The etiology of lung cancer is relatively clear compared to other tumors. It is closely related to environmental factors such as smoking, occupational factors and atmospheric pollution. For the general population, atmospheric pollution and smoking are the main factors of lung cancer, while for workers who are exposed to occupational carcinogenic factors, occupational factors are the main ones. In addition, there is also a relationship with intrinsic factors such as immunity, genetics, lung diseases and viral infections. First of all, let’s understand the association between smoking and lung cancer incidence. 1.Smoking and lung cancer: In the past two or three decades, the relationship between smoking and lung cancer has received much attention, and most researchers now believe that smoking is an important cause of lung cancer. Through a large number of retrospective and prospective surveys, it was found that the number of lung cancer patients who smoked was higher than the number of non-smokers, and it was also related to the large amount of smoking, the depth of inhalation, and the early year of smoking. The risk of smoking paper cigarettes is greater than that of smoking pipes and cigars. In 1952, Doll (doll) and Hill (hill) two of the statistics 1357 cases of lung cancer, smokers accounted for 99.5%, of which heavy smokers accounted for 25%, while nonsmokers accounted for only 0.5%. Therefore, Doyle et al. pointed out that if smoking could be abolished, 90% of lung cancers could be prevented. The United States reported that those who smoked more than two packs (40 cigarettes) of paper cigarettes per day had a 65-fold increased risk of lung cancer compared to nonsmokers; France reported that those who smoked ten cigarettes per day had a 13-fold higher risk of lung cancer compared to nonsmokers, and Japan reported that a prospective survey of 200,000 people found that lung cancer mortality was related to the amount of cigarettes smoked per day. The lung cancer mortality rate was 4801,100,000 for those who smoked more than 50 cigarettes per day, 20/l0,000 for those who smoked l to 9 cigarettes per day, and 17/100,000 for nonsmokers. This shows how much the amount of smoking affects the incidence and mortality of lung cancer. The risk of lung cancer is four times greater in people who start smoking under the age of 15 than in those who start smoking at the age of 25 or older, so it is important to discourage the younger generation from smoking as a powerful measure to prevent lung cancer in the future. In addition, smoking and other lung cancer-causing factors, such as asbestos, ionizing radiation and other occupational cancer-causing factors, as well as air pollution, have synergistic effects. It has been shown that a variety of polycyclic aromatic hydrocarbons extracted from tobacco can cause cancer in different experimental animals. There are additional substances in tobacco that can promote the development of carcinomas. Among the many carcinogens contained in tobacco, the most important is 3, mare pyrene. In recent years, many scholars have also raised the issue of passive smoking. A Japanese survey found that the incidence of lung cancer in the wives of heavy smokers was twice as high as in the wives of nonsmokers. West Germany surveyed 15,000 mothers, found that parents who do not smoke perinatal neonatal mortality rate of 2.9%; fathers smoke, mothers who do not smoke mortality rate increased to 4% the greater the amount of smoking, the greater the risk of having deformed children. Therefore, smoking is not only harmful to themselves, but also to others, and will affect the health of the next generation.