Causes

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Cigarette Smoke. Smoking causes 87% of all cases of lung cancer, accounting for 28% of all cancer deaths (about 157,000 in 2001). Cigarettes, nicotine or both may contribute to lung cancer in one of more of the following ways:

In general, chronic exposure to nicotine may cause an acceleration of coronary artery disease, peptic ulcer disease, reproductive disturbances, esophageal reflux, hypertension, fetal illnesses and death, and delayed wound healing.

• The smoke is the most dangerous component of the cigarette. Chemicals formed during smoking trigger genetic mutations that lead to cancer. When people inhale cigarette smoke, they bring tar into their lungs that include 4,000 chemicals, some of which are carcinogenic. Other inhaled chemicals in cigarette smoke that may increase the risk for cancer include cyanide, benzene, formaldehyde, methanol (wood alcohol), acetylene (the fuel used in torches), and ammonia. Smoke also contains nitrogen oxide and carbon monoxide, both of which are harmful gases.
• Nicotine itself may be a hazard. A 2000 laboratory study suggested that the human body might be converting inhaled nicotine into a chemical called aminoketone, which has been linked to the formation of tobacco-related lung cancer. And a 2001 study reported that nicotine triggered new blood vessel growth, which could theoretically promote growth of any existing tumors. Whether or not these studies apply to long-term use of nicotine replacement products (such as patches), as well as from cigarette smoking, is still unclear. (They should certainly not discourage people from using nicotine replacement methods for quitting, but may indicate that these devices should not be used on a long-term basis.)