Comparison of inflammation elicited in animals receiving various mass doses of UFCB and FCB suspended in BALF. A comparison of inflammation elicited in animals receiving various mass doses of UFCB and FCB suspended in BALF at 1 day (Panel A), 7 days (Panel B), and 42 days (Panel C) post-exposure. Rats were exposed to various mass doses of UFCB and FCB by intratracheal instillation. Animals were euthanized at 1 day, 7 days, and 42 days post-exposure, and bronchoalveolar lavage was performed. Inflammation was assessed by BAL PMN counts. Values are increased PMN number above the BALF control and are given as means ± SEM of 8 rats. Control PMN values were 1.45 ± 0.22 × 106, 1.09 ± 0.14 × 106, and 1.01 ± 0.14 × 106 cells/rat for 1, 7 and 42 days respectively. Linear regression analysis with a 95% confidence interval reveals that on a mass dose basis UFCB causes significantly more inflammation than FCB at all post-exposure time points. On a mass dose basis, UFCB is shown to be approximately 65 times more potent than the FCB at all post-exposure time points. * indicates a significant increase from control (p < 0.05; ANOVA).