The average, of course, is just that, an average. There are some places that are naturally around 100 mSv dose annually, or some 50x higher, and places that ar

The average, of course, is just that, an average. There are some places that are naturally around 100 mSv dose annually, or some 50x higher, and places that are much lower than average. Under truly non-ideal conditions, like having a poorly-ventilated basement made out of uranium-rich limestone, it could probably get even higher than 100 mSv a year just from the radon. Speaking of which, radon gas is the main way in which uranium affects the health of people. Depending where you live and the construction methods, it may be worth getting your basement checked, and ventilated properly if necessary. Even the extreme scenario there is still far short of causing acute radiation sickness. People who live in such regions are sometimes exposed to such levels their whole lives, which can still be long and healthy. But not quite as long and healthy as those without such exposure, on average.