Smokers may have pre-cancerous lesions in their mouth that can lead to cancer of the mouth and larynx.

The smoke weakens the free-roving scavenger cells that remove foreign particles from the air sacs of the lungs. Continued exposure to smoke affects elastin, protein that keeps the lungs flexible, predisposing you to emphysema.

The compounds you inhale are deposited on the lining of your throat and bronchi, and in the delicate air sacs of your lungs. A pack-a-day for one year amounts to 8 ounces of tar in your lungs. This tar has high levels of cancer causing chemicals including radioactive polonium 210.

When carbon monoxide is inhaled into the lungs, it preempts oxygen, readily combining with hemoglobin, as a result, poorly oxygenated blood is circulated out to the body. Low levels of carbon monoxide causes shortness of breath; higher levels can result in death by asphyxiation. (This is why people die when they inhale car fumes in an enclosed space.)

The chemistry of cigarette smoke includes:

• cyanide (which has been used for executions)
• formaldehyde
• methanol (wood alcohol)
• acetylene (the fuel used in torches)
• ammonia.