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Public Summary
Pages 1-16

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From page 1...
... Both the US Congress and citizens of the Northwest became keenly interested in knowing whether these radiation releases had caused human health effects. They were particularly concerned about whether Hanford releases of iodine-131 had led to an increase in thyroid disease among the population of the area.
From page 2...
... The HTDS investigators estimated individual radiation exposures for the 3,190 people who, during 1944-1957, had ever lived in the geographic area for which dose calculations were made. Estimating radiation exposures of 50 years ago is a daunting task for scientists because of the many unknowns about people's lives, habits, and diet.
From page 3...
... The primary finding of the HTDS draft report was that there was no evidence linking radiation exposure from Hanford to the rate of thyroid disease found in the study population. The lack of evidence of an effect, in scientific terms, is often caller!
From page 4...
... Detailed comments concerning the HTDS Draft Final Report are included in various chapters of the main report. The executive summary following this section highlights the views of the NRC subcommittee.
From page 5...
... But those criticisms were not important enough to invalidate the findings of the study. Estimated Radiation Exposures The NRC subcommittee's review found that the precision of the exposure estimates ranged from one-third or
From page 6...
... The NRC subcommittee found that the resulting exposure estimates for the HTDS participants were probably fairly accurate, mostly within a factor of 2 or 3. This statement is based on the results of valiclation exercises using the HEDR models (Napier and others, 1994~.
From page 7...
... The NRC subcommittee found that the HEDR and HTDS investigators probably assessed individual exposures as being more precise than they actually were because some sources of uncertainty were underestimated or not dealt with. The subcommittee noted that exposures that took place 40-50 years ago could not be precisely estimated and that such a situation could substantially reduce the ability of the study to detect a radiation effect.
From page 8...
... The NRC subcommittee was critical of the HTDS investigators' exclusive use of the HEDR estimates of thyroid exposure for the data analysis and suggests supplemental analyses that could help to confirm or weaken the conclusions of the study. The subcommittee also found the analyses of the radiation effect (called "dose-response relationship" in the study)
From page 9...
... Third, the analysis of a radiation effect is a valid guide to the risk to the Hanford population even without the use of an unexposed control group, as long as there is a sufficient range of exposure levels and they are estimated with reasonable accuracy. The subcommittee is concerned that the results of the study were reported- and interpreted-in black and white terms of whether a statistical test was passed or failed.
From page 10...
... Statistical Power and the HTDS Interpretation The subcommittee believes that the assumptions used by the HTDS investigators to estimate the needed sample size and to calculate statistical power were incorrect; their assumptions did not acknowledge that exposures could be estimated only very imprecisely. The subcommittee found that HTDS ignored five sources of imprecision, which decreased the ability of the study to detect a small radiation effect.
From page 11...
... the HTDS investigators redo the ~ 1~ 7 _ statistical-power calculations to take into account all the sources of imprecision and that they reinterpret the study results in accordance with the limitations of statistical power. The subcommittee believes that the findings of the HTDS cannot be reliably distinguished from the findings of the study of thyroid disease among children in Nevada and Utah who had been exposed to fallout resulting from atmospheric nuclear weapons tests conducted at the Nevada Test Site in the 1950s.
From page 12...
... Some of the public outcry on release of the draft report might have been avoided if the onginal communication plans outlined in the HTDS draft had been followed. The draft report outlined a good communication plan for its release, which included an admirable concern for translating the technical information in the report into an understandable booklet for the public and other efforts, including a Web site, to share information with the public.
From page 13...
... The subcommittee believes that in the media and public briefings the HTDS investigators paid insufficient attention to the audience's health concerns and fears and that HTDS investigators and CDC officials should have offered more balanced, and possibly alternative, interpretations of the findings and discussed their implications for individuals. During the media briefing and public meeting held to announce the findings of the HTDS, the investigators emphasized
From page 14...
... The complicated briefing strategy used for releasing the Draft Final Report did not work well, and the subcommittee suggests that a more simple and efficient briefing plan be devised for releasing the final report. in particular, it recommends that telephone briefings be abandoned because all involved with release of the draft report disliked them.
From page 15...
... This carefully designed study, with sound followup and sound medical methods, has examined a large fraction of the most heavily exposed population and failed to find any obvious evidence of a radiation effect, that is, there was no evidence of abnormally high rates of thyroid disease in the Hanford "downwinders" examined who had the largest estimated exposures. Thus, at face value, the study was negative, and no increased risk was found.
From page 16...
... The small numbers of thyroid-cancer cases and the lack of precision in estimating individual exposures mean that one can have little confidence in the size of the risk estimates found in the HTDS. At the time of the initial release of the Draft Final Report, it was indicated by the HTDS investigators that residents of downwind areas should fee]


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