Subchronic Vapor Inhalation Toxicity Studies on 3.1 Oil in Male Fischer 344 Rats

Abstract

3.1 Oil is a chlorofluorocarbon oil consisting of C6 and C8 oligomers of chlorotriflu-oroethylene. Physical properties such as high thermal stability, good lubricity, and high dielectric strength make 3.1 oil promising for potential use in hydraulic fluid systems. A previous inhalation study indicated that the liver is the target organ of 3.1 oil toxicity. Cross liver hypertrophy and microscopic hepatocytomegaly were the prime lesions noted. To determine a no-effect concentration, male Fischer 344 rats were exposed to air only, or vapor concentrations of 10, 50, or 250 mg 3.1 oil/m³ for 13 wk. Mean body weights of the highest concentration test group were slightly, but not significantly, depressed during the final two-thirds of the study. Alkaline phosphatase and blood urea nitrogen values were increased in this group at sacrifice. Significant concentration-related increases in relative kidney and liver weights occurred in the 250 and 50 mg 3.1 oil/m³ groups. Hyaline droplet distribution and severity was greater in the high-exposure group of rats. Hepatocytomegaly was a common finding in all rats exposed at these concentrations; however, this lesion resolved by dmo postexposure. Examination of hepatocytic ultrastructure revealed slightly swollen mitochondria in the two highest exposure groups. The number of peroxisomes per visual field was significantly greater in the highest exposure group only. The associated activity of peroxisomal β-oxidation of palmitoyl coenzyme A (CoA) also showed a concentration-dependent increase. Although an increase in this enzyme was noted, 70 mg 3.7 oil/m³ was identified as a no-effect level based on light and electron microscopic, hematologic, and in-life data.