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EC number: 202-705-0
CAS number: 98-83-9
In this study (design comparable to OECD Guideline 474),
groups of 10 male and 10 female B6C3F1 mice were exposed by whole-body
inhalation to alpha-methylstyrene at concentrations of 0, 75, 150, 300,
600 or 1000 ppm for 6 hrs per day and 5 days per week for 14 weeks.
No significant increases in the frequencies of
micronucleated erythrocytes were seen in blood samples of male mice
obtained at the conclusion of the 3-month study.
However, in female mice from the 3 -month study, a
significant increase in micronucleated NCEs was observed at the highest
exposure concentration of 1000 ppm, resulting in a negative call for
male mice and a positive call in this assay for female mice.
Reticulocytes (polychromatic immature erythrocytes; PCEs) were also
scored for frequency of micronucleated cells in male and female mice. No
increase in micronucleated PCEs was observed in either sex at the
highest exposure concentration of 1000 ppm, indicating that the damage
observed in the mature erythrocyte population in 1000 ppm females was
reflective of long-term accumulation of damage and was not detectable
immediately after exposure by analyzing recently-formed (within 48
Toxic effects (see also section 7.5.3):
Two females in the 1000 ppm group died before exposure on
day 3. Final mean body weights of 75, 300, and 1000 ppm females were
significantly less than those of the chamber controls; final mean body
weight gains of mice exposed to >= 300 ppm were also significantly less.
Ataxia was observed at 1000 ppm. The absolute liver
weights of >= 600 ppm females and the relative liver weights of >= 300
females were significantly increased. The oestrous cycle lengths of >=
600 ppm females were significantly longer than that of the chamber
controls. Minimal to mild centrilobular hypertrophy was present in the
livers of females at >= 600 ppm. The incidences of exposure-related
nasal lesions, including atrophy and hyperplasia of Bowman’s glands and
atrophy and metaplasia of the olfactory epithelium, were significantly
increased in all exposed groups. The incidences of hyaline degeneration,
characterized by the accumulation of eosinophilic globules in the
cytoplasm of the respiratory epithelium, were significantly increased in
females at >= 150 ppm.
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