Toxicological Sciences, Vol 48, 21-29, Copyright © 1999 by Society of Toxicology
W Daughtrey, P Newton, R Rhoden, C Kirwin, L Haddock, J Duffy, T Keenan, W Richter and M Nicolich
The carcinogenic and chronic toxicity potential of commercial hexane
solvent was evaluated in F-344 rats and B6C3F1 mice
(50/sex/concentration/species) exposed by inhalation for 6 h/day, 5
days/week for 2 years. Target hexane vapor concentrations were 0, 900,
3000, and 9000 ppm. There were no significant differences in survivorship
between control and hexane-exposed groups, and clinical observations were
generally unremarkable. Small, but statistically significant decreases in
body weight gain were seen in rats of both sexes in the mid- and
high-exposure groups and in high-expsoure female mice. The only noteworthy
histopathological finding in rats was epithelial cell hyperplasia in the
nasoturbinates and larynx of exposed groups. This response was judged to be
indicative of upper respiratory tract tissue irritation. No significant
differences in tumor incidence between control and hexane-exposed rats were
found. In mice, uterine tissue from the high-exposure females exhibited a
significant decrease in the severity of cystic endometrial hyperplasia
compared to controls. An increase in the combined incidence of
hepatocellular adenomas and carcinomas was observed in high-exposure female
mice. The incidence of liver tumors was not increased in the mid- or
low-exposure female mice or in male mice exposed to hexane. An increased
incidence of pituitary adenomas was observed in female, but not male mice.
This finding was not believed to have been treatment-related because the
incidence in the control group was unusually low, and the incidence in
exposed groups was not dose-related and was within the historical control
range. No other neoplastic changes judged to be treatment-related were
observed in tissues from male or female mice. In conclusion, chronic
exposure to commercial hexane solvent at concentrations up to 9000 ppm was
not carcinogenic to F-344 rats or to male B6C3F1 mice, but did result in an
increased incidence of liver tumors in female mice.
ARTICLES
Chronic inhalation carcinogenicity study of commercial hexane solvent in F-344 rats and B6C3F1 mice
Exxon Biomedical Sciences, East Millstone, New Jersey 08875-2350, USA.
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