49
to that of the phantom, which was counted for 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 amounts of other
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 werecollected in plastic bottles and sent to BNLforradio-
chemical analysis. A modification of the method
of Farabee*® was used for the analysis of Sr®°. Sr
was precipitated as the alkaline phosphate, ashed
with HNO, and H,O,, 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 was adjusted to
5.5. The solution was then passed through an 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 wasthenrinsed with 6
N HNO,to removethe 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 supernatantfrom the alkaline phosphate
precipitation was measured anddivided into two
portions. One portion was scavanged for cesium
with added carrier by means of a double precipi_ tation 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
muffle furnace at 800°C. The ash was weighed,
and a small portion was counted for gross beta
activity. The ash was dissolved in dilute HNO,
andprocessed by the method described above for
urine analysis.
All counting was donein a low-level beta anticoincidence type of counter, designed and built at
BNL. Samples were mountedon glass fiberfilter
discs with nylon rings and discs and Mylar film.
Samples were counted against NBS standards
C2
CD
a)
¢
C4
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 for
radiochemical analyses.
Environmental Estimate
One method used (the least quantitative) was
the environmentalestimate of body burden. The
‘environmentalestimate 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 numberof rats were collected
on RongelapIsland 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
humanbeings inhabiting this area, the rat analy-.
ses might serve as indicators of the humaninternal
radiation contamination. The Sr°°/Ca ratios of
varioustissues of these rats were measured direct-
ly and comparedto theratios of the food andsoil
on Rongelap collected 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 measurementgives the
value at the time of measurement (and thusthe
percentof the equilibrium valuefor the individual
radionuclides).
The Sr*°/Caratios for different plant foods on
Rongelap varied greatly, and the diet of the rats
wastoo uncertain for an “average” diet to be assumed. Therefore, for a body burden estimateit
wasnecessary to use the Sr°°/Ca valuesofthesoil
itself.
The “strontium-calcium observed ratio” (OR)
of Comar*? was used to denote the preferential
utilization of caicium in the following manner:
Sr/Ca of sample
OR sample-precursor —™ Sr/Ca of precursor
The Sr®® discrimination ratio in the chain from
soil (s) to bone (6) via plants ( p) can be expressed
as follows:
‘
OR,.,=(OR,,)(OR,.,)=(0.7)(0.25)=0.18 .