Second-hand smoke is one of the high-risk factors for lung cancer, but it does not mean that second-hand smoke will definitely cause lung cancer. The etiology and pathogenesis of lung cancer have not been fully clarified, and it can only be said that it is related to certain factors, such as smoking, external air pollution, electric radiation, genetic factors and other triggering factors. Second-hand smoke, also known as environmental tobacco smoke, and passive inhalation also belong to one of the causative factors of lung cancer. Tobacco has been listed as a class A carcinogen, and smoking is associated with the risk of all pathological types of lung cancer. Therefore, from a health perspective, unfavorable triggers such as smoking and secondhand smoke should be avoided. If you have uncomfortable symptoms, you should seek medical attention and follow the doctor’s instructions.