| That's actually a fascinating question! It turns out we don't know enough to answer one way or another. The model commonly used in radiation protection to assess cancer risk with respect to radiation dose is called the Linear No-Threshold (LNT) model [1]. The model critically assumes that (1) total radiation dose is the only predictor of cancer risk, and (2) any radiation exposure results in an increased cancer risk. This model works at high absorbed doses, however, its applicability is highly controversial when used with low abosorbed doses or with relatively high absorbed doses that occur over a long period of time (ie: low dose rate). The thing is, the human body has built-in defense mechanisms against cancer such as DNA repair. There is a good body of evidence that small doses and low-rate exposures do not result in cancer risk (ie: there is a threshold absorbed dose and probably also a threshold dose rate), but the model does not account for this. This is particularly problematic when trying to assess excess mortality from things such as radiological accidents: when you multiply the small LNT-predicted risk for a low dose times a very large population, you end up with a lot of cancers. This is one of the reasons you'll see estimates for deaths from the Chernobyl accident vary by orders of magnitude. It's also problematic when assessing something like a Mars mission: yes, the astronauts would get large cumulative doses, but the dose rate is pretty low over most of the mission (other than during high dose rate solar events where they would need radiation shielding). How much of an elevated cancer risk is it actually? Nobody is quite sure. [1] https://en.wikipedia.org/wiki/Linear_no-threshold_model |