Air pollution referable to increased ambient levels of sulfur dioxide and suspended particulates is associated with increased episodes of acute bronchitis and is also causally related to some cases of chronic bronchitis. Oxidant air pollution is associated with abnormalities of pulmonary function in children and is a major contributory factor in COP, especially bronchitis, in some areas of the United States. The relationship of nitrogen dioxide atmospheric contamination to COPD is still controversial. In our opinion, the epidemiologic studies conducted to date have been inadequate and further elucidation is indicated. Cadmium fumes and compounds have been found to be instrumental in the development of some cases of chronic bronchitis and emphysema in Sweden. This association is unproved in the United States and warrants a thorough clinical and epidemiologic evaluation.