The main cause of COPD is smoking. In Canada, smoking causes over 80% of COPD cases. The longer and heavier a person smokes, the higher their risk.

Other causes of COPD include:

  • second-hand smoke
  • long-term exposure to air pollution, dust, chemicals and fumes
  • frequent and severe chest infections as a child
  • alpha-1 antitrypsin deficiency (a rare genetic condition)

COPD takes years to develop, so it is more common in people 40 and over.