Radon gas is the leading cause of lung cancer in non-smokers. Children are most at risk of exposure in homes, especially during the winter months. (Shutterstock) 13 décembre 2017 Have you tested your home for cancer-causing radon gas? Aaron Goodarzi, University of Calgary Radon is a radioactive gas that seeps into buildings through foundation cracks. It is the leading cause of lung cancer in non-smokers. And it only costs around $60 to test your home.