Smoking damages the flexible air sacs, or alveoli, that help the lungs absorb oxygen and remove carbon dioxide when a person breathes in and out, the American Lung Association states. Damaged air sacs gradually lose flexibility and circulate less oxygen into the bloodstream, causing frequent shortness of breath.
The lungs have a natural cleaning system made up of hairlike projections, or cilia, that help trap irritants, the University of Pittsburgh Medical Center explains. Smoking affects the amount of cilia and how quickly they respond to irritants, leaving the lungs vulnerable to foreign particles. At the same time, smoking increases the number of mucus-producing cells, clogging the airways and making them susceptible to infection from irritants that the lungs normally clear.
Prolonged smoking causes irreparable deterioration of the air sacs and cilia, often leading to chronic conditions, such as emphysema, according to the American Cancer Society. The breakdown of alveoli decreases the amount of surface area available to support oxygen flow, hindering the lungs’ ability to store enough air to power the respiratory system even when a person is at rest. In the most severe cases, irreversible lung failure forces patients to rely on oxygen tubes. Chronic smoker’s cough is a common symptom of damaged cilia, which stop working for hours after cigarette exposure. During and after periods when an individual isn’t smoking, such as sleep, the cilia must work harder to clean out the harmful backup of mucus and pollutants.