1.1 Nature of the Event and Description of the Exposed Groups Fotrowinc THE Deronarion 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 Allinginae_ atol] from the time of the fallout until they were evacuated (Group IE). as duties would permit, they remaied inside of aluminum buildings. In contrast, most of the Marshallese remained out-of-doors and thus were more heavily contaminated by the material falling on the atolls. Some of the Marshallese, however, went swimming during the fallout and many of the children waded in the water, thus washing a considerable amount of the material from their skin. The exposed personnel were evacuated to Kwajalein by air and surface transportation. Since a survey of all individuals showed that there was sigmificant contamination of skin, hair and clothes, prompt decontamination was instituted. Clothes were removed and laundered and repeated washings of the skin and hair with fresh water and soap were carried out. In ‘Their calenlated dose was smaller than that of the other members of the parent group. -The American service men (Group I]]) were located on Rongerik atoll. The largest group of Marshallese (Group IV) were located on Utinikatoll and received the smallest Quse, The Marshallese were living under relatively primitive conditions in hghtly constructed palm houses many of the Marshallese, it was difficult to wash the radioactive material from the hair because of the heavy coconut-oi] hair dressing. The exposure groups with individuals involved, the calculated doses of radiation, the probable times of beginning of the fallout and (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 additional clothing fo protect their skin. As far the evacuation fimes are given in Table 1.1. Table 1.1—Exposed, and Control Unexposed Groups In Grove Group ].—Rongelap Group I1J.— Rongerik Group IV —Utirik . 18 | ; | Marshallese, Control] 1 Group A | Americans, Control Kwa- | jalein-American TiMe OF Evacuation a Fatlour | H+ 4to6 hrs. | H + 4to6 hrs. 28; H+ 6.8hrs. 157 . | }i + 22 hrs. diz | ”, 105 | Total Exposed—267- Total Controls—222 5002 1b! ! | 64 Group ]].—Ailinginae | Tine or Cos: MENCEMEST OF || Tmo _ APPRORIMATE | j| NUMBER xPOTL . Drsicnation eae Grove t+ SQ-hrs.-(16 people} + 51 hrs. (48 pecple) + 55 hrs. Wo+ 28 Shrs. (8 men} H + 34 hrs. (20 inen) Started at H + 53 hrs. Completed at H + 76 hrs. INSTRUMENT READINGS Usen ix Dose CarcrLATIONS Hest Ess. “Tora. GaMsa DOrE Ix AIR (1) 375 mr/hrs., H + fp: L¥s7 days 100 mr/hrs., H + 9 days 280 mrjhrs., H + 9 days 40 mr/hrs., H-- 8 davs 69 75 14