26
or nonexposureto fallout in 1954, since the body
burdens of the two groupsare indistinguishable
(see mean values for the two groupsat the end of
Table 15), and the present environmental contamination appears to be the importantfactor in
determining their present body burdens. The
island of Eniaetok {about 10 miles north of Rongelap Island) where some 50 Marshallese were living
is slightly more contaminated than Rongelap
Island itself where the majority of the peoplelive.
The Eniaetok group, however, had movedto
Rongelap about a month priorto arrival of the
team for the whole-body gamma analysis, and the
lack of appreciably higher body burdensofthis
group is probably influenced by this fact. The
Ebeye group had also moved to RongelapIsland
from an uncontaminated island about three
monthsprior to the May determinations, which
probably accounts for the fact that their body
burdens approach the Rongelap levels.
Samples for Sr’° analysis were taken from a
vertebra and from the ileum of the 35-yr-old
Rongelap man (No. 31) who died in April 1958.
The results indicated a concentration in these
bones of 3.7 puC Sr*°/e calcium.*
Analysis for Sr°° was carried out on 7 premolar
and molar teeth (pooled) removed in May 1958
from Rongelap residents (exposed and unexposed).
A value of 0.95 wuC Sr°°/g calcium was found.
This is considerably lower than the bone values
found in case No. 31, as would be expected, because of the relatively slower turnover rate of
strontium in teeth compared with bones.
A summary of the data on urinary excretion of
radionuclides by the Rongelap people for the past
4 years is presented in Figure 19, and on estimated
bodyburdenin Figure 20.
Discussion of Body Burdens.
In a discussion of
the body burdensof the Marshallese it is well to
recall the following historical points: (1) For the
first 2 days after the accidentin 1954, the people
lived in a highly contaminated environmentwith
little or no effort to avoid ingestion of fallout materials. This was reflected in their initially high
urinarylevel of radionuclides. (2) For the following 3 years (until July 1957) they lived on relatively uncontaminated island at Majuro Atoll,
during which time the radiochemical urinalysis
showed a rapid decrease of radionuclide concen-
lap, which had been carefully surveyed for radioactivity and was consideredto be safe for their
habitation. However, low levels of activity do re-
main on theisland, and these low levels are re-
flected in the increased body burdens and urinary
concentrationsobserved.
In Table 15 the urine concentrations are expressed in ppC/l. Since 1 puC/! corresponds to
2.22 d/m/1, the 1958 concentrations of Cs'** are
increased by factors of up to 100 over the 1957
concentrations, and that of Sr*° is increased by a
factor of about 20 (see Figure 19). As previously
noted (Figure 18), gammaspectroscopy shows a
concomitantincrease in the Cs'*’ and Zn" body
burdenlevels in 1958 over those seen in 1957 (see
also Figure 20).
Considerable individual variation in body burdens is apparent, but the various groups in Table
15 are not greatly different from one another.
Thereis some correlation of body Cs'*" and Zn"
with body weight, but the variation is great. The
correlation of body burden with urinary concentrations of Cs'*’ and Zn® is not very good. The
high urinary Cs'*? level in Eniaetok residentsis
not matched by muchhigherbody burdens ofCs'"".
Using the average values and an estimated 24hr urine volumeof 1450 ml, division of the urinary
excretion rates by the body burdens indicates that
1.05% of the body burden of Cs'*’ is excreted
daily, but only 0.106% of the body burden of Zn”
is excreted daily. It is not known whetherthe
people are in metabolic equilibrium with the
radionuclidesin this environment. However, taken
as steady-state values and assuming only urinary
excretion, these figures would indicate biological
half-times of 140 days for Cs'*” and 110 daysfor
Zn*°, values considerably at variance with the 17
days for Cs'*’ and the 23 days for Zn** quoted in
the recommendationsof the National Subcommittee on Permissible Internal Dose.*** A value of
145 days for Gs'*’ has been calculated by Anderson.*’ The shorter value for the Cs'** biological
half-time can probably be explained as being due
to prompt excretion of recently ingested cesium.
The zinc data, on the contrary, suggest an unusual
retention, which could, for example, result from
trations. (3) In July 1957 they returned to Ronge-
a deficiency of this element, but there are no data
at hand to support such a theory.
The body burdens of Sr°® appear to be well
below the maximum permissible levels (100 Sr®®
*This analysis was obtained through the Health and Safety
Laboratory, AEC, NYO.
*However, the new Handbook values soon to be published
indicate a biological half-time for Cs'*" of 70 days.*