Smoking is the leading cause of COPD. The more a person smokes, the more likely that person will develop COPD. However, some people smoke for years and never get COPD.In rare cases, nonsmokers who lack a protein called alpha-1 antitrypsin can develop emphysema.Other risk factors for COPD are:Exposure to certain gases or fumes in the workplaceExposure to heavy amounts of secondhand smoke and pollutionFrequent use of cooking fire without proper ventilation