Table 3.
Estimated whole-body (gamma) and thyroid doses (rad).
Thyroid dose (incl. gamma),
at exposure age:
Population
Rongelap
Ailingnae
Utirik
No.
Whole-body
dose
65
18
158
175
69
14
<10
810-1800
275-450
60-95
10-18
>18
335-810
190
30-60
335
135
30
estimated average dose of 1000 rads to the thyroids of young children appears
to be low; certainly for two boys who developed thyroid atrophy and myxedema.
The calculated doses are obviously rough estimates.
The incompatibility of
these observed effects with the calculated doses based on !3!1 must be related
partly to the short-lived iodine isotopes (see refs.
188-192).
However, the
Option must be kept open that the actual doses were higher than those esti-
mated and that possibly other radionuclides may have been absorbed by the
bones and contributed to the dose.
B.
Residual Radiation (Accumulated Exposure From Habitation on Rongelap or
Ucirik Atoll)
1.
Early Calculations
The subject will be only briefly reviewed here.
More detailed treatment
for earlier estimates can be found in the refs. 1, 13, 18, and 22.
lands,
When the Rongelap and Utirik people returned to live on their home isthese atolls, although considered radiologically safe for habitation,
still had low levels of residual radiation.
Before the Utirik people returned
in July 1954 and the Rongelap people in July 1957, they had largely excreted’
the radionuclides initially absorbed at the time of the fallout. By six
months, radiochemical analyses of urines of the Rongelap population revealed
barely detectable radioactivity (see Table 2).
A number of radiological surveys on Rongelap and Utirik following the
accident showed low levels of residual gamma radiation and small amounts of
radionuclides in the soil, water, and
plant, animal and marine life.
The
principal isotopes were 137¢5, 906 r, 657. and >>Fe, though very low levels of
several other isotopes were found.
When the people returned, personnel moni-
toring procedures showed low body burdens of these isotopes absorbed from the
enviromment.
(The short-lived isotopes of iodine had long since died out.)
The major contributing food plants were pandanus and coconut.
The coconut
crab, a food delicacy, had to be banned from the diet for >15 years because
of unacceptable levels of radioactivity. Measurable levels of °Fe were found
in the blood of Rongelap people (1,236), but since they were <1/100 of the
maximum permissible body burden, this was not considered a significant hazard.
~- 114 -