Lung cancer is primarily caused by changes or mutations in the DNA of lung cells, which lead to uncontrolled cell growth and tumor formation. The biggest cause of these DNA changes is smoking, which introduces carcinogens that damage lung cells and lead to cancer. Exposure to secondhand smoke also increases risk. Besides smoking, other causes include exposure to radon gas, asbestos, arsenic, chromium, nickel, and air pollution. Lung cancer can also occur in people with no clear exposure to these risk factors.

How Smoking Causes Lung Cancer

Smoking is the leading cause, responsible for about 80-90% of lung cancer cases. Cigarette smoke contains many carcinogens that damage the DNA in lung cells, causing them to mutate. Repeated exposure overwhelms the body's repair mechanisms, leading to cancer development. People who have never smoked can still get lung cancer, especially if exposed to secondhand smoke or other carcinogens.

Other Causes and Risk Factors

• Radon, a naturally occurring radioactive gas found in some homes and buildings, is the second leading cause.
• Workplace exposures to carcinogens like asbestos, arsenic, chromium, and nickel increase lung cancer risk.
• Air pollution and certain lung diseases may also contribute to the development of lung cancer.
• Genetic mutations may happen randomly or be induced by environmental toxins.

Lung cancer includes two major types based on cell appearance: small cell lung cancer (mostly linked to heavy smoking) and non-small cell lung cancer, which comprises several subtypes. Overall, avoiding tobacco smoke exposure and reducing contact with known carcinogens are key to lowering lung cancer risk.