How is cigarette smoking linked to lung cancer?

Cigarette smoking is causally linked to lung cancer, with active smoking and exposure to secondhand smoke estimated to account for 80 to 90 percent of all cases in countries with a long history of tobacco use.123

The link is primarily attributed to the presence of more than 60 known carcinogens in tobacco smoke, such as polycyclic aromatic hydrocarbons and nitrosamines. When these toxins are inhaled, the body’s enzymes may fail to metabolize them effectively, allowing the carcinogens to bind to and damage cellular DNA. If cells with this damaged genetic material survive and replicate, they can develop into cancerous tumors that may metastasize.12

The risk of developing the disease is strongly associated with the duration and intensity of exposure; heavy smokers and those who began smoking at a young age face a significantly higher risk. Furthermore, cigarette smoking can potentiate the cancer-causing effects of other environmental hazards, such as asbestos, radon, and arsenic.231