After many years of research and studies, the following factors are now recognized to be closely related to the etiology of lung cancer I. Smoking. Cigarette is an extremely acidic substance, which can easily lead to acidification of human body, and an acidic body is prone to induce cancer. According to a large number of survey data from various countries, the cause of lung cancer is closely related to paper cigarette smoking. The increase in the incidence of lung cancer has a parallel relationship with the increase in the sale of paper cigarettes. Paper cigarettes contain many carcinogenic substances. The incidence of lung cancer in 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. Second, occupational factors. In the 1930s, there was a report on the high incidence of lung cancer in a mining area in Europe. After years of research, it is now recognized that long-term exposure to radioactive substances such as uranium, radium and their derivatives, carcinogenic hydrocarbons, arsenic, chromium, nickel, copper, tin, iron, coal tar, asphalt, petroleum, asbestos, mustard gas and other substances, due to changes in human diet and living habits, acidification of the body causing metabolic cycle to slow down, the overall immune function decreases, giving these radioactive elements the opportunity to induce cell carcinogenesis. Chronic diseases of the lung. Such as tuberculosis, silicosis, pneumoconiosis, etc. can coexist with lung cancer, and the occurrence of these chronic diseases is the result of lung cell infection, cellular hypoxia and reduced cellular activity due to acidification. The incidence of cancer is higher in these cases than in normal subjects. In addition, chronic inflammation of lung bronchus and lung fibro-scar lesions may cause squamous epithelial chemosis or hyperplasia during the healing process, on the basis of which some cases may develop into cancer. Symptoms due to primary foci of lung cancer: 1. Cough: mostly irritating cough. 2.Blood in sputum: mostly blood sputum. 3. Chest tightness and chest pain: generally the symptoms are light and the localization is vague. When the cancer tumor invades the pleura and chest wall, the pain increases and the localization is clearer and more constant than before. 4.Shortness of breath: pneumonia, pulmonary atelectasis, malignant pleural effusion and diffuse alveolar lesion caused by cancer tumor obstruction can cause. 5.Fever: caused by obstructive pneumonia or cancerous toxin. 6.Late stage patients may have more obvious cachexia.