> An adverse effect of ionizing radiation is that it could cause a mutation that replicates - cancer. It's therefore intrinsically probabilistic. This stateme

> An adverse effect of ionizing radiation is that it could cause a mutation that replicates - cancer. It's therefore intrinsically probabilistic. This statement betrays a very naive understanding of cancer and complete ignorance of DNA repair pathways. Don't take it personally - nobody understands cancer completely. However, we know that a single mutation will not cause cancer. Cells have "defense in depth" against adverse mutations. There are multiple repair mechanisms, DNA exists in four copies usable for reconstruction, and there are crowbar mechanisms that kill a cell when it detects damage, and there is an immune system which can kill rogue cells. Therefore, to cause cancer, a number of mutations is needed (probably around ten). Clearly, the risk of cancer isn't linear in the dose, it grows approximately with the tenth power. There are other mechanism absent from your naive view. Ionizing radiation typically doesn't damage DNA directly (alpha radiation can cause double strand breaks, but beta and gamma don't). Rather, it creates reactive oxygen radicals which can oxidize DNA, causing miscoding lesions. (These are repairable, to some extent.) But cells contain compounds that scavenge such radicals (the most important one is glutathione). If glutathione has be exhausted before oxidative damage occurs, that creates a threshold effect. So response to ionizing radiation is likely nonlinear and has a threshold. LNT is twice wrong. > Your distinction between the words "model" and "assumption" is moot by the way. Then I will make it more clear. A model is something that is tested and discarded if it turns out to be no good. An assumption is something that is kept despite failing the tests. LNT was based on nothing (Herman Muller made it up, claiming knowledge about how DNA is affected; and that was before the structure of DNA, let alone the existence of DNA repair was known), which may be forgivable. But it should have been discarded after its predictions didn't match the reality of the Nuclear Navy dock workers study, or the Taiwanese radioactive high rise buildings, or how low dose full body irradiation suppresses cancer instead of causing it. I shouldn't have said assumption. Let's be honest and call it a dogma.