Time course of ozone-induced neutrophilia in normal humans

Five normal human subjects were exposed for 1 h to filtered air (FA) once and to 0.3 ppm O₃ on 3 separate days. Bronchoalveolar lavage (BAL) fluid was obtained < 1 h after FA and either < 1, 6, or 24 h after O₃ exposure. FEV₁ was measured before the exposures and the BAL. The first aliquot [proximal airway (PA) sample] was analyzed separately from the pooled Aliquots 2 through 4 [distal airway and alveolar surface (DAAS) sample]. The data from the PA and DAAS samples were then combined to calculate the values that would have been obtained by pooling all BAL washes. FEV₁ was significantly (p < 0.05) decreased 1 h after O₃ exposure, but it returned to preexposure values at 6 and 24 h after O₃. The percent of neutrophils in the PA sample was significantly elevated at < 1 h (3.7%) at 6 h (16.5%), and at 24 h (9.2%) after O₃. The percent of neutrophils in the DAAS sample and calculated pooled values were significantly elevated at 6 h (4.1 and 7.6%) and at 24 h (5.1 and 5.8%) after O₃. These data demonstrate that O₃-induced symptoms, FEV₁ decrements, and airway neutrophilia follow different time courses and indicate that the pooling of BAL washes may obscure the detection of an O₃-induced bronchiolitis. The degree of neutrophilia in the BAL did not correlate with the sensitivity of the individual subjects when measured by acute changes in FEV₁, suggesting a dichotomy of pathways that result in O₃-induced airway neutrophilia and pulmonary function decrements.