So radon gas is present most anywhere in the world. There can tend to be a higer concentration around granite rock which is very prevelant in western north carolina. If you have a basement level in your home, I would suggest testing your home to make sure it's within the epa guidelines.  You can hire someone to do it or you can do what i have done, purchase a radon detecting device.  I purchased one, the Safety Siren. It was very simple to use and i found it very accurate when compared to a professional coming in and testing. It only ran 130 dollars and i picked one up at this site, http://www.safehomeproducts.com/shp2/showcategories.aspx?category=1260