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.