No marked differences were found in serum aspartate aminotransferase and alkaline phosphatase activity between the two groups. No studies were available that report the effects of JP-8, JP-5, or DFM vapors on the liver in humans.
Studies in rats and mice had examined the toxic effects of JP-8 on the liver (MacEwen and Vernot 1983, 1984,1985). In subchronic inhalation studies, male and female F344 rats (10 of each) and male and female C57BL/6 mice (10 of each) were continuously exposed to JP-8 vapor at 500 or 1,000 mg/m3 for 90 days. Some groups of animals were killed immediately after the 90-day exposure, and others 2 wk, 2 months (mo), 9 mo, or 21 mo after the exposure. Immediately after exposure ceased, male rats showed increases in liver weights and liver:body weight ratios at 1,000 mg/m3, decreases in serum glutamic-pyruvic transaminase (SGPT) activity at 500 and 1,000 mg/m3, and decreases in alkaline phosphatase activity at 1,000 mg/m3; and female rats showed increases in liver weights and liver:body weight ratios at 500 and 1,000 mg/m3, increases in alkaline phosphatase activity at 1,000 mg/m3, and decreases in SGPT activity at 500 and 1,000 mg/m3. Nine months after exposure, male rats showed decreases in SGPT activity at 500 and 1,000 mg/m3. Twenty-one months after exposure, male rats showed concentration-related increases in liver:body weight ratios at 500 and 1,000 mg/m3; and female rats showed decreases in serum glutamic oxaloacetic transaminase (SGOT) activity at 500 mg/m3 and decreases in SGPT activity at 500 and 1,000 mg/m3. It should be emphasized that despite the significant changes observed in SGOT and SGPT activities, the alterations were within the normal range and thus not clinically relevant. Support for relevant changes in liver function would necessitate the measurement of liver enzyme functions and histopathologic studies, which were not conducted. No data on mice were presented.
The available data on potential hepatic toxicity associated with subchronic exposure to JP-8 vapor are not definitive, because histopathologic examinations were not performed. The liver weight changes observed in rats might indicate hyperplasia or hypertrophy. Alternatively, the increases in liver:body weight ratios might reflect a loss of body weight in the test animals during the study. It is also possible that JP-8 was offensive to the animals, nauseating them and decreasing their food intake.
Animal studies had also examined the liver effects from dermal or inhalation exposure to JP-4 or JP-5. Mild liver changes were observed in male and female beagles, male and female F344 rats, and male and female C57BL/6 mice exposed to JP-5 vapor continuously at 150 or 750 mg/m3 for 90 days (MacEwen and Vernot 1978, 1980, 1981, 1982, 1983, 1985; Gaworski et al. 1984). Similar results were reported in beagles, F344 rats, and C57BL/6 mice exposed to JP-4 vapor at 500 or 1,000 mg/m3 for 90 days (MacEwen and