INTRODUCTION
Under a memorandum of understanding concluded with the US Department of Energy (DOE) in December 1990, the US Department of Health and Human Services, through its Centers for Disease Control and Prevention (CDC), has been conducting a series of studies to assess the possible health consequences of exposure to releases of radioactive materials from DOE-managed nuclear facilities throughout the United States. In recent years, persons living around those facilities have become increasingly concerned that radioactive materials emanating from the facilities have affected their health. At CDC's request, the Board on Radiation Effects Research in the National Research Council (NRC) Commission on Life Sciences organized the Committee on an Assessment of CDC Radiation Studies to provide scientific advice to CDC's Center for Environmental Health and Injury Control and to evaluate the quality and completeness of CDC's assessments.
The NRC committee's charge is as follows:
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To review and comment on the design, methods, analysis, statistical reliability, and scientific interpretation of dose-reconstruction studies and related epidemiologic followup studies.
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To recommend ways to strengthen study protocols and analyses so that the scientific validity of the study results can be ensured.
The first specific task requested by CDC was a review of draft reports prepared by the Radiological Assessments Corporation (RAC) pertaining to its efforts to reconstruct environmental doses due to releases of radionuclides in the vicinity of the Fernald, Ohio, nuclear facility, the Feed Materials Production Center (FMPC). FMPC, some 15 miles to the northwest of Cincinnati, began operation in 1951 and continued production activities until 1988. FMPC converted uranium feed materials (uranium concentrates, uranium compounds recycled from various stages of nuclear-weapons production, and some uranium ores) to uranium metal ingots for machining or extrusion in tubular form. Although uranium
processing was the primary activity at FMPC, smaller amounts of thorium were processed intermittently during the middle 1950s and in 1964-1980, and some recycled uranium feed materials were processed beginning in late 1963. These activities and the storage of waste production materials containing radionuclides in silos at the facility led to the release of substantial amounts of uranium dust and radon gas into the environment. The releases raised the possibility of detrimental health effects in people living in the vicinity of the facility. It was that possibility that RAC was charged with assessing.
RAC approached its charge through a series of 6 tasks: (1) identifying the release points on the Fernald site; (2) developing the source terms, that is, the quantity, chemical and physical form, and time course of contaminants released to the environment from the facility; (3) identifying the uncertainties or level of confidence in the assessment of the source terms; (4) developing environmental transport and dose calculations; (5) identifying and compiling environmental and other data to verify the transport and dose calculations; and (6) presenting the final doses and health risks with their attending uncertainties. Each task culminated in an interim report that was reviewed by the committee. Consequently, there has been some feedback between the committee and RAC in the course of this work as the committee communicated some of its concerns in the earlier stages.
The first RAC drafts reported on by the Research Council committee covered the period 1960-1962 and dealt with radionuclide source terms (task 2) and uncertainties (task 3); the committee's review, Dose Reconstruction for the Fernald Nuclear Facility, was published in 1992 (NRC 1992). Next, the committee was asked to review the report of task 4, to develop methods that could be used to translate the release estimates into concentrations of radioactive materials in the residential environment. The committee's review of those methods, Dose Reconstruction for the Fernald Nuclear Facility: A Review of Task 4, was published in 1994 (NRC 1994). In 1995, the committee submitted a letter report to CDC in response to a request for advice on the methods and future directions of the Fernald project and on their appropriateness and scientific soundness. In that letter, the committee reported its findings and commented on 6 issues for which CDC requested further clarification. The committee endorsed the overall approach being used by RAC in the dose-reconstruction project, judged that the project was generally headed in the right direction, and commended RAC for its thoroughness in addressing all issues carefully, soundly, and persuasively.
On August 1-2, 1996, at the National Academy of Sciences Beckman Center in Irvine, California, the committee was briefed by John Till and members of the RAC staff on the methods used for task 6; however, no information was presented on the dose estimates themselves. RAC 's draft report, Task 6: Radiation Doses and Risk to Residents from FMPC Operations from 1951-1988, was released in 2 volumes on August 22, 1996. Volume I, summarizes the major releases of radionuclides, including releases to the atmosphere, surface water, and groundwater; discusses transport of radionuclides in air and in water; compares environmental measurements with predictions, and estimates the doses received by the public from FMPC releases, the health effects of the estimated doses, and the lifetime risk of cancer associated with each of 9 exposure scenarios. Volume II sets forth in technical detail the methods used in assessing doses and includes 20 appendixes that provide information on the data that were used, the analytic models and methods, and the assumptions inherent in the computations. A second briefing was held on September 19-20, 1996, in Washington, DC, after the public release of the report; on this occasion the committee completed its review of the task 6 draft documents, including a third document, a summary addressed to the lay audience. The present committee report consists of the committee's review and assessment of those 3 documents.
