Radiobiological Resurvey of Rongelap and Alilinginae Atoll, Marshall Islands, October - November 1955

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UNITED STATES ATOMIC ENERGY COMMISSION RADIOBIOLOGICAL RESURVEY OF RONGELAP AND AILINGINAE ATOLLS, MARSHALL Applied Fisheries Laboratory University of Washington Technical Information Service Extension, Oak Ridge, Term.

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This report was prepared as an account of Government sponsored work. Neither the United States, nor the Commission, nor any person acting on behalf of the Commission: A. Makes any warranty or representation, express or implled, with respect to the accuracy, completeness, or usefulness of the Information contained in this report, or that the use of any mformatlon, apparatus, method, or process disclosed m this report may not infringe privately’ owned rishts; or B. Assumes any lla~illtles with respect to the use of, or for damages resulting from the use of any lnforma[!un, apparatus, method, or process disc Losed in this report. ployee or contractor uf tne Cummlsslon to the extent that such employee or contractor prepares, bandies or a)str;hutes, or provides access to, any information pursuant to his This report has been reproduceddirectly from thebest availablecopy. Printed in USA. Price 50 cents. Avaiiablefrom theOffice of TechnicalServ-

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RADIO1310LOGICAL RESURVEY OF RONGELAP AND AXLINGINAE ATOLLS MARSHALL ISLANDS By the Staff of the Applied Fisheries Laboratory University of Washington Operated by the University of Washington uncier Contract No. AT(45- 1)540 with the United States Atomic Energy Commission.

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Radiation readings on the islands of Rongelap and Procedures usedin collecting and processing samples and recording radioactivity 7 Rate of decline of radioactivity in food items 9 Evaluation of radioactivity in the biological samples 13 Evaluation of radioactivity in the soils 52 Physical decay of samples 62

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The radiological contamination of Rongelap and Ailinginae Atolls in the eastern Marshall Islands has been evaluated from samples of material collected and from surface readings. The results of expeditions sponsored by the United States Atomic Energy Commission, Division of Biology and Medicine, and carried out by the Applied Fisheries Laboratory, University of Washington, between March 26, 1954 and June 30, 1955 are summarized in UWFL-42. Additional observations and collections made during OctoberNovember, 1955, are evaluated in this report. and steeper than the rate of decay for mixed fission products at a year and The radioactive content of most samples collected from the northern part of Rongelap Atoll continues to be higher than similar samples from the southern part of the atoll. The birds continue to be an exception to Soil and lagoon bottom samples were collected extensively during October-November, 1955. These samples show great variability. Activity levels in the top 3 inches of soil at Kabelle and Labaredj Islands varied from 4.4 to 11.5 He/kg. The highest value (20. 3 uc/kg) of any soil sample of the October-November collections, oddly, was found in the top 3 inches of soil from Rongelap Island. Other Rongelap Island values averaged

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1.7 #c/kg for the top 3 inches of soil. Similar samples from Enibuk Island, Ailinginae Atoll, averaged 0.61 pc/kg. The decline curves and the chemical separations show a great variability in the materials contributing to the radioactivity of the various samples. In the samples separated chemically, SrgO “M virtually absent in the coconuts and in the marine animals sampled, but constitutes 2 - 5 percent of the total activity in other land plants and 50 percent of the skeletal salts of the land crabs. Radiocesium was found in only slnall amounts in marine animals, but accounted for up to 100 percent of the activity in some of the 144 than the land plants.land plants. The marine animals contained more Ce Fission products do not account for all of the activity in most samples.

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RADIOBIOLOGICAL RESURVEY OF RONGELAP AND AILINGINAE ATOLLS MARSHALL ISLANDS During the weapons testing program in the spring of 1954 (Operation Castle), radioactive fallout on some of the atolls was of sufficient intensity to make necessary the evacuation of the native peoples as a health protec - tive measure 1’ ‘J 3. The contamination from radioactive material falling upon the islands was especially heavy in the northern portion of Rongelap Atoll and much less at A~linginae Atoll. The summary statement from the Eighteenth Semiannual Report of the U S. Atomic Energy Commission outLines the contaminant ion due to fallout as follows. “The highest radiation measurement outsl de of Bikini Atoll indicated a dosage of 2300 roentgens for the same period (the first 36 hours). This was in the northwestern part of the Rongelap Atoll, about 100 miles from the point of detonation. Additional measurements in Rongelap Atoll indicated dosages, for the first 36-hour period, of 2000 roentgens at 110 miles, 1000 roentgens at 125 miles, and farther south, only 150 roentgens at 115 miles from Bikini. “ 4 , In addition to the external radiation problem, there is also interest in the fate of radioactive materials adsorbed or absorbed by the btota and their possible inclusion into the food of the native people, should they be returned to the area. Numerous expeditions have been made to the atolls to study the problem;

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radiation readings have ccrded. The results of been taken, samples cGllected, and changes rethe expeditions sponsored by the U. S. Atomic Energy Commission Division of Biology and Medicine and carried out by the .Applied Fisheries Laboratory, University of Washington, between March 26, 1954 and June 30, 1955 are summarized in UWFL-42 5. The results of the jointly- sponsored expedition of the AEC and the U. S. Naval Radiological Defense Laboratory during January 1955 are summarized in The need for further studies to bring the evaluations up to date was expressed by the AEC Division of Biology and Medicine in a communication fr~m Dr. Charles L. Dunham, Director, on September 19, 1955. Acting on this request from Dr. Dunham, a field party from the Applied Fisheries ham, and Frank G. Lowman left Seattle on October 12, 1955 and returned November 13, 1955. Collections of material for radiological contamination evaluation and survey meter readings of residual contamination were obtained by the field party on their visits of October 21-23 and November 1955 to Rongelap and Ailinginae Atolls. The fine support and cooperation from all the organizations concerned made it possible to conduct this program with the maximum of efficiency. We are especially ~grateful for the support received from the Division of Biology and Medicine, the Eniwetok Field Office, Holmes and Narver, the U. 5. Naval Station, Kwajalein, and the units of the Department of Defense stationed at Eniwetok.

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Radiation Readings on the Islands of Rongelap and Atlinginae Atolls A summary of the radiation readinga obtained on the five study-collecting trips in which the Applied Fisheries Laboratory participated from March 26, 1954 to November7, 1955 is givenin Table 1. On the October 21-23 survey, Mr. Robert Taft, Radiological Safety Officer of the AEC Resident Engineer’s staff, accompanied the field party and made the survey readings with a Beckman MX-5 meter. All readings were obtained one inch above ground and were recorded in millireps per hour. The highest readings were again obtained on the more northern islands of Kabelle and Labaredj where maximum readings were 4 mrep/hr with the shield closed and 14 mrep /hr with the shield open, Readings at Rongelap Island and Enibuk Island (Ailinginae Atoll) were much lower than the northern islands, in some cases approaching the background range of the The individual readings for the October 21-23, 1955 visit, with the locations and terrain conditions, are recorded in Appendix A. It was learned after the survey group of October 1955 had returned to the Eniwetok Marine Biological Laboratory that the Division of Biology Medicine was in need of a complete survey of the islands with readings the three-foot level in addition to those level. On November 7, 1955, Se~our previously taken at the one-inch and Held were flown to Rongelap

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and Labaredj Islands by the U. S. Navy plane, PBM 612. Their extensive survey readings are recorded in detail in Appendix A.

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Procedures Used in Collecting and Processing Samples and Recording The procedures used in collecting samples of biological material hlarshall Islands have evolved over a period during each expedition to obtain as complete adequate evaluation of the problems studied, of years. An effort was a sample as necessary for an without completely swamping the Laboratory with samples. To carry out the program of sampling, specific animals and plants with wide distribution have been selected for study. From these selected samples certain tissues are evaluated to determine the distribution of radioactivity. Collections made in the field were retained on ice or frozen until they could be returned to the Division of Biology and Medicine field laboratory at Parry Island. There the or:anisms were identified, selected tissues were dissected, weighed and then dried. The packaged dried samples, together with the data cards, were sent by airmail t~ the Ap$plied Fisheries Laboratory, University of Washingtoqfor further processing. At the Applied Fisheries Laboratory, the dried samples were ashed at temperatures up to 540”C, cooled, slurried, dried, and then counted in an date of collection, counting chamber. The counts per plate were converted per minute per gram (d/m/g) of wet tissue, as of the by correcting for sample weight, geometry, backscatter, . self-absorption, coincidence, and decay. For a more c~mplete discussion

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In preparing the summary tables as used in this report the radioactivity expressed in disintegrations per minute per gram (d/m /g) was converted to mlcrocuries per kilogram in the following manner:

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Rate of Decline of Radioactivity in Food Items—— The rate of decline is the rate of change of activity in isms and is the consequence of the interaction of physical decay, of biologi - uptake, and of biological decay. The activity of the principal food items for the five dates of collection presented in Table 2 and Figure 2. The values were obtained by averaging sample counts from all areas. The individual counts from which the values for the October 1955 collection were determined can be found in Appendix B, For the earlier dates the values are taken from UWFL-42, Table I. Table 2 and Figure 2 give the general picture of radioactivity of the food items and are useful to those who wish to calculate the health hazard. The coefficient of variation (standard deviation + mean) for these values averages about 60 percent, which indicates considerable variability. Area and species differences and sampling error acc”ount for this variability. In the sections on fish, invertebrates, plants, etc. , the samples are gr:)uped in smaller divi6ions, with area and species differences eliminated. From Table 2 the absolute values of the food items can be obtained, and from Figure J the rate of decline can be directly calculated. These data are closest to being points on a straight line when plotted on a log-log scale with March 1, 1954 as the date of origin. For the purpose of making an approximation of the general rate of decline, the slope of a least-squares line determined from the average values for all items on each collecting

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DAYS AFTER MARCH 1, 1954 Figure 2. Rate of decline of radioactivity in food Items from collections at Rongelap Atoll between March 26, 1954

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for mixed fission products at a year and a half is less, being about -1. 55). One use of the decline curve is to predict the level of activity of food items at some future date. For example, if the value for a food item was 100 on November 1, 1S55 it wGuld be 85 on January 1, 1956 and 56 on July 1,

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Evaluation of Radioactivity in the Biological SamDles As part of the prGgram to evaluate the residual radioactivity in the food items of the Marshall Islands, reef fish and some lagoon fish were collected from several areas in Rongelap and Ailingirzae Atolls (Tables 3 and 4). The fish were collected by underwater detonations using Primacord or by poisoning with derris root. Some specimens were caught in the deeper waters of the lagoon with hook and line. The species selected for analysis were those commonly found in the Marshall Islands and included damseifish. groupers, parrot fish, squirrelfish, surgeonfish, goatfish, wrasse, snappers, mullet and tuna. The scientific names of the species are given in the appendix of UWFL-42. The tissues used for analysis of radioactivity were skin, muscle, bone, liver and other viscera. The latter included part of the stomach contents as well as part of the alimentary canal, in most cases. From the October 1955 collections only the muscle, bone and liver were used, as these three tissues represent, in the above order, the minimum, intermediate and maximum amounts of radioactivity found in the tissues and serve as the best examples of the trends. The itemized data for the October 1955 collections of tissues and specimens of fish are listed in Appendix B. The collections from Kabelle Island, which were taken over a longer period than those from the other islands, offer the best data for determination of the decline of radioactivity in the fish. The collections from this

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island were made open to the sea at in approximately the high tide, lying near same area, a coral-filled channel the north end of the island. The data are summarized in Table 3 and Figures 3 and 4. The radioactivity in Kabelle Island fish muscle tissue showed leveIs of about 2.7 pc/kg on March 26, 1954. By October 1955 levels had dropped to less than .030 #c/kg, which is less than (1 /2)6 that of the March 1954 samples and the liver samples (1 /2)7 for the same period. Decline and decay of radioactivity show differences in rate, the former declining at a slower rate than decay the first 100 days after March 1, 1954, and then at a greater rate thereafter; thus the curves appear to be approximating each other at the present time. Differences in rate of decline and decay might be explained by the postulate that in the first 100 days after March 1, 1954, the radioactive materials existed in greater abundance than could be utilized by the fish so that during this period the fish tissues were more or less llsaturatedl’ with the materials. As the radioactivity decayed and was dispersed with time, the tissues declined in radioactivity at an increasing rate commensurate with the amounts available in the food chain and in the surrounding water. Decline in amounts of radioactivity in omnivorous and carnivorous fish indicates some differences in rate, at least for the first 100 days (Fig. 4 ). These differences decreased with passage of time. The grouper and damselfish in Table 3 represent rather common species 1 of carnivorous and omnivorous fish, respectively, and are the best repre - sented, of all the species, in the collections. F~r the most part the avera&s

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DAYS AFTER MAR. 1,1954 DAYS AFTER MAR. 1, 1954 of average amounts of radioof three specimens collected March 2%, 1954. All specimens from Kabelle Island, Rongelap Figure 4. Decline of average amounts of radioactivity in fish tissues of carnivores solid line) and omnivores broken line) from Kabelle Island, Rongelap Atoll l$@+-

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compare with those of omnivores and carnivores generally. In the data there appears to be …