Pathologic Sequences from Exposure to Ozone and NO2

Abstract

Exposure of the lung to ozone and nitrogen dioxide leads to interesting acute and chronic injury. Brief exposure to low levels of these gases results in desquamation of epithelial cells and transitory reduction in the number of pulmonary macrophages. Inflammation of the airway, as evidenced by an influx of polymorphonuclear cells, also occurs at this stage. Very rapid regeneration of epithelial cells occurs, resulting in distinctively altered epithelial pattern, and is fairly complete by 72 hours after exposure. Macrophages also increase in number. If exposure is continued over longer periods of time, chronic changes ensure. These consist of fibrosis of the terminal airway, gross enlargement of the lung, loss of air spaces, and subtle derangement of the connective tissue fibrils. Eventually, the experimentally exposed animals possess an enlarged, inelastic lung occupying a distorted thoracic cage. Other changes will be described from slides.