Risk factors for lung cancer include:

• Tobacco use. Smoking and chewing tobacco are related to developing lung cancer, as well as to cancer of the mouth and throat. Over 85% of lung cancers are related to smoking.² More than half of the people who are newly diagnosed with lung cancer are former smokers. Smoking unfiltered, high-tar cigarettes may put you at a higher risk than smoking filtered or low-tar cigarettes, although this has not been proved. The risk of developing lung cancer increases:
  • The longer you smoke.
  • The more cigarettes you smoke each day.
• Exposure to tobacco smoke, such as living with a smoker. If you live with a smoker, you have 2 to 3 times the risk for lung cancer compared with a person who lives in a nonsmoking environment.⁵ About 25% of nonsmokers who develop lung cancer probably get it from being exposed to secondhand smoke.³
• Marijuana use. Smoking one marijuana cigarette, or a joint, may affect the lungs as much as smoking a pack of cigarettes.⁸
• Exposure to certain chemicals, such as arsenic, asbestos, radioactive dust, or radon.
• Radiation exposure from occupational, medical, or environmental sources.