The end result: they left an area of lesser radiation to an area where there is more radiation (the natural background radiation here is higher than the elevated levels were in Japan). And when doing so, they took an airplane where the in-flight radiation levels are even higher.
But on the other hand quantitatively measuring and comparing radiation effects is hard problem as there is essentially nothing that can be precisely measured and at the same time has any meaning as to biological effects, in practice the conversions between various units are just done using various experimentally determined constants that may or may not be relevant to given situation.
As for all the comments on how nuclear isn't all that dangerous -- how much do we really know about people leaving 4-5 generations in an area with elevated radiation, eating produce etc? I guess we have some data from the Bikin Islands[1] -- but those levels might very well be much higher -- at least it's not an example of how we can live safely in a radiation zone.
Speaking of [1]: "The special International Atomic Energy Agency (IAEA) Bikini Advisory Group determined in 1997 that "It is safe to walk on all of the islands ... although the residual radioactivity on islands in Bikini Atoll is still higher than on other atolls in the Marshall Islands, it is not hazardous to health at the levels measured ... The main radiation risk would be from the food: eating locally grown produce, such as fruit, could add significant radioactivity to the body...Eating coconuts or breadfruit from Bikini Island occasionally would be no cause for concern. Eating many over a long period of time without having taken remedial measures, however, might result in radiation doses higher than internationally agreed safety levels." IAEA estimated that living in the atoll and consuming local food would result in an effective dose of about 15 mSv/year."
It will be interesting to see if removing topsoil in Fukushima will be enough for radiation to reach safe levels. Hopefully the water tables are safe.
[1] https://en.wikipedia.org/wiki/Nuclear_testing_at_Bikini_Atol...
There are a few places on earth that have naturally high radiation levels (up to 250mSv/year), including many places with large granite deposits or hot springs. However, these places often do not show any higher cancer incidence (or other relevant health problems) than other areas, possibly suggesting some sort of limit before radiation becomes harmful (the Threshold model).
Some studies actually show significantly lower cancer incidence than other areas. This has prompted the idea of Radiation hormesis, that low doses above background have some benefit. We do know that low doses do stimulate cell repair mechanisms in different ways than large doses do, so it does seem possible (although real-world data is mixed). The effects are not well understood at present, and it's an area that is under ongoing study. Unfortunately, it's an absolute devil to research!
Still, ~43[1] mSv/year is pretty close to the "safe" limit (and it makes sense to set a safety limit well below what can be documented as being harmful) -- and that's just from irradiation. Who knows the effect of breathing in pollen, never mind eating local produce, over a period of ~50 years?
Are there different safety levels for children/infants? If the 50mSv/year is set for workers, I assume they're for adults?
[1] I accidentally dropped a significant digit when rounding off too. It comes to ~42924.0, not ~49...
... I mean, yes, they probably aren't statistically very harmful! Nothing like the Chernobyl exclusion zone, at least in the areas this person visited, and considering only ambient exposure.
Still, over the limit, and, like I said, drastically elevated. Fukushima unquestionably harmed its surrounding area.