COPD can be caused by many factors, although the most common cause is cigarette smoke. Environmental factors and genetics may also cause COPD. For example, heavy exposure to certain dusts at work, chemicals, and indoor or outdoor air pollution can contribute to COPD. The reason why some smokers never develop COPD and why some never-smokers get COPD is not fully understood. Hereditary (genetic) factors probably play a role in who develops COPD.