Wiester, Mildred J., William P. Watkinson, Daniel L. Costa, Kay M. Crissman, Judy H. Richards, Darrell W. Winsett, and Jerry W. Highfill. Ozone toxicity in the rat. III. Effect of changes in ambient temperature on pulmonary parameters. J. Appl. Physiol. 81(4): 1691-1700, 1996.Pulmonary toxicity of ozone (O₃) was examined in adult male Fischer 344 rats exposed to 0.5 parts/million O₃ for either 6 or 23 h/day over 5 days while maintained at an ambient temperature (T_a) of either 10, 22, or 34°C. Toxicity was evaluated by using changes in lung volumes and the concentrations of constituents of bronchoalveolar lavage fluid that signal lung injury and/or inflammation. Results indicated that toxicity increased as T_a decreased. Exposures conducted at 10°C were associated with the greatest decreases in body weight and total lung capacity and the greatest increases in lavageable protein, lysozyme, alkaline phosphatase activity, and percent neutrophils. O₃ effects not modified by T_a included increases in residual volume and lavageable potassium, glucose, urea, and ascorbic acid. There was a progressive decrease in lavageable uric acid with exposure at 34°C. Most effects were attenuated during the 5 exposure days and/or returned to normal levels after 7 air recovery days, regardless of prior O₃ exposure or T_a. It is possible that T_a-induced changes in metabolic rate may have altered ventilation and, therefore, the O₃ doses among rats exposed at the three different T_a levels.