DOSE ASSESSMENT ACTIVITIES IN THE REPUBLIC OF THE MARSHALL ISLANDS

Dose assessments, both retrospective and prospective, comprise one imp ortant function of a radiological study commissioned by the Republic o f the Marshall Islands (RMI) government in late 1989. Estimating past or future exposure requires the synthesis of information from historic al data, results from a recently completed field monitoring program, l aboratory measurements, and some experimental studies. Most of the act ivities in the RMI to date have emphasized a pragmatic rather than the oretical approach. In particular, most of the recent effort has been e xpended on conducting an independent radiological monitoring program t o determine the degree of deposition and the geographical extent of we apons test fallout over the nation. Contamination levels on 70% of the land mass of the Marshall Islands were unknown prior to 1994. The env ironmental radioactivity data play an integral role in both retrospect ive and prospective assessments. One recent use of dose assessment has been to interpret environmental measurements of radioactivity into an nual doses that might be expected at every atoll. A second use for dos e assessment has been to determine compliance with a dose action level for the rehabitation of Rongelap Island. Careful examination of expos ure pathways relevant to the island lifestyle has been necessary to ac commodate these purposes. Examples of specific issues studied include defining traditional island diets as well as current day variations, s ources of drinking water, uses of tropical plants including those cons umed for food and for medicinal purposes, the nature and microvariabil ity of plutonium particles in the soil and unusual pathways of exposur e, e.g., that which might be associated with cooking and washing outdo ors and inadvertent soil ingestion. A study on the prevalence of thyro id disease is also being conducted and the geographic pattern of disea se may be useful as a bioindicator of the geographic pattern of exposu re to radioiodine. Finally, an examination is underway of gummed film, fixed-instrument, and aerial survey data accumulated during the 1950' s by the Health and Safety Laboratory of the U.S. AEC. This article gi ves an overview of these many different activities and a summary of re cent dose assessments.