Causes
Smoking is the main cause of COPD. It causes the airways to produce excess mucus that lines the walls of the airways, making the air passages very narrow. This makes it easier to get a bronchial infection. An infection can cause even more damage to the airways by causing more mucus production. Cigarette smoking also destroys the air sacs where gas exchange takes place, making the lungs more "floppy" and work less efficiently.
Less common causes of COPD include a rare genetic disorder called alpha-1 antitrypsin deficiency, air pollution, exposure to occupational dusts and chemicals, and frequent lower respiratory infections during childhood.