C , Camyrbel 410190 Health Physics Pergamon Press 1972. Vol. 22 (March), pp. 245-250. Printed in Northern Irelana IRON-55 IN RONGELAP PEOPLE, FISH AND SOILS T. M. BEASLEY,* E. E. HELD — =m.= Laboratory of Radiation Ecology, College of Fisheries, University of Washington, Seattle, Washington and R. M. GCONARD Medical Department, Brookhaven National Laboratory, Upton, L.I., New York (Received 5 February 1971; in revisedform 12 April 1971) Abstract—The 5*Fe body burdens for 60 residents of Rongelap Atoll are reported. The measured burdens are approximately 3 times higher than those of a similar numberofresidents from Tokai-mura, Japan. Since previous measurements in 1966 revealed substantial *°Fe body burdens in Japanese residents, the current Rongelapese Fe body burdens pose interesting questions. INTRODUCTION Since 1965, the distribution of =5Fe in the bio- reef fishes; goatfish (Afulloidicthys, sp.), mullet (Neomyxus, sp.) and surgeon-fish (Acanthurus, sp.). in Alaskan Eskimos, residents of Richland, There are no apparent qualitative differences in the diets of males or females. Thus, the deter- sphere has been studied both in the United States and in the Scandinavian countries. Initially, 55Fe concentrations were determined Washington, and in representative foodstuffs of both.) Subsequently, 55Fe concentrations in environmental samples and in residents of Finlandand Sweden'® were reported which generally confirmed the findings of the earlier study. Additiona] research shows that (i) marine organisms and people whose diet is largely seafood contain the highest concen- trations of 55Fe;) (ii) residents of the northern hemisphere have higher 55Fe body burdens than those of the southern hemisphere;'®) and (iii) the ®5Fe levels in people reached peak concen- trations in 1966 and continue to decrease.‘& 7) JasKkoxa!®) has recently presented an excellent summary of the measurements of ®5Fe in Finnish Lapps which includes a valuable bibliography. We determined thé ®5Fe body burdens of natives at Rongelap Atoll in the Marshall Islands. Ourinterest in this particular population derives from two importantconsiderations. First, the Rongelapese are a maritime culture, and they derive a large portion of their diet from the sea.'®» Prominent in this diet are the * Presentaddress: Environmental Sciences Branch, Division of Biology and Medicine, U.S. Atomic Energy Commission, Washington D.C. 20545. Estimates of fish consumption vary, but daily intakes between 75-150 g appear reasonable. mination of **Fe in this populationis of interest for comparison with other maritime cultures. Second, Rongelap Atoll received high-level fallout following the detonation of a thermo- nuclear device at Bikini Atoll in 1954.00 We considered it probable that retention of *5Fe at the atoll from that event, coupled with input from world wide fallout from large-scale nuclear device testing in 1961-1562 might lead to elevated concentrations of 55Fe in marine species in the Rongelapese diet and therefore unusual body burdens of this radionuclide in Rongelap residents. METHODS AND TECHNIQUES The method ofseparation of 55Fe was identical to that previously described. The counting technique was changed slightly; a gas filled (Xe) proportional counter operating in anti- coincidence with an umbrella of nine GeigerMiller tubes was used to detect the 5.9-keV X-ray emitted in the electron capture decay of 55Fe, Pulses from the proportional counter were recorded in a 512-channel multichannel analyzer. The detection system was surrounded by 4in. of lead shielding and the resultant background counting rate under the ®5Fe photopeak was 1.7 counts/min—}. 245