Pulmonary Function Studies in the Rat Addressing Concentration Versus Time Relationships of Ozone

Abstract Recent data from human studies suggest that the current 1 hr National Ambient Air Quality Standard (NAAQS) for O 3 may not be appropriate for exposures of several hours. Animal studies are being used to further investigate this issue: (1) A polynomial model has been developed to depict lung injury from the interaction of O 3 concentration (C) and exposure duration (T). The model was derived from lung fluid protein values in rats exposed in a matrix design to 0.1 to 0.8 ppm O3 for 2, 4, or 8 hrs. Airway dysfunction was correlated only at the highest CxT products. (2) Rats, exposed to 0.5 or 0.8 ppm O 3 for 2 or 7 hours with intermittent 8% CO 2 to augment ventilation, were evaluated with static and dynamic lung function tests. Protein leakage into the airspace was also assessed. Although, the impact of T on O 3 toxicity appeared to be C-dependent, loss of function was not necessarily linear. Collectively, these studies provide a preliminary basis for the evaluation of duration of exposure on the pulmonary response to O 3 .