For exposure-response array data display purposes, the following results were coded (control and no effect findings were coded as "0", treatment-related increases were coded as "1", and treatment-related decreases were coded as "-1".

"Microscopic examination of specimens taken from all study animals did not reveal any treatment-related lesions. Lesions noted were considered to be nonsignificant, spontaneous findings not related to exposure."

"Statistical analysis of the histopathologic results revealed no treatment-related effects as a result of the 13-week inhalation exposure. In the 21-day inhalation study (Kinkead et al., 1990), foci of hepatic single cell necrosis was reported as a significant treatment-related finding at 0.25 mg CPFB/liter. This finding was not noted in the histologic results of this study at the same exposure level. Because of the different findings between the two studies, the hepatic tissues of both studies were reviewed. Using incidence defined as present or absent, and a severity scoring system based on relative number of necrotic foci in liver sections, the review disclosed that the finding was present in the original study. However, the slightly increased number of these foci in dosed animals compared to control animals, coupled with a severity that did not exceed minor or very slight, suggests an exposure-induced lesion that is statistically significant (p < 0.01), but biologically insignificant."

Female F-344 Rats