The cause of lung cancer is not yet fully understood, but current research has found that the occurrence of lung cancer is related to the following factors 1. Smoking Smoke contains carcinogenic substances such as nicotine and benzo(a)pyrene, which can lead to phosphoepithelial hyperplasia of bronchial mucous membrane epithelial cells and induce carcinogenesis. Higher 20 times higher than non-smokers. China is a major smoker, there are nearly 300 million smokers, Beijing, Tianjin, Shanghai and other major cities, the male adult smoking rate of nearly 50%, especially in recent years, there is a growing trend of female and teenage smokers. 2, atmospheric pollution industrial soot, automobile exhaust and other pollution of the atmosphere, which contains benzo(a)pyrene, hydrocarbon compounds and a series of carcinogenic substances, it is worth noting that now the rural air pollution also tends to serious. 3.Occupational factors Long-term occupational exposure to radioactive substances, uranium, radium and its derivatives, heavy metal carcinogens, arsenic, chromium, nickel, copper, tin, iron, coal tar, asphalt, petroleum, asbestos, mustard gas and other substances can induce lung cancer. Chronic lung diseases, such as long term chronic tuberculosis, silicosis, pneumoconiosis, chronic lung infections, lung fiber scar lesions, etc., have the chance to become cancerous. Intrinsic factors such as family genetics, reduced immune function, metabolic activities, endocrine dysfunction, etc. may play a role in the development of lung cancer.