Respiratory tract lesions in guinea pigs exposed to sulfuric acid mist.

Guinea pigs were exposed inhalation chambers to 25 mg/m3 sulfuric acid mist 6 h/d for 2 d, and the acute respiratory effects were correlated by light and electron microscopy. This concentration of acid was selected since lower concentrations result in only slight effects while higher concentrations result in death. By light microscopy, the most prominent pulmonary lesion at 48 h was segmental alveolar hemorrhage and edema accompanied by proliferation of alveolar macrophages and type 2 pneumocytes. The segmental distribution of the pulmonary lesion was reaffirmed by scanning electron microscopy, while transmission electron microscopy showed injury to the distal airways and changes in the vascular endothelium.