Radiological Assessments for the Resettlement of Rongelap in the Republic of the Marshall Islands (1994)

The committee has concluded from its study of available information (Chapters 2-6) that the annual-dose criterion might not be met for every individual. However, the annual-dose criterion may be considered as an arbitrary action level that does not present an absolute barrier to resettlement. Remedial actions should not be judged solely on the basis of a need to meet an action level, but as a means to increase the physical and psychological well-being of the Rongelap people if they decide to resettle.

Knowledge of the chemistry of cesium and plutonium and an understanding of tropical ecosystems can be used to devise a set of potential remedial actions. The following constitute means of remedial actions—not meant to be all-inclusive—that could substantially reduce the amount of radiation received by people living on Rongelap.

1. The first generally accepted remedial action, implied in the MOU, and recommended by this committee is that the local-food-only diet is limited to food gathered on the southern islands of Rongelap Atoll. The potential consequences of not following this recommendation and of consuming food collected on the northern islets of Rongelap or Rongerik Atoll are summarized in column E of Table 5-4. Exposure to cesium-137 could be increased by a factor of 8-32 if all pandanus, coconut, and breadfruit were collected on the northern islets. A major consequence of restricted access to the northern parts of these atolls will be to limit available food resources.

2. People living on Rongelap will receive most of their exposure to cesium-137 from surface soil, either through direct irradiation of the body (external dose) or through ingestion of plants that have extracted cesium-137 from the soil during growth (internal dose). It is recommended that the returning population restrict the quantities of some local foods in their diet. The effectiveness of this act is obvious in the dose projections of Table 5-4. Exposure to cesium-137 may be reduced by a factor of greater than 5 when imported foods are substituted for some local foods (i.e., diet A versus diet C in Table 5-4). A modest supplementary food program would help the returning Rongelap people to obtain the necessary quantities of imported food.

3. Actions that reduce the direct exposure from subsurface cesium-137 or reduce the uptake of cesium-137 from the soil by local foodstuffs are also likely to reduce the maximum annual dose. One such action is to remove the upper layer of surface soil from the village and on each houseplot (Robison et al., 1993). Another is to add a layer of crushed coral around the houses and to common areas of congregation throughout the village. Both these actions are recommended as they could be accomplished as housing is rebuilt on Rongelap Island before resettlement with little impact on resettlement activities.

4. The committee also recommends the application of KCl as fertilizer and for remediation in agricultural areas. The application of KCl would reduce the uptake of cesium-137 by coconut, breadfruit, and pandanus fruit. Robison and Stone (1992) have demonstrated the effectiveness of KCl in reducing cesium-137 in coconuts grown on Bikini and in increasing plant growth in the relatively potassium-deficient tropical soils of the northern Marshall Islands. Potassium chloride is a common fertilizer used in the United States with no known detrimental health effects when used in the concentrations commonly applied as a commercial fertilizer. This form of remediation requires only modest effort and has no reported detrimental effects for humans or other parts of the ecosystem.

5. The removal of the top 30-40 cm of soil from the island is another potential remedial action. However, this approach is not recommended; it has had substantial effects on life style and on the environment of Enewetok Atoll. Given the fragile ecology of these coral islands the regeneration of topsoil removed in such an extreme procedure may require decades, or even centuries. Such an extreme measure should be one of last resort; on the basis of the projected doses achievable with more moderate means of remediation, it appears unnecessary.

Continuation of remedial actions 1, 2, and 4 might be relaxed if monitoring indicates that whole-body burdens are lower than estimated.