The first thing you need to do is test your home.
The Surgeon General and the EPA recommend testing for radon in your home. If your levels are 4 picoCuries per liter (pCi/L) or higher then get this problem repaired immediately. Radon levels less than 4 pCi/L still are a serious risk, and can usually be reduced. If you smoke your risk of lung cancer is especially high.
Many states require radon professionals to be licensed, certified, or registered. Find a qualified radon mitigation contractor to fix your home by Contacting Your EPA Regional Office
Radon reduction systems are extremely effective. Some radon reduction systems (or Mitigation Systems) can reduce radon levels by up to 99%. The cost generally ranges from $800 to $2,500 (average is about $1,200). Costs vary depending on your home's size and design. Hundreds of thousands of homes have had radon lowered to safe levels.