1.1 Nature of the Event and Description of the Exposed Gr bups Fotitowine THE Detonation of a nuclear device at the Pacific Proving ground in the Spring of 1954, significant amounts of radioactive material fell on neighboring populated atolls. The Marshallese inhabitants of Rongelap atoll (designated as Group I) received the highest calculated dose of radiation. Some of the Rongelap people were located temporarily on Ailinginae atoll from the time of the fallout until they were evacuated (Group II). ‘Their calculated dose was smaller than that of the other members of the parent group. The American service men (Group III) were located on Rongerik atoll. The largest group of Marshallese (Group IV) were located on Utirik atoll and received the smallest dose. The Marshallese were living under relatively primitive conditions in lightly constructed palm houses (Fig. 1.1). The American military personnel had the second highest exposure. They were more aware of the significance of the fallout than were the Marshallese, and promptly put on ad- ditional clothing to protect their skin. As far as duties would permit, they rerhained inside of aluminum buildings. In contr ist, most of the Marshallese remained out-of-d oors and thus were more heavily contaminated by the material falling on the atolls. Some of the Marshallese, however, went sw imming during the fallout and many of the ch idren waded in the water, thus washing a consi erable amount of the material from their skin. The exposed personnel wer > evacuated to Kwajalein by air and surface transportation. Since a survey of all individu: Is showed that there was significant contaminat ion of skin, hair and clothes, prompt decontamMation was instituted. Clothes were removed and laundered and repeated washings of the skin and hair with fresh water and soap were rarried out. In many of the Marshallese, it was Hifficult to wash the radioactive material from the hair because of the heavy coconut-oil hair Hressing. The exposure groups with individuals involved, the calculated doses of radiation, the probable times of beginning of he fallout and the evacuation times are given in Table 1.1. Table 1.1—Exposed, and Control Unexposed Groups Grovur Designation NUMAER In Group Group I.—Rongelap 64 Group II.—Ailinginae 18 ‘ PPROXIMATE TeeorCom FaLour 28 H+ 4to6 hrs. H+ 4to6/ brs, H + 6.8hrs.| Group IV.—Utirik 157 H + 22hrs. Marshallese, Control | Group A Americans, Control Kwajalein- American | 117 Group ITI.—Rongerik _ Time or Evacuation H + 50 hrs. (16 people) H + 51 hrs, (48 people) H + 58 hrs. ’ H + 28.5 hrs. (8 men) H + 34 hes. (20 men) Started at H + 55 hrs. Compieted at H + 78 hrs. Jones UsepINDose PatcuLATIONS 375 mr/hrs.,H days 100 mr/hrs., H days 280 mr/hrs., fH days 40 mr/hrs., H days MERE aerate / Dose IN AIR (fc) + 7} 175 + 9 69 + 9 78 + 8 14 105 Total Exposed—267; Total Controls—222 3