The incidence of lung cancer is very clearly related to smoking, and current studies have concluded that the incidence of lung cancer is 10 times higher in smokers than in non-smokers, while the incidence of lung cancer is significantly higher in passive smokers by about 20-30%. What is the relationship between air pollution and lung cancer that the public is concerned about? Is the relationship as strong as that of smoking? The relationship between different pollution components and lung cancer, as well as different tissue types, is being studied. A recent report from Canada summarized the data of nearly 6000 cases of different environmental groups and concluded after years of research that the increase of PM2.5 and nitrogen dioxide in the air significantly increased the incidence of lung cancer.