What causes lung cancer?

What causes lung cancer?
Most lung cancer is caused by smoking. 2, 3 Harmful substances in tobacco smoke damage the lung cells. Secondhand smoke is also a risk factor for lung cancer. 3

Besides smoking, exposure to harmful substances such as arsenic, asbestos, radioactive dust, or radon can increase the risk for lung cancer. If you have more than one of these risk factors—for example, you are a smoker and you are also exposed to asbestos—you greatly increase your risk of developing lung cancer. Radiation exposure from work, medical, or environmental sources may also increase your risk for lung cancer.

The most effective way to prevent lung cancer is not to smoke. If you do smoke, you can reduce your risk for lung cancer by quitting now. Your risk will gradually decrease over 10 to 15 years as your lungs recover. The sooner you quit, the better.