Which is the most significant risk factor for bronchogenic carcinoma?

• A. HIV infection
• B. Asbestos exposure
• C. Environmental exposure to radon
• D. Smoking and tobacco smoke exposure

Answer: (D)

Smoking and tobacco smoke exposure is the most significant risk factor because tobacco smoke delivers a large load of carcinogens that directly damage bronchial epithelium and drive malignant transformation. The risk increases with the amount and duration of smoking (pack-years) and, although risk declines after quitting, it remains elevated for many years compared with never-smokers. Other factors like radon exposure, asbestos exposure, and HIV infection indeed raise lung cancer risk, but none match the overall impact of active smoking on bronchogenic carcinoma, and asbestos can further amplify risk when combined with smoking. So the dominant driver is tobacco use.