I grew up in a townhouse area built with radon-containing blue concrete. My own analysis after following the area for 40 years (my mother is a real gossip) is that indeed one or two people have died of lung cancer in the area. All of them were smokers.
As children, we used to break off pieces of the foundation wall and draw hopscotch grids on the street. No children died of cancer. In 40 years.
As children, we used to break off pieces of the foundation wall and draw hopscotch grids on the street. No children died of cancer. In 40 years.
Radon + Smoking (indoors) is of course an extremely bad combination. Increases the risk of lung cancer about 50x compared to normal. Radon itself increases the risk (at the given levels and if I remember correctly) about 1.5x. Also, drawing on the street with lightweight concrete was so much fun.
back to ts question!! 
Where does the chart come from? I've seen another one before....