Lung cancer is the leading cause of cancer death in Canada for both men and women, with approximately 6,900 deaths expected in Ontario alone in 2014. When most people think about the causes of lung cancer, cigarette smoke is the only thing that comes to mind. While smoking is the main cause of lung cancer, there are also many other contributors that can cause lung cancer. These include things in the environment, such as outdoor air pollution and radon in homes, and occupational carcinogens, which are found in many workplaces. More info.