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1 Background UNDER A MEMORANDUM of understanding concluded with the U.S. Department of Energy (DOE) in December 1990, the Department of Health and Human Services, through its Centers for Disease Control and Prevention (CDC), has undertaken a series of studies to assess the possible health consequences of off-site emissions of radioactive materials from DOE-managed nuclear facilities in the United States. At the request of CDC, the Board on Radiation Effects Research, in the National Research Council's Commission on Life Sciences, has organized the Committee on an Assessment of CDC Radiation Studies to provide scientific advice to CDC's National Center for Environmental Health and Injury Control. The committee's charge was as follows: Review and comment on the design, methods, analysis, statistical reliability, and scientific interpretation of dose reconstruction and related epidemiologic follow-up studies. Recommend ways to strengthen study protocols and analyses to enhance the quality of these studies. In the course of the committee's review of CDC's dose reconstruction efforts in the vicinity of the Fernald, Ohio, Feed Materials Production Center (NRC 1992, 1994a) and the Hanford Nuclear Site in southeast Washington State (NRC 1994b, 1995a), the committee and the National Center for Environmental Health and Injury Control decided that it would be timely to assemble scientists with expertise in the major areas of radia-
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tion dose reconstruction. The goal was to define the criteria to be met in studies that reconstruct exposure and to provide guidance for their epidemiologic use. Radiation dose reconstruction methodologies are developing rapidly. Dose reconstruction projects during the past 50 years have resulted in an accumulation of considerable experience. Such projects have been considered at Hanford, Washington; Fernald, Ohio; and the Sellafield Nuclear Processing Facility, United Kingdom. Dose reconstruction also has been suggested in the aftermath of accidents in such places as Chernobyl, Ukraine; Goiania, Brazil; Palomares, Spain; and Kyshtym, Russia; and after the detonation of nuclear weapons (Hiroshima and Nagasaki, Japan, and at the Nevada and Pacific test sites). Little effort has been made to assemble the lessons learned from these projects or to identify criteria for a cost-effective dose reconstruction. The committee sought a remedy through a workshop designed to achieve three objectives: Summarize past and current dose reconstruction studies in the United States and elsewhere, detailing the techniques used and the scientific problems encountered. Establish not only the criteria for a thorough dose reconstruction but minimum requirements for a study that is used to determine possible health effects. Identify the information needed to specify doses for particular persons or groups to be used in epidemiologic studies. A 3-day workshop was held at the National Academy of Sciences in Washington, D.C., Oct. 25–27, 1993, which convened 47 scientists from around the world with experience in one or more of the four areas listed below that are central to the reconstruction of radiation doses resulting from releases of radioactivity: Estimating the environmental release of radioactive material (the so-called source term). Environmental pathway analysis, which leads to estimates of radionuclide deposition on the ground or in surface and groundwater and to estimates of radionuclide concentrations in ground-level air, drinking water, and foodstuffs. Identifying exposed populations and collecting dietary and lifestyle data to facilitate valid estimates of exposure to external irradiation and of the inhalation and ingestion of radionuclides. Dose assessment for specified persons or population groups or for representative individuals in a general population. The degree to which any of these areas can be studied effectively varies from one site or episode to another because the circumstances of
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each event differ, for example, in the meteorologic conditions during the episode, in the nature of the terrain, and in the sources of surface water and groundwater. However, the participants were asked to identify a set of general criteria that would apply to most dose reconstructions. To do this, participants were assigned to one of five focus groups to discuss and define the important steps of dose reconstruction. After they attended a series of general lectures in each area, the group members were charged with summarizing knowledge in their topic areas, highlighting the lessons of the past, and identifying new areas for research. The summaries drafted by the groups form the bases of the chapters in this report. Chapters 3–7, respectively, are ''Estimating and Confirming the Source Term," "Environmental Pathways," "Radiation Dose Assessment," "Biologic Dosimetry and Biologic Markers," and "Epidemiologic Considerations." During the workshop, the need for a sixth working group was identified to provide guidelines for priority criteria for dose assessment studies. Chapter 8 summarizes that group's deliberations and addresses the process of setting priorities for dose assessment studies that use criteria based on scientific evidence. Appendix A briefly describes seven dose reconstruction studies, Appendixes B and C are the workshop agenda and a list of participants, respectively, and Appendix D is a glossary.
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