Although smoking is the leading cause of lung cancer it is by far not the only cause. This includes cigarette, cigar and pipe smoke. Exposure to radon is the second leading cause of lung cancer. It is the leading cause of lung cancer in people who have never smoked. Other risk factors include: occupational or environmental exposure to second hand smoke, radiation, asbestos, air pollution, certain metals (chromium, cadmium, arsenic) and some organic chemicals. Risks are also increased among people with a medical history of tuberculosis. Through research we now know that genetic susceptibility plays a contributing role in the development of lung cancer, especially in those who develop the disease at a younger age. To prevent new cancers from starting, scientists look at risk factors and protective factors. Anything that increases your chance of developing cancer is called a cancer risk factor; anything that decreases your chance of developing cancer is called a cancer protective factor.