The maps showing county-by-county distribution of radioactive dose is an important aid to public understanding of exposure distributions but could be improved in two ways. First, the display of doses for each county projects a false precision in that distinct boundaries (county boundaries) may be identified as separating various doses. Sophisticated viewers of such a map understand that there is considerable overlap in potential exposure between adjacent but differently coded counties, but this may not be recognized by the general public. A smoothed color-graded contour plot with state or county borders overlaid would be useful in representing visually the true state of limited knowledge about small-scale local differences in exposure.

Second, the maps lack a contextual framework. It would be useful to compare graphically, using histograms or other visual presentation tools, the distribution of fallout exposures relative to estimates of natural background radiation either over the country as a whole or by region (East, Midwest, West, and South). That should be done for selected birth cohorts and for selected organ doses to illustrate, for example, that thyroid doses from fallout to children born in 1950 are estimated to be higher than thyroid doses from background for many regions of the country. In contrast, for almost all other organ doses or age cohorts, the estimated doses from fallout are smaller by an order of magnitude or so than background throughout the country, and this should be depicted graphically as well.

The committee notes that the main text of the draft report does not always appear to reflect what was done as stated in the appendixes. For example, the committee finds it disturbing that a footnote on page E-36 alludes to a probable error in the 131I deposition values associated with four or more weapons tests that is not mentioned in the main text; nor is the impact of this error on estimated doses described. This error, although it would affect the estimated doses, would not alter the draft’s basic conclusion about the feasibility of the study of the health consequences of exposure to the fallout from weapons testing in the United States or elsewhere. It would have been helpful if, in the presentation of their conclusions, the authors had set out a summary of the possible changes that might occur with further refinement and had essayed an evaluation of how much better the results might be if a major effort were made.

ASSESSMENT OF THE DOSE RECONSTRUCTION

To estimate radiation doses to the US public due to fallout from nuclear-weapons tests conducted at the NTS and global fallout from nuclear-weapons tests conducted at other sites around the world, it is necessary to estimate the deposition density of fallout radionuclides across the United States as a function of time during and after the period of testing. With this information in hand, calculations of external and internal doses can be based on a number of assumptions such as route of exposure, lifestyle, age, and diet. Recognizing that they were preparing a feasibility study, not a complete detailed analysis of exposure to all radionuclides under all conditions, the authors of the draft report note that the dose estimates given are relatively crude values based on approximate evaluations. The calculations, of moderate complexity, are based on data obtained from readily available publications in the open literature. Some of the data sources and analytic approaches used are discussed below as are some of the key results. Calculations related to the NTS are discussed first, and then those related to global fallout.



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