A Radiological Study of Rongelap Atoll, Marshall Islands, During 1954-1955 (Resurvey of Effects of Bravo Event, Castle Operation)

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Applied Fisheries Laboratory University of Washington operatedby the University of’Washington under Contraot No. AT(45-1)540with the United States Atomic Energy Commission.

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The detonation of shot one at Bikini Atoll on March 1, 1954,produced a fallout of radioactive ash upon Rongelap Atoll, NfirshallIslands. The distribution of the radioactive ash on the islands and i.n the plants and animals of the area has been studiedand evaluated by the Applied Fisheries Iaborato~*y, During the first expedition to Rongelap Atoll on March 26, 1954,biological samples were collected and measurements made of theradiation contamination. On t~ee additional expeditions extensivecollections of material The decllne in radioactivity were made for this study, the was measured in 1499 samples of fish, invertebrates, land plants, algae, birds, plankton, soil and water from the Rongelap area. During this study particular emphasis was placed upon evaluationof the radioactivity In food used by the natives. Coconut ~ilkcollected on March 26, 2954, contained 1,03 microcuries per - kilogramof wet tissue while the coconut meat had 1.16 uc/kg. BY J~uary 25-30, 1955, the level in coconut milk had declined to 0.041uc/kg and the meat to 0.036 uc/kg. Fish muscle on March 26, 1954,averaged 2,74 uc/kg and fish liver 264. uc/kg. The decltne theliver of fish. Somewhat similar declines were found for clammuscle’ crab muscle, bird muscle and liver, and for squash,

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The level of radioactivity was highest in the northern portionof the atoll, except for samples of algae and fisheatingbirds, collected during January 1955 from the southern part of’the atoll, which had higher levels of radloactlvlty than samples collected from the northern islands on the same date. This may indicate a translocation of radioactive mterials within the Mgoon.

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Sample processing procedure and techniques Rad:oactivlty and Ita rate of’decline in food Evaluation of radioactivity in the biologic~l Land plants and algae Evaluation of the chemical analyses of the Study of the rate of physical decay of radfation ~1 In the biological samples

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Radloactivlty of foods from Rongelap Atoll, Coefficient of variation in percent for values In Table I Radioactivity of fish caught at Kabelle Island, Rongelap Atoll Radioactivity of fish caught at Rongelap Atoll, other than at Kabelle Island Radioactivity of Rongelap birds and bird Fission products and radio-calcium in soil from Rongelap Atoll biological samples from Rongelap Atoll Decay rates of Rongelap samples ex~ressed as the slope of the log-log relationship of activity to time after March 1, 1954 Radioactivity of fish from Rongelap Atoll, Scientific names of fishes Radioactivity of invertebrates other than corals collected at Rongelap Atollj Radioactivity of coral from Rongelap Atoll, Radioactivity of coconuts from Rongelap

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Iaclioactivityof edible plants other than ct..Juts from Rongelap Atoll, 1954-55 Radioactivity of plants other than those commonly eaten from Rongelap Atoll, 1954-’;3 3’., ,’:tivit of marine algae from Rongelap Radioactlvit of’birds collected at Rongelap Radioactlvlt of tern eggs.from Rongelap samples from Rongelap Atoll, 1954-55 Data for computing percent activity of fission products and calcium in Rongelap SO1l sample’: based on 1 milliliter replicates Physical decay rates of Rongelap samples

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Collecting areas at Rongelap Atoll Rate of decline of radioactivity of Rongela? Avmmge amounts of radioactivity in microcu,riesper kilogram in fish tissues from Average amounts of radioactivity in mlcrocuries per kilogram in liver, bone and muscle )f carnivorous and omnivorous fishes ~<~.~i.oactivltyin microcuries per kilogram in fish tissues collected in the vicinity of Rongelap Atoll, December 1954 and J~uaw Radloactivlty in sea cucumber (Holothuria atra) tissues from Kabelle Island 1954-1955 Radioactivity in giant clam tissues: HiPPOPUS on.March 262 1954 at Kab~lle; Tridacna on July 16, 1954 at Kabe~le~ on January 2~~ 1955 at Labaredj and on January 30j 1955 at Gejen Radioactivity in tissues of the land hermit crab, Coenobita, on March 26 at Labaredj, m July 16, 1954 at Kabelle, and on January 26, 1955 at Rongelap Rate of decline in land plants, algae and soil samples at Kabelle 1954-1955 and kidney samples from north Rongelap exmessed as a ratio to the March 26, 1954 Decline of radioactivity in bone and ileum samples from north Rongelat expressed as ratio to the March ~~~ 195 collection

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Semi-1og plots of decay curves of gastric mfll of crabj Grapsus graps~ls$and muscle of sea cumuuber, ~olothuria atra, collected Log-1og plots of Rongelap decay samples of muscle and mantle of giant clam, HiPPOpus, from Kabelle; and soil on which decay correction factors were based Log-1og plots ‘of radioactive decay rate of coconut milk, (Cocos) collected December 8, 1954 at !tabelle,and of’liver and muscle of

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A RADIOLOGICAL STUDY OF RONGELAP ATOLL, MARSHALL The program of study of the Applied Fisheries Laboratory, Universityof Washington, (Program 19.1 of Operation Castle) was outlinedin the Laboratoryfs report UWFL-36. This program involved detailed studies of radiological contamination of the fauna and floraof Eniwetok Atoll, with exploratory trips to Bikini Atoll on 3 quarterly basis to ascertain the levels of radiation remaining during the year following the test program. ? The unexpected pattern and m~gnttude of the fallout of Q radioactivemater?.~lsfrom the March IS 1954 experiment introduced the need for new areas of study over and above the planned program. One such area was Rongelap Atoll where the fallout resulted In the evacuation of the native people. On March 21, 1954, the Laboratory recieved a request from h. Paul B. Pearson, AEC Division of Biology and Medicine, to tnakea survey Of the islands at Rongelap Atoll to determine the extent of radl.ologicalcontamination of the native foods. The expedition to Rongelap, in response to this request, was Organfzedby ~sk Group 7.1, with transportation and sUppOrt tionto aid the natives in capturing some of their animals on RongelapIsland and to make radiation readings on some of the

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Collections of plantc o~:lMnhials, soil samples and radiationreadin@ were made at w~aredj Island on March 26, 195h, SerialNo. 89) under a variety of conditions. The shield of the !nstr~nent was closed for the first reading and open for the Secandfop each OS the locations ilsted below. Open grass area Open grass area Beach rock slabs Beach above high tide line north side of island East side of island 200 220 above high tide 350 700

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Beach sand at Edge of brush 11.ne on island lagoon Open area in vegeportion of island Coconut grove on Edge of trees Lee side of trees Windward side of trees tl 2800 second expedition to Rongelap Atoll was made on 1954. A U.S. Navy Grumman Albatross plane (U.S.N. A9R-16,No, 902) from the U.S. Nsval Station, Kwajalein, was used to transport the group to the atoll. program 19*1 members Mking the trip were Lauren R. Donaldson, Frank l.mman~ Arthur Col-lectionswere again made at Kakelle Island and radiation readl.ngstaken in the same general areas as those recorded on

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High tide mark 20 high tide lina On Scaevola brush 28—— Lee edge of cooo- 20 Middle of island 25 in dead brush Open clearing in 27 middle of island During the month of December 1954 three collections of sampleswere made at Rongelap Atollm For the first trip on Decem- (Mo.2471) with a fine crew. Landings were made at both Kabelle ogyand Medicine, accompanied Edward Held, Paul Olson, Robert Tqlor and William 131akenWnon this expedition. Film strips were placedat a number of locations by Claus, Taylor and Blakemn to recordradiation over an interval of times On December 18, the Navy again furnished a FBM for the trip toRongelap to pick up the film strips and to collect additional

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biologicalsamples. A successful landing was made at Rongelap Islandvhere-t~e objective was accomplished. An accident to the uohoring mechanism of the plane, however, prevented completion of the sampling at Kabelle Island. Robert Rinehart and Paul *. *, hvls, Edward Held and Paul Olson on this trip. The most extensive survey and biological collecting trip:,, was conducted at Rongelap Atoll from January 25 to January 30~ 1955, This ~urvey was made in conjunction with U.S.N.R.D.L., transportationand support facilities, Allyn H. Seymour ad ‘“ FrankLowman, Program 19.1, shared the responslbtlity for the , biologicalsampling. Readings were again made with the survey meter on almost all of’ the islands visited. The readings were takenat a height of three feet unless otherwtse noted. Radiation Levels Rongelap Atoll ,+ Eniaetok Island 2.0,, Busoh Island 1*5 5.0 at ground level The colleotiorasat Rongelap Atoll during this period ofi i-,,.,# OtildyprovMed material for 1499 samples which have been prooQosedtthe radloaative content determined and the results tabu-j

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The technl.quesand procedures used in collecting, storing, preparing,and counting the Rongelap samples were similar to those used in former years. For complete details see WT-616 (UWF%-33).* The specimens were put on ice while in the field. ‘l’issuesvere dissected, weighed and dried at the Eniwetok laboratory. At the University of Washington, the dried samples were &shed at temperatures up to 540°C, cooled, slurried, dried, and then counted in an Internal gas-flow counting chamber. Counts per plate w~re converted to dlsint%grations per minute per grab of wet tissue as of the date of collection by correcting for For the summary tables as used h this report, the radioactivity expressed in disintegrations per minute per gram (d/m/g) vas converted to microcuries per kilogram by Radioactivityand Its Rate of Decline in Food Items A g&eral survey of the radioactivity of foods is given in Table 1, with the rate of decline** of these items shown In Fi6ure 2. It should be noted that the differences due to species and l Radiobiological Studle=t Eniwetok Before and After Mike Shot, S* The rate of decline i8 a phrase coined to express the combined physical decay and the biological uptake and de~~?~~,ate~”,.

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areas whtch are considerable and which are evident .inthe tables— of the eppendlx where all the individual sample counts are tabulated,are not apparent in this generalization. The significance ~1’these differences, however, is discussed on pages 11 to 34. FromTable I and Figure 2 the past, present, and future gross Mioactlvi.ty in the prl.noipalfood items of Rongelap Atoll can The method selected to indicate the error in estimating the values in Table I Is the “coefficient of variation” which f-s the ratio of the standard deviation to the mean. These values~ range in values from 10 percent to 178 percent indicates a high degree of variability. These data are closest to being points on a straight line Vhenplotted on a log-log scale using the time of the blast, March1, 1954, as time of origin. From this date It appears that mixed fission products are the principal source of radioactivity in the food stuffs. Exceptionsare bird thyroids, for which the decay curve was logplot. For the purpose of In which the radioactivity was gastric mill in a coconut crab, nearly a straight llne on a semi- ‘ making an approximation of the averagerate of decline, the slope of a least-squares line throughthe averages of the points In Figure 2 was determined andfound to be -1.75. The variation in radioactivity associated with area, in mostinstances, is related to fallout. Rongelap A’Lollwas on

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thesoutherr~.ed~ Of the fallout from experimentand as a consequence t~.ere radioactivityin tb.enorthern part or was considerably more u~rnplesshow the sarlepattern except for the bird collections ~d the algae and sand samples from deep waiers of the lagoons

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Evaluatiofiof-Radloactivlty in the Biological Samples Almost all of the fish specimens, as in former years, were collectedby poisoning with derris root In shallow waters on or near the reefs. Some specimens were caught in the deeper uaters of’the lagoon with hook and line. Two flying fish vere c’ :lned outside the atoll when they landed aboard ship are those commonly found vrasse, snappers, mullet ami Ltiw, The scientific names of the 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 the alimentary canal, in most In an attempt to compare similar species from the same locality, analysis was limited to the samples from Kabelle Island. Collections of fish were made in waters adjacent this Island on March 26, 1954, July 16, 1954, and Jan~w 1955. The collecting area lies near the north end of the island and consists of a coral-filled channel open to the at high tide. The radioactivity of the tissues from the fish collected at Xabelle is summarized In Figure 3. The data are

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FIG. 3 AVERAGE AMOUNTS OF RADIOACTIVITY IN MICROCURIES FISH TISSUES FROM KABELLE ISLAND 1954- i955

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Sarl:er in thts report, that the radioactivity in the tissues appeaPE m he due principally to mixed fission products. Devlatlons from a straight line in the curves might be due to selective uptake, either by the tissues themselves or because there was selective uptake in the animals used as food by the f’sh~s. In general the slope of the curves compares favorably decline curve used for all food items dtscussed of this report. t between the omnivo~ous and carnivorous fishes Q radioactivity in comparable tissues were great1954. These differences decreased with passage of time :.:tdby January 29, 1955, were negligible in some tis~z~s (Ftgure 4, Table 111), These same data when analyzed

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DAYS AFTER MARCH I , 1954 FIG. 4 AVERAGE AMOJNTS OF RADIOACTIVITY ;!4 MICROCUR:Z$ PER K!L.OGRAM IN FROM KABELLE ISLAND 1954- 1955 .ti:,’,”;.

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COLLECTEO IN THE VI CINTY OF f?ON GE LAP ATOLL, OECE?+5EP>1334 A NO

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Rongelap invertebrates showed levels of activity of fron 102 to 104 uc/kg on March 26, 1954. By late January 1955 the levels had dropped about two orders of magnitude. The almost ubiquitous black sea cucumber, Holothuria atra, serves best to exemplify the trend (Figure 6). Next best as indicatorswere giant clams, HipPOPUS and Tridacna; land hermit crab, Coenobl.ta; coconut crab, Blrgus; corals; and spider snaill Pterocera. Radioactivity was highest in the digestive and excretory organs, intermediate in the integumentary &gans, and love~t in the muscle. Actual values for the samples are tabulated in the appendix. The kidney of the giant clam (Figure 7) is of special interest because of its high level of activity and slow rate of decline. A graph of activity of the tissues of’land hermit crabs collectedat the more radioactive northern islands in March and July 1954,and from a less radioactive southern fsland in January 1955, shows the effect of geographical differences in radioactivity upon the trend of decline, accentuating the slope in the later period (Figure 8). The spider snail was similar to the hermit crab in the level of activity of lts tissues, while the corals were about an order of magnitude lower. Land Plants and Algae Land plant and algae collections were made Kabelle, Lomuilal, Gejen, and Rongelap Islands. Most of the edible plants were collected in December 1954 and January 1955 at Rongelap Island. These were coconut, squash, papaya, arrow-

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MARCH 26 AT LARAREDJ , ON JULY 16, 1954 AT KABELLE ,

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Pint, pandanus+ spinachj and Morinda. The algae were collected ‘bothin the shallow water near shore and in the deeper water of the lagoon, usually in the vicinity of the fish-collecting Sample values are given in Appendix Tables IV, V, VI and VII. From these tables it can be seen that the activity varies widely even within samples of the same kind. In January, for example, the pulp from …