When you breathe air containing radon, you increase your risk of getting lung cancer. Radon is a carcinogenic gas that is hazardous to inhale and to your health. Radon is estimated to cause many thousands of deaths each year. That’s because when you breathe air containing radon, it can cause lung cancer. In fact, the Surgeon General has warned that radon is the second leading cause of lung cancer in the United States today. Only smoking causes more lung cancer deaths each year. If you smoke and your home has high radon levels, your risk of lung cancer is higher!