46
and 7 years after the accident were about the same for
exposed and unexposed persons of comparable age.”°
FERTILITY, MISCARRIAGES, STILLBIRTHS,
AND GENETIC EFFECTS
Effects on fertility were not apparent as judged
by comparisonofbirth rates for the exposed and
unexposed populations. During the first 4 years
after exposure an increase in miscarriages and
stillbirths was noted in the exposed women, 41%
of the births (13 in 32 births) in this group terminating in nonviable offspring compared with 21%
(8 in 38 births) in the unexposed women. Since
that time, the incidence has been about the same
in the two groups. One cannotbe certain that this
effect is actually due to radiation exposure because
of the small number of women involved.
No specific genetic studies have been carried
out, but differences in incidences of abnormalities
in children of exposed compared with those of un-
exposed women have not been observed. The gen-
erally negative results of large-scale genetic studies
on the offspring of exposed Japanese”? indicated that
detailed studies on the Marshallese would notbe fruitful.
GROWTH AND DEVELOPMENT STUDIES
Comparison of exposed with unexposed children
of the same agesindicated slight retardation effects
in the exposed males. The boys exposed at ages 1
to 5 showed retardation of statural growth as well
as bone age. This was most markedin those exposed at 15 to 18 months of age. The average
skeletal maturation in the exposed boys was about
7 months behind that of their unexposed peers.
Though weight gain also appearedslightly retarded in this group,it was notstatistically significant. The exposed girls showed nosignificantdifferences compared with unexposedgirls.
The slight retardation of growth in the male
children who were exposed when <5 years of age
as compared with unexposed males of the same
age suggests that radiation may be a causalfactor
although possible mechanismsare not clear. The
dose to bones from internally absorbed isotopesis
believed to have been too small to have affected
bone growth. Adverse effects on growth and development of Japanese children exposed to the
atomic bomb have been reported by Greulich,””
Reynolds,?* and Nehemias.** However, the evalu-
ation of such effects in these Japanese children
was complicated by physical and psychic trauma
and by malnutrition factors not operative in. the
case of the Marshallese children. The 175-rad
gamma dose would seem to be too small to cause
any direct effect on bone growth, and the estimated dose to the bones from internally absorbed
isotopes probably can also be disregarded since
this source contributed only about 3 to 4 rads over
a 10-year period. Bone growth studies in weanling
tats given sublethal exposures have shownan indirect effect on subsequent growthofshieldedlegs,
but this appears to be based largely on a radiationinduced lowered food consumption.”*® It is of interest that 25 of 31 exposed children were noted to
lose several poundsof weight duringthefirst 6 to 8
weeks following exposure. However, the influence
of change in environmentin producingthis effect
cannot be ruled out.
DEVELOPMENT OF THYROID NODULES
Thyroid nodules were removed from 3 teen-age
exposed girls after the 10-year survey. Most pathologists consulted did not feel that radiation
could be implicated as the etiologic agent on the
basis of the pathological findings alone, though
some considered the findings typical of the lesions
seen in children treated medically with radioactive
iodine. However, the evidenceis strong that the
thyroid nodules in the Marshallese girls were induced by radiation. Correlation of the thyroid
nodules with radiation exposure was substantiated
by statistical analysis which showedthe difference
in thyroid nodule incidence between the exposed
and the unexposedchildrento besignificant at the
1% level.* Moreover, Sheline et al.*° and Lindsay
et al.*’ have reported the development of thyroid
nodules 5 to 11 years after treatment of children
with radioiodine for thyrotoxicosis. Dr. Lindsay
reported that the sections of the glands removed
from the Marshallese girls were similar to the
glands of children who had been given I’**
therapy. On the basis of a calculated dose of 150
rads! to the adult thyroids from isotopesof iodine,
it was estimated that the smaller thyroid glands of
the girls exposed at 3 to 4 years of age received a
total dose of the order of 1000 rads** (probable
*Mr. Keith Thompson of Brookhaven National Laboratory
carried out the x? test.
**Mr. Ralph James and Dr. John Gofman, Lawrence Radia-
tion Laboratory, Livermore, California, re-examined the early
data and recalculated the thyroid doses.