There was a brief, but interesting discussion in Twitter about risks from exposure to low levels of ionizing radiation. Among pro-nuclear people this discussion erupts with some regularity. For some background there is this really clear discussion by @kasilas which you should read. The thing is that some (I suspect mostly people with engineering background) dislike LNT (linear no threshold) assumption in radiation protection. They say that below a dose of about 100 mSv it doesn’t have observational support and therefore one should not talk about “risk” below some threshold. Such risk is speculative and just gives ammo to anti-nuclear crackpots. On the other hand experts in radiation biology and protection gather around the “party line” and tend to see LNT, if not perfect, then at least good enough and certainly better justified than supposed alternatives. The sane on both sides nevertheless conclude that whatever risk model we use for low doses, the risks will be small compared to many other risks we face on a routine basis. Both, by and large, hold the opinion that radiation from nuclear power is not an important public health concern relative to more pressing concerns.
I think this discussion is interesting not so much from the scientific perspective, but mainly from the sociological perspective. I suspect that engineering types dislike going through the trouble of minimizing all sources of exposure as much as possible while knowing that it adds to costs and that this work has no observable consequences. They feel that they could be working on much more important things. Radiation protection people on the other wish to protect scientific standards and probably feel a civic duty to maintain and built public trust on experts. Playing fast and loose with radiation risks might undermine that work. They dislike fear mongering by anti-nuclear folks as well as nonchalant attitude to small doses expressed by some pro-nuclear people. They are the doctors trying to keep inmates from running the asylum. (Although this task is complicated by the fact that only pro-nuclear folks have the courtesy to loiter close to the asylum. Antis have always been running free.)
Personally I have sympathy for both sides of this discussion, but I think this is fundamentally not a scientific question, but a question of public perception of risks and how that relates to policies. Due to decades of misinformation many people have fundamentally wrong perception of radiation risks. When we start by saying that radiation dose, no matter how small, poses a risk, we do not question that underlying default setting. We might then continue telling how this risk is nevertheless tiny, but many people have already tuned out. And in any case people are very bad at evaluating risks so they are more than likely to compress the message to “radiation BAD”. The conspiracy minded among the public will of course go even further. When official tells them small amount of radiation has risks, they will conclude that it is in fact deadly and the level that is really safe will be something much much lower. As the safety level is thus adjusted downwards possibilities for exceeding those “safe levels” multiply and the sense of danger will probably go up rather than down. Of course this is a complex issue. If on the other hand we say that the risk is not there, some will simply decide that you are not credible and tune out immediately. You have to adjust your message in response to craziness on the other side and hope they will gradually move to a sensible position. But does anybody know, how nuanced accurate discussion actually influences people whose opinions are at the start of the discussion bizarrely off base? Such discussion certainly is preferable with people whose opinions are more or less sensible to begin with, but with others? I am really not sure and would love to learn of some research on this topic.
Given my background I was (of course) thinking that isn’t this kind of similar to importance of quantum mechanics? We live in an imperfect world where most people do not need Planck’s constant in their daily lives. This natural constant is at the heart of quantum mechanics and indeed our world be inexplicable without it. (In fact some of those who actually need it in their daily lives, define their units in terms of it so that for them Planck’s constant has a value one. Being so down to earth and organic they even call such units “natural”.) However, as a practical matter it doesn’t make sense to incorporate the effects of Planck’s constant into building codes or environmental impact assessments etc. Most people will find it easier to just set Planck’s constant to zero and as a practical tool that is usually perfectly OK, even though it is fundamentally wrong. In fact, if we were to do the opposite, the risk of a backfire would be large. People would not know how to deal with Planck’s constant in practice and if asked about its magnitude they would be off by a large amount. (If we were to give them some additional information such that “Planck’s constant is related to the energy of particles of radiation”, many would probably increase the value of the constant even more.)
Given the horrendously wrong public perception of radiation risks, I often feel they would be better served if their default settings were based on the idea of zero risk. This is fundamentally wrong, but it is less wrong, in a practical sense, than their current perceptions. Once the lowest order term has been correctly established we could start adding nuance and even move to discussion of such regimes where radiation risk is actually large. Nowadays people start from fears of cities attacked with nuclear weapons and then we expect them to make a reasonable extrapolation of risks into their daily lives. For most people I don’t think that will ever happen. On the other hand, I do not know how that more sensible starting point can be established in practice. Currently people pickup nonsense from NGO:s and media already as children and accurate information gets drowned in the noise.