I. Smoking Almost all lung cancer patients are related to smoking. The lung cancer mortality rate of smokers is 10-13 times higher than that of nonsmokers. The more cigarettes smoked, the longer the number of years smoked, and the earlier the age at which smoking began, the higher the lung cancer mortality rate. Smoking cessation lasted 15 years before it was similar to nonsmokers. Paper cigarette smokers have a higher rate than cigar smokers and pipe smokers. Paper cigarettes contain various carcinogenic substances, such as benzo(a)pyrene, which is the main carcinogenic substance. Passive smoking is also likely to cause lung cancer. The risk of lung cancer increases by 50% in women whose husbands smoke. A survey in Shanghai shows that women who do not smoke but live with a husband who smokes have a 19% higher risk of lung cancer on average, and those who live with a husband who smokes heavily for a long time have a 30% higher risk. Occupational carcinogenic factors Occupational factors that have been identified to cause human lung cancer include asbestos, inorganic arsenic compounds, dichloromethyl ether, chromium and other compounds, nickel smelting, radon and radon daughters, mustard daughters, vinyl chloride, polycyclic aromatic hydrocarbons in soot, tar and oil, heating products of tobacco, etc. The lung cancer mortality rate of smoking workers working in asbestos factories is 8 times that of general smokers and 92 times that of non-smokers who are also not exposed to asbestos. It can be seen that asbestos has a carcinogenic effect, but also shows that smoking and asbestos have a synergistic effect of carcinogenesis. Third, air pollution, including indoor small environment and outdoor environmental pollution. Such as indoor passive smoking, fuel combustion and cooking process may produce carcinogens. Some information shows that indoor use of coal, exposure to soot or its incomplete combustion products are risk factors for cancer, especially for female adenocarcinoma. Oil fumes released from heating during cooking are also carcinogenic factors and should not be ignored. It has been reported that the risk of lung cancer for women in smoke-filled rooms during cooking is 60% higher than that for women in rooms with no or less smoke, and the more often and the longer the exposure to cooking fumes, the greater the risk of lung cancer. Carcinogenic substances are found in automobile exhaust, industrial exhaust, and highway asphalt in cities. The main one is benzo(a)pyrene. Ionizing radiation High dose of ionizing radiation can cause lung cancer. The effects produced by different rays of radiation are also different. About 49.6% of ionizing radiation sources in the general population come from nature, 44.6% from medical exposure, and 36.7% from X-ray diagnosis. V. Diet and nutrition A large number of studies have shown that vitamins A, B, C, E and beta carotene can inhibit tumors induced by chemical carcinogens. Some research reports suggest that the risk of lung cancer increases when the vitamin A content in food is low or the serum vitamin A content is low. History of previous lung diseases A large number of epidemiological surveys have shown that after adjusting for confounding factors such as smoking, the risk of lung cancer is 5 times higher in men and 10 times higher in women than in the normal population with a history of lung diseases (such as tuberculosis, chronic bronchitis, etc.), especially tuberculosis scarring. Genetic factors A person suffering from lung cancer is not only related to environmental factors, but also genetic factors play an important role. The main risk factors for lung cancer in young and middle-aged people are heredity and smoking. Japanese scholars further conducted genetic epidemiological studies on the incidence of different tissue types and found that 35.8% of patients with squamous lung cancer had a family history of lung cancer, which was significantly different from other populations; 58.3% of female patients with alveolar cell carcinoma had a family history of lung cancer, and 3/4 of them had two parents with lung cancer. Genetic factors are important risk factors for lung cancer in women, which not only support that family history of lung cancer increases the risk of lung cancer in individuals, but also indicate that women have higher genetic susceptibility to lung cancer. Psychosocial factors A controlled study on the relationship between lung cancer patients and psychosocial factors before the onset of lung cancer suggests that the OR of those with long-term mental depression is 4.14, and the population attributable risk is 21.6% based on a population exposure rate of 8.8%. A 1:1 matched case-control study of 350 cases of lung cancer in suburban areas of Beijing was conducted by the Beijing Institute of Oncology Control and Prevention, which found multiple risk factors for strong lung cancer effect in Beijing, namely respiratory diseases, history of smoking, pollutants, family history of tumors, family discord and mental trauma as the main causes of lung cancer. The mechanism of cancer caused by adverse life events has not been elucidated. It is generally believed that adverse life events cause stress in the body and negative emotions such as depression, apprehension, sadness, tension, anger or anxiety. Excessive or continuous stress can lead to imbalance of the body’s internal environment, immune function disorder and cancer. Other risk factors such as endocrine status, immune status, body mass index, etc. are related to lung cancer; female lung adenocarcinoma is related to estrogen level, etc.