Abstract
Abstract The comparative toxicity of NO 2 was studied in five species: mice, rats, guinea pigs, rabbits, and dogs. Fifty parts per million was a critical concentration; below this value mortality rarely occurred with exposures up to 8 hours. A study was made of the sequential development of pathologic changes in the lung with grading of edema, congestion, interstitial irritation, bronchiolitis, and interstitial fibrosis. Acute deaths were characterized by marked bronchiolitis, desquamated bronchial epithelium, infiltration by polymorphonuclear cells, and edema fluid in the alveoli. Interstitial fibrosis occurred in about one-third of the surviving animals at 30 days and persisted in some for periods up to 6 months. Stress induced by exercise following exposure, by adrenalectomy, or by high levels of CO 2 increased mortalities. Toxic responses were separated into four clinical and pathologic entities: acute asphyxia secondary to laryngeal edema and spasm; acute pulmonary lung edema; bronchiolitis and pneumonia; and permanent, nonincapacitating residua in the lung.
Published Version
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