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EC number: 202-049-5
CAS number: 91-20-3
Effects of Naphthalene on Nasal Passages
Dose in ppm
Eosinophilic inclusions (total)
Occasional degenerate cells (total)
Hyperplasia of basal cells (total)
Rosette formation (total)
Early squamous metaplasia - minimal
Loss of glands around dorsal meatus
Dilated gland ducts
Rats were exposed to test atmospheres containing naphthalene at
concentrations of 2, 10 and 58 ppm. Exposures were 6 hours continuous
each day, 5 days a week for 13 weeks.
Statistically significant reduced body weight gain was seen in
rats of both sexes exposed to 58 ppm and in male rats exposed to 10
ppm. The reductions in weight gain were associated with reduced food
consumption. Body-weight gain and food consumption were also minimally
lower than control values for other exposed groups/sexes, but did not
reach statistical significance.
Laboratory investigations revealed no evidence of
treatment-associated changes or systemic toxicity, and organ-weight
analysis and macroscopic findings at necropsy also revealed no adverse
Microscopic examination revealed treatment-related effects on the
nasal epithelium at all exposure levels. The severity of the effects was
dose-related. At the highest level (58 ppm) changes included erosion of
the olfactory epithelium, hyperplasia of basal cells in the olfactory
epithelium, loss of Bowman’s glands, hypertrophy of the respiratory
epithelium and other inflammatory changes.
At the lowest level of exposure (2 ppm) changes in the olfactory
epithelium were less marked but included slight disorganisation,
eosinophilic inclusions, occasional degenerate cells, minimal atrophy,
minimal erosion (in a single rat), minimal hyperplasia of basal cells,
minimal rosette formation, atrophic cells in Bowman’s glands and loss of
Bowman’s glands and presence of cysts. In addition dilated gland ducts
and squamous metaplasia (in a single rat) were also seen at the low
level of exposure (not dose-responsive).
A "No-Effect Level" for the nasal lesions was not established in
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