Most cases of lung cancer are caused by smoking, although people who have never smoked can also develop the condition and Smoking cigarettes is the single biggest risk factor for lung cancer. It is responsible for about 90% of all cases.
Tobacco smoke contains more than 60 different toxic substances, which can lead to the development of cancer. These substances are known to be carcinogenic (cancer-producing).
If you smoke more than 25 cigarettes a day, you are 25 times more likely to get lung cancer than a non-smoker.
While smoking cigarettes is the biggest risk factor, using other types of tobacco products can also increase your risk of developing lung cancer and other types of cancer, such as esophageal cancer and mouth cancer ,but Passive smoking, or the inhalation of tobacco smoke from other smokers sharing living or working quarters, is also an established risk factor for the development of lung cancer because Research has shown that non-smokers who reside with a smoker have a 24% increase in risk for developing lung cancer when compared with other non-smokers. An estimated 3,000 lung cancer deaths occur each year .