1.Men over 45 years old with a smoking history, especially those with a smoking index of 400 or more: smoking index = number of years of smoking history × number of cigarettes smoked per day. For example, a man has 20 years of smoking history, smoking 20 cigarettes per day, his smoking index is 20 × 20 = 400. Some survey analysis data pointed out that men over 45 years of age with a smoking index greater than 400, the incidence of lung cancer is 9.9 times higher than that of non-smokers of the same sex and age. The risk of lung cancer depends on the age of initiation of smoking, intensity of smoking and duration of smoking. Of all the factors, time is the most important one. It is often assumed that the longer one quits smoking, the more the risk of lung cancer decreases, but in fact the risk for quitters does not decrease, but stays at the level of risk already achieved at the time of quitting. Of course, the longer a smoker continues to smoke, the greater the risk increases substantially. 2.People who have direct contact with raw materials and products for a long time in industrial and mining enterprises with a history of lung cancer epidemic: the carcinogens that have been confirmed to cause occupational lung cancer include asbestos, arsenic compounds, dichloromethyl ether, chromium compounds, nickel compounds, soot, tar, polycyclic aromatic hydrocarbons in oil, and radioactive substances in mine air, and long-term contact with these carcinogens can cause cancer. 3. 60-80 years old men and women: this age group is at the peak of cancer incidence and is a high-risk group for many cancers, and is also a high-risk group for lung cancer. In addition, men and women in this age group are subject to passive smoking, environmental pollution, air pollution and indoor small environment pollution (such as cooking oil fumes and radioactive materials in decoration materials) for a longer period of time, which is also one of the risk factors for lung cancer. 4.Any disease has internal and external causes. Therefore, lung cancer has a certain degree of heredity, and people with family history of lung cancer should also be listed as high-risk groups and need to be closely screened. Among the above high-risk factors, smoking is the most important cancer-causing factor and should be the most controllable factor. However, smoking is in fact the most poorly controlled factor. Quit smoking and stay away from lung cancer!