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Utrok Atoll

People & Events | Historical Data


Utrōk is an atoll in the Ralik Chain of the Marshall Islands. The land area of Urōk is 0.94 square miles. The lagoon covers approximately 22 square miles.

People and Events on Utrōk Atoll

Utrōk Atoll is located about 500 kilometers east of Bikini Atoll. The atoll experienced significant radioactive fallout deposition from atmospheric nuclear weapons tests conducted in the Northern Marshall Islands during the 1950s. The most significant contaminating event on Utrōk Atoll was the Bravo test conducted at Bikini Atoll on March 1, 1954. The 167 residents (including 8 in utero) living on Utrōk Atoll at the time of the blast received significant external and internal exposures to fresh fallout contamination before being evacuated to Kwajalein Atoll on March 3, 1954. The Utrōk community returned to their home atoll 3 months later but continues to seek assurances from the United States Government that the atoll is safe for habitation.

The U.S. Department of Energy originally assigned responsibility for the internal dosimetry program on Utrōk Atoll to the Brookhaven National Laboratory. Through the 1990s scientists from Brookhaven conducted periodic whole body counting missions to the Marshall Islands to determine the body burdens of gamma-emitting radionuclides, such as cesium-137, cobolt-60, and potassium-40 in Marshallese from Bikini, Enewetak, Rongelap and Utrôk Atolls (Sun et al., 1997c). More recently, the U.S. Department of Energy has developed a series of initiatives to address long-term radiological needs in the Marshall Islands. Under a working agreement between the Utrōk Atoll Local Government, the Republic of the Marshall Islands and the U.S. Department of Energy (MOU, 2002), a permanent whole body counting system was established on Majuro Island (Majuro Atoll)* during May 2003. With the cooperation of the Utrōk Atoll Local Government this facility also serves the general public, especially for those residents and visitors who return from the northern Marshall Islands who are concerned about being exposed to residual fallout contamination in the environment. Under supervision from scientists from the Lawrence Livermore National Laboratory, the Utrōk Whole Body Counting Facility on Majuro is maintained and operated by Marshallese technicians. It is expected that Utrōk Atoll residents will be able to receive whole body counts during scheduled visits to Majuro under the routine medical surveillance program or on occasional outings.

* Majuro is the capital city of the Republic of the Marshall Islands and is the main hub for the local airline.

Historical Data

Today, exposure to residual fallout contamination on Utrōk Atoll represents only a small fraction of the dose that people receive from natural sources of background radiation in the Marshall Islands. The radiological dose delivered to inhabitants living on Utrōk Atoll from residual fallout contamination in the environment is dominated by the external exposure and ingestion of cesium-137 (and to a lesser extent, strontium-90) contained in locally grown food crop products such as coconut, breadfruit and Pandanus. According to Robison et al., (1999), the estimated population average maximum annual effective dose on Utrōk Atoll, based on a mixed diet containing imported foods, is less than 0.04 mSv (4 mrem) per year and has no consequence on the health of the population. Moreover, the predictive dose assessments based on environmental data and dietary models developed by the Lawrence Livermore National Laboratory appear to be in excellent agreement with estimates based on whole body counting (Robison and Sun, 1997).

Justification for establishing a permanent whole body counting system on Majuro Atoll for use by the Utrōk community comes from renewed concerns about high-end doses to maximal exposed individuals on Utrōk Atoll and that the associated health risk may exceed current guidelines adopted by the Marshall Islands Nuclear Claims Tribunal for cleanup of radioactively contaminated sites. Such high-end individual doses in the Utrōk population have not been clearly demonstrated but the potential does exist for members of the population to binge on a local foods only diet or eat more foods containing higher than average radionuclide concentrations, e.g., coconut crab. Consequently, a permanent whole body counting program on Utrōk Atoll will provide a basis for conducting more accurate dose assessments across the entire population, and yield more detailed dosimetric data according to gender, age-group and seasonality. Justification for intervention could then be made on the presumption that high-end doses are reasonably achievable, and that the risks from radiation exposures can reduced by means of remedial actions taking into account the relative cost:benefits as well as social and economic factors.

Whole body counting technicians in charge of the Utrōk Whole Body Counting Facility (Majuro Atoll, Republic of the Marshal Islands). Mr. Sherwood Tibon (standing) and Ms. Lolieta Chee (seated) (used with permission).

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