Radon Map
I found this little number on Wikipedia:
http://upload.wikimedia.org/wikipedia/commons/3/37/Mean_atmospheric_rado...
It gives a heatmap for average Radon readings in different parts of the world.
Our area near SF averages 2-5 Bq/m3 of internal emitting Radon (i.e. you breathe it constantly). Other parts of the country are much higher.
Just something to keep in perspective.

