According to the EPA, radon is estimated to cause 21,000 lung cancer deaths per year, and is the second leading cause of lung cancer in the US.  You can’t see, smell or taste radon gas, so you would probably have no idea if it is in your home or not unless you test for it.

Radon is a radioactive gas that comes from the decay of uranium that is found in nearly all soil and moves up from the ground into a home through cracks and holes in the foundation.

You can test for it by buying a ‘do-it-yourself’ kit or by hiring a professional qualified tester.  Kits can be found at Home Depot, on-line or possibly other home/hardware stores.