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Pages 1-8

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From page 1...
... The NASA model in current use was last updated in 2005, and the proposed model would incorporate recent research directed at improving the quantification and understanding of the health risks posed by the space radiation environment. NASA's proposed model is defined by the 2011 NASA report Space Radiation Cancer Risk Projections and Uncertainties -- 2010 (Cucinotta et al., 2011)
From page 2...
... . However, NASA's proposed model has significant changes with respect to the following: the integration of new findings and methods into its components by taking into account newer epidemiological data and analyses, new radiobiological data indicating that quality factors differ for leukemia and solid cancers, an improved method for specifying quality factors in terms of radiation track structure concepts as opposed to the previous approach based on linear energy transfer, the development of a new solar particle event (SPE)
From page 3...
... For example, as presented in its 2011 report EPA Radiogenic Cancer Risk Models and Projections for the U.S. Population, the Environmental Protection Agency has developed an alternative approach for breast cancer mortality estimation, and this could serve as a suitable approach to be applied by NASA.
From page 4...
... Differences in risks between space radiation charged particles and gamma rays at low dose rate are encompassed entirely within the quality factor, QF, discussed below. A number of publications issued since the NIH report are relevant to this issue, and although these were discussed in the 2011 NASA report, they were not used by NASA in its choice of DDREF or in the associated uncertainty analysis.
From page 5...
... Conclusion: According to NASA's proposed model, the observation that the use of a fixed relationship between two track structure parameters reduces the uncertainty is a potentially valuable finding that may provide a method to reduce uncertainty in estimations of the risk of exposure-induced death. However, little indication is given in the 2011 NASA report as to why such a fixed position might be justified or expected.
From page 6...
... to match the estimated risks to the various tissues in representative space radiation environments. NASA proposes to use this as a summary quantity for mission operational purposes and, in NASA's proposed model, it is simply termed "effective dose." Effective dose is, strictly speaking, a quantity defined by ICRP that includes the ICRP-defined specification of numerical values for weighting factors and sex-averaging.
From page 7...
... Conclusion: The revised value for the threshold dose value proposed by ICRP suggests that NASA may need to consider how it might account for cardiovascular disease in its calculations of dose limits. However, it is noted that to date there exists very little of the information on relative biological effectiveness for non-cancer effects that is needed for estimates of risks posed by exposure to space radiation.
From page 8...
... Probabilistic Risk Assessment The committee notes that the risk projections discussed in NASA's proposed space radiation cancer risk assessment model and uncertainties are not presented or intended as being based on a probabilistic risk assess ment (PRA) approach.


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