Lung Cancer Causes: The Primary Risk Factor

Cigarette smoking is the number one cause of lung cancer, responsible for approximately 85–90% of cases in the United States.

Dose-Response Relationship

• Duration: Risk rises with years smoked (pack-years = packs/day × years).
• Intensity: Cigarettes/day; even light smoking (1–4/day) confers significant risk.
• Age at initiation: Earlier start → higher cumulative exposure, greater susceptibility.

Other Tobacco Products

• Cigars, pipes: increase risk (though lower than cigarettes if not inhaled deeply).
• Smokeless tobacco: not linked to lung cancer (oral/esophageal/pancreatic).
• E-cigarettes: long-term risk unknown; not harmless.

Non-Smoking Causes (10–15% of cases)

• Radon (2nd leading cause overall).
• Secondhand smoke.
• Occupational carcinogens (asbestos, silica, diesel, metals).
• Air pollution (PM2.5).
• Prior chest radiation.
• Genetic susceptibility (see separate article).

Prevention Priority

1. Never start smoking.
2. Quit at any age – benefit immediate and cumulative.
3. Protect from secondhand smoke.
4. Test/mitigate radon.
5. Occupational hygiene.
6. LDCT screening if eligible.

Smoking cessation remains the most impactful public health intervention for lung cancer.