Many of the causes of lung cancer are unknown but there are certain factors that make lung cancer more likely, eg smoking. Passive smoking has also been linked to lung cancer. If you stop smoking, you will be less likely to develop lung cancer with each year that passes. Environmental causes like radon gas, a naturally occurring radioactive gas, has been linked to lung cancer in people who have been exposed to high levels, eg miners. Exposure to chemicals such as asbestos increases your risk of developing lung cancer; and so does a diet low in fruit and vegetables.
Attribution: BUPA