RESULTS AND DISCUSSION.
Cesiunt37 Excretion Levels and Body Burden
The urinary excretion levels of cesiuml37 for the years 1954, 1957, and 1958
are shown in Tables 1 - 4.
On 24 ~ 25 March, 1954, the mean excretion level of
cesiuml37 for all age groups was 4C5 uuc per liter.
With an excretion rate of
O.46 percent (4) of cesium!37 poay burden per 24 hours, the mean body burden
from fallout 24 - 25 days after exposure was 1405/4. 6x10" 3 x 10°
(+ 54 percent).
6 or 88 muc
This value is about 20 times the average body burden reported
by E. C. Anderson, et al (5, 6) for people measured during 1956 - 1957 in the
United States.
The cesiun!37 urinary excretion levels for the six months follow-
ing cxposure can be expressed as an exponential function, and a best line of
fit drawn through the data resulted in a half time for elimination of about
110 days (Fig 1).
A biological half time of about 140 days has been observed
on volunteers who ingested one microcurie of radio-cesium (4).
From the 1957 Cst37 excretion levels (Table 2) the Rongelap group exposed
to fallout was estimated to have an average burden of about 7 muc, whereas the
Rongclap control group was about 2 mic.
Body burden in either group in 1957
is comparable to levels measured in the U. S. population (6).
With a half time
for climination of the order of 150 days, the body burden of the exposed Rongelap
group should have decreased from the March 1954 level to 7 muc in about 550 days,
or late in 1955.
<A body burden of 7 muc for this group in March 1957 could then
indicate a continuing exposure to Cts during 1956 of the order of 32 micromicrocuries per day from stratospheric-tropospheric fallout while residing on
Majuro.
Since the Utirik group was returned to their atoll in 1954, the mean body
burden in 1957 was elevated to an estimated 337 muc, some 48 times the Csl37
burden of the exposed Rongelap people who resided on Majuro.
This long residency
C2)
time on Utirik atoll after fallout contamination, as compared to the excretion