The Hanford Environmental Dose Reconstruction Project: A Review of Four Documents (1994)

Since the 1940s, the Atomic Energy Commission (AEC) and its successor organizations (now the Department of Energy, DOE) have operated facilities to produce materials for nuclear weapons for national-security purposes. In recent years, persons living around those facilities have become increasingly concerned that radioactive emissions from the facilities have affected their health. Under a memorandum of understanding concluded with 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 emissions of radioactive materials from DOE nuclear facilities throughout the United States.

At the request of CDC, the Board on Radiation Effects Research, in the National Research Council's 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 committee is charged to

• Review and comment on the design, methods, analysis, statistical reliability, and scientific interpretation of dose-reconstruction studies and related epidemiologic followup studies.

• Make recommendations to strengthen study protocols and analyses to ensure the scientific validity of study results.

The Research Council committee visited the Hanford Nuclear Site in October 1992 to tour the facility. During this visit, the committee received an extensive briefing by members of the Hartford Environmental Dose Reconstruction (HEDR) project, administrative officials from the contractor Battelle, Pacific Northwest Laboratories (PNL), and members of the independent Technical Steering Panel (TSP). In addition, the

committee held a meeting at which the public was invited and encouraged to present concerns about the dose-reconstruction activities underway at Hanford and the perceived potential exposure to radiation resulting from operation of the facility for almost 50 years.

In late 1992, the committee received several documents that had been produced as part of HEDR and was asked to review critically four documents prepared by PNL for review and approval by TSP and CDC under contract 200-92-0503 (CDC)/18620 (BNW). To address this task, the committee held three meetings in Washington, D.C., (in March and July 1993 and March 1994) and one meeting in Irvine, California (in February 1994), to evaluate the documents and to write this report.

In an earlier report (National Research Council, 1992), the committee had identified a series of criteria for an ideal dose reconstruction to provide a frame of reference for its evaluation of dose-reconstruction documents received from CDC. Seven steps were recognized as central to the reconstruction of doses received by members of the public because of environmental releases of radioactive materials:

• Estimation of the identity, composition, physical nature, and amount of historical environmental releases of radioactive materials over the duration of active plant operations and since then, with a possible extrapolation of the source term to future impacts.

• Environmental-pathway analysis, leading to estimates of the movement, behavior, and transportation of the radioactive material within the environment, including radionuclide deposition on the ground and radionuclide concentrations in ground-level air, drinking water, and foodstuffs.

• Collection of dietary and lifestyle data for the surrounding population to estimate rates of exposure of offsite persons resulting from external sources of radiation and from intakes of radionuclides by inhalation and ingestion.

• Metabolic modeling to predict the distribution of radioactive materials within persons.

• Dose assessment, either for specified persons or for general population groups (the task, as framed, did not include health effects of chemical releases or health effects in onsite personnel).

• Uncertainty assessment to indicate the degree of reliability and statistical error in the determination of estimated reconstructed doses, and including an assessment of the degree of reliability for the tissue-weighting factors used.

• Designation of the exposed population, its demographic characteristics, and its mobility.

  From the steps above, it follows that important criteria of an ideal dose-reconstruction study are

• Completeness of data. All relevant available information should be compiled and evaluated, including current measurements of soil and water samples and any important gaps in available records should be identified.

• Extensive quality control. The methods used should be reviewed not only by experts in dose reconstruction, but also by personnel at the facility who are familiar with the facility processes and pathways of exposure. For example:

  • The data to be used in the study to calculate doses should be analyzed and checked for accuracy as much as possible.

  • The doses obtained should be validated to as great an extent as practical, and the way in which uncertainties are estimated and their meaning should be clearly explained.

• The models used must be validated against measured data or be verified at other locations relevant to the site under evaluation.

• Clarity and detail of the report. One should be able to recalculate individual doses on the basis of the information presented.

• Public involvement. The public should be kept informed about how the study is conducted and how the results are obtained and should be encouraged to provide additional, even anecdotal, information on plant operations. The outcome of these studies must be presented in a fashion open to public understanding and scrutiny.