Occupational asthma: a spectrum of acute respiratory disorders

Occupational asthma is a general term applied to a variety of clinical disorders, each characterized by acute, reversible respiratory symptoms caused by exposure to environmental or work-related stimuli. The diverse pathologic basis for this group of disorders includes bronchoconstriction, airway inflammation and edema, toxic or inflammatory alveolitis/bronchiolitis, or noncardiogenic pulmonary edema. On the basis of the abnormalities and the mechanisms responsible for lung injury, occupational asthma may be classified as (1) toxic or inflammatory reactions: (2) immediate "allergic" hypersensitivity reactions; (3) hypersensitivity reactions of unknown origin; (4) irritant reactions; and (5) delayed hypersensitivity reactions. Physical and chemical properties of the causative agent, host factors, and intensity of exposure largely determine the type of reaction produced. At the practical level, different reactions may be distinguished on the basis of characteristic clinical features and laboratory findings. Therefore, an understanding of the different reaction categories is useful in the identification of specific causative agents, in successful patient management, and in the development of environmental safeguards.