Effects of fall-out radiation on Marshallese 277 and Reynolds (1952) who reported slight growth retardation and delayed maturation in the Japanese children following exposure to the atom bomb. 2.2.7. Genetic effects Specific studies for genetic effects of their radiation exposure have not been conducted in the Marshallese. The babies born of irradiated parents have shown no gross abnormalities that can be detected on routine physical examinations. In view of the generally negative findings in the first-generation offspring of the irradiated Japanese reported by Neel and Schull (1956),it is unlikely that genetic studies in the Marshallese will be fruitful. 2.3. Effects of beta-irradiation of the skin About 90 per cent of the people in the more heavily exposed Rongelap group developed beta-burns of the skin beginning about two weeks after exposure. A lesser number of people also developed spotty epilation of the scalp. The burns occurred as a result of fall-out deposition on parts of the body not covered by clothing. Most of the burns were superficial and healed within a few weeks. About 15 per cent of the people, however, had deeper burns which healed with someatrophy,scarring, and pigmentaberration. Complete regrowth of normal hair occurred in all cases by six months. Gross and microscopic descriptions of the lesions were given in detail in the earlier reports. The past survey revealed that there were 12 cases which showedresidual atrophy, scarring and pigment aberrations at the site of deeper lesions. However, none showed evidence of pre-malignant or malignant change. 2.4. Internal irradiation The Rongelap people lived under conditions of severe radioactive contamina- tion for two days following the accident until they were evacuated from their island. This was reflected in significant absorption of radioactive materials, mostly from ingestion of contaminated food and water. Radiochemical urine analyses during the first 24 days showedinternal levels of isotopes which were roughly estimated as follows in microcuries: 1!-!Todine, 6:4; ®®Strontium, 1:6; Barium, 2-7; rare earths, 1-2; and smaller amounts of !*"Caesium, 8°Strontium, and '“Ce—Pr. Radioiodine probably delivered a dose of 100-150 rep to the thyroid glands of the people, but absorption of isotopes was too small to result in any acute effects. Rapid diminution of body levels of these isotopes occurred, so that by six months urinary activity was barely detectable. Only the indirect method of body-burden estimation, based on urinaryexcretion rates, was available until three years’ post-exposure, when a direct method of measuring body levels of gamma-emitting isotopes was possible through the use of crystal detectors and a spectrum analyser in conjunction with a thick-walled steel room to lower backgroundradiation. This madeit possible to measure directly very low levels of isotopes. Several Marshallese were measured by this procedure at the Argonne National Laboratory -in 1957. Later a steel room, constructed specifically for these surveys (figure 6), was taken aboard Navy vessels to Rongelap tor the four- and five-year surveys where a large number of Rongelap people have been measured.