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APPENDIX A Specific Comments on the Working Group's Draft Report p. 13, line 2: Clarify whether the excess risk, excess relative risk, or some other measure was assumed to be lognormally distributed over time since exposure. p. 13, section 5, line 5: The reference to section TT.C.l appears to be incorrect. p. 14, line 3: Why would risk 5-14 years after exposure have been overestimated? p. 16, section B. last sentence: Is there any reason to be concerned about possible differential ascertainment by calendar time or dose? p. 20, section 2 ff: Although the discussion of whether radiation accelerates the appearance of cancer or increases the risk is relevant to some of the points made by Robins and Greenland, a more fundamental issue is the bias in AS as an estimator of the mean of individual PCs produced by heterogeneity in baseline rates. This point is discussed elsewhere in the National Research Council Oversight Committee's report, but merits some discussion in the working group's report. p. 29, lines 2-3 after the formula: The g following ~ should be omitted because it is not the parameter, but the observed covariate value (sex). p. 32, in analyzing the Japanese atomic-bomb survivor data, very little uncertainty in neutron RBE is allowed. That seems incongruous with the current debate over neutron RBEs in that study and with the wide range of findings in the experimental literature regarding neutron RBEs. pp. 32-33, no indication is given of what the "systematic biases" in the atomic-bomb dose- estimation procedure consist of. p. 34, no justification is given as to why 5 hours is the critical value to distinguish acute from fractionated exposures in the assigned-shares model. p. 37, figure {V.F.3 might be easier to interpret if presented in terms of the dose-response curves themselves, that is, ~ + ,8 D X DDREFaCU~e (D). p. 37 and elsewhere, the mode of presentation (especially graphic) of the DDREF is counterintuitive and might confuse many people who are not conversant with the lingo of radiobiology. One normally thinks of a ``factor'' as multiplicative or additive, but in the case of DDREF it is a division factor. It would be better to plot I/DDREF (to show that a higher DDREF yields less effect, not more, as the graph seems to imply). Text should be 36

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added on p. 33 to clearly indicate that, for example, a DDREF of 2 implies half as large a slope. p. 41, arguably, one should attach some uncertainty to the low-LET doses, because gamma exposures are believed to have a slightly lower RBE than 250-kVp x rays, and low- energy x rays are thought to have a higher RBE than 250-kVp x rays. o. 46. section 2: Did Land and others tI994] restrict their analyses to age at first full-term pregnancy, or were the other standard breast-cancer risk factors also examined? How was this variable coded for nulliparous women? Even though these authors adopted the parameterization given here, elsewhere in this report ~ = ~ corresponds to the multiplicative model and ~ = 0 to the additive model. Perhaps internal consistency would be less confusing. p. 47, last paragraph: The three references to tables {V.G should be to tables IV.~. Some discussion of the literature on alternative forms of mixture models (such as multiplicative, Guerro-Johnson, and Box-Cox models) might be worth while. I, p. 49, section J: The possibility of an interaction of the ATM gene with ionizing radiation should be mentioned here. Although experts differ about the ATM-radiation interaction, it would be right to raise the concerns that there is some controversy about it (Won" et al., 1997; Nichols et al., 1999; Shaman et al., 2000~. p. 49, it is doubtful that xeroderma pigmentosa patients have increased susceptibility to carcinogenesis induced by ionizing radiation, even though they are exquisitely sensitive to ultraviolet radiation. Did the authors instead mean nevoid basal-cell carcinoma syndrome patients who have a well-documented radiosensitivity? p. 5 I, section 2: Why were these two situations excluded? section 5b: It seems inconsistent with the treatment of other uncertainties to fix the coefficient of D2 at I.0 as though it is known with certainty. p. 54, section 7: The reference to section IV.G appears incorrect; was IV.D intended? p. 70-76, it would be useful if these tables gave the 99th percentile estimate from the ~ 985 calculations for comparison with the new calculations. 37