67
incidence in the exposed Rongelap people than in
the unexposed group and the low-level exposed
Utirik group. Whether or notthis is correlated
with radiation exposure cannot be ascertained.
The data must be interpreted with considerable
caution since (a) the populations are small, (b)} the
unexposed population was not examined before
1957 and has undergone changes due to both attrition and addition, (c) the diagnosis of mailignancyis not certain in all cases because ofthe difficulty of obtaining autopsies for verification. and
(d) the types of malignancy were not those that
have beencorrelated with radiation exposurein the
Japanese exposed at Hiroshima and Nagasaki.!77
Vi. Radiological Monitoring
of Personnel and Environment
A. GENERAL
During their 3-year sojourn on Majuro (19541957), the Rongelap people’s body burdens of
radionuclides decreased rapidly, as shown by
radiochemical analyses of urine. By 6 months
radionuclides in the urine were barely detectable.?
The Utirik people were moved back to their home
island after the initial examinations and were exposed to very low levels of residual radioactivity
there. In 1957 (3 years after the accident) gamma
spectrographic analyses were carried out on 4
Rongelap and 2 Utirik people at Argonne National
Laboratory in Chicago.!55 The findingofdetect-
able levels of 137Cs and ®5Zn (higher in the Utiriks)
indicated thefeasibility of using this technique in
the islands. When the Rongelap people returned
to their home island in 1957, the low levels of en-
vironmental contamination were soon reflected in
increased body burdens of some radionuclides.” A
numberof radiological surveys!56-164 at Rongelap
and Utirik have been carried out in conjunction
with personnel monitoring, largely by University
of Washington staff and more recently also by a
group from the BNL Health Physics and Safety
Division. These studies have provided important
information on the movementsof radionuclides
from the soil through the marine andplantfood
chain to man and should proveuseful in predicting future body-burden patterns of people returning to Bikini and Eniwetok. The principal residual
radioactive elements on Rongelap and Utirik were
137Cs, 99Sr, 65Zn, and *5Fe, with small but measur-
able amounts of otherfission products and neutron-
Figure 53. Steel room used
for whole-body gammaspectroscopy.’
Figure 54. Arrangement of lead bricks
used for whole-body counting.