Paper DOSES FROM EXTERNAL IRRADIATION TO MARSHALL ISLANDERS FROM BIKINI AND ENEWETAK NUCLEAR WEAPONS TESTS André Bouville,* Harold L. Beck,’ and Steven L. Simon* Castle series, all of which were high yield. The measurement data used for those estimates of exposure were collected by two methods: (1) stationary, ground-level continuous reading Geiger-Miiller type instruments with paper strip chart recording mechanisms, and (2) aerial surveys using fixed wing aircraft that carried scintillometer instruments. Mostof the atolls of the Marshall Islands, including all that had populations of signifi- Abstract—Annual doses from external irradiation resulting from exposure to fallout from the 65 atmospheric nuclear weaponstests conducted in the Marshall Islands at Bikini and Enewetak between 1946 and 1958 have been estimated for the first time for Marshallese living on all inhabited atolls. All tests that deposited fallout on any of the 23 inhabited atolls or separate reef islands have been considered. The methodology used to estimate the radiation doses at the inhabited atolls is based on test- and location-specific radiation survey data, deposition density estimates of "’Cs, and fallout times-of- cant size, were monitored in the aerial radiological arrival provided in a companion paper (Becketal.), combined with information on the radionuclide composition of the fallout at various times after each test. These estimates of doses from external irradiation have been combined with corresponding estimates of doses from internal irradiation, given in a companion paper (Simonetal.), to assess the cancer risks among the Marshallese population (Landet al.) resulting from exposure to radiation from the nuclear weaponstests. Health Phys. 99(2):143-156; 2010 surveys in 1954 (Breslin and Cassidy 1955). The range of estimated cumulative exposures from the Castle series reported by Breslin and Cassidy (1955) covered approximately five orders of magnitude, similar to the range of '*’Cs concentrations measured in the environ- ment of the Marshall Islands by the Nationwide Radiological Study conducted approximately 40 y Key words: '’Cs; dose, external; fallout; Marshall Islands later (Simon and Graham 1994, 1997). The USAEC- placed instrument on Rongerik Atoll was responsible for alerting the U.S. military weather observers on Rongerik to high levels of early fallout, leading to their evacuation and to the evacuation of Marshallese from Rongelap, Ailinginae, and Utrik following the INTRODUCTION DEsPITE NUMEROUSefforts to monitor the Marshall Islands for radioactivity during the United States Pacific nuclear testing program andafterwards, there has beenrelatively little effort towards estimating radiation doses to all Marshallese exposedto the fallout from the testing. The United States Atomic Energy Commission (USAEC) issued a report on radiological surveys following Operation Ivy of 1952 (Eisenbud 1953) and Operation Castle of 1954 (Breslin and Cassidy 1955). The latter report estimated cumulative exposures from the tests of the test Bravo in 1954 (Eisenbud 1987; Simon 2000). Other than atoll-specific values for the external exposure (reported in Roentgens or R) published in the USAECreports (Eisenbud 1953; Breslin and Cassidy 1955), and later estimates of external dose by Lessard et al. (1985) for Rongelap and Utrik, few, if any, external dose estimates have been reported for Marshallese. One significant source of information on nuclear testing in the Marshall Islands, a special issue of Health Physics (Simon and Vetter 1997), was largely concerned with * Division of Cancer Epidemiology and Genetics, National Can- land contamination, resettlement issues, and assessments cer Institute, National Institutes of Health, Bethesda, MD 20892; * New York, NY 10014 (retired from U.S. DOE). For correspondence contact: Steven L. Simon, National Cancer Institute, National Institutes of Health, 6120 Executive Blvd., Bethesda, MD 20892, or email at ssimon@mail.nih.gov. of doses received decades after nuclear tests were conducted in the Marshall Islands. Until the publication of this paper, no systematic effort had been made to (Manuscript accepted 5 March 2010) estimate the annual doses from external irradiation, received from 1948 to 1970, from all tests at all 0017-9078/10/0 Copyright © 2010 Health Physics Society inhabited atolls. DOI: 10.1097/HP.0b013e3 18 1de521d 143