A TWENTY-YEAR REVIEW OF MEDICAL FINDINGS IN A MARSHALLESE POPULATION ACCIDENTALLY EXPOSED TO RADIOACTIVE FALLOUT 1. Background A. THE ACCIDENT The testing of nuclear devices in the Marshall Islands (see Hines?5), beginning with Operation Crossroads at Bikini in 1946 and ending with the moratorium in 1958, did not result in significant radiation exposure to personnelorfallout contamination outside the test area except in onecase. On March 1, 1954, the detonation from a towerof a thermonuclear device, Bravo, in the Castle Senes oftests at Bikini resulted in a seriousfallout accident. The yield was about 17 megatons, considerably greater than expected, and an unpredicted shift in winds in the upper atmosphere caused the radioactive cloud to drift over and deposit fallout on several inhabited atolls to the east: Rongelap with 64 people, Ailingnae with 18 people, Rongerik with 28 American servicemen, and Utirik with 157 people (see Figure 1). A Japanese fishing vessel in the area, the Lucky Dragon, with 23 fishermen aboard was also exposed (see Appendix 3). The fallout is thought to have com- menced at Rongelap about to 6 hrafter the det- onation, at Rongerik about7 hr after it, and at Utirik about 22 hr afterit. Its duration on the islands is uncertain but has been estimated as about 12 hr, the greater part of the fallout occurring early in the period.” The estimated dose of gammaradiation to the island populationsis discussed in Section II. A. The American servicemen on Rongerik noted that the needle on a telemetering instrumentsuddenly beganrising and wentoff-scale in 30 min, beginning about6 to 7 hrafter the deto- nation. An alarm was radioedto the task force, and a plane flying low confirmedthatsignificant fallout had occurred. The exposed people were evacuated by planes and Navyships within about two days and taken to Kwajalein, 175 miles to the south. They were first examined bythe medical groupat the Naval Dispensary there. Eight daysafter the accident a medical team consisting of 21 doctors and technicians, largely from the Navy, which had beenrequested by the AEC, arrived at Kwajalein. For two months the team took medical histories, did repeated physical examinations including studies and photographsof beta burnsof the skin, made numerous hematological tests, and monitored for external and internally absorbed radioisotopes. Complete removalof the radioactive contamination from the skin and hair required manycleansing procedures; the coconut oil used on the hair was particularly retentive. At the end ofthe examination period, most of the skin burns had healed and, althoughsignificant hematological depression had occurred, no serious illnesses were evidentthat could berelated to radiation injury. The Marshallese people were taken to a tent encampment on EbeyeIsland for a stay of several weeks. Since Utirik Atoll was only veryslightly contaminatedfrom thefallout, it was considered safe for habitation, and the Utirik people were returned there with fresh supplies, clothing, and livestock. Rongelap Atoll was too contaminatedto allow immediate return and its people (along with the 18 from Ailingnae) were taken to a temporary village built for them on Ejet Island in Majuro Atoll, where they tived for 3 years until their return to Rongelap. The American servicemen were taken to Tripler Army Hospitalfor further examinations andlater returned to duty. B. ANNUAL EXAMINATIONS Medical examinations of the Rongelap people were conductedat their temporary home on Majuro in Septemberof 1954 and in March of 1955, 1956, and 1957. In 1954 an unexposed group of Marshallese living at Majuro was chosen as a comparison population for these examinations. This group, however, was composed of people from manyof the Marshall Islands who were not easily located for subsequent examinations. Unexposed Rongelap people gradually moved to Ejet to live with their fellow islanders, and this group increased further on the return to Rongelap. These unexposed Rongelap people were included in the examinations and haveserved as an excellent comparison population since they are blood relatives ' of the exposed Rongelap people, match reasonably well for age and sex, and live under the same environmental conditions (see Section III. A.).