
Rongelap varied greatly, and the diet of the rats
was too uncertain for an “‘average”’ diet to be assumed. Therefore, for a body burden estimateit
was necessary to use the Sr*°/Ca valuesofthesoil
itself.
The “strontium-calcium observed ratio” (OR)
of Comar*? was used to denote the preferential
utilization of calcium in the following manner:
Sr/Ca of sample
ORsamote-orecussor= precursor
The Sr®° discrimination ratio in the chain from
soil (s) to bone (d) via plants ( p) can be expressed
as follows:
OR,.,=(OR,.,)(OR,_,)=(0.7)(0.25)=0.18