An Updated Dose Assessment for Rongelap Island

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An Updated Dose Assessment for Rongelap Island Health & Ecological Assessment Division

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Thta report haabeenreproduced dlrdy from the bestavallebk copy. Availableto DOE andDOE contraetorafrom the Ofllceof Scientifk andTechnical Infonndlon Prkee avalkble from (61S)576-8401,ITS 626-8401 Availabk to thepubttcfrom the US. Department of Commerce warranty, exprss or implied,or assumeaany legalliability or responsibilityfor theaccuracy,comptetenea% w the Univerekyof Califomd+ and*all not beusedfw advertisingw productendorsementpurpoeea.

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Dose Assessment for Rongekp Mand, Lawrence Livermore National The authors regret that a typographical error went undetected thro Ighout the review of this report. On page 7, Table 3, in the fourth column hea ding of Plutonium aerosol concentration, the heading under concentration (B- m-s) should be corrected to (~Bq m-s). We apologize for any inconvenience this error may have caused the readers.

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An Updated Dose Assessment for Rongelap Island Manuscript date: July 1994 LAWRENCE LIVERMORE NATIONAL LABORATORY University of California QLiverrnore, California l 94551

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Table of Contents External Exposure Measurements ......................................................................! External Beta-Particle Ex sure Radionuclides in Soil ............................................................................................ Radionuclides in Terrestrial Foods .................................................................... Body Weights and Biological Half-Life of 137CS............................................. Comparison of Estimated Doses to Adopted Guidelines and Mitigation of Food-Chain Dose i Uncert@ty and Interindividual Variability in Estimated Doses ............ ndix A: Radionuclide concentration summary of all soil profile san co ected during the 1978 NMIRS, and from 1986 through 1993 .................... ndix B: Concentrations of radionuclides in vegetation from sample co ected during the 1978 NMIRS, and from 1986 through 1993 .................... Appendix C: External dose at Rongelap Island in mrem ................................

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List of Tables Comparison of the EG&G aerial gamma measurements with the LLNI gamma measurements for 137CS....................................................................... ur~rate measurements in and around the and village area of Ronge ap Island ................................................................f Resuspension data for high and low resuspension conditions on Bikin Diet Model-Rongelap Island. Local and imported foods availabie for Diet Model-Ron clap Island. Imported foods umvailable (only local %for adults greater t an 18 years ......................................................................... Comparison of the average adult diet model for the Northern Marsh with the average adult diet for the United States . ....................................4 Body weights of Marshallese adult males in kg. .......................................4 Maximum anruud organ equivalent dose rate and effective dose rate The 30-,.50-, and 70- integral effective dose for Rongelap Island resid The 30-,50-, and 70-y integral effective dose for Rongela Island resid Comparison of the doses estimated in 1982, based on the 1978 NMIR$ those in this report for the case of imported foods available. ................ Annual effective dose rate i%om natural background in the United S{ Adopted guidelines for the eneral public, natural background doses %United States and Marshall hinds, and estimated doses from man-r sources at Rongelap Island ............................................................................. ~%; W, 50-, and 70-y integral effective dose for the various exposure The average committed effective dose from Pu and Am at Rongelap

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the adjusted ICRP ann Parameters -used in analysis of u Diet Model-Rongelap Island for adults 1

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List of Figures 3. Corn arisen of 137CS body burdens estimated using various diet mod ls with 4. Probability plot of the biological half-life for 137CS in Marshallese mal .............27 5. Percentage reduction in estimated doses to residents of Rongelap Id as a 6. Probability plot for the body weights of 167 adult Marshallese females ...............38 7. Probability plot for the body weights of 188 adult Marshallese males...38..............38 8. Probability plot of the dietary intake of 34 Marshallese females ............. ...............39+ 9. Probability plot of the dietary intake of 36 Marshallese males ................ ................39I 10. Probability plot of 239+240Puconcentration in the top Oto 5 cm of soil n the village area at Rongelap Island I lot of 239+Z40PUconcentration in the top Oto 5 cm of soil n the 12. Probability plot of 24Glrn concentration in the top Oto 5 cm of soil in the village lot of 241AXII concentration in the top Oto 5 cm of soil in e interior o ongelap Isldnd. ...........................................................................P................41 14. Probability plot of 137CS concentration in drinking coconut meat on ongelap 15, Probability plot of 137CS concentration in drinking coconut fluid on ongelap 16. Sam le distribution of interindividual variabili in daily intake of 1 7CS per y weight based on survey data for 34 a ult Ujelang females, t to a 17. Estimated distribution of interindividual variabili in expected 30-y ose Y Pcorresponding to hypothetical residence on Ronge ap Island st~ng n 1995....48 18. Population-average expected dose from h othetical residence on R ngfhp Island starting in 1995 (middle curve) an corresponding two-tail 950 confidence limits on interindividual variability in expected dose as function of 19. Twmtail 95% confidence limits on intenndividual variabili in e from hypothetical residence on Rongelap Island startin in 995 as r ties of the

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Estimated distribution of interindividual variability in the maximum expected 1- doses corresponding to hypothetical residence on Rongela Population-average expected dose from h othetical residence on Ron PIsland starting in 1995 (middle curve) an corresponding twetail 95% confidence limits on uncertainty in population-average dose as a func hypothetical residence on Rongela Island starting in 1995 as ratios of {corresponding expected value oft is dose (horizontal line) at specified Estimated distribution characterizing uncertainty in po ulation-averaf Ydose corresponding to hypothetical residence on Ronge ap Island start 1995 (bold curve), contrasted with that for the component (X) of the lat distribution reflecting random dietary sampling only (light curv~ Estimated distribution of uncertainty in po ulation-avera e lifetime d ! Ecorresponding to hypothetical residence of 00 people on ongelap Isk {inhalation dose (solid points) corresponding to ypothetical residence t~gelap Island starting in 1995, compare with exponential approxir E ?ypothetical residence on Rongela Island starting in 199, compared’ corres riding EY 1ctation, denoted in Eq. A8), where these quantiti= no ized by t 1 2 and by f, respectively, evaluated for 13 values of tir ran .ng from 0.5 to 30 (corresponding to 13 sets of connected points: f J &an five ually space values of P in e ran e 0.9 to 1.107 (coqespon~ 7 c?each set o five points, shown here connecte by simple linear mterp

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We have u dated the radiological dose assessment for Rongela rRongelap Atoi using data generated from field trips to the atoll ( through 1993. ‘T’hedata base used for this dose assessment is ten fold that available for the 1982 assessment. Details of each data base are presented along with details about the rn to calculate the dose from each exposure pathway. The doses are calculated for a resettlement date of Janua 1, maximum amual effective dose is 0.26 mSv 50-, and 70- inte al effective doses are 0.009 Sv (0.59 rem), 0.0082 ST lyand 0.0097 v (0.9 rem), respectively. More than 95% of these estimat[ due to 137-Cesium (137CS). About 1.5% of the estimated dose is cor On March 1, 1954, a nuclear weapon test, code-named BRAVO, was conducted at Bikini Atoll in the northern Marshall Islands. The explosive yield of the detonation greatly exceeded expectations, with the result that radioactive material in the cloud was three-tofive times what was expected. Thus, despite the attention that was given to meteorology in the operational pbnin~ moderate to heavy fallout was experienced at the Rongerik, Rongelap, Ailinginae, Ailuk, Taka, Mejit, and Utirik Atolls, located to the east of BikiN. Rongelap and Utirik were inhabited by Marshallese. A small number of Rongelap residents were visiting uninhabited Ailinginae, and a small detachment of U.S. military personnel were stationed on Rongerk These people were removed from ail four atolls as soon as evacuation resources could be deployed. The Rongelap evacuation cogunenced about 47 hours after the first arrival of fallout and was completed within a few hours. Most. of the acute dose received by these residents was attributable to many short-lived radionuclides. In contrast, by the time they returned to their atoll three years later (June, 1957), many of these radionuclidea had decayd. and @-Cobalt (Ko), did contribute to the dose people received in the first two or three years (Lessard et al., 1980a) after their return. inhabitants of Rongelap Id In 1978, in anticipation of the its role as trustee under the C Trusteeship Agreement, the government decided to conduct a of several atolls east of Bikin] direction of the BRAVO fallo determine the external gamma+ The sumey, known as the Nort Islands Radiological Survey (NM conducted using the USNS 1 helicopters in which the EG&G & had been mounted. Based on Enewetak and Bikini Atolls indi terrestrial food chain was poten recommended that mpling 01 marine spies, and water be in the survey to cover all exp Consequently, the survey w include terrestrial and marine the same vesel to provide 10 support, and limited on-board The high cost of ship operati required to do the aerial sun were important factors influem the mpling program. The terrestrial and marin designed as a scmming progran acquire samples at as manyisls possible in the time availabl data for a preliminary dose a 0, was to be ur work at ing that the al and boat the extent of is at an atoll as essment at the

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islands and (2) identify those islands or atolls where additional sampling and analysis may be required (Robison et al., 1981a). A dose assessment was made based on the limited data from the screening survey to determine the dose people living on Rongelap Island would receive between 1978 and 2050 (Robison et al., 1982). Estimates of the dose Rongelap inhabitants received from 1957 through 1978 were reported by Lessard et al. (Lessard et al., 1980s0. Since the 1978 sumey, we have collected and analyzed additional samples from Rongelap Atoll. This has resulted in an extensive expansion of the data base for both Rongelap and In 1985, the Rongelap people I to an island at Kwajalein Atol remain today. In this report we I the 1978 NMIRS and the larger al developd from sampling trips to I from 1986 through 1993, to estim that people would receive if 1 resettle on Rongelap Atoll. The doses are calculated resettlement date of 1995. As noted below, we also have and have found useful data from e for example, those done by the Washington (LRE) in 1959 and 1% The radiological dose to inhabitants at a contaminated atom occurs from both external and internal exposure. Each of these two categories can be broken down further into the following A. Natural Background Radiation A. Natural Background Radiation 1. Radionuclides in Terrestrial Foods 3. Radionuclides in Marine Foods 4. Radionuclides in Drinking Water The above internal exposure pathways are listwi in descending order of their contribution to the total estimated radiological dose at the atolls (Robison et al., 1987). The terrestrial foods are of importance because of the uptake of 137CSby vegetation; these foods account for about 60’%of the total estimated effective do: from the external gamma pat] of the total estimated effective do! Island is due to 137G. The conti 5% of the total estimated effective vary at different atolls and ishnd The external natural backgro exposure in the northern Marshal cosmic radiation. The external baf due to terrestrial radiation is ve Marshall Islands. The internal ef Occurnng radionuclides such as imported foods The natural backi not included in the doses presente unless specifically stated. External Exposure Measurements The external exposure rates at Rongelap measured by EG&G in 197 as prt of the aerial survey conducted in the contours for 137Cs are shown in Fi 1978 NMIRS (Tipton and Meibaum, 1981). The we made a series of ext( average exposure rate on Rongelap Island as measurements at the two atolls 1 Iunt of data te the dose ad access to ray is also Mien of the Uy less than se, but does low in the tive dose is of local and

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with me EG&G aerial gamma measurement of 1978. As part of this process, an independent reviewer, Dr. Herwig Paretzke of the German Radiation Institute in Munich, Germany, participated in the measurements to evaluate our methodology and compare our results with the EG&G 1978 data. The results of the measurements made using our in-situ sodium iodide crystal spectrometer system and the EG&G data are listed in Table 1. EG&G’s data were listed as ranges for each contour. Our locations were within the specified contour In addition, in 1988, LLNL staff took more specific external gamma measurements of 137CSand ~ inside and outside of houses and other buildings as well as around the village area. These measurements could not be taken with the aerial-measurement system used in 1978. The buildings provide shielding so that the exposure rate is reducd compared to the exposure rate determined from oper unpublished data from Bikini 1s1 based on measurements at Rong (Table 2) the reduction factor is abou is customary in the MarshaIl Islan crushal coral around the hotuws anc area. This provides an additiona factor. The shielding by buildings a coral must be considered when est dose to the people living on the i! results from our measurements insid~ and in the surrounding area of the hol village are shown in Table 2. The data presented here from lx aerial survey mnducted by EG&G ax own more specific measurements nu are decay corrected to 1995 and form our estimate of the external dose pe receive while living on Rongelap I maximum effective dose occurs in d Table 1. Comparison of the EG&G aerial gamma measurements with the LLNL in-s a Decay corrected to 1995.

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Table 2 External lSTCSgammii exposure-rate measurements in and around the houses J of Rongelap Island General village sites 16 2.2 2.4 a Decay corrected to 1995. The unshielded beta contribution to the exterral dose was estimated for Enjebi Island at Enewetak Atoll in 1980 (Crase et al., 1982). The average beta dose at 1-m height over open ground was 29% of the external gamma dose. The beta dose is deliveral, for the most part, to the first centimeter of tissue, the so-called “shallow dose” and, therefore, should not be added to the external gamma dose in estimating the whoie-body dose. More recent studies at Bikini Atoll using new, thinner thermoluminescent dosimeters (TLDs) indicate that the dose over open ground at 1-CMheight is about three times that at l-m height (Singleton et al., 1987). Thus, the unshielded beta dose at l<m on Rongeiap Island could be equal to, or slightly greater than, the external gamma dose. For some portion of one day, people do sit or lie on the ground where the l-cm exposure may be relevant. However, for a significant part of the day, the eyes, upper body, and gonads am at 0.8 m or more in height above the ground surface. Moreover, it is important to realize that the beta dose tos@ for a number of reasons, will be significantly less than that determined from the unshielded TLDs placed over open ground. The walls and floors of the houses and the crushed coral customarily placed around houses and the village area absorb most of the beta radiation. Because people spend a significant amount of their time in these areas, their exposure to beta particles is greatly reduced. In addition, any clothin& shoes, zmies, …