Last updated: Sep 26, 2016

The top three causes of chronic obstructive pulmonary disease (COPD) are smoking, smoking, and smoking.

Tobacco smoke inflames and irritates the airways in your lungs and gradually damages the air sacs that provide oxygen to the blood. This limits the amount of air that can flow into and out of the lungs.

However, even nonsmokers and ex-smokers can get COPD. Exposure to secondhand smoke, air pollution, and chemical fumes can also cause COPD, as can exposure to dust in the workplace or in the environment. Other COPD risk factors include low birth weight and rare genetic factors.

In rare cases, an alpha-1 antitrypsin deficiency can play a role in the development in COPD. Alpha-1 antitrypsin is a naturally occurring enzyme that protects your lungs from damage. Some people are born with a gene variant that results in a deficiency of alpha-1 antitrypsin. There are no symptoms of this deficiency, but if you have the gene, you can develop chronic obstructive pulmonary disease (COPD) more easily and at a younger age than those with adequate amounts of alpha-1 antitrypsin. 

Smoking is particularly dangerous for those with alpha-1 antitrypsin deficiency; if you smoke and develop COPD at an early age (before age 45), your doctor may test you for the gene. However, because the condition is rare, not everyone is tested for an alpha-1 antitrypsin deficiency.