Lung Cancer: Causes & Risk Factors Make an Appointment Refer a Patient Ask a Question Reviewed by Bronwyn Long, DNP, MBA, RN, Jeffrey Kern, MD, Laurie L. Carr, MD (October 01, 2019) Lung cancer is caused by a variety of exposures to things in your environment over time, as well as the genetics of your family. Ongoing exposure to these environmental 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 people smoke 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 is lowered after giving up smoking, but never completely goes away. Secondhand smoke: Secondhand 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 is a fiber that occurs naturally. It is mined and milled and in the past was used in many applications and industries including in construction, ship building, and the automotive industry Family history of lung cancer in your immediate family, which 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, or having, 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 it depends on the type of exposure, how long you were exposed and your body’s response to these agents. Lung Cancer: Treatment Options Lung Cancer: Lifestyle Management Clinical Trials For more than 100 years, National Jewish Health has been committed to finding new treatments and cures for diseases. Search our clinical trials.