Franke, Bernd, R.Schupfner, H.Schüttelkopf & Spennemann, Dirk H.R. (in press) Transuranics in bone of deceased former residents of Rongelap Atoll: a comparison with data from urine analysis and pathway modeling. Health Physics
Abstract: The compliance criterion stipulated by the agreement for the resettlement of Rongelap Atoll of 1 mSv a-1 to individuals includes the contribution of transuranics. Both pathway modeling on the basis of assumed values of intake via inhalation and food/soil ingestion as well as recent results of urine analysis benefit from an independent verification provided by bone tissue analysis. As part of the Rongelap Resettlement Project, the Rongelap community endorsed the exhumation of bones of deceased former atoll residents to provide an independent determination of plutonium intake. Particular emphasis was placed on the potential increased uptake in early childhood. Therefore six graves (4 adults, 2 children) of individuals with 8 to 28 years of residence time on Rongelap Atoll including early childhood years were selected for exhumation. Femora and tibiae were selected as well as humeri from the children's graves. The rest of the remains was left undisturbed. Whereas the median transuranic soil concentration for southern islands of Rongelap Atoll is considerably larger than the levels deposited from global fallout, the transuranics activity of <6 to 46 mBq 239,240Pu per kg bone ash and of <6 to 19 mBq 241Am per kg bone ash is in a range comparable with those found in other areas of the world. The highest concentration was found in bo- ne tissue from one individual who was also exposed to direct fallout from the Bravo thermonuclear test in 1954.The committed dose equivalent was assessed for future resi- dents within 50 years following resettlement for a variety of as- sumptions regarding age, exposure time and pathways of intake. The 241Pu activity was conservatively inferred from measured 241Am activities. The development of dose equivalents is shown as a function for time of potential resettlement as well as retrospectively for the potential exposure times of the six individuals. The dose estimates from bone tissue analysis are compared with those based on pathway modeling (including the contribution from soil ingestion) as well as with data obtained from recent urinanalysis performed by Brookhaven National Laboratory. As a result of the comparison, concentration of transuranics in bone tissue are in reasonable agreement with recently obtained urinalysis data for former Rongelap residents as well as with results from pathway modeling for the southern part of Rongelap Atoll. The resulting estimated exposures are in the order of 0.01 mSv effective dose equivalent per year. Therefore, transuranic activities in the southern part of Rongelap Atoll are not a limiting factor for a future resettlement.