Epidemiological studies of the general population conducted over the past thirty years have demonstrated a causal relationship between exposure to dust, gases, fumes, and vapors and chronic bronchitis or the development of obstructive lung disease (OLD). The proportion of chronic obstructive pulmonary disease (COPD) risk attributable to occupational exposure has been estimated at approximately 15%. The mining industry, construction and public works, foundries and steel mills, the textile industry, the grain sector (silo workers), dairy production, and pig farming are the occupational sectors for which the existence of a causal relationship is best established. The main hazards causing occupational COPD are crystalline silica, coal dust, cotton dust, grain dust, and endotoxins. Since 1988, regulatory measures have been gradually implemented to provide compensation for certain occupational COPD cases, but the medical criteria are very restrictive, and many causes are not listed in the occupational disease schedules. (R.A.)