Why does smoking increase the risk of lung cancer?

Smoking increases the risk of lung cancer primarily because cigarette smoke contains more than 60 known carcinogens, such as tobacco-specific nitrosamines and polycyclic aromatic hydrocarbons.12

When these substances are inhaled, the body’s enzymes sometimes fail to metabolize and excrete them effectively. This allows the carcinogens to bind to and damage cellular DNA. If cells with this damaged DNA survive and replicate, they can accumulate and develop into cancer.1

The risk is strongly linked to the duration and frequency of exposure, as persistent inhalation promotes the accumulation of these genetic mutations. Furthermore, cigarette smoking can potentiate the cancer-causing effects of other environmental hazards, such as asbestos, radon, and arsenic. It is estimated that approximately 85 to 90 percent of all lung cancer cases are attributable to active smoking or exposure to secondhand smoke.12