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The Legacy of U.S. Nuclear Testing and Radiation Exposure in the Marshall Islands



The United States conducted 67 nuclear explosive tests in the Marshall Islands between 1946 and 1958.  In 1962, the United States halted atmospheric nuclear explosive tests, like those conducted in the Marshall Islands, and ended all nuclear explosive testing in 1992.  President Barack Obama announced in Prague in 2009 that the long-term goal of the United States is a world without nuclear weapons.  The President remains committed to a worldwide ban on all nuclear explosive testing and Senate ratification of the Comprehensive Nuclear-Test-Ban Treaty.  Nuclear explosive testing was deemed to be critical during the Cold War and we honor the contribution the people of the Marshall Islands made to America’s international security goals.

Twenty-three tests were conducted on Bikini Atoll, and 44 were conducted on or near Enewetak Atoll.  The hydrogen bomb test on March 1, 1954, code-named Castle Bravo, far exceeded the size expected by scientists.  This factor, combined with shifting wind patterns, sent some of the radioactive fallout over the inhabited atolls of Rongelap and Utrik.  Within 52 hours, the 86 people on Rongelap and 167 on Utrik were evacuated to Kwajalein for medical care.  The Marshallese living on Utrik returned permanently a few months later, while those on Rongelap returned in 1957 but chose to leave again in 1985.

Misconceptions about the history of nuclear testing in the Pacific and the present situation in the Marshall Islands hinder the full understanding of the importance of the testing, and of the lessons that have been learned on how to remediate the environment to a state where people can make a choice about resettlement of their home atolls knowing they are safe.  Addressing and correcting those misconceptions is part of the healing process and affirms the U.S. commitment to continuing dialogue and cooperation with the Marshallese people, their government, and the international community. 

This website is designed as a resource for those interested in understanding more about the legacy of the U.S. nuclear testing program in the Marshall Islands.


As referenced in the U.S. government’s 2004 Report on the Republic of the Marshall Islands (RMI) Changed Circumstances Petition and data from the Department of Energy (DOE) and Department of the Interior (DOI), the United States provided a total of more than $604 million to the affected communities.  Adjusting for inflation, this amount equals $1.055 billion in 2010 dollars, or $1.87 million per original inhabitant of the four affected atolls (Bikini, Enewetak, Rongelap, and Utrik) at the time of the testing, in funds and programs designed to support those impacted by the nuclear testing program.  Among other programs, this compensation included direct financial settlement of nuclear claims, resettlement funds, rehabilitation of affected atolls, and radiation related health care costs.  The Department of Energy Special Medical Care Program and the Environmental Monitoring Program continue to provide services to the affected atolls at a $6.3 million annual level.  Enewetak receives $1.8 million (inflation adjusted) annually for its food and agriculture program.  Enewetak, Bikini, Utrik, and Rongelap local governments continue to manage trust funds originally endowed by the United States for their communities.

Two distinct medical programs are included in the Compact of Free Association: DOE’s Medical Care program and DOI's Section 177 Health Care Program.  As of February 2012, there were 135 individuals remaining in DOE’s Program for people on Rongelap and Utrik atolls exposed to local fallout from the Bravo test.  In addition, with funds from the DOI, the RMI provides a basic medical care program titled the “Four-Atoll Health Care Program (Marshall Islands)” for people of the four affected atolls.  When testing began, the four atolls population was approximately 600; currently, there are more than 14,000 people enrolled in the Four-Atoll Health Care Program, largely because legislation permits people to self-identify as being from one of the four atolls. 

Under the terms of the original Compact, and as part of the total compensation described above, the United States provided $150 million to the RMI to establish a nuclear claims fund.  From 1991 to 2003, the RMI Nuclear Claims Tribunal awarded over $2 billion for personal injury, property loss, and class action claims.  The amount of claims awarded thus far exceeded the settlement amount, and payments from the Tribunal ceased in 2009 after having disbursed all existing funds.

Findings of the Advisory Committee on Human Radiation Experiment (ACHRE)

In the early 1990s, in part to address a growing concern regarding the number of reports describing unethical conduct by the United States in the use of, or exposure to, ionizing radiation, President Clinton established the Advisory Committee on Human Radiation Experiments (ACHRE).  Over fifteen months, the Committee reviewed all available documentation on the subject and interviewed hundreds of witnesses.  Regarding the Marshall Islands, ACHRE concluded that there was “no evidence to support the claim that the exposures of the Marshallese, either initially or after resettlement, were motivated by research purposes.”

The United States has expressed regret about the Bravo accident when 253 Marshallese were exposed to high doses of radiation from a nuclear test.  While international scientists did study the effects of that accident on the human population unintentionally affected, the United States never intended for Marshallese to be hurt by the tests.  Today, the United States is committed to a full and open collaboration with the Republic of the Marshall Islands in radiological monitoring, rehabilitation of affected atolls, and nuclear related health care assistance. 

Scientific Studies

Dozens of scientific studies have been carried out in the Marshall Islands over the decades to characterize the residual radioactivity so as to better understand the risk to inhabitants.  For example, the U.S. Atomic Energy Commission (AEC) Health and Safety Laboratory developed a nuclear fallout surveillance program during the Pacific nuclear tests campaigns of the early 1950s.  These surveys included aerial monitoring of the mid and western Pacific and development of fallout monitoring stations in the United States as well as other locations around the globe.  The first evidence of post-Bravo fallout was recorded by AEC Health and Safety Laboratory instrumentation placed on Rongerik Atoll.  The results of the surveys conducted immediately after Bravo along with subsequent studies of medical investigations, radiological studies, and dose assessments conducted by many laboratories over the decades have made available a wealth of publically accessible data and information on the health and ecological consequences of the nuclear testing program in the Marshall Islands.  More information about the continuing radiological program.

In the post-testing era, the AEC and the University of Washington’s Laboratory of Radiation Biology, followed by the Lawrence Livermore National Laboratory (LLNL), played key roles in helping establish a radiological survey program to assess fallout contamination in soils, animals, plants, and marine life, primarily across Bikini, Enewetak, and Rongelap.  Large-scale screening surveys covering other parts of northern atolls began with the Northern Marshall Islands Radiological Survey (NMIRA) under a contract with DOE.  DOE continues to provide ongoing environmental monitoring for the four affected atolls and annual medical screening examinations and cancer treatment for people on Rongelap and Utrik atolls exposed to local fallout from the Bravo test.  A thorough analysis of the radiological conditions at Rongelap Atoll was conducted by the U.S. National Research Council (NRC) and published in 1994.  The NRC report also contained recommendations for post-resettlement radiological monitoring of the Rongelap population.  These recommendations have been incorporated into the general resettlement strategy that DOE has proposed to Rongelap officials.

Studies on assessing changes in radiological conditions across the four affected atolls continue through to this day.  Over the past 25 years, there have been a number of independent peer reviews of the LLNL Marshall Islands Radiological Monitoring program.  The most recent reviews were conducted by a 15-member panel of scientists convened by the U.S. National Academy of Sciences in 1994 and a 12-member panel of international scientists coordinated by the International Atomic Energy Agency (IAEA) from 1995–1996.

During the late 1980s, the Nitijela adopted a resolution to contract with an advisory group of scientists to perform a comprehensive Nationwide Radiological Study (NWRS) of the Marshall Islands. Dr. Steven L. Simon, a radiation physicist and professor from the University of North Carolina at Chapel Hill, was appointed by the RMI government to lead the study, which was conducted under the RMI Ministry of Health and Environment.  The study included an independent scientific advisory group from the UK, Germany, the Netherlands, and New Zealand.  Scientists of the NWRS made radiation measurements in the environment and gathered samples of food crops, soil, and water at all atolls and islands of significant size within the Marshall Islands for laboratory testing.[1]

From that study, the radiation levels at every atoll in the nation were characterized for the first time.  The data were reported in detail to the RMI Government and Nuclear Claims Tribunal and published in peer reviewed scientific journals.  This study formed the first and only comprehensive assessment of radiological conditions throughout the entire Marshall Islands.

Among the conclusions, the NWRS reported that “the current levels of radioactive contamination of the territory of the Marshall Islands pose no risk of adverse health effects to the present generation.  Similarly, on the basis of current genetic knowledge, we judge the risk of hereditary diseases to future generations of Marshallese to be no greater than the background risk of such diseases characteristic of any population.” With respect to contamination, the NWRS report did note that northern parts of Enewetak and Rongelap atolls, as well as some parts of Bikini atoll, exceeded safe dose limits at the time of the study.  However, because the study did not find residually high rates of radiation throughout the RMI, the Nitijela formally rejected it in a 1995 resolution and did not make the findings public.

Subsequent studies have confirmed Dr. Simon’s findings and measurements as well as those of DOE.  For example, in 1997, the International Atomic Energy Agency (IAEA), responded to a request of the RMI Government to review the status of the Bikini nuclear test site.  The IAEA “determined that no further corroboration of the measurements and assessments of the radiological conditions at Bikini Atoll is necessary.  The data that have been collected are of sufficient quality to allow an appropriate evaluation to be performed.”

DOE has sponsored a number of scientific assessments of radiation doses and conditions in the RMI.  Many of these studies have been published in peer reviewed scientific journals and were summarized in a special edition of Health Physics in 1997.  An updated assessment of radiation doses and cancer risk in the Marshall Islands from U.S. nuclear weapons testing was prepared by the U.S. National Cancer Institute and published in Health Physics in 2010.  This research concluded that approximately 0.4% to 3.6% “of all cancers among those residents of the Marshall Islands alive between 1948 and 1970 might be attributable to radiation exposures resulting from nuclear testing fallout.”

The last nuclear test in the Marshall Islands was conducted over fifty years ago, and through the passage of time and cleanup efforts by DOE, radiation doses in the RMI have been steadily declining.  Today, the greatest source of radiation being absorbed by all persons living in the world, including the RMI, is from natural sources.

Looking Forward

While the Compact of Free Association included a full and final settlement of all nuclear-related claims, the United States agreed to a provision that allows the Marshall Islands to present a petition for additional compensation if there are “changed circumstances” as defined in the agreement.  The RMI submitted such a petition in 2000, and although the Executive Branch concluded that it did not meet the definition of “changed circumstances” under the agreement, it remains pending before the U.S. Congress. At the same time, the United States continues to support the Marshall Islands through radiation-related health care services and continued monitoring and environmental assessments on the affected atolls.  U.S. scientists from the national laboratories and from other U.S. agencies and universities will continue their decades-long engagement in the Marshall Islands.  The health and environmental programs the United States provides to Marshallese affected by the testing are the best in the world.  These programs include technical support to provide information to help the RMI make responsible decisions and use the resources available to take the steps necessary for the future. 

Today, Secretary of State Hillary Clinton is seeking Senate ratification of the Comprehensive Nuclear-Test-Ban Treaty.  Universal ratification of and adherence to the Comprehensive Nuclear-Test-Ban Treaty would end nuclear testing in all environments.  Creating a world without nuclear weapons will require a strong commitment from all international partners, including the Marshall Islands, working towards this collective vision. 


1994. Radiological Assessments for the Resettlement of Rongelap in the Republic of the Marshall Islands. National Research Council.

1995. Advisory Committee on Human Radiation Experiments (Final Report). Chapter 12: The Marshallese.

1997. Consequences of Nuclear Testing the Marshall Islands. Health Physics.

1998. Conditions at Bikini Atoll. International Atomic Energy Agency (IAEA).

2004. Report Evaluating the Request of the Government of the Republic of the Marshall Islands Presented to the Congress of the United States of America.

2005. Republic of the Marshall Islands Changed Circumstances Petition to Congress. Congressional Research Service.

2005. Nuclear Testing in the Marshall Islands: Hearing before the Committee on Energy and Natural Resources, United States Senate.

2010. Radiation Doses and Cancer Risks in the Marshall Islands from U.S. Nuclear Weapons Tests. Health Physics.

[1] The survey focused on assessing the degree of fallout contamination across the Marshall Islands, and included in-situ gamma spectrometry measurements of over 400 islands as well as sampling and radiometric analysis of native food products and more than 800 surface soil samples. Samples were measured for radioactive cesium and plutonium and other isotopes.