At the end of this article, which has one expert questioning why the Japanese government is setting such a relatively low level of background radiation as being needed before residents can return to land around Fukushima, there is this caution:
Of course this is a ferociously complex issue, and many will argue that IYes, it seems to me (without knowing anything concrete about this) that the matter of how a background radiation level is being maintained is important. If you live in an area where the rocks and minerals around you are naturally radiative, but are in a more or less solid state, wouldn't that be better than being in an area with a lower background reading that's come from dust that descended from the sky? Because I would have guessed that getting that dust into your lungs is likely to do worse damage than standing near (say) a block of granite that has a naturally high reading.
am ignoring the dangers of "hot spots" and from ingesting radioactive
Caesium particles in food or water or dust. But five years after the
meltdowns at Fukushima 100,000 people are still unable to go home. That
is a massive human tragedy.
But how do scientists take this difference (assuming I'm making a legitimate point) into account when declaring an area safe or not for long term residence? Surely it's hard to measure the likelihood of dust ingestion?