ACUTE AND SUBCHRONIC INHALATION STUDIES ON TRIFLUOROIODOMETHANE VAPORIN FISCHER-344 RATS

Trifluoroiodomethane (CF3I) is being considered as a replacement compo und for halon fire suppressants. Its structure is similar to that of H alon 1301 (CF3Br), but it has very low ozone depletion potential compa red to CF3Br. As part of the process of developing environmental and h ealth effects criteria, acute, 2-week, and 13-week nose-only inhalatio n toxicity studies were conducted in Fischer 344 rats. In the acute st udy, three groups of 30 male rats each were ex-posed to 0 (control), 0 .5, or 1.0% (v/v) CF3I for 4 hr and euthanized immediately following e xposure, 3 days postexposure, or 14 days postexposure. There were no d eaths and no clinical signs of toxicity throughout the study. Histopat hologic examination of select tissues showed no lesions of pathologic significance. In the 2-week study, four groups of 5 male rats each wer e exposed for 2 hr/day, 5 days/week to 0, 3, 6, or 12% CF3I. No deaths were observed, though lethargy and slight incoordination were noted i n rats of the 6 and 12% groups at the conclusion of each daily exposur e. Mean body weight gains were depressed in rats of the 6 and 12% grou ps. Serum thyroglobulin and reverse T-3 (rT(3)) values were increased at all exposure levels. At necropsy, no gross lesions or differences i n absolute or relative organ weights were noted. Histopathologic exami nation of the thyroid and parathyroid glands indicated no morphologica l abnormalities in the CF3I-exposed rats. In the 13-week study, four g roups of 15 male and 15 female rats were exposed to 0, 2, 4, or 8% CF3 I 2 hr/day, 5 days/week for 13 weeks. Rats exposed to 4 or 8% CF3I had lower mean body weights than the controls. Deaths observed in the 2 a nd 8% groups were attributed to accidents resulting from the restraint system employed. Hematologic alterations were minimal and considered insignificant. Increases in the frequency of micronucleated bone marro w polychromatic erythrocytes were observed in rats of all three CF3I g roups. Serum chemistry alterations observed in rats of all CF3I exposu re groups included decreases in T-3 and increases in thyroglobulin, rT (3), T-4, and TSH. Relative organ weight increases (8% CF3I group) occ urred in the brain, liver, and thyroid glands; decreases were observed in the thymus and testes. A decrease in relative thymus weights and a n increase in relative thyroid weights were observed also in rats of t he 2 and 4% groups. Histopathological findings included a mild inflamm ation in the nasal turbinates of rats exposed to 4 or 8% CF3I, mild at rophy and degeneration of the testes (4 and 8% CF3I groups), and a mil d increase in thyroid follicular colloid content in rats of all CF3I e xposure groups. Though NOAELs were observed far select target organs ( e.g., nasal turbinates, testes), NOAELs were not apparent in all targe t organs examined (e.g., thyroid glands, bone marrow). (C) 1997 Societ y of Toxicology.