Cause
Most
lung cancer is caused by smoking. Over 85% of lung
cancers are related to smoking.2 Cancer-causing
substances (carcinogens) in tobacco smoke damage lung cells. Over time, these
damaged cells may develop into lung cancer.
The risk of getting lung cancer is related to how long you have
smoked and how many cigarettes you smoke each day.3
Quitting smoking reduces your risk for getting cancer, and your risk continues
to go down as long as you do not smoke. Even cutting down how much you smoke
may reduce your risk (but not as much as quitting completely).4
If you live with a smoker, you have 2 to 3 times the risk of
developing 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
Studies show that women have a similar risk of lung cancer as
men.6 However, the chemicals in tobacco smoke may
affect women differently than men.
Exposure to other harmful substances, such as
asbestos, radioactive dust, or
radon, increases the risk for lung cancer. Exposure to
radiation such as X-rays later in life may also increase risk.7