De. Dodd et al., ACUTE AND SUBCHRONIC INHALATION STUDIES ON TRIFLUOROIODOMETHANE VAPORIN FISCHER-344 RATS, Fundamental and applied toxicology, 35(1), 1997, pp. 64-77
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.