Radon is the number one cause of lung cancer in non-smokers. For children, radon and second-hand smoke are the biggest risks for developing lung cancer later in life. Unless you test with a radon test kit, you can't tell whether your home has radon, because radon is a gas that has no smell, no color, and can't be seen. Radon is an invisible, odorless radioactive gas in the earth that can enter into lower level rooms of your home, like a basement. The longer you and your family are exposed to radon, the greater risk you have of developing lung cancer.
Resources available through the links below provide more information about radon health risks and means to find test kits or measurement and mitigation professionals.