- 345 - AGEING STUDIES IN A MARSHALLESE POPULATION EXPOSED TO RADIOACTIVE FALL-OUT IN 1954 Robert A, Conard, Austin Lowrey, Maynard Eicher Keith Thompson and William A. Scott The Marshallese people who had been accidentally exposed to radioactive fall-out in 1954 have been examined annually since the accident for possible late effects of radiation, including the development of premature ageing. The accidental exposure of these people occurred on March 1, 1954 as a result of an unpredicted shift in winds following experimental detonation of a large thermonuclear device at Bikini in the Marshall Islands, <A white, snow-like, highly radioactive material was deposited on the island and its 82 inhabitants. There were 64 people (55 now living) who received about 175 rads of whole-body gamma radiation, exposure of the skin from fall-out deposited thereon, and also significant internal absorption of radionuclides, Eighteen other Rongelapese (14 now living) were on a fishing expedition on a nearby island and received less than half the exposure of the other group. Evacuation of the islanders was accomplished two days after the accident. They were returned three years later (1957) when radiation levels on the island were considered safe. Since the accident over 200 Rongelap people or their relatives who had not been exposed to fall-out returned to live with the exposed people and have formed the comparison population. Acute effects from exposure were noted in the Rongelap people during the first few months and consisted largely of early transient gastrointestinal and skin symptoms, followed by depression of lymphocytes, neutrophils, and platelets to one-half to one-third normal levels. The hematopoietic depression however did not result in any obvious infections or significant bleeding. ''Beta burns'' of the skin along with spotty epilation of the head were wide-spread during the first several months after exposure. No acute effects from the internal absorption of radionuclides were noted. No fatalities occurred, and the people had largely recovered from these acute effects of exposure by the end of the first year. Subsequent examinations have largely been concerned with the possible late effects of radiation. The most significant such finding has been the development of thyroid nodules and hypothyroidism during the past three years among the exposed people. This development is believed to be a late effect of radiation of the thyroid gland from internal absorption of radioiodines and from external gammaradiation at the time of the fall-out. During the two day period following the accident, before the evacuation of the people occurred,