gamma dose
stad
Dunng the past ten years, a disturbing finding has been the further
OM va
development of thyroid hypofunction, even in some Rongelap people
14 rad
without other detectable abnormalities. Table 3 showsthe present status
of thyroid hypofunction. The positive category represents individuals
who have exhibited two TSH (thyroid-stimulating hormone) levels of 6
uUrm! or greater. The suggestive category represents individuals who
ire was not
5 began to
.ed dose of
J rad in the
loses were
ye children
fhe Jargest
have two TSHlevels of 4 to 6.
The association of radiation exposure with the development of 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
cularly 2],
radiation therapy.
Ona risk per rad basis, the induction of thyroid nodules and cancer in
of growth
the Marshallese appears to be about equal to that following X-ray
‘ater corre‘ed funcwas about
larly in the
1 to appear
967, in the
» have had
exposure. Since ™'I is believed to be only about one-tenth as effective as
X irradiation in producing thyroid abnormalities, it seems likely that ir
the Marshallese the exposure to the short-lived isotopes of iodine ¥71,
331, and '51, which have more energetic betas and deliver a faster dose
rate than '"{, 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
which radioiodines are released. Exposure to penetrating gammas or
neutrons is a more serious hazard not only because of their acute effects.
v increased
tink group
but also because of the fatal nature of malignancies such as leukemize
unexposed
which may develop. Deaths due to thyroid abnormalities including cancer
Table 3.
Cancer?
Group
4.7%
(4/86)
0.9%
(4/437)
” Rongelap + Ailingnae
Woe ese
1.9%
(3/158)
eM I Tw ee eb
_—-.
USES are
Thyroid Hypofunction in Marshallese Populations
Positive
15%
Suggestive
9.3%
Total®
14 A%
(135-1150 rads)
(13/86)
Utirik
0.8%
(1/158)
(6/158)
Unexposed
0.6%
1.5%
3.0%
AL/155)
(1/67)
(2/67)
(30-95 rads)
(8/86)
(21/86)
3.8%
4.4%
(7/158)
* Some of these subjects appear also in the nodule table, ie., they have both hypofunction
and nodularity.
ye eeead
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.
Estimated