What causes lung cancer to develop?

Lung cancer develops when cells in the lungs undergo uncontrolled growth, typically triggered by damage to cellular DNA. When cells with damaged DNA survive and replicate, they can form cancerous tumors that may eventually metastasize to other parts of the body.12

The primary cause of lung cancer is tobacco smoking, which is responsible for 80 to 90 percent of cases in countries with a long history of tobacco use. Tobacco smoke contains more than 60 known carcinogens that can bind to and damage DNA. Other significant risk factors include:321

• Environmental Exposure: Inhalation of secondhand smoke and exposure to radon gas, particularly in homes with poor ventilation.32
• Occupational Hazards: Exposure to asbestos, arsenic, chromium, nickel, and various hydrocarbon-related processing materials.32
• Genetic Factors: While lung cancer is rarely caused directly by inherited mutations, mutations in specific genes known as proto-oncogenes can lead to the uncontrolled cell division characteristic of cancer.42

It is important to note that lung cancer is a multifactorial disease, and while smoking is the leading cause, the precise contribution of individual factors cannot always be quantified.3