Radiobiological Studies of the Fish Collected at Rongelap and Ailinginae Atolls, July 1957

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UNITED STATES ATOMIC ENERGY COMMISSION RADIOBIOLOGICAL STUDIES OF THE FISH COLLECTED AT RONGELAP AND AILINGINAE ATOLLS, JULY 1957 Applied Fisheries Laboratory University of Washington Technical Information Service Exten ~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 implied, with respect to the accuracy, completeness, or usefulness of the information contained in this report, or that the use of any information, apparatus, method, or process disclosed in this report may not infringe privately owned rights; or B. Assumes any liabilities with respect to the use of, or for damages resulting from the use of any information, apparatus, method, or process disclosed in this report. As used in the above, “person acting on behalf of the Commission” includes any employee or contractor of the Commission to the extent that such employee or contractor prepares, handles or distributes, or provides access to, any information pursuant to his employment or contract with the Commission. This report has been reproduced directly from the best available copy. Printed in USA. Price $1.00. Available from the Office of Technical Services, Department of Commerce, Washington 25, D. C. AEC Techmcal Information Servtce Extcnslon

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RADIOBIOLOGICAL STUDIES OF THE FISH COLLECTED AT RONGELAP AND AILINGINAE ATOLLS JULY 1957 Laboratory of Radiation Biology University of Washington Operated by the University of Washington under Contract No. AT(45- 1)540 with the United States Atomic Energy Commission

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Radiobiological analysis of the reef fishes of Rongelap and Ailinginae Atolls indicated that a recontamination of the area occurred in 1956. Gross levels of beta activity in muscle tissue ranged from O. 016 to O. 038 uc/kg wet weight. The levels of radioactivity in bone and muscle tissues of fish collected during 1957 were about the same as the levels for similar tissues collected in 1955. Gamma spectra analysis and ion-exchange methods Radiostrontium was found only in small amounts (about .0014 uc/kg wet weight) in the bone of fish from Kabelle Island, Rongelap Atoll. Approximately 40 per cent of the total radioactivity in the reef fishes was due to Zn65, 28 per cent to cobalt, 26 per cent to Fe55, and 6 per cent to other radionuclides.

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RADIOBIOLOGICAL STUDIES OF THE FISH COLLECTED AT RONGELAP AND AILINGINAE ATOLLS JULY 1957 During July 1957 collections of fish for radiobiological analysis were made at Ailinginae and Rongelap Atolls. The data from these collections represent part of the information from a continuing program of radiobio - logical studies which was begun on March 26, 1954, soon after the first radiological contamination of Rongelap and Ailinginae Atolls. Subsequent collections were made on July 16, 1954, January 29, 1955, and October 10, 1955. All of these investigations have been reported by Donaldson, et al. ( 1955). Data from the investigations in the Rongelap area by this.— Laboratory and other organizations have been summarized and coordinated by Dunning (1957). Results of the analyses of additional material collected August 3, 1956 are included in this report. Materials and Methods Fish were collected at Enibuk Island, Ailinginae Atoll, on July 11, 1957, by poisoning an area of the inner reef. One large grouper also was taken by hook and line in Mogiri Pass. On July 17, 1957, a collection was made in the lagoon in front of the village on Rongelap Island, Rongelap Atoll, and

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on July 18, 1957, a collection was made in the channel off the northwest end of Kabelle Island, Rongelap Atoll. All fish were obtained in water 15 feet or less in depth, and the collections were made in localities almost identical to those of the 1954, 1955 and 1956 surveys. Locality, date of collection, common names, genera, species and number of specimens for the 1956 and 1957 collections are listed in the appendix. The fish were placed on ice in insulated containers within two hours of capture and transported to the Eniwetok Marine Biological Laboratory where they were frozen. There the fish were identified and dissected, except in the case of fish collected in 1956 when the frozen fish were shipped to the base Laboratory at the University of Washington for dissection and subsequent radiological analysis. Tissues used for analysis were muscle, bone, liver and stomach contents or viscera. Specimens which were too small to dissect were processed as whole fish. Partly because of the omnivorous food habits of the Marshallese natives and partly because of variations in the samples, it is advisable to analyze many specimens of a variety of species to obtain reliable estimates of levels of radioactivity (We lander, 1957). Consequently, twogram samples of muscle tissue were taKen from each fish and the aggregate was homogenized in a Waring Blendor. Plates were made of aliquots of this homogenate and the remainder dried for radio chemical analysis. All samples were dried at 100° C and the plated samples ashed at temperatures up to 540° C, cooled, slurried, dried and counted in

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internal methane gas-flow counting chambers at the Laboratory of Radiation Biology in Seattle. Counts per plate were converted to disintegrations per minute per gram of wet tissue by correcting for sample weight, georr, etry, backs catter and self-absorption. For a more complete discussion of these procedures see Donaldson et al. (1953)..— Other tissues were treated similarly, with the exception of liver, in which case the whole organ was removed from each specimen. If a sufficient number of specimens of a single species was obtained, the tissues were treated separately as in the case of goatfish and halfbeak from Decay rates for radioactivity of tissues of fish collected in 1956 were calculated because there were indications that Ron~lap Atoll was contaminated during the Redwing operation. Gamma spectra and total gamma counts were made on dried or ashed samples in a single channel, 50-position, automatic advance, gamma spectrometer using a two-inch, well-type sodium iodide crystal. Chemical analyses were made by ion-exchange resin column and radio chemical precipitation techniques The radioactive isotopes contained in the separate fractions were identified by determination of the gamma energies, and by beta mass absorption studies using aluminum foil. Correction factors for converting beta and gamma counts to disintegrations per minute were calculated by the use of standards of known energies. Details of the procedures . (1957).used are given by Lowman et al

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Gross Beta Radioactivity Table 1 shows gross levels of beta radioactivity in the fishes during July 1957. Of the three islands visited the highest levels were found in the fish liver tissue from Kabelle Island. In all ca~es, for comparable tissues, the least radioactivity was found in fish collected near Rongelap Island. Radioactivity in muscle tissue of fish from Enibuk Island, Ailinginae Atoll, was as great or greater than that of Kabelle Island. Comparatively minor differences are seen in the levels of radioactivity in similar tissues of omnivorous and carnivorous fishes from Rongelap Island, except for stomach contents. in the stomachs of many omnivorous fish would levels in these fishes. Two species, the goatfish and quantities for separate analyses. brates, principally crustacea, of The presence of algae account for the higher were taken in sufficient The goatfish feeds on small inverte - the sandy bottom areas. Levels of radioactivity in the stomach contents and liver of these fish were much higher than in other fish of the same area; however, radioactivity in muscle tissue was not much higher. The halfbeaks from Kabelle Island had about the same amount of radioactivity as fish from Rongelap, reflecting, perhaps, a different feeding habit than that of other fish of Kabelle Island. The halfbeak normaUy feeds at the surface on macroplankton ,

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which includes small fish, invertebrates and algae. Table 2 contains data on the rate of decline of the beta radioactivity in reef fish collected at Rongelap and Ailinginae Atolls between March 26, 1954 and July 18, 1957. The rates of decline in liver, bone and muscle tissue of fish from Kabelle Island are given in Figure 1. The decline rates are similar for all three tissues, especially during the first two years. Recontamination by other nuclear devices during the summer of 1956 is indicated by the increase of radioactivity in muscle al. bone and a temporary decrease in rate of decline in liver tissue. At present, the radioactivity in liver tissue appears to be declining at rapid rate than in bone or muscle, while the radioactivity in the or stomach contents has declined more rapidly than that of other tissues (Table 2). It has been suggested (Welander, 1957) that some of the long-lived isotopes may be accumulating in the bone and muscle of fish, whereas the radioactivity in liver tissue is similar to that in the stomach, bearing out the fact that the liver is an organ for the temporary storage and passage of food and waste products. It is of interest to note that the levels of radioactivity in the bone and muscle are about the same as those of the, 1955 samples. Data on radioactive decay were obtained from bone and liver tissue of groupers (Epinephalus merra) from Kabelle and Rongelap Islands, and from homogenized muscle tissues from 13 species of reef fish. The decay rates of muscle and bone (Figure 1) are more rapid than declirie rates for the

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Fig. 1. Rate of decline (solid line) of radioactivity in reef fish collected at Kabelle Island, Rongelap Atoll b~tween March 26, 1954 and July 18, 1957. Broken lines indicate decay in tissue of fish collected August 3, 195$ .

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same period; however, liver tissue decay and decline rates are similar. The differences in rate of decay and decline in both bone and muscle may indicate greater retention as well as continued uptake of long-lived radioactive materials in these tissues. Figure 2 illustrates the rate of decline in the tissues of fish from . Rongelap Island between January 25, 1955 and July 17, 1957. Again it will be noted that the rate of decline Of radioactivity is somewhat greater in the liver tissue than in bone or muscle. All tissues show a definite increase in radioactivity after the summer of 1956, reaching a relatively higher level than for the same tissues in fish declining at a more rapid rate after 1956. Decay and decline rates of radioactivity of from Kabelle Island, but muscle and bone tissue from fish from Rongelap Island are approximately the same, decay being slightly more rapid. The radioactivity in liver tissue declines at a more rapid rate than it decays. Gross Gamma Radioactivity, 1957 Table 3 contains data on gross levels of gamma radioactivity in the homogenate of many reef fishes collected at Rongelap and Ailinginae Atolls. As with the beta radioactivity, Rongelap Island fish generally had less gam_m radioactivity than fish from either Enibuk or Kabelle Islands. Also differences were not great between similar species from different islands. A markedly higher amount of radioactivity was noted again in the liver of

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Fig. 2. Rate of decline (solid line) of radioactivity in reef fish collected at Rongelap Island, Rongelap Atoll between January 25, 1955 and July 17, 1957. Broken lines indicate decay in tissues of fish collected August 3, 1956.

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Table 3. Gross levels of gamma radioactivity h reef fishes collected at Rongelap and Aill.nginae Atolls, July 1957, expressed as c/m/g wet tissue l Collection Cormnon Number Muscle Bone Liver Stomach date and name of content *Tissues were counted for radioactivity durfng

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goatfish caught at Kabelle Island. The radioactivity in muscle tissue was <enerally about the same in Kabelle and Enibuk reef fish. Gamma radioactivity in the muscle averaged about 26 per cent that of the liver with variation of from 7 to 48 per cent. Beta activity was slightly lower, the muscle to liver ratio averaging about 19 per cent, with a range of from 5 to 27 per cent. The greatest difference in the amounts of both gamma and beta radioactivity between liver and muscle was found in the goatfish. Gamma spectra were made on dried samples of tissue to determine if gamma peaks other than those from expected fission products were present. The gamma spectrum curves obtained from various fish tissues are compared with spikes of radioactive cobalt and radioactive zinc in Figure 3 (top, center panel). The gamma spectra (made in October 1957) on whole samples exhibited certain common characteristics with peaks at several positions as follows: O. 12 MEV considered to be from C057 1.12 MEV II 1! II 11 zn65 1.33 MEV II II II “ C060

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The Zn65 peak at 1.12 MEV occurred in every tissue sample tested, indicating the common occurrence of this isotope compared with other gamma emitters. This radioisotope has been observed in fish tissues by many authors, as summarized by Lowman et al. (1957). Additional—— data from this Laboratory are given in Table 4. The C057 peak of O. 12 MEV was present in the liver of all fish ~=~ed; however, it appears to be rather low in the liver tissue of 4 omnivorous fish taken at Rongelap Island. This radioisotope was not detected in goatfish gut or goatfish bone, in goatfish muscle. No distinct peak at muscle tissue of reef fish or in halfbeaks The peak of Mn54, at O. 84 MEV, was peak at O. 81 MEV. One or both of these but occurred in small amounts O. 12 MEV appeared in the taken at Kabelle Island. partially obscured by the C058 radioisotopes appeared to be present in the muscle and liver of reef fish from Enibuk Island, in the muscle and liver of halfbeaks from Kabelle Island, and possibly were present in the muscle of reef fish from Kabelle Island. Verification of the presence of both of these isotopes in Enibuk reef fish liver was later obtained by ion-exchange resin column analysis (see below). The C060 peak at 1.17 MEV was obscured by the Zn65 peak at 1.12

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general, the gamma spectra of the fish tissues from different have definite similarities, even when compared to results ob - from other atolls (Lowman et al. 1957). Differences in Eamma—— spectra appear to be greater between different organs of the same fish than between the same organs of fish from different islands or atolls. Separation and identification of the Nuclides by Ion-exchange Techniques To identify the various radionuclides contained in the reef fish liver samples collected at Enibuk Island, Ailinginae Atoll, July 11, 1957, the of the sample after filtering, was passed through an ion-exchange column of Dowex 50. The anions and HC1 wash fractions were combined and later passed through an ion-exchange column of Dowex 1 anionic resin to further separate the fractions and to obtain the excess of the nuclides resulting from overloading the cationic resin. The radioassay of the fractions obtained from both summarized in Table 5. Details of these procedures have by Lowman et al. (1957). The methods generally follow those developed—. by Tompkins et al. (1947), Kraus and Moore (1953), Kimura et al. (1956),—— —. Takanobu et al. (1956), and Ishibashi et al. …