MARCH 1957 MEDICAL SURVEY OF RONGELAP AND UTIRIK PEOPLE THREE YEARS AFTER EXPOSURE TO RADIOACTIVE FALLOUT Background This report presents the results of a medical survey carried out in March 1957 on the Marshallese people who were accidentally exposed to radioactive fallout in March 1954. The accident occurred following the detonation of a large thermonuclear device during experimentsat Bikini in the Pacific Proving Grounds. An unpredicted shift in winds caused deposition of significant amounts of fallout on four nearby inhabited Marshall Islands and on 23 Japanese fishermen aboard their fishing vessel, the Lucky Dragon. Sixty-four inhabitants of the island of Rongelap, 105 nautical miles away from the detonation, received the largest fallout exposure among the inhabited islands: an estimated dose of 175 r whole-body gamma radiation, beta lesions of the skin, and epilation from contamination of the skin and slight internal absorption of radioactive material. The Japanese fishermen probably received a similar exposure, although estimation of their dose is much less certain. Also 18 Rongelap people away on a nearbyisland (Ailingnae), whereless fallout occurred, received only abouthalf this exposure. Twenty-eight American servicemen on an island (Rongerik) further awayreceived about the same amountof radiation as did the 18 people on Ailingnae. Lastly, 157 Marshallese on Utirik Island, some 200 miles distant, received only about 14 r whole-body radiation. The fallout was not visible on this island and noskin effects were seen. Theinitial findings have been reported on the Marshallese and Americans’ and the Japanese fishermen.” Subsequent examinations of the Rongelap people have been reportedat thefollowing times after exposure: six months,” oneyear,’ and two years.* The present report concerns the examination of the Rongelap and Utirik people three years after exposureto fallout radiation. In addition examinations were carried out on an un- exposed comparison population. SUMMARY OF PAST FINDINGS The following is a brief summaryof the past findings which can be foundin detail in thereferences.?"°~* Duringthefirst 24 to 48 hr after after exposure, about two-thirds of the Rongelap people experienced anorexia and nausea and a few vomited and had diarrhea. At this time manyalso experienced itching and burning of the skin and a few complained of lachrymation and burningof the eyes. Following this, the people remained asymptomatic until about two weeksafter the accident, whencutaneouslesions andloss of hair developed, due largely to beta irradiation of the skin. The effects of the radiation can best be summarized under three headings according to the mode of irradiation: penetrating irradiation, skin irradiation, and internalirradiation. Penetrating Irradiation The people on the island of Rongelapreceived an estimated whole-body dose of 175 r gamma radiation. Depression of peripheral blood elements occurredas follows (see Figures 7-15): Lymphocytes fell promptly and by the third day were 55% of control values (unirradiated Marshallese) in adults, and about 25% in children. There was only slight recovery by six months. Through the two-year examinations the mean values of these cells werestill below the control levels. At two years the lymphocytes were about 75 to 80% of the mean level of the comparison population. Neutrophils fluctuated considerably during the first few weeks butfell gradually to a low of about 50% of control values by the sixth week after ex- posure; recovery was slow. At six months counts