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 CS 2 (AL CS 2) concentration and the modified iodine-azide test (IAT) were compared as indicators of CS 2 exposure. Rats were exposed to 15 (∼5 ppm), 30, 60, or 120 mg/m 3 of CS 2. Exposure to 15 or 30 mg/m 3 of CS 2 could not be detected by the modified IAT. However, a linear relationship between blood CS 2 (free or AL CS 2) concentrations and these exposure levels was observed. Free CS 2 is eliminated rapidly, while AL CS 2 is eliminated very slowly from the exposed subjects. Repetitive daily exposures (8 hr/day) to 120 mg/m 3 of CS 2 were carried out in rats. Blood AL CS 2 concentrations in exposed rats increased with each successive exposure while the free CS 2 level remained relatively constant. By the sixth or seventh daily exposure the blood AL CS 2 concentration was about 2.5 times that of the first 8-hr exposure and about 3 times the level of free CS 2. These results indicated an appreciable accumulation of CS 2 in subjects repeatedly exposed to low concentrations of the solvent. Rats were also exposed to CS 2 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 CS 2 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 CS 2 was not totally eliminated during the 2-day nonexposure period. In in vitro experiments, the binding profile of CS 2 to human blood was remarkably similar to that of rats exposed to CS 2 by inhalation.