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Figure 18.
Figure 19.
THYROID FINDINGS
exposed on Rongelap: 150 rads (from direct measurement of urinary **'I),*° 100 rads (byindirect
measurements on pigs removed from Rongelap
plus Marshallese urinary excretion data),”* and
160 rads (based on recent recalculationsof early
data*’ — see Appendix 2). Thelast recalculations
were based on analysis of pooled urine samples
mainly from adult Rongelap people taken 15 days
after the detonation; an estimate of the one-day
thyroid content of ?*"I was 11.2 pCi (3.6 to 22.4
uCi), assuming that 0.1% (0.005 to 0.2%) of the
maximum thyroid burden (not corrected for physical decay) was excreted in the urine on the 15th
During the past 3 years, the development of
thyroid abnormalities in a significant numberof
the people exposed on Rongelap, and in one from
the Ailingnae group, has resulted in extensive thyroid studies and surgical intervention in some
cases. The examination andtherapyof thefirst 6
cases of nodules of the thyroid gland have been
described.'°-*3-?4 Since then, the number ofcases
of nodules and hypothyroidism has increased to
18, and the new cases are described below.
The Radiation Dose to the Thyroid Glands
The dose to the thyroid gland from radioactive
iodine is determined byits uptake by the gland, its
half-life in the gland, thesize of the gland, and the
relative proportion of the several radioisotopes of
iodine involved. Therelative distribution of radio1odinesin fallout depends on the type of explosion
but in general is well known. In addition to '""l,
the isotopes '**I, '*I, and to a less extent '**I contributed significantly to the thyroid dose. The only
direct data available on the Rongelap people are
radiochemical analvses of pooled urine samples
taken 15 days and longerafter the fallout. Three
separate estimates have been made of the dose
from radiolodines to the thyroid glands of adults
5008308
|
25
day. The dose of 160 rads to the adult thyroid was
calculated from oral intake and inhalation of the
various lodine isotopes, considering their fission
yield, the average energy deposited in the thyroid
gland per disintegration, and the time of absorption. The dose tg the thyroid glands of children
<4 years old was then calculated by means of
these factors with consideration of pulmonary
function and the thyroid size of a child that age.**
The main sourceof iodine ingestion was considered to be water, and since it was being rationed
at the timeofthe fallout, it was assumed that the
children drank the same amount of water as adults
and therefore had the same thyroid burden of
radioiodines. The small size of the childhood thy-
o
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