soe eo4 ' t tu we S fy } W - Fp. ta », 1 tee ob a mee seer k ABSTRACT Following the detonation of Shot ton Bikini Atoll en T March 1954, 28 Americans and 239 Marshallese were exposed to fallout. One hundred fifty-seven of the Marshallese were on Utirtk Atoll, 64 were on Rongelap Atoll, and 18 were on the neighboring atoll of Arlinginac. The 28 Americans wore on Rongeritk Atoll The presence of sagnittcant fallout on these atolls was first detertimed by a recording dostmeter, located on Rongerik, when this device weat off scale at 100 anr hr shortly after (he detonation. Emergency surveys detected radiation on the imbhabited atalis, and evacuation of inhabitants to the Naval Station at Kwajalem was promptly carried out. The dose of radiation to which the individuals were exposed was calculated from the mtensities found on the istinds and the decay exponent of the fallout material. The individuals on Rongelap recerved upproximatcly 175 ¢, those on Ailinginae re@eived 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 individuals on Rongelap suffered from mild nausea and one or two individuals vomited on the day of the exposure. With the exception of nausea in one Ailing:nae individual, there were no other definite gastrointestinal symptoms in the other Marshallese or the Americans. The Marshallese 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 eptlation 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, weeping lesions. There was no full thickness necrosis of the skin. The Americans developed only minor skin lesions without alecration. There were no skin lesions in the Utirik natives. All lesions healed rapidly with ho further breakdown of the skin noted during the period of observation, Microscopie ¢xamiHatton of bropstes of the lesions showed changes usually associated with radiation myury. Fully cTothed individuals and those remaining tnside of buildings or huts were protected to varying Hhagprees fron development of lesions. Hematologic changes were definite im Che Rongelap, Arbnyinae, and the American groups. Lymphopenia appeared promptly and was persistent for a prolonged poriod of time, Neutropenia occurred in all of the individuals with mitral minimum values oecurring around the Lith day followed by an increase in the counts and a secondary intnimum around the 40th to 45th day. The most consistent hematologic change was the depression inthe platelet counts. Platelets were below normal when first counted on the 10th day of post-exposure and progressively decreased attaining a minimum between 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. , ST wigs} a * Net Re bei petty ee lf nee Be