Status Report - Dose Reassessment for Populations on Rongelap and Utirik Following Exposure to Fallout from the Bravo Incident (March 1, 1954) (Enclosure)

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fallout from tl~ebwyo incident (March 1, 1954). Incidence of Lhyrc’idnodules, beni~n and malignant, in the exposed populatfong of Utirik and ltong~,laplIasindicated critical differences in correspondence between lWdUle incidencu and tljyrofddose for the populaclous (Table 1). Tileestimated external dose rt.ceivt!dfrom the time fallout began to the time of evacuation shows that the Rongtilnppopulation received an external dose (175 rads) which was ubuut IJ times that fur tiw Utirik population (14 rads), and the thyroid dose was abIJUL 10 cimes larger, whereas the incidence of thyroid nodules in the two populatloll% were not significantly dilterent. A preliminary study has indicated that the critical area of investigation that could shed light is the period during fallout and evacuation for both the lsl~nds. In addition, the fact chat the Utirik population returned within 120 days folluwlng evacuation, whereas tl~e Rongelap population returned only aftef three years, requires that we look close]y at the Utirik population in ucrrisof a longer exposure period, buch internal and external. Further studies would, therefore, Iiaveto concentrate on the reexamination of all available data in reports issued by various agencies Guring that period, consultationswith scientific personnel involved at that time, identifying the areas of uncertainty, and using appropriate computer programs to analyze the data. The end result will enable us to look for correlations between the incidence of thyroid nodules afiathe reassessed dose estimates. To examine the external and internal dose estimates to the Rongelap and Utirik populations following the “Bravo” test in order to: -- a. increase the confidence in the reported values b. test the hypothesis that radiation effects can be translated into meaningful dose estimates c. look for correlacionship between the thyroid cancer cases and the reassessment dose estimates (if any). Method of Study: 1. Literature Search: This would require examining the various research reports Naval Research Defense Laboratory (NRDL) Reports Reports fra. various other laboratories (University of Washington, etc). 2. Personnel ContJcts: Efforts will be made to contact as many of the scientists and technical ptrsons, who were involved in the early ye~rs for infornIaLion on measurement techniques and analytical procedures.

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USU UJ iilm badge datu at Rongerik to quantify the fallout building curveupslope mi downsloper and to extrapolate t,his information to RcIngelupand estimating the Y depth dose; for example, the @ activity dose duc to Plot all the available data on external radiation and determine decay factors. The question to be raised will be: Do the data res~lt in a curve similar to the esti~tes T-1*5 relationship, or does it exhibit different values, such Examine the question on internal dose estimations from, urine analysis, food ingestion, inhalation and data from animal studies. In this procuss all available intormutiun on diet and lifestyle would br compiled tia*as to derive realistic dose estimates from uxternal and internai sources. Examine ocher studieu done elsewhere on Y e thyroid noduAest for example; thti Chicago Group Study, and also the use of 29I to determine the early thyroid doses . Historic samples collected soon after fallout will be used in determining the 1291 concentrations. In addition, 95Tc would also be determined since it is known to be retained in the @yroid gland. If possible, excised thyroid Use a “state-of-the-art” computer simulation program to determine the transport and deposition of radioactive fallout following the BRAVO test. This study a. plots of integrated air concentration isopleths for fission products iodine, cesium and strontium b. deposition fsopleths for the aforementioned fission products, plus 239Np/239PU if possible, and c. time plots of the buildup and decline of airborne fallout concentrations near sea level at the points of interest, and/or the building of ground deposited fallout. Status of Study: 1. External Radiation Measurement a. Figure 1 shows a plot of the gamma dose rate in roentgens per hour at three feet above ground at 24 hours after the BRAVO test explosion. Figure 2 shows the estimated total dose contours in roentgens at 96 hours after the BRAVO test explosion indicating 175 racts of whole body gamma radiation for the Rongelap inhabitants and 14 rads for the Utirik inhabitants. In view of these observations, an exhaustive search of all reports generated Tables 2 and 3 for Rongelap and Utirik respectively. This data has been plotted in Figures 3 and 4. These plots will be further examined when results from Item 8 above will be received.

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Dose Rates Consequent To The “Bravo’)Shot, March 1, 1954 Based on plot Return to Utirik Return to Utirik 3 Based on plot 5

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Glas4ttvne: The Effvcts of Nuclear Weilpotw,1957, pgs. 424, 426. Figures Dr. Harley’s Letter of October 27, 1976 to Dr. Conard. Plot of All Available Data - Figures I 6 II. University of Washington Data, September 1959.

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2. Diet and Lifetityle Study a, All available reports concerning fallout on Allingirw, Rmgelap, Rongerik and Utirjk have been exam~raedand pertinent llif~jrmatior~ has been coLlated into one location. The data collected concerns exttmml radiation measurertrunts$ radionuclide concentrations in soil, water, vegetation, animals and food items. In addition, efforts are being made to collect information on whole body analysis and bioas~ay sampltis. b. A recent diet and lifestyle study completed in November 1978 w1l.1 provide a firm basis to estimate internal and external doses. a. Historic samples collected by University of Washington during the period 1954-1974 have been analyzed for 1291 (Table 4). These samples are also being analyzed for 99Tc. Information from Item 8 (Methods of Study) will be required to correlate the findings. Additional samples from these areas (Rongelap, Ronerik, Utirik) will be analysed for 1291 and 99Tc if required. In addition, we are exploring the possibility of analyzing “Bikini-ash’’-the fa~~out that settled on “Tl~eLuckyD ragon”. This sample should provide the most accurate description of the fallout. a. All available data pertaining to meteorological conditions before, during and after the BRAVO test have been collected and transmitted to Lawrence LiverrnoreLaboratory for the computer analysis. These results should be available by February/March 1979. b. A recent Marshall Islands Radiological survey completed in December 1978 should provide iso-dose lines for recent times. Comparison of the two plots should be very valuable in assessing 1954 5. Discussions are being continued with the scientists and technical people who were involved during Operation Castle.

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This rqsoct was prepared .asanaccount 01 w{lrk qxmsorcd b$ an agcncv of the Unitrd States Govcrnmms[. Nei!her the United Smtm Guvrrnrrwrr nor wry amnm thereof. plovcca,makesanywarrant~,cxprcm or !mpllmi, or owurnm arw Iqal Iiabilltv m rr. rm, prorht, w process discloser or reprrserrts Ihat IIS use would nnt inirin<c privately owned rights. Reference herrin 10 .inv specttic cnmnwrclal prndtlcl. prwess. [Jr service hv trade uamr. trademark. maouiacturrr. ur otherwise, CIWS nut ncccssaniv PrinwcJ in the United States of America Nalirxral Technical Informatirm Scrwice 3285 Port Roval Road

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A RECONSTRUCTIONOF CHRONIC DOSE EQUIVALENTS FOR RON(;I(LAP AND UTIRIK RESIDENTS - 1954 TO 1980 From June 1946 to August 1958, the U.S. Department of Defense %nd Atomic Energy Cotmisaion conducted nuclear weapons tests in the Northern Marshall Islands. BRAVO, an above-groundtest in theoCastle series) resulted in radioactive fallout contaminatingRongelap and Utirik Atolls. On March 3, 1954$ the inhabitantsof these atolls were relocated until radiation exposure rates declined to acceptable levels. Environmentaland personnel radiological monitoring programs were begun in the mid 1950’s by Brookhaven National Laboratory to ensure that dose equivalents received or coaauitted remained within U.S. Federal Radiation Council Guidelines for members of the general public. Body burden and dose equivalent histories along with activity ingestion patterns post return are presented. Dosimetric methods, results, and internal dose equivalent distributions for subgroups of the population are also described.

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On March 1, 1954, at Bikini Atoll, BRAVO, teats in the Castle series~ was detonated, The the first of ftix nuclofir WC~}JOIIS BRAVO device caused sltbstantinl . surface contamination on inhabited atolls within a 2,000 square mile area. T!]c . contaminated region was cigar shaped and included Ailinginaev Rongelap, Rongerik, and Utirik Atolls which lay eaet of ground zero at distances from 60 to 300 miles. The fallout on Rongelap, initiallyvisible at H+6 hours, had thinned out to the extent that it was no longer seen at H+1O hours (G162).” On March 3, 1954, the 64 residentsof Rongelap Atoll and 18 residentsof Sifo Island, Ailinginae Atoll, were evacuated. On March 3 affd4, evacuationof 157 Utirik Atoll residents also took place. During the first few weeks and at least once every year from 1957 to the present, a Brookhaven National Laboratory medical team, organized by the Departmentof Deferiseand by the Atomic Energy Conmiasion and its successor organizations,has provided medical examinations to monitor the health of the persons initiallyaffected by the fallout from the nuclear testing program, plus a comparison population. Reports of their findings The Utirikese and Rongelapese returned to their home atolls in June 1954 and in June 1957 respectively. The earlier repatriationof Utirik Atoll was based on the low level of external radiation exposure measured after the initial . 3 month observation period (March to June 1954). The Utirik populationwas not w:. examined by a Brookhaven medical team until March, 1957, when 144 people received comprehensive physical examinations. Following the 1957, medical survey, two men, removed from Utirik for medical reasons, were whole body counted at Laboratory and provided urine samples for radiochemicalanal-

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I ysh of J37C8, Four peroono visited Argonne from Rongelap 8nd, in addition,I l ** pooled urine sample. from both atolls were analyzed radiochemicallyfor ‘J’Cs the Medical Department and Safety and EnvironmentalProtection Division utilized whole body counting and radiochemicalanalysis of urine and blood samples to identify and quantify the radionuclidesthat were present in the body. The results of theee radiologicalmeasurements are given in terms of body burden in s. Tables 1 and 2. Throughout this paper the units of quantities are S1 derived lnd those which l re accepted for use with the S1 for the time being. ThU8 both the Curie and the Becquerel may be used as units for the quanrity activity. The aforementionedbody burden tables illustrateadult mean values for Rongelap and Utirik. An adult, as classified here, was a person over 16 years of age. The mean body mass in this age interval was 60 kilograms. The observed body mass versus age distribution is shown in Figure I for Rmgelw residents. The same body mass versus age distributionwas observed at Utirik. Because of the paucity of measurements Zn, and Fe was in some instances derived burdens between Rongelap and Utirik. A mean at Utirik, information on ) from the ratio of adult mean body ratio of 2.6 was observed in body reached their maximum values. The standard deviation of this ratio was 15%. In the following analysis, personal tervals, in conjunction with contemporary body burden histories and residence indosimetric models, are used to estimate internal dose. Dosimetric distributionswere constructed from the results and a summary of the derived activity ingestion rates and dose equivalents was provided for various subgroups of the population. Additionally,exposure rz?te history curves were constructed for each atoll for the period following the

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together with appropriate conversion factors and living an estimate of external dose equivalent. Exponentially declining activity concentrations have been observed in ~ur- : face soil for 137 C8~ 129 1, and 90 Sr from 1954 to the present on Rongelap .,, atwl Utirik Atoll@. Declining activity concentrations have also been observed in vegetation at a rate greater than that predicted by radioactive decay. Thu’sexponential decline in diet-y activity was a-umed and the following general equatione were derived.

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instantaneous fr8ction of atoms decaying per unit time, day -1 initial atom ingestion rate, atoms day-~$ the number of fraction of atoms removed from compartment i by atoms in compartment i relative to the number in all compartments at the onset of declining continuous uptake! (t=O)l instantaneous urine activity concentration Bq 2-1, subject urine excretion rate, & day-l, fraction from GI tract to blood, fraction excreted by the urine pathway? instantaneous fraction of atoms removed or per unit time, day ‘1, due to factors other q s instantaneous body burden, BqS q0 s body burden at the onset of uptake, Bq? added to the atom uptake than radioactive decay, Dz the number of disintegrations in all compartments occurring during the uptake interval, Bq days, The development of Eqs. (l), (2), and (3) was based on the following convolution integral. At some variable time, T, defined during a fixed uptake interval, T, the daily activity ingestion rate crossing the gastrointestinal tract to blood is given by

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The whole body reteotion at any time t- of the fraction of initial radio~~tivity Thus, the instantaneous activity at time t-? that remains following input during It follows that the instantaneous activity at time t- that remains following input during T is The solution of the inte8ral yields a general expression that depends on the user defining t. For example, if t is the fixed uptake interval, T, plus an additional fixed post uptake interval? $$ then the body burden at T + (1 is As previously stated, Eq. (Z) applied at Rongelap and Utirik, it was for the situation that variable time t was the uptake interval. Additionally, persons who returned to the atolls in June 1954 and June 1957 did so with an initial body burdenj q“. The behavior of this contribution to q, was embodied in the q“ tem of Eqc (2). A similar ~del was used to relate

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urine activity concentration to body burden. Equation 3 wan obtained by EquaCions (1) and (2) were used to determine atoms removed or added to the atom uptake per unit the intitantaneoug fraction of tial daily activity ingestion rate required to produce the measured or derived body burden. Equation (3) was used to determine the number of disintegrations < that occurred in the body during the residence interval of an individual living on Rongelap or Utirik Atoll. If the mean residence time in the diet is much much longer than the residence interval, then constant continuous uptake is achieved@. Equations (11 and (2) can be converted,to the constant continuous equations bY replacing ‘E with -A . Single uptake expressions are obtained by setting ~ equal to zero. In some cases only radioactive decay may remove the nuclide from dietary items; for these casea % would equal zero. In the case of the former Bikini residents, the mturing of coconut trees during residence on Bikini Atoll caused a continuously increasing dietary uptake of 137 Cs. Thus, Kg was found to have a negative value. In the case of Rongelap and Utirik, KE was “found to have a positive value for ? Zn, 9 . This indicated that in addition to radioactive decay$ some other removal mechanism decreased the radioactivity in dietary items during the residence interval. For the nuclide 55 Fe, only one measurement was published by the BNL Medical Program (Be72); thus an estimate of. % . was not possible. “. KE was determined by using Eq. (1) or (2) and the population subgroup mean body burden or urine activity concentration. Portions of these bioassay data are illustrated for adult males and females in Figures 2 to 6. Two consecutive urine or body …