This paper presents values as well as the bases for calculating internal dose coefficients suitable for estimating organ doses from the exposure to radioactive fallout that could result from the detonation of a nuclear fission device. The 34 radionuclides discussed are the same as those given in a priority list of radionuclides for fallout dose assessments presented in a companion overview paper. The radionuclides discussed are those that are believed to account for a preponderance of the organ doses that might be received by intake by persons of all ages (including in utero and via breast feeding for infants) following exposure to radioactive fallout. The presented dose coefficients for ingestion account for age and include modifications for variations in solubility with distance as discussed previously in the literature, and those for inhalation similarly account for age, solubility, and particle sizes that would be relevant at various distances of exposure as discussed in a companion paper on ingestion dose methods. The proposed modifications peculiar to radioactive fallout account for systematic changes in solubility and particle sizes with distance from the site of detonation, termed here as the region of "local fallout" and the region "beyond local fallout." Brief definitions of these regions are provided here with more detailed discussion in a companion paper on estimating deposition of fallout radionuclides. This paper provides the dose coefficients for ingestion and inhalation (for particle sizes of 1 mm, 5 mm, 10 mm, and 20 mm) for the region "local fallout." These dose coefficients for "local fallout" are specific for particles formed in a nuclear explosion that can be large and have radionuclides, particularly the more refractory ones, distributed throughout the volume where the radionuclide has reduced solubility. The dose coefficients for the region "beyond local fallout" are assumed to be the ones published by the International Commission on Radiological Protection (ICRP) in 1995. Comparisons of the presented dose coefficients are made with values published by the ICRP.
This paper presents gastrointestinal absorption fractions (f 1 values) for estimating internal doses from local and regional fallout radionuclides due to nuclear tests. The choice of f 1 values are based on specific circumstances of weapons test conditions and a review of reported f 1 values for elements in different physical and chemical states. Special attention is given to fallout from nuclear tests conducted at the Marshall Islands. We make a distinction between the f 1 values for intakes of radioactive materials immediately after deposition (acute intakes) and intakes that occur in the course of months and years after deposition, following incorporation into terrestrial and aquatic foodstuffs (chronic intakes). Multiple f 1 values for different circumstances where persons are exposed to radioactive fallout (e.g. local vs. regional fallout and coral vs. continental tests) are presented when supportive information is available. In some cases, our selected f 1 values are similar to those adopted by the ICRP (e.g. iodine and most actinides). However, f 1 values for cesium and strontium derived from urine bioassay data of the Marshallese population are notably lower than the generic f 1 values recommended by ICRP, particularly for acute intakes from local fallout (0.4 and 0.05 for Cs and Sr, respectively. The f 1 values presented here form the first complete set of values relevant to realistic dose assessments for exposure to local or regional radioactive fallout.
Soon after the Bravo nuclear test at Bikini Atoll in the Marshall Islands on 1 March 1954, urine samples were collected for analysis of excreted radioactivity from native residents exposed to radioactive fallout on two atolls as well as from U.S. military personnel on a third atoll. The earliest acquired samples, obtained by the Los Alamos Scientific Laboratory (LASL), were assayed for various radionuclides and provided the first known measurements of 131I in urine following exposure to fallout from a nuclear test. Over the course of 1954, many additional samples were collected by the LASL, as well as by the Atomic Energy Commission New York Operations Office’s Health and Safety Laboratory and the Naval Radiological Defense Laboratory. Collectively, the groups sampled included Marshallese exposed on Rongelap and Ailinginae Atolls, American military weather observers temporarily resident on Rongerik Atoll, and sailors from the Japanese fishing vessel, the Lucky Dragon. While the bioassay measurement data and individual urine volumes have been crucial to various attempts to assess intakes of radioactivity and the related internal radiation doses among the Marshallese, those data have never been published in any peer-reviewed journal, but have been restricted to agency memoranda, laboratory reports, and summaries in some publications and book chapters. Reconstructions of internal doses to Marshallese in 1954 and in later years have depended on these data and, hence, they have considerable historical importance as well as importance to ongoing health risk projections for Marshallese. This paper presents much of the original data on urine volumes and radioactivity from the various assays of urine for radionuclides, and compares estimates of 131I intakes made in 1954, 1985, 1987, and 2008.
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