Blood-bound carbon disulfide: an indicator of carbon disulfide exposure, and its accumulation in repeatedly exposed rats

Abstract

Carbon disulfide is present in exposed subjects in free and bound or acid-labile forms. Sensitivities of the blood acid-labile CS2 (AL CS2) concentration and the modified iodine-azide test (IAT) were compared as indicators of CS2 exposure. Rats were exposed to 15 (approximately 5 ppm), 30, 60, or 120 mg/m3 of CS2. Exposure to 15 or 30 mg/m3 of CS2 could not be detected by the modified IAT. However, a linear relationship between blood CS2 (free or AL CS2) concentrations and these exposure levels was observed. Free CS2 is eliminated rapidly, while AL CS2 is eliminated very slowly from the exposed subjects. Repetitive daily exposures (8 hr/day) to 120 mg/m3 of CS2 were carried out in rats. Blood AL CS2 concentrations in exposed rats increased with each successive exposure while the free CS2 level remained relatively constant. By the sixth or seventh daily exposure the blood AL CS2 concentration was about 2.5 times that of the first 8-hr exposure and about 3 times the level of free CS2. These results indicated an appreciable accumulation of CS2 in subjects repeatedly exposed to low concentrations of the solvent. Rats were also exposed to CS2 8 hr/day for 5 days. After a 2-day nonexposure period (Days 6 and 7), the animals were reexposed on Day 8. The blood AL CS2 concentration in animals exposed on Day 8 was substantially higher than in those that received a single 8-hr exposure (Day 1), despite the hiatus on Days 6 and 7. These results indicated that blood AL CS2 was not totally eliminated during the 2-day nonexposure period. In in vitro experiments, the binding profile of CS2 to human blood was remarkably similar to that of rats exposed to CS2 by inhalation.