There is a higher cancer risk because of radon. If present, uranium, thorium or radium will decay into radon, a colorless, odorless, radioactive gas that may cause lung cancer, according to the EPA. It is the second leading cause of lung cancer and is estimated to cause tens of thousands of lung cancer deaths in the U.S. each year. But radon originating from the soil beneath homes poses a much bigger risk. You can buy do-it-yourself home radon test kits.