57
red
dose
people. In the Rongelap-Ailingnae group, 65% of those exposed as
children had nodules compared with 27% of those exposed as adults.
Paradoxically, in the Utirik population a greater percentage of adults had
nodules in spite of a higher dose to the children’s glands.
During the past ten years, a disturbing finding has been the further
development of thyroid hypofunction, even in some Rongelap people
without other detectable abnormalities. Table 3 shows the present status
of thyroid hypofunction. The positive category represents individuals
who have exhibited two TSH (thyroid-stimulating hormone) levels of 6
2U/mi or greater. The suggestive category represents individuals who
have two TSH levels of 4 to 64.
The association of radiation exposure with the developmentof thyroid
abnormalities in the Rongelap population seems apparent though the
Utink findings are less clear-cut. The development of thyroid tumors
following radiation exposure is well documented in the Japanese exposed
to the atomic bomb and in patients, particularly children, following
radiation therapy.
On a risk per rad basis, the induction of thyroid nodules and cancer tn
the Marshallese appears to be about equal to that following X-ray
exposure. Since ''I is believed to be only about one-tenth as effective as
X irradiation in producing thyroid abnormalities, it seems likely that in
the Marshallese the exposure to the short-lived tsotopes of iodine '"1,
337 and '51, which have more energetic betas and deliver a faster dose
rate than ''I, might account for the high incidence.
The findings in the Marshallese emphasize the importance of thyroid
exposure to radioiodines that may result from warfare or accidents in
sed
DUP
sed
which radioiodines are released. Exposure to penetrating gammas or
neutrons is a more serious hazard not only because of their acute effects.
but also because of the fatal nature of malignancies such as leukemia
which may develop. Deaths due to thyroid abnormalities including cancer
Table 3.
Thyroid Hypofunction in Marshallese Populations
Group
Positive
a)
Rongclap + Ailingnae
(135-1140 rads)
15%.
(13/86)
9.37
(8/86)
24.47
(21/86)
38)
Utirik
(30-95 rads)
0.8%
(1/158)
3.8%
(6/158)
4.4%
(7/458)
Unexposed
0.69%
1.5%
3.0%
(1/1585)
(1/67)
(2/67)
=
7)
Suggestive
Total?
“Some ofthese subjects appear also in the nodule table, ie. they have both hypolfunction
and nodutarity. .