In Section 2.4 (Estimation of risks at low dose and low dose rates), there appears to be a major omission - namely the study of people living in high natural background areas, and their cancer rates in comparison to similar populations. I have seen some published studies of such populations that show a reduction in incidence of cancer in populations exposed to higher radiation levels in comparison to similar populations exposed to lower levels of radiation. Please evaluate these studies and include them in your document with your criticisms. Thanks.