THE NORTHERN MARSHALL ISLANDS RADIOLOGICAL SURVEY: RADIONUCLIDE CONCENTRATIONS IN FISH AND CLAMS AND ESTIMATED DOSES VIA THE MARINE PATHWAY ABSTRACT A radiological survey was conducted in 1978 to assess the concentrations of persistent manmade radionuclides at 12 atolls and 2 islands in the Northern Marshall Islands. The survey consisted, in part, of an aerial radiological reconnaissance to map the external gamma-ray exposure rates over the atolls or islands. As a secondary phase of the survey, shore parties collected terrestrial and marine samples to assess the radiological dose from pertinent food chains to current or potential atoll inhabitants. Over 5000 terrestrial and marine samples were collected for radionuclide analysis from 76 different islands. Here we present the assessment methodology 2 + 38, u, and 239 24054, clam muscle except Bikini marine as well and 241 an, tissue from and as and the any the Enewetak. radionuclide concentrations sample collection, : concentration of the different Doses other species are processing, 9 data gamma for . in fish and clam muscle °c, > emitters collected calculated and from at dose 137 : in all the Cc Ss, . fish atolls average tissue at each atoll or island assuming an average daily intake of 200 to 10 g, respectively. The 700, concentration in muscle tissue is very low (for the most part undetectable) from the and there different is fish little from concentration in the muscle than that in pelagic difference different atolls tissue of all lagoon fish. In in reef the or average islands. species, contrast, 137¢. concentrations The however, 2394240, is higher concentrations are lowest in the muscle tissue of the bottom-feeding reef species such as mullet and goatfish and highest in pelagic lagoon fish. Recent measurements of radionuclide concentrations in fish muscle tissue and other marine dietary items from a variety of national and international sources compared with our analysis of radionuclide concentrations in fish from the Marshall Islands show that the average concentrations in species from the Marshall Islands are comparable to those in fish typically consumed as food in the United States and are generally marine dietary items. lower than those in most international