aoe eo ob. 24 ‘ : iS ut Natl ME . er te Te ete ame ood , Fie ark Bp ABSTRACT Following the detonation of Shot 1 on Bikini Atoll on lL March 1954, 28 Americans and 239 Marshallese were exposed to fatiout. One hundred fifty-seven of the Marshallese were on Utirik Atoll, 64 were on Ronpelap Atoll, and 18 were on the neighboring atoll of Arlinginae. The 28 Americans were on Konrerik Atoll The presence of surmificant fallout on these atolls was first determined by a recearding dosimeter, located on Rongertk, when this device went off scale at HOO mr he shortly after the detonation. Emergency surveys detected radiiion on the mbhabited atolis, and ovacuation of inhabitants to the Naval Station at Kwajalein was promptly carried out. The dose of radimtron to which the individuals were exposed was calculated from the intensities found on dhe ashinds and the decay exponent of the fallout material. The individuals on Rongelap received approximately 175 7, those on Ailinginae received approximately 69 r, and the Americans op Rongerik received an average calculated dose of 78 r. The Marshallese on Utirik received approximately 14 r. The fallout on Rongelap, Ailinginae, and to a lesser extent on Rongerik was distinctly visible. No fallout was observed on Utirik. A significant number of individuais on ’ sngelap suffered from mild nausea and one or two individuals vomited on the day of the expe. ure. With the exception of nausea in one Ailinginae individual, there were no other definite gastrointestinal symptoms in the other Marshallese or the Americans. The Mar»hallesec on Rongelap and Ailinginae, and the Americans experienced to a varying degree burning of the eyes and itching of the skin from 1 to 3 days. Later, signs of radiation injury included definite cpilation in the Rongelap and Ailinginae groups, and the development of spotty, superficial, hyperpigmented skin lesions that desquamated from the center of the lesions outwards, In some cases the skin damage was sufficient to result in raw, wecping lesions. There was no full thickness necrosts of the skin. The Americans developed only minor skin lesions without ulceration, There were no skin besions in the Utbrik natives. AHL lesions healed rapidly with no further breakdown of the skin noted during the period of observation. Microscopic examiation Of broapsies of the lesions showed changes usually assocuited with radiation myury. Fully dothed individuals and those remaining inside of buildings or huts were protected to varying Hegrees from development of lesions. Hematologic changes were definite in the Rongelap, Attinginac, and the American groups. Lymphopenia appeared promptly and was persistent for a prolonged period of time. Neutropenia occurred in all of the individuals with initial minimum Values occurring around the Lith day followed by an increase in the counts and u secondary intjnimunt around the 40th to 45th day. The most consistent hematologic change was the depression in the platelet counts. Platelets were below normal when first counted on the 10th day of post-exposure and progressively decreased attaining a minimumbetween the 25th and 30th day. Although recovery commenced following this minimum, the platelet counts had not returned to normal by the completion of the initial study on the 76th post-exposure day. The incidence of various respiratory and cutaneous infections was identical in all exposure groups and bore no relationship to the hematologic changes. Urinary excretion of radioisotopes was studied. Small amounts of radioactive material were found. Estimates of total body burden indicate that there is no long term hazard and that ingestion and inhalation of isotopes did not contribute significantly to the initial radiation exposure.