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RADIOLOGICAL SCIENCES DIVISION Upton, New York 11973 Date of Transmittal: January 31, 1990 NO. of Pages: 5 lncludlng cover sheet B8ttelle Pacific Norlhwest Lab ~qe: Hope this helps. Please feel free to call Caaper Sun [f you have any quest .;r,s. ‘.c number Is (516) 282-3469. If you want a hard copy, let us know, DOCUMENT DOES NOT CONTAIN ECI, BEST COPY AVAIMBLE
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Current Status of the Plutonium Level in the Rongelap and Utirik Urine Samples. Bravo, was tesred at Bikini Atoll. Cr?expected weapon yield and tropospheric transport caused radioactive fallout to sweep over Rongelap and Utirik Atolls, 100 miles east trom Bikini, a few hours later. As a result, thirty-five years following this incident, we are still studying the Northern Marshall Islands’ radiological environments and evaluating the radiological impact on the Marshall islands people. As part of this effort, a comprehensive safety and dose reassessr.ent project was conducted by Brookhaven National Laboratory (BNL) scientists beginning in 1981. Based both of the Lawrence Livermore Laboratory’s (LLL) environmental measurements of air, water, food, and soil samples and the BNL’s whole-body counting measurements, we presented a table of average annual effeccive dose equivalents (mrem/yr) from internal and external radiation (not including the dose from plutonium) to the people living at Rongelap Atoll. The total 3U years dose living on Rongelap Island was projected to be of less than 5,000 mrem. This is below the 170 mrem/yr of United States federzl radiation protection guidelines for members of the public. On May 1985, Ehe people of Rongelap choose to leave their homeland ar,d relocate on Majatto island although the living conditions on Majatto were inferior to those on Nor.gelap. The basis for their relocation was never communicated to us, but it seem reasonable to assume that it may have been over their concern of plutonium in the environments taken from our polonium biased plutonium data in late 1984 from the Photon Electron Rejection Alpha Liquid Scintillation (PERALS) analytical methods. In !iarch 1, 1989, Dr. Kohn used the dose rate table mentioned above in his “Rongelap Reassessment Project Report.” He showed that even using the 1987 maximum transuranic activity (5 fCi/sample) we found in urine, the estimated committed dose (i.e. , the total dose to be received over the next 50 years), internal and external, from 1978 to 2008 still falls below an average As a sesulc of our extensive evaluation of existing plutonium measurement for ultra-low activities in urine, a detection sensitivity of about 100 aCi/liter using fission track analytical (FTA) method was established at BNL in 1986, As of December 1988, over 500 urine saaples collected from 1981 to 1584 from the Kongelap and Utirik people was completed. These measurements have met rigorous quality assurance standards for chemical analysis, However, some inconsistencies still existed in the FT.4 data which we presented during the Livermore meeting in February 1988, Furthermore, all the 1988 urine samples (67 samples from the Rongelap people and 1(I1 samples from the Utirik people) taken by Dr. Sun last September were just analyzed, The results support the thesis that soil contamination in some of the earlier urine samples was giving false information. Because of Dr. Sun’s careful attention to collecting
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uncontaminated urine samples, whtch was facilitated by Majatto’s low soil concentration of plutonium, we were not surprised to find the statistics of our current Rongelap measurement reflect a median value far below the 250 aCi per sample as presented at the Liverrnore meeting, Past studies of plutonium concentration in urine samples obtained from the Marshall Islands people have indicated levels much higher than those now known to be present. This is due, in part, to improved bioassay sample collection and analytical technology, Furthermore, from reanalyses of earlier samples and a more comprehensive review of the data, it now appears that earlier “high” plutonium results, were very likely due to: (1) naturally occurring polonium-210 inhaled in cigarette smoke and (2) by water ax-d soil contamination of the urine samples during collection. The polonium problem was resolved by che adaption of our FTA method. the soil contamination of the urine sample, the analysis of the 1988 uri~e samples provided the following information: From the samples taken in Majatto, all of the plutonium results are below 170 aCi (a committed effective dose equivalent 95 mrem) . The median of the distribution is 27 aCi (a committed With one exception, the results from Utirik are similar to those of Rongelap. Including the one unverified high outcome, the median of the Utirik population is 24 aCi (a committed effective dose equivalent 12 mrem). Statistical analyses indicate there are no differences between the mean and standard deviation of the distribution describing Rongelap’s and Utirik’s population at this time. A most interesting observation is that the plutonium concentrations in the Islanders’ urine samples is similar to that of our BNL individual which was used as our laboratory control up Using the maximum activity (200 aCi) and the most conservative retention model it would appear that all of the Islanders, but one, have a committed effective dose equivalent of less than 100 mrem (1 mSv), Even the one individual with the invalidated sample result mentioned above have a committed effective dose equivalent of less than 400 mrem (4 mSv). With the greatly improved sensitivity of our FTA method and our newly developed urine sampling protocol we are confident that the Islanders’ plutonium concerns can be satisfactorily answered,
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