Smoking is the leading cause of lung cancer, contributing to about 85% of cases. The combustion of tobacco releases carcinogens, such as benzene and formaldehyde, which damage lung cells and DNA, leading to mutations that can initiate cancer. The risk is dose-dependent, meaning the more cigarettes smoked and the longer the duration, the higher the risk.
Smokers have a 15–30 times higher risk of developing lung cancer or passing away from the disease than nonsmokers do. The risk of lung cancer is increased even by smoking a few cigarettes a day or sporadically.
