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Before we go into the development of
thyroid abnormalities in the Rongelap
people, I would like to say a few words
about the calculations of the radioiodine
dose to the thyroid gland that they sus-
tained during the first 2 days on theisland.
There was no doubt considerable absorption of radioactive iodines from both inhalation as the radioactive cloud passed
over them andalso from contaminated food
and drinking water. Their drinking water
was caught in cisterns drained from the
roof, and contamination of the water was
no doubt increased by a slight rainfall on
the night of the fallout. There were few
direct data available on which to make an
evaluation of the dosimetry, so we had to
rely on indirect methods—that is, on radio-
chemical urinalyses. The first of these were
obtained at 15 days after exposure. It was
estimated that 0.1% of the isotope would
be present at 15 days,
back, it was calculated
gland contained roughly
Rall pointed out that
and extrapolating
that the thyroid
11.2 ue of 87. Dr.
there are several
iodine isotopes present in fallout. In addi-
tion to 1I, the isotopes 187I, ‘831, and 151
contributed substantially to the dose. In
making the calculations, energy dependence
per disintegration and the time of absorption
of the different isotopes were considered.
It was estimated that the adult thyroid
gland received approximately 160 rads from
radioiodines and of course an additional
175 rads from the gamma radiation. In
approximating the dose to 3- to 4-year-old
children, the above factors were considered,
and, in addition, we considered the difference in pulmonary function and smaller
size of the thyroid gland in the child. We
know that water rationing was in effect at
the time of the fallout, so it is assumed
that the children drank as much contaminated water as the adults did, thus absorbing the same amount of radioiodine.
It is estimated that the child’s thyroid
received roughly between 700 to 1,400 rads
from the radidiodines in addition to 175
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Annals of
Internal Medicine
rads of gamma radiation. That most of
these people had beta burns in the neck
region over the thyroid was not believed
to contribute ‘significantly to the dose to
the thyroid gland because of the low energy
of the beta radiation in the fallout material.
- Over the years we have carried out care-
ful thyroid examinations during the annual
surveys. Until 3 years ago the people were
considered to have normal thyroid function
with no obvious evidence of any thyroid abnormality. Numerous serum protein-bound
iodine (PBI) determinations were done,
and all appeared in the normal range for
these people. The PBI levels in the Marshallese are considerably higher than American levels, which was found to be because
there is a large amount of iodoprotein
present (12), as we shall discuss later. This
may have misled us during these early
years. The diet of these people apparently
had sufficient iodine but with no overabundance apparent. Urinary excretion
studies showed that they averaged about
105 pg in 24 hr in 28 people, which ts in
the normal range. Cholesterol studies have
not shown anysignificant differences in the
exposed and the unexposed people. Thus,
there was no reason to suspect that there
was any thyroid trouble.
Three years ago we detected the first thyroid nodule in a 12-year-old girl. Since that
time the prevalence has been increasing,
and we now have 18 cases of thyroid ab-
normalities, 16 with nodules and 2 with
hypothyroidism, the latter showing no nadules. All of these except 1 case occurred in
the more heavily exposed Rongelap group
that received 175 rads of whole-body radia-
tion. Table 3 lists the thyroid abnormalities with age at exposure, sex, and time of
detection. It is noteworthy that the 2 cases
of hypothyroidism occurred in the 2
dwarfed boys.
Table 4 showsthe distribution of thyroid
pathology in the different populations examined. The interesting fact emerges that
the highest incidence, 78.9%, of these ab-
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