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EC number: 232-140-5
CAS number: 7789-00-6
All mice survived to the end of the study. Final mean body weights and
body weight gains of mice exposed to 125 mg/L or greater and the body
weight gains of 62.5 mg/L male mice were significantly less than those
of the controls. Male and female mice exposed to 125 (except males at
week 13), 250, 500, or 1000 mg/L consumed less water than the respective
control groups. Exposure concentrations of 62.5, 125, 250, 500, and 1000
mg/L resulted in average daily doses of approximately 9, 15, 26, 45, and
80 mg/kg to mice. No clinical findings were attributed to sodium
dichromate dihydrate exposure.
Mice demonstrated an erythrocyte microcytosis (decrease in mean cell
volume) similar to that seen in the NTP rat study. However, the mice
were much less affected, and no contradictory data from hematocrit
values or mean cell hemoglobin concentrations, as described for rats,
occurred for mice. The decreases in mean cell hemoglobin reflected the
mean cell volume decrease. Similar to the occurrence at week 14 in the
rat studies, erythrocyte counts increased, and hemoglobin concentrations
decreased, but only in females.
Absolute liver weights of males exposed to 250 mg/L or greater and
females exposed to 500 or 1,000 mg/L were significantly less than those
of the respective controls, but liver weights relative to body weights
were unchanged. Relative kidney weights of males exposed to 1,000 mg/L
were significantly greater than those of the control group. Other
differences in organ weights were attributed to the reduced body weights
of the mice.
In the duodenum, the incidences of minimal to mild epithelial
hyperplasia were significantly increased in all exposed groups, and
severities increased slightly with increasing exposure concentration.
Compared to the controls, the duodenal villi were short, thick, and
blunted, the crypts elongated, and diffuse hyperplasia of the crypt
epithelium extended towards the tips of the villi. The hyperplasic
epithelial cells were tall, columnar, densely packed, and stained more
basophilically than the shorter columnar epithelial cells lining the
duodenal villi of the control mice. There were also increased numbers of
mitotic figures in the hyperplastic epithelium. In addition, the
epithelial cells lining the tips of the villi of many of the exposed
mice were swollen and had vacuolated cytoplasm. Collectively, these
duodenal lesions suggest regenerative hyperplasia secondary to previous
epithelial cell damage or degeneration. In mice receiving 125 mg/L or
greater, the incidences of minimal to mild histiocytic cell infiltration
in the duodenum and mesenteric lymph nodes (except 500 mg/L males) were
significantly increased. Histiocytic cell infiltration in the duodenum
and the mesenteric lymph nodes was morphologically similar to that
observed in the duodenum and pancreatic lymph nodes of rats. Slight
glycogen depletion in hepatocytes was noted in exposed groups, but
because it was associated with poor weight gain or diminished food
intake, it is not considered to be a direct effect of treatment.
Reproductive tissue evaluations in found no significant differences from
controls in left cauda epididymis, left epididymis, or left testis
weights or in spermatid measurements or epididymal sperm motility for
any of the exposed groups.
In study 1, groups of 10 male and 10 female B6C3F1 mice were given
drinking water containing 0, 62.5, 125, 250, 500, or 1000 mg sodium
dichromate dihydrate/L for 3 months. Dose levels were equivalent to
average daily doses of approximately 9, 15, 26, 45, or 80 mg/kg; on a
molecular weight basis, doses are equivalent to approximately 3.1, 5.2,
9.1, 15.7, and 27.9 mg/kg Cr (VI) per day. All mice survived to the end
of the study. Reduced body weights occurred in male and female mice
exposed to 125 mg/L or greater. Water consumption by male and female
mice exposed to 125 mg/L or greater was generally less than that by the
control groups. A microcytic hypochromic anemia was seen in mice, but
the severity was less than in the comparable NTP rat study. The
incidences of histiocytic cellular infiltration were generally
significantly increased in the duodenum and the mesenteric lymph node of
mice exposed to 125 mg/L or greater. Incidences of epithelial
hyperplasia of the duodenum were significantly increased in all exposed
groups of mice.
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