Toxicological Sciences, Vol 52, 278-288, Copyright © 1999 by Society of Toxicology
MJ Derelanko, WE Rinehart, RJ Hilaski, RB Thompson and E Loser
The toxicity of trivalent chromium compounds; chromic oxide and basic
chromium sulfate, was investigated in rats in a 13-week nose-only
inhalation study that included a 13-week recovery period. Nose-only
exposures to insoluble chromic oxide dust at 4.4, 15, or 44 mg/m3 or
soluble basic chromium sulfate dust at 17, 54, or 168 mg/m3 (trivalent
chromium equivalent concentrations of 3, 10, and 30 mg/m3) were carried out
for 6 h/day, 5 days/week. No compound-related mortality occurred. General
toxic effects, only observed with high-exposure levels of basic chromium
sulfate, included sporadic signs of labored breathing and depressed body
weights. No apparent compound-related effects were noted for sperm motility
or morphology, for any concentration of either test material.
Bronchoalveolar lavage fluid evaluations showed test material in
mononuclear cells with chromic oxide and increased neutrophils, protein,
lactic dehydrogenase and cellular debris with basic chromium sulfate. The
principle effects for both materials were primarily to the respiratory
tract. Chromic oxide caused pathological changes in the bronchial and
mediastinal lymphatic tissue and lungs, consisting of the presence of
pigment-laden macrophages, lymphoid and septal hyperplasia, and
interstitial inflammation similar to that observed with other inert dusts.
Basic chromium sulfate produced more severe and widespread effects in the
nasal cavity, larynx, lungs, and mediastinal lymph node. Effects were
characterized by accumulation of foreign material, infiltration of alveolar
macrophages, septal cell hyperplasia, and granulomatous and chronic
inflammation. Pigment was still present in chromic oxide and, to a lesser
extent, in basic chromium sulfate- treated animals after the 13-week
recovery period, with partial recovery of the pathological lesions. A NOAEL
was not established for either test material, but 4.4 mg/m3 was thought to
be near the NOAEL level for subchronic exposure to chromic oxide. The
results of this study indicate significant differences in toxicity to the
respiratory tract between trivalent chromium compounds chromic oxide and
basic chromium sulfate. These are likely related to differences in acidity
and water solubility, rather than chromium concentration per se. This
conclusion is substantiated by the lack of effect on other internal organs.
ARTICLES
Thirteen-week subchronic rat inhalation toxicity study with a recovery phase of trivalent chromium compounds, chromic oxide, and basic chromium sulfate
AlliedSignal, Inc., Morristown, New Jersey, USA.
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