The leading cause of lung cancer is caused by smoking.
Tobacco smoke contains many harmful substances that damage cells.
Over time, these cells can become cancerous. A person who smokes a lot, has a higher risk of getting cancer not just lung cancer, but also cancers of the mouth, esophagus, throat, kidney, larnyx, cervix, bladder, and pancreas. It is quite clear that thousands of lives could be saved each year if people did not smoke. The risk of lung cancer begins decreasing slowly as soon as a person quits smoking. The earlier the age at which a person quits, the closer a former smoker's risk of lung cancer will approach the risk for a person who never smoked.