A Method for Assessing the Physiological Impairment Produced by Low-level Exposure to Pulmonary Irritants

A sensitive means is needed for discovering and measuring early and minimal degrees of pulmonary impairment following exposure to pulmonary irritants. Reduction in the rate of respiratory uptake of carbon monoxide is shown to provide such early and sensitive test. A simple apparatus and test procedure are described for measuring CO uptake in unanesthetized rats. By this method, measurable degrees of pulmonary impairment were demonstrated following short exposures (30 minutes) to phosgene in the concentration range from 5 ppm down to less than 1 ppm. Measurable reduction in CO uptake rate was found in animals, the lungs of which could not be distinguished histologically from those of unexposed animals.