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EC number: 203-733-6
CAS number: 110-05-4
Table – Clinical chemistry at the end of the exposure period (mean
N=10; * p<0.05
Table – Absolute and relative organ weights (mean value±SD):
N=10; * p<0.05; ** p<0.01
The toxicity of di-tert-butyl peroxide CAS#
110-05-4 upon repeated exposure by inhalation was studied in a
sub-chronic (90-day) study with Wistar Hannover rats. The study included
a micronucleus test. The target concentrations for this study (100, 300
and 1000 mg/m3 as low-, mid- and high-concentration, respectively) were
selected on the basis of a 14-day range-finding study in which groups of
five male and five female Wistar Hannover rats were exposed to target
concentrations of 100, 1000, and 10,000 mg/m3 for 6 hours/day, 5
days/week. In this 14-day study treatment-related findings at 10,000
mg/m3 consisted of signs of discomfort during exposure in rats of both
sexes (trembling of the tail, restlessness), slightly retarded growth in
males (mainly on exposure days), and increased relative weights of the
liver in both sexes and of the adrenals and kidneys in males. Trembling
of the tail and restlessness during exposure were also observed at the
lower exposure levels but to a lesser extent than at the high exposure
level. The only other treatment-related change at the lower exposure
levels was a slight increase in relative kidney weight in males of the
The sub-chronic (main) study included four
groups of 10 rats/sex. The animals were exposed nose-only, 6 hours/day,
5 days/week for 13 consecutive weeks (resulting in 65 exposure days in
total) to the above target concentrations or to clean air for the
control group. Endpoints to assess toxicity included clinical and
ophthalmoscopic observations, growth, food consumption, haematology,
clinical chemistry and organ weights. In addition, the animals were
examined grossly at necropsy, and a large number of organs and tissues
were examined microscopically. Five male rats of each group were used to
examine possible damage to the chromosomes and/or mitotic apparatus in
bone marrow cells collected at scheduled sacrifice.
The target concentrations were accurately
achieved as demonstrated by the results of total carbon analysis of the
test atmospheres. The overall mean actual concentrations (± standard
deviation of the daily mean concentration) were 101 (± 3), 299 (± 3) and
993 (± 10) mg/m3 for the low-, mid- and highconcentration level
All animals survived until scheduled
sacrifice. Clinical and ophthalmoscopic observations, growth and food
consumption results, haematology values, most clinical chemistry values,
most organ weights, and necropsy and histopathology findings showed no
Clinical chemistry values showed slight but
statistically significant changes in the plasma levels of cholesterol
(increased) and creatinine (decreased) at the high concentration in male
and female rats, respectively. These findings were considered to be of
no toxicological significance.
The relative weights of the liver and
kidneys were slightly (about 10%) but statistically significantly
increased in male rats of the high-concentration group. In female rats
of this group relative liver weight was increased to about the same
extent but the difference from controls was not statistically
significant. Though these organ weight changes were related to
treatment, they were considered not to represent adverse effects of the
test material because of the modest magnitude of the increases and the
absence of corroborative histopathological alterations or clinical
chemical indicators of organ damage.
Microscopic examination of bone marrow
smears of male rats revealed no signs of toxicity to the bone marrow and
no evidence of chromosomal damage and/or damage to the mitotic apparatus
of bone marrow erythrocytes. There was no reason to assume that the
negative bone marrow response was due to lack of systemic exposure
because treatment-related systemic effects (including increases in liver
and kidney weight) occurred in male rats of the high-concentration
group. Positive controls (five male rats treated with the mutagen
Mitomycin C) showed the
expected bone marrow response (cytotoxicity
and increased number of micronucleated polychromatic erythrocytes).
Under the conditions of this study exposure
to di-tert-butyl peroxide CAS# 110-05-4 resulted in a few modest changes
at the highest concentration tested (increases in liver and kidney
weight and altered plasma levels of cholesterol and creatinine). No
treatment-related changes were observed at the lower concentrations.
Since the changes at the high-concentration were considered not to
constitute adverse effects, this exposure level (993 mg/m3 actual
concentration) was a No-Observed- Adverse-Effect Concentration (NOAEC).
The micronucleus test incorporated in this
study revealed no chromosomal damage and/or damage to the mitotic
apparatus of bone marrow erythrocytes.
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