- When a burning cigarette is inhaled, thousands of different chemicals enter the lungs, including nicotine, carbon monoxide and tar. These toxins affect the lungs in a variety of ways.
- The lungs are lined by a network of fibers called cilia, which strip inhaled air of antibodies. Smoking both slows cilia down and destroys it, hampering the lungs' primary cleaning mechanism.
- Cells amidst the cilia produce mucus, which transfers dirt and other pathogens back up the throat and out of the body. Smoking causes these cells to produce excess amounts of mucus, making the smoker congested and prone to coughing.
- Because the cigarette smoke has also impaired the cilia, some of the mucus remains in the lungs and airway, increasing the smoker's chances of bronchial infection.
- Smoking also damages lung tissue, harming the organ's elasticity and subsequently, its ability to contract and exhale old air. The smoker becomes unable to properly draw in new air and grows short of breath, even while at rest. This condition is called emphysema.
- The chemicals in cigarettes have been shown to alter cells, making them cancerous. Because cigarette smoke impacts the lungs first and foremost, smokers are far more susceptible to lung cancer than nonsmokers.