Executive Summary
AT THE OUTSET OF THE nuclear age, and for some years thereafter, radioactive materials were released to the environment at many places. Because these materials might have affected the health of populations living near the sites of the releases, public concern has led to the need to reconstruct doses, to define how such reconstructions should be accomplished, and to determine how the results should be used. Dose reconstructions must meet two criteria: They must withstand scientific scrutiny, and they must satisfy public concern. The Committee on an Assessment of CDC Radiation Studies was convened to provide scientific advice to the National Center for Environmental Health and Injury Control of the Centers for Disease Control (CDC) and Prevention and to evaluate the quality and completeness of CDC's dose reconstructions and epidemiologic studies. To assist with continuing dose reconstruction studies and to help in planning those that might be conducted in the future, a workshop was convened to identify criteria for dose reconstruction studies and to recommend needed areas of research. Forty-seven scientists from around the world with expertise in dose reconstruction, dose and risk assessment, and epidemiology, among other disciplines, were invited to the workshop, which summarized the state of the science, highlighted lessons of the past, and delineated general principles useful for undertaking radiation dose reconstruction studies. These principles could be extended to chemical hazards.
Discussions during the workshop and subsequent reviews have led the committee to recommend that preliminary studies, to be called scoping
studies, be performed before full-scale dose reconstruction studies begin. Scoping studies should establish the magnitude of the estimated exposure, the size and the composition of the potentially affected population, and the feasibility of conducting rigorous dosimetric and epidemiologic studies. The committee made two recommendations:
-
Scoping studies should be based on realistic assumptions about the dose distribution, the population size, and the expected harm to public health resulting from a radiation release.
-
Full-fledged dose reconstruction and epidemiologic studies should be proposed only when scoping studies show that rigorous studies are possible, given the probable dose distribution and size of the exposed population.
Full-scale dose reconstruction and epidemiologic studies should provide for the following elements:
-
All pertinent data relating to the source term and environmental pathways should be collected and evaluated. Insofar as possible, the original source data, rather than derived or summary information, should be used.
-
Quality control should be required at all stages of data collection and evaluation. Where possible, alternative approaches should be used to estimate the components of the dosimetry (source term, environmental transport, metabolic disposition, behavioral variation).
-
Best estimates of doses should be used rather than maximal doses; uncertainties in doses (defined by confidence intervals) also should be estimated.
-
Biologic markers of dose, effect, and susceptibility should be considered. The committee cautions, however, that at most of the sites of potential concern in the United States, the doses are probably not large enough for biologic markers to be useful.
The committee recommends that scoping of both the dosimetry and the epidemiology be performed interactively and in parallel because both are needed to inform decisions about further studies of one site or to establish priorities among several. This also applies to full-scale studies because it is important to have epidemiologists involved from the outset of any dose reconstruction to ensure that dosimetric information is appropriate for epidemiologic use.
The committee recommends that questions that are to be answered by any dose reconstruction study should be specified carefully and that the scientists involved should work with persons who have an interest in the study. The committee further recommends that studies be conducted with full disclosure and with the greatest degree of public participation
practical. There should be an interactive process that communicates the details and methods of the study in a timely and understandable manner to the public, and an oversight committee, consisting of impartial scientists and citizens whose meetings are open to the public, should be established at the earliest possible moment and maintained throughout the study.
Finally, the committee recommends that, to arrive at a credible and cost-effective decision-making process for identifying and prioritizing sites for study, the criteria used to proceed from a scoping study to a comprehensive dose reconstruction study should be adopted before the scoping study begins.