vA
mvelogenous form, since his past: hemograms
showed a fairly consistent depression of neutrophil
counts compared with these of other exposed boys
of the same ave.
The inability to demonstrate clear-cut aging ef-
fects ia the exposed group in spite of repeated atlempis with a variety of tests is in accord with the
generally negative results of similar attempts in
the much Jarger expased Japanese populations.
The absence of radiation-induced cataractsis
nut unex pectedsince the dose tu the lens was prob-
ably below threshold and neutrons (knows to
have a higher RBE for cataract induction than
wanna radiation) were not divolved in the Mar-
shallese exposure.
to the higher dose to the cluld’s thyroid because of
its sutaller size. The rapid growth of the glands
during childhood probably increased the chances
for neoplastic changes. Vhe growth retardauon
in some of these children was thought to be related
to reduced thyroid function resulting in lower hoe:
sone levels. This deliciency was not recognized
during the early years because of falsely high PBI
levels resulting from unusually high todopratein
levels, which turned out to occur generally in the
Marshallese and are now being further studied.
Mast of the thyroid glands of the exposed people
undergoing surgery contained multiple nodules or
arcas of adenomatous change. MLany microscepic
areas, although considered benign, were composed
of discrete areas of atvpical cells, suggestive in
£. THYROID EFFECTS
The high incidence of thyroid neoplasms (in 27
of 8b exposed Rongelap peuple, including 3 with
carcinomas) and the development in some children of hypothyroidism and growth retardation
provide clear evidence for the seriousness ofthyroid
some Ges of malignant potential,
The cisk of developing benign and malignant
neoplasms in the Rongelap people appeared to be
about the same as that noted in peaple exposed to
x-radiation. Clinical experience with MT sug.
gested that the risk would have been less, but the
higher energyof the short-lived isotopes ofiodine
injury due to radioiodine absorbed fromfallout as-
(particularly !!T, PW aod 21), resuliing in
medical studies in the population been instituted
soon after the exposure and continued to the present date. the extent of thyroid etlects might nut
the thyroid, is thought tu have been the important
factor in increasing the number of thyroid abnormalities above that expected from similar doses
sochated wilh atomic detonations. Had not careful
have beea discovered,
Vheroid exposure is likely to be greater whea
individuals are exposed within 100 to 150 mites of
the bomb ifdetonated near the ground. In such
higher dose rate and more uniform exposure off
from MT alone. fis not unreasonable to speculate
that (uanor incidence ia the Marshallese would
have been considerably smaller if only "1 had
been invelved in the exposure. ‘he lesser amount
of short-lived tadine isatopes in the Utirik expo-
situadians, if lethal exposure to penetrating radiaVion does not occur, the principal hazard appears
sures (because of the later arrival of the fallout)
leukemia, Since the latter is ultivvately fatal, it is
the dose effeet to their thyroids, but the muniber af
to be the late development of thyroid tumors and
may have been an important factor in reducing
tore serious than Chvroid maligaancies, most of
which are well diilticntiated and have an excellent prognosis. Phe relative incidence of thyroid
malignancies from cadiauon appears to be about
people involved is too small far any firm conclusan lo be drawi.
‘Treatment of the expascd Rongelap people with
higher than vhe martalite from it, OF 40) cases
Unsroid hormone has been of beneficin enlianci
growth and development inthe growth-retarded
children aad tnomatntaining a onortial metabele
slic The operated cases. Etis notcertaln wheiber
1974, and only ene death had been attributed to
noxdules.
the same as thatofl ukeriaenatper rad’ bo GF
The incidence of thyroid cancer is considerably
wong the cxpasca Japanese, $4 were living ina
this cause. No evidence of thy roid dysfunction had
been noted at the time of diagnosis. bathe Marshallese reduced function was not found in two of
the cancer cases exposed as adults, but was an the
cast exposed us achild.
The high incidence of thyroid clfeets in children
exposed at <0 vears of ave was no doubt related
Wohas prevented the development of thyroid
The documentation of these tivroid effects has
inpartaney notenty for she peapte involved but
also for the advancement of inedical knowledge
aod for planning with reward to Civil Defense and
remotely possible future accidents tavealving release of radiotudines (ce. froma nuclear puwer
plant). The Marshallese accident represents ex+