It is widely recognized that smoking causes lung cancer, but some smokers believe that switching to low-tar cigarettes will reduce the risk of lung cancer. This is a very dangerous misconception. Smoking low-tar cigarettes does not reduce the risk of lung cancer at all. This is because the tar and nicotine content indicated on the cigarette pack may not match the actual amount inhaled, which is related to the depth of smoke inhaled, the length of time it is held, and the amount of smoke smoked. The American Cancer Society has done a survey: 364,000 men and 576,000 women aged 30 to 36 years, smoking medium tar content cigarettes and low tar content cigarettes, there is no significant difference in the proportion of deaths from lung cancer. Instead, these people take a chance and tend to increase the number of cigarettes they smoke each day, inhale more nicotine, and the smoke stays in their lungs longer. Cigarette tar content below 14 mg is low tar content, 15 to 21 mg is medium tar content, and 22 mg or more is high tar content. Whether high tar content or low tar content, smoking produces more than 40 kinds of carcinogenic substances, which are closely related to lung cancer, such as polycyclic aromatic hydrocarbons, benzene, arsenic, propylene, nicotine (nicotine), carbon monoxide and tobacco tar, etc. These carcinogens can lead to bronchial epithelial cell damage, activation of certain oncogenes, mutation and inactivation of oncogenes through different mechanisms, leading to cancer. The most effective way to prevent lung cancer is to quit smoking, not smoking low tar content cigarettes, and the faster you quit, the greater the benefit. According to the National Cancer Institute (NCI), adults who quit smoking for one year have a 50 percent reduced risk of heart disease; smokers who quit 10 to 15 years later have little significant difference in health status from nonsmokers. Not only does it reduce the risk of lung cancer, but it also helps to stop the development of chronic lung diseases.