Currently Skimming:
The Committee's Review
The Committee's Review
Pages 15-34
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From page 15... ...
However, the committee has a number of suggestions for improvements and has identified some weaknesses of the feasibility study and the draft report that are detailed below. TECHNICAL APPROACH AND CONTENTS OF THE DRAFT REPORT The draft report of the CDC-NCI feasibility study consists of two volumes, the first presents the study's general findings and suggestions regarding further research, and the second sets out in a series of eight appendixes the technical details that support the main text.
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From page 16... ...
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 Carl be based on a number of assumptions such as route of exposure, lifestyle, age, and diet.
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From page 17... ...
The data from which the matrix was generated need to be published and archived. The feasibility study used a simplified approach that assumed that the milk and food pathways throughout the United States are similar to those near the NTS.
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From page 18... ...
Of the six test series covered in the feasibility study, two, UPSHOT-KNOTHOLE in 1953 and PLUMBOB in 1957, accounted for about half the total population-weighted external dose Tom NTS fallout.
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From page 19... ...
: D=PxIxFg, where D = absorbed dose, Gy, or equ~valent/effective dose, Sv; P = deposition density of radionuclide of interest at time of fallout arrival, Bq ma; T = integrated intake by ingestion of radionuclide per unit deposition, Bq per Bq my; and Fg = ingestion-dose coefficient for radionuclide, GyBq~~ or SvBq~~. The factors I were estimated in the ORERP study for the integrated intakes in states near the NTS and were used In the feasibility study for all other counties in the coterm~nous United States.
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From page 20... ...
External Doses from Global Fallout Given the fallout deposition densities calculated above, external doses were computed for each county for each year from 1953 to 1972, together with a single calculation for external dose for 1973-2000. The calculations showed that 137Cs and 95Zr-95Nb accounted for 70°/O of the total external dose from global fallout.
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From page 21... ...
It also identifies over sources of potentially informative data that were unavailable when the feasibility study was performed. Some of those data are in well-archived repositories, but many are poorly stored and cataloged.
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From page 22... ...
A linear non-threshold (LNT) model was assumed for projecting possible cancer risks in the feasibility study.
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From page 23... ...
The feasibility study could not conduct a detailed uncertainty analysis based on the specific uncertainties that go into dose estimates. Such an approach is acceptable as a rough guide, but if a more comprehensive stud is nerformerl thorough uncertainty analysis of doses and risks would be needed.
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From page 24... ...
Nevertheless this comparison will make the point that the mode} is used by the authors to extrapolate to magnitudes of risk that are far outweighted by risks due to other factors. Putting aside thyroid dose due to Ill, the cement est~ates for the other radionuclides yield population external dose estimates that are only a small fraction of the external doses due to background radiation.
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From page 25... ...
Such medical exposures, rather than fallout, appear to be principally responsible for the increases in thyroid cancer seen beginning in the 1930s (Pottern et al., 1980~. If the thyroid doses Tom fallout can be estimated with sufficient accuracy, the committee believes that it would be useful to compare these doses at the individual or collective dose level or both with the thyroid doses from some of the earlier therapeutic procedures.
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From page 26... ...
THE VALUE OF FURTHER REFINEMENTS OF THE HI NEVADA TEST SITE CALCULATIONS AND UNCERTAINTY ANALYSIS Dosimetric Refinements Improvements in some aspects of the 1997 NCT report on 13~} exposures from the NTS are possible based partly on what has been learned from the Chernobyl experience. In particular, parts of the pasture-milk pathway of exposure are probably better known now than they were in the 1980s and early 1990s (when the dose reconstruction for the NTS 13~} exposure was performed)
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From page 27... ...
Only if the correlation between true and estimated dose were substantially improved would the re-examination of the i3~} exposures lead to better risk estimates of the effect of Me NTS exposures on public health. Epidemiologic Refinements The only radionuclide whose exposure is examined in the draft report and for which the combination of dose estimate and assumed dose-response relationship may produce a number of excess cancer cases that is potentially detectable in epidemiologic work in the United States 27
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From page 28... ...
The existence of a highly specific pasture-milk pathway, concentration of iodine in the thyroid gland, a remarkable dependence of risk of thyroid cancer on age at exposure, and apparent continuing risk decades after exposure add up to a pattern of risk in the US population that may still be detectable. Exposure to '3'I from global fallout was estimated in the feasibility study to be much less important as a cause of thyroid cancer because, owing to its short half-life, much of the HI had decayed before reaching the United States.
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From page 29... ...
Although not directly incorporated as one of the feasibility study's proposals, it is worm commenting here on the feasibility of further screen~ng-based epidemiologic investigation of NTS fallout. The committee is not in favor of such investigation directed at the effects of 13~{ fallout, except perhaps for a re-screen~ng of participants in the Utah study.
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From page 30... ...
The ~3~/Nevada Test Site Communication Plan Much of the communication planning in the feasibility study is based on experience with the 3/Nevada Test Site Communication Plan, which seeks to communicate to the public the results of NCI's report Estimated Exposures and Thyroid Doses Received by the American' Public Tom lodine-131 in Fallout Following Nevada Atmospheric Nuclear Bomb Tests and which has been evolving and under test for more than 2 years. The plan involves providing materials for venous public audiences and educating health professionals.
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From page 31... ...
The committee strongly suggests timely disclosure in the development of communication materials for the feasibility study. The draft report says that materials from the Nevada Test Site Communication Plan would be distnbuted, evaluated, and perhaps modified before materials from the feasibility study are added.
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From page 32... ...
Option 3. Conduct a more detailed dose reconstruction of radioactive fallout from global nuclear-weapons tests for Todine-13l, the most significant radionuclide identified in the feasibility study.
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From page 33... ...
Elective 2: If the draft report becomes the final product of the feasibility study, develop a public summary as rapidly as possible to add to the feasibility study, to put on the NCT and CDC Web sites, and to distribute as a stand-alone item. Elective 3: Update materials Tom the 13~} NTS Communication Plan to include results of the feasibility study related to other nuclides at NTS and global fallout.
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From page 34... ...
Elective 4: Develop an extensive communication plan to make both the feasibility study itself and its results transparent and readily accessible to the American public. The NTS 13~} co~ication project can be used as a bluepnnt, but both speed and accuracy are important.
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