Lung cancer is the most common primary malignant tumor of the lung. Most lung cancers originate from the bronchial mucosa epithelium, so it is also called bronchopulmonary cancer. The etiology of lung cancer is still not completely clear. A lot of information shows that the risk factors of lung cancer include smoking (including second-hand smoke), stone wool, radon, arsenic, ionizing radiation, halogenated alkenes, polycyclic aromatic compounds, nickel and so on. So, what are the risk factors for lung cancer? The following are the risk factors for the development of lung cancer. 1. Air pollution: It is known that air pollution caused by industrial waste gas, coal and gasoline combustion is one of the factors for the high incidence of lung cancer in urban areas compared with rural areas. Long-term exposure to radioactive substances such as uranium radium and its derivatives carcinogenic hydrocarbons arsenic chromium nickel copper tin iron coal tar asphalt petroleum asbestos mustard gas and other substances can induce lung cancer mainly squamous and undifferentiated small cell carcinoma. 2.Chronic lung diseases: such as pneumoconiosis, tuberculosis, silicosis, etc. can coexist with lung cancer and the incidence of cancer in these cases is higher than normal. In addition, chronic inflammation of lung bronchus and lung fiber scar lesions may cause squamous epithelial metaplasia or hyperplasia during the healing process. 3.Occupational factors: It refers to occupations related to coal tar, asbestos, chromium, arsenic, nickel and radioactive elements, which have a high incidence of lung cancer due to long-term exposure to carcinogenic substances. 4.Nutritional status: The lack and deficiency of vitamin E and B2 are more prominent among lung cancer patients. Long-term lack of vitamin A, vitamin A, beta carotene and trace elements (zinc and selenium) in food is prone to lung cancer. 5.Smoking: The etiology of lung cancer is rather complicated. Its occurrence is closely related to smoking and environmental factors. Long-term smoking can lead to bronchial mucosa epithelial cell hyperplasia squamous epithelial growth induced squamous epithelial carcinoma or undifferentiated small cell carcinoma non-smokers can also suffer from lung cancer but adenocarcinoma is more common. The composition of tobacco and the smoke when burning contains 3-4 benzpyrene, arsenic, nitrosamines and other carcinogenic and pro-carcinogenic substances. According to statistics, 70-80% of lung cancer is caused by long-term smoking, lung cancer mortality rate of smoking population is 10-20 times higher than that of non-smoking population, the longer the smoking time, the more cigarettes smoked and the younger the age of starting smoking, the greater the chance of lung cancer; passive smoking in women, the incidence of lung cancer is more than 2 times higher than that of non-smoking spouses. 6. Intrinsic factors: such as family genetics and lowered immune function, metabolic activity, endocrine dysfunction, etc.