Lung Cancer: Causes & Risk Factors

Reviewed by Jeffrey Kern, MD
Lung cancer is caused by a variety of exposures over time.

lung cancer infographicOngoing exposure to these factors increases your risk of developing lung cancer. Exposures that are associated with developing lung cancer include:

  • Smoking is the most common cause of lung cancer. The longer a person smokes and the more often they smoke, the higher the chance they will develop lung cancer. Your doctor quantifies your smoking exposure by calculating the number of years you have smoked multiplied by the average number of packs of cigarettes you smoked per day to come up with "Pack-Years". The risk of developing lung cancer symptoms is lowered after giving up smoking, but never completely goes away.

  • Second-hand smoke - Second-hand exposure to smoke or being around smoke increases the risk of lung cancer.

  • Radon gas, often in the home or mining work - Radon is a radioactive colorless, odorless gas that comes from uranium found in granite rock. Radon is more common in certain parts of the country.

  • Asbestos.

  • Family History of lung cancer in your immediate family that suggests a genetic cause.

  • Personal history of a previous lung cancer.

  • Radiation therapy for another type of cancer, especially if the radiation therapy is in the chest area.

  • Age over 65 years old.


Being exposed to several of these factors further increases your chance of developing lung cancer. If a person who smokes is also exposed to asbestos, then the risk of developing lung cancer is increased further than if that person had only been exposed to one lung cancer risk factor.

Not everyone exposed to these agents develops lung cancer.  It is a complex interplay that we don’t completely understand but depends on the type of exposure, how long you were exposed, and your bodies response to these agents.


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