Smoking cigarettes causes lung cancer. Harmful substances (carcinogens), found in tobacco, damage cells in the lungs. Over time, the damaged cells may become cancerous. The likelihood that a smoker will develop lung cancer is affected by the age at the person began smoking, how long the person has smoked, the number of cigarettes smoked per day, and how deeply the smoker inhales. Stopping smoking greatly reduces a person's risk for developing lung cancer.
…
