[ RadSafe ] LNT Dogma? - Future of Radiation Safety Regulations

[KARAM, PHILIP]

There are a few ways that an incorrect model might still be useful.

First - real life might have hundreds of variables, the majority of which have only second- or third-order effects. A completely accurate calculation might have to consider all of these, but ignoring them might put you in error by only a few percent. In this case, the simplified model is easier to use and, perhaps, the chance of keystroke error in a more involved calculation might be larger than the errors from using a simplified model. Or, also, the combined measurement error in multiple parameters might exceed the error from using the "best" solution. 

Second, the practical ("on the ground") results might turn out the same anyhow. Consider, for example, a world in which everybody agrees that there's a threshold of 10 rem (100 mSv), below which there are no adverse effects from radiation exposure. If we assume that people can be exposed to radiation for 70 years, this means that someone could receive about 1.5 mSv (150 mrem) annually while remaining below the threshold dose by the end of their lives. It would make sense to round this down to 1 mSv (100 mrem) for the sake of safety and to allow for a longer life - and we'd end up exactly where we are for public radiation exposure under a regulatory system based on LNT. 

Of course there's more to it than that. For example, a really precise regulatory structure based solely on risk should also take into account the latency period of cancer, radiation sensitivity of various tissues at various ages, maybe diet and lifestyle, travel habits, genetic propensity for cancer, and so forth. But this would mean generating an annual radiogenic risk profile for every person every year - something that's currently beyond our abilities, not to mention a huge time-suck, and hard to regulate. So even though LNT is very likely wrong, it does make the book-keeping easy, and it's a lot easier to administer than the most precise (and most accurate) model we can imagine.


One last thing is that we cannot look at radiological risks in isolation because there are all sorts of risks out there. If I think I might have cancer, I'll gladly accept the radiation from a CT or x-rays because the risk of not having diagnostic information is substantially higher. And as a society, the number of lives that can be saved with universal vaccination programs (or smoking cessation programs) is far higher than the number of lives that can be saved by reducing dose limits slightly (or by cleaning up a mildly contaminated site). I am familiar with at least a few remediation projects in which the risks from traffic accidents and construction accidents was far higher than the risk from a little extra radiation exposure. But LNT alone will not help with this issue since LNT simply tells us to get dose as low as we can. Similarly, more people died during evacuation from the area around Fukushima than would have been affected by elevated radiation exposure - again, looking solely at radiation dose reduction would not suggest that the safer course of action would be to simply hunker down in a contaminated area for a few days (or weeks). The bottom line is that dose reductions only help with reducing radiological risk (and maybe not even there if dose is being reduced below a threshold) - they cannot impact any of the non-radiological risks that society faces. And, in some cases, pursuing greater radiological "safety" can increase overall societal risk.

Andy


P. Andrew Karam, PhD, CHP
NYPD Counterterrorism
One Police Plaza, Room 1109
New York, NY 10038
(718) 615-7055 (desk)
(646) 879-5268 (mobile)