1.Smoking Cigarettes contain more than 1,400 ingredients, and there are more than 40 kinds of carcinogenic substances in the smoke produced by smoking, and more than 10 kinds of substances that will promote the development of cancer, among which the most harmful to humans are nicotine, carbon monoxide tar and many other metal compounds. A large number of epidemiological studies have proven the close relationship between smoking and lung cancer, and the incidence and mortality of lung cancer continue to rise due to smoking. More than 80% of lung cancer deaths are caused by smoking, including passive smoking, and the lung cancer mortality rate among male smokers is 8-20 times higher than that of nonsmokers. Passive smoking in women also predisposes to lung cancer, and the current increase in female passive smokers has increased their lung cancer risk. The incidence of lung cancer among smokers and nonsmokers only gradually approached after about 15 years of quitting smoking. Shandong Qianfo Mountain Hospital, Department of Respiratory Medicine, Lu De 2, environmental factors Atmospheric and environmental pollution is another risk factor for the occurrence of lung cancer. A foreign study confirmed that serious air pollution can lead to a high incidence of lung cancer, and the incidence of lung cancer is significantly higher in cities than in villages, with incidence rates of 4%-9% and 1%-3% respectively. The incidence of lung cancer is significantly higher in cities than in the countryside, with incidence rates of 4-9% and 1-3%, respectively. In addition to air pollution, the fuel and fumes used in cooking are also risk factors for lung cancer in women, and the combustion products of fuel contain many carcinogenic substances. It is recommended that cooking should be done in a well-ventilated kitchen. The relationship between certain occupational exposures and lung cancer is relatively clear, and more than ten industrial toxicants or occupational processes have been identified as related to lung cancer. For example, the incidence and mortality rate of lung cancer among miners of Yunnan Jinlao Yunxi Company are among the highest in the world, with the incidence and mortality rate of lung cancer among male miners reaching 1180.3/100,000 and 729.6/100,000, respectively. Through the research on the working environment of tin mines, it is found that the presence of radon gas and arsenic-containing dust in the working environment are important factors for the high incidence of lung cancer among miners. In addition, lung cancer can be induced by large amount of inhalation of radioactive substances such as uranium and radium, long-term exposure to metal minerals containing radioactivity and microwave radiation. In addition, occupational exposure to silica, inorganic arsenic, asbestos, chromium, nickel, coal tar, mustard gas, dichloromethyl ether, etc., can increase the risk of lung cancer. 4.Dietary and nutritional factors It is generally believed that regular intake of fresh vegetables and fruits can also reduce the incidence of lung cancer. Dietary phytoestrogens have estrogen-like effects, and in vitro studies have shown that they have chemopreventive effects on lung cancer. A study from the United States confirmed that high dietary intake of phytoestrogens reduces the risk of lung cancer, comparing self-reported dietary intake of 12 phytoestrogens in 1526 lung cancer cases and 1483 healthy controls, and found that the intake of 10 of the 12 estrogens was significantly lower in lung cancer patients than in healthy controls. Another study from the Czech Republic also confirmed the effect of dietary factors on lung cancer, finding that for women who smoked, dietary intake of milk or dairy products, vegetables and exercise reduced the risk of lung cancer; for women who did not smoke, drinking more black tea had a significant protective effect. 5, psychosocial and genetic factors It is generally believed that poor psychological adaptability, long-term mental depression, type A personality (referring to fast action, impatience, aggressiveness and excitement), etc., may increase the risk of lung cancer. An unhealthy lifestyle will bring “pollution” to the body and mind, which will lead to the decline of immune function and induce diseases. In addition, genetic factors play a role in the process of tumor development. If there is a history of tumor in the family, they are also at risk of developing lung cancer.