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National Cancer Institute U.S. National Institutes of Health www.cancer.gov
Radiation Epidemiology Branch

Last updated 03/2009


Radiation Dosimetry and Cancer Risk Estimates for the Republic of the Marshall Islands

In June 2004, the U.S. Senate Committee on Energy and Natural Resources requested the National Cancer Institute (NCI) provide its expert opinion on the baseline cancer risk and number of cancers expected among residents of the Marshall Islands as a result of exposures to radioactive fallout from U.S. nuclear weapons tests that were conducted there from 1946 through 1958. In September 2004, the NCI provided the Committee preliminary cancer risk estimates and a discussion of their basis in a report titled Estimation of the Baseline Number of Cancers Among Marshallese and the Number of Cancers Attributable to Exposure to Fallout from Nuclear Weapons Testing Conducted in the Marshall Islands. That analysis was based on a number of conservative assumptions designed to avoid underestimating the actual cancer risks and used information that could be collected quickly to provide a timely response.

In the summer of 2005, the U.S. House Committees on Natural Resources and on International Relations, Subcommittee on Asia and the Pacific, convened a joint oversight hearing on the "United States Nuclear Legacy in the Marshall Islands: Consideration of Issues Relating to the Changed Circumstances Petition". The Senate Committee on Energy and Natural Resources conducted a hearing on the same topic. At those hearings, NCI investigators summarized their 2004 analysis and specified plans to develop and submit for publication in the peer-reviewed literature refined estimates of doses and cancer risks and the methods employed to derive them. Since then, NCI radiation dosimetrists and statisticians have worked to improve the 2004 estimates and their documentation.

Improved estimates were obtained by an extensive effort over three years to collect and analyze additional relevant data, including a large number of historical documents from the Atomic Energy Commission (AEC) laboratory that conducted the fallout monitoring for the U.S. nuclear testing program. These and other measurements have been collected, re-reviewed, and systematically integrated with historical radiation measurement data collected by the AEC and with more contemporary environmental radiation measurement data. In addition, scientists at the National Oceanic and Atmospheric Administration (NOAA) assisted NCI investigators with interpreting historical meteorological data and provided meteorological models to assist in reconstructing fallout deposition patterns. These new resources allowed investigators to construct exposure estimates for every atoll and from all nuclear tests conducted in the Marshall Islands.

Using the refined estimates of radiation doses, the investigators and collaborators calculated cancer risks by applying statistical models for dose-specific risks from a recent report by an expert committee of the U.S. National Academies. As with any historical risk assessment of this kind, fallout-related radiation doses and associated cancer risks cannot be determined exactly and so are presented in the form of a "best" estimate and a range, consistent with the available data. This range is based on dose estimates from the study and the larger body of information from other studies of cancer risk in exposed populations. NCI investigators believe these efforts have resulted in substantially more accurate and judicious conclusions. More detailed documentation on the methods employed is also now available.

Eight manuscripts describing the estimates of external dose, internal dose, cancer risk projections, and the methodologies employed have been prepared, reviewed internally at NCI, and submitted for peer-review and publication in the journal Health Physics, the largest circulation scientific journal in the field of radiation protection. It is anticipated that the papers will be published before the end of 2009. At that time, NCI will make the publications widely available.

2004 Request and Related Correspondence

Correspondence Related to House Hearing 5/25/05

Correspondence Related to Senate Hearing 7/19/05

Some Related Publications

  • Bouville A, Simon SL, Miller CL, Beck HL, Anspaugh LR. Estimates of doses from global fallout. Health Physics 82(5):690-705. 2002.
  • Gilbert E, Land C, Simon, SL. Health effects from fallout. Health Physics 82(5):726-735. 2002.
  • Simon, SL, Bouville, A. Radiation doses to local populations near nuclear weapons test sites worldwide. Health Physics 82(5):706-725. 2002.
  • Takahashi T, Trott KR, Fujimori K, Nakashima N, Ohtomo H, Minouk J, Schoemaker MJ, Simon SL. Thyroid Disease In The Marshall Islands, Findings from 10 Years of Study. Tohoku University Press, Sendai, Japan. 2001.
  • Simon SL, Graham JC. Findings of the First Comprehensive Radiological Monitoring Program of the Republic of the Marshall Islands. Health Physics 73(1):66-85. 1997.
  • Simon, SL, Vetter, RJ. Consequences of Nuclear Testing in the Marshall Islands. Health Physics 73(1). 1997.