Pathology of Pulmonary Disease From Exposure to Interdependent Ambient Gases (Nitrogen Dioxide and Ozone)

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Abstract
Nitrogen dioxide (NO2) and ozone (O3) are capable individually of inducing emphysema in rats exposed to high subacute concentrations. Mixtures of NO2 and O3 at levels reached in severe smog were used to estimate the degree of injury sustained by rats exposed to these ambient, interdependent, photochemically produced gases. Histologically, the major site of injury was at the level of the junction of the respiratory bronchiole and the alveolar duct, somewhat more peripherally than the lesion caused by NO2 alone. Ozone, the more toxic component, was largely responsible for the injury at the selected concentrations and for the characteristic fibroblastic activity in that region. The observations suggest that potential injury from ambient smog would result mainly from O3, whereas injury from tobacco smoke would be due largely to its relatively high concentration of NO2. The indications are that smoking and residing in smoggy areas would be additively injurious.