The main risk factor for COPD is smoking. Most people who have COPD smoke or used to smoke. People who have a family history of COPD are more likely to develop the disease if they smoke.
Long-term exposure to other lung irritants also is a risk factor for COPD. Examples of other lung irritants include secondhand smoke, air pollution, and chemical fumes and dust from the environment or workplace. (Secondhand smoke is smoke in the air from other people smoking.)
Most people who have COPD are at least 40 years old when symptoms begin. Although uncommon, people younger than 40 can have COPD. For example, this may happen if a person has alpha-1 antitrypsin deficiency, a genetic condition.