18
beings with a remarkable reserve margin of safety
in protecting against infection. Even at the lowest
shallese was most probably dueto the penetrating
dose of gamma irradiation. Certainly external
half their normal values, there was no detectable
evidence of increased susceptibility to infection or
increased tendency to bleeding. Indeed, at no
time during the past three years has there been
any increased incidence of diseases, infectious or
noninfectious, in the exposed population compared with the unexposed groups. These people
the bones, and the internal adsorption of boneseeking isotopes is not believed to have been large
enough to have contributed significantly. The
Marshallese children probably received slightly
higher dose than did the adults becauseoftheir
shorter stature and thinner bodies in field of
radiation producedbythe fallout. Even so, the
dose of penetrating radiation received was prob-
ebb of hematopoietic depression, when the leukocytes and platelets in the Marshallese were about
have sustained epidemics of measles, chicken pox,
upperrespiratory infections, and gastroenteritis,
apparently without any greater incidence or
severity of these diseases compared with unexposed groups. A limited study of immuneresponses
at three years post-exposure showed thatthe antibody response to tetanus toxoid antigenic stimulus
was notsignificantly different in the exposed and
unexposed people. However, had this type of
study been carried out soon after irradiation,it is
possible that some degree of impairmentof antbedy production might have been demonstrated.
Metabolic effects: Weight changes. A possible effect
of penetrating radiation noted duringthe first few
months after exposure was fairly constant weight
loss of several pounds in manyof the people, both
adults and children. This occurred despite thefact
that their appetites were good andtheir food consumption was greater than had beentheir custom.
It is not known whetherthis weight loss represented an effect of radiation on metabolism or
whetherit was related to the change in environ-
ment.
Growth and development. It is difficult to evaluate
the effects of the radiation exposure on growth
and development because of the small numbers of
children involved. The lag in growth and developmentas evidenced by differences in weight and
height of the 4 to 10-year age group of exposed
children was slight, and definite statements cannot
be made at this time about the significance of
these differences. However, the bone development
studies seem to indicate a slight degree of retardation in the exposed group. Lag in growth and development was observed in the Japanese children
exposed to the atomic bombs at Hiroshima and
Nagasaki.'? It was uncertain whether psychic and
physical traumaor economic conditions might be
responsible in the Japanese children. Theslight
effect on growth and developmentin the Mar-
beta radiation would not contribute to the dose to
ably too small to have produceda direct effect on
the epiphyses. It would seem morelikely that arrest of bone maturation might be from some nonspecific or indirect metabolic effect or possibly
hormonaleffect resulting from the radiation. Irradiation of the thyroid gland may have depressed
thyroid hormonesecretion and thus delayed bone
growth. Further studies of thyroid activity are
planned.
In utero effects and effects on pregnancy. Four women
were pregnantat the time of exposure, two in the
first, one in the second, and onein the third tri-
mester. These pregnancies progressed uneventfully to normal-term deliveries. The babies all appeared normal in every way, and no microencephaly was presentas has been reported in some
babies irradiated zn utero in Japan.'*** Since the
event, nine other normal births have taken place.
One miscarriage and two infant deaths have occurred, butthis incidence does not seem greater
than that in unexposed Marshallese people based
on limited numbers of observations.
Fertility. It is entirely possible that a temporary
loss of fertility may have occurred shortly after exposure in someof the people. However, careful investigation of the possible effects of the radiation
exposure onfertility has not been possible. Comparison ofthe frequency of pregnancies in the ex-
posed and unexposed groups does notindicate any
detectable effect of radiation exposure on fertility.
As pointed out, however,satisfactory vital statistics are lacking, and the numbers ofindividuals
are too small to reach any definite conclusions. In
a limited medical survey of the Central Pacific
Islands carried out by the U.S. Navy in 1949 and
1950,'* limited statistics on pregnancies in the
Marshallese were reported. Pregnancies among
the exposed Rongelap women during the past
three years are within the range 18 to 32 per 1000
population reported in the above survey.