[NeedMoreTea]

There's loads of cities built on and with granite, and long before any awareness of Radon came about, without undue health effects. Scotland particularly - Aberdeen is even nicknamed the Granite City. Modern levels of draught exclusion can make for a little more of a problem of course.

[Spooky23]

You can map a specific radon level to probability of getting lung cancer. At high levels, it's equivalent to smoking cigarettes, and for smokers, it increases your cancer risk 7-8x.

At the levels where it is recommended that you remediate your home, your likelihood of dying from lung cancer is equivalent to dying in a car accident. That's potentially 50 people a year when you look at a population of 200,000 people.