As many people don’t know the causes of lung cancer, some of them only know that smoking can cause lung cancer, but they don’t know much about any other causes of the disease. For this reason, the following is to introduce what are the causative factors of lung cancer, hoping that it can help people understand the causes of lung cancer. 1. Tobacco factor Smoking is one of the factors that cause lung cancer, and the growth of lung cancer incidence is parallel to the increase of paper cigarette sales. Paper cigarettes contain benzo(a)pyrene and other carcinogenic substances, and experimental animals can be induced to have cancer of whistle and skin by inhaling paper cigarette smoke or applying tar. The incidence of lung cancer in habitual smokers is 10 times higher than that in nonsmokers, and the incidence in heavy smokers is even higher, 20 times higher than that in nonsmokers. At the end of this century, with the increasing number of women smokers in Western European countries, the incidence of lung cancer in female patients has also increased significantly. In the clinical diagnosis of lung cancer cases, the daily smoking of paper cigarettes is more than 20 cigarettes for more than 30 years, accounting for about 80% of the cases. In the past 20-30 years, the situation of smoking in China is very serious, nearly 300 million people have smoking habit, the smoking rate of male adults in Beijing, Tianjin, Shanghai and other big cities is nearly 50%, and the rate of women is nearly 5%, and the number of smokers among teenagers is also not small. If we don’t take necessary measures to control and discourage smoking, the incidence of lung cancer in China will further increase in the next 10-30 years. 2.Air Pollution According to the survey, atmospheric pollution is also a factor that triggers lung cancer, and the incidence of lung cancer is higher in factory and mining areas than in residential areas, and higher in cities than in rural areas, and higher in industrial developed countries, mainly due to the developed areas of industry and transportation, the pollution of the atmosphere by hazardous substances such as benzopyrene carcinogenic hydrocarbons produced by the combustion of petroleum, coal, and combustion engine, etc., and dust from the asphalt highway. The survey material shows that the incidence of lung cancer increases in areas with high concentration of benzo(a)pyrene in the atmosphere, and the incidence of lung cancer may be promoted and synergized by atmospheric pollution and smoking paper cigarettes. Lung diseases such as tuberculosis, silicosis and pneumoconiosis can coexist with lung cancer. The incidence rate of cancer in these cases is higher than that of normal people. In addition, chronic inflammation of lung bronchial tubes and fibrous scar lesions of lungs may cause squamous epithelial hyperplasia or hyperplasia during the healing process, and on the basis of which, some of the cases may develop into cancer. 4. Immunity, such as family heredity, lowered immune function, metabolic activity, endocrine dysfunction, etc., may also play a certain role in the development of lung cancer.