Chronic obstructive pulmonary disease is the only one of the top four or five leading causes of death in the U.S. with worsening epidemiological trends. Cigarette smoking accounts for approximately 85 percent-90 percent of cases, but the other 10 percent-15 percent of the attributable risk still represents a substantial fraction of this disease that remains unexplained. Recently, several studies, in various countries, have addressed whether certain occupational exposures (primarily those relating to dusts, vapors, gases, and/or fumes) are potential risk factors for COPD. Most of these studies have shown elevated odds ratios or relative risks, although not always to a statistically significant level.