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EC number: 203-052-4
CAS number: 102-77-2
In vitro data
Several Ames test results for MBS have been reported. Although the study
results are reliable the test design of the studies does not comply with
the current guideline with regard to the number and kind of tester
strains. However, several assays are comparable to a guideline study
(Monsanto Co 1976, 1978ab, CMA 1981). In these studies no biologically
relevant and dose dependent increases in revertants was evaluated in any
of the tester strains evaluated with and without metabolic activation.
This finding was confirmed in two HGPRT-assays with CHO cells. The test
substance was evaluated at concentrations of 0, 0.1, 0.3, 1, 3.0, 10,
30, 50, 100, 150, 300 µg/ml with and without metabolic activation.
Cytotoxicity was indicated at 100 µg/ml and higher without metabolic
activation and at 300 µg/ml with metabolic activation. At 50 µg MBS per
ml (without metabolic activation) the relative survival was 43 % and the
150 µg MBS per ml (with metabolic activation) gave a 36 % relative
survival. The test substance (OBTS purified) was negative in the
CHO/HGPRT assay with and without metabolic activation (CMA 1981). In the
second HGPRT assay, done with OPTS commercial, comparable results were
obtained (CMA 1984).
However, the test substance MBS induced in several mouse lymphoma assays
positive responses, mainly in presence of metabolic activation (Monsanto
1979, CMA 1981, Hinderer 1983). But all of these mouse lymphoma studies
reveal limitations which lower the validity of these findings.
Moreover, the test substance was evaluated in an in vitro chromosome
aberration assay, with limitations. CHO cells were treated with the test
substance up to 10 µg/ml in presence and absence of metabolic
activation. No biologically relevant increase in chromosome aberration
was noted (Hinderer 1983).
Inconsistent findings were noted in two E. coli DNA repair assays and
cell transformation assays, which showed positive and negative responses
(CMA 1981, Hinderer 1983).
In vivo data
The test substance MBS was evaluated for genotoxicity in the dominant
lethal test in groups of 10 Sprague-Dawley rats treated by gavage at
dose levels of 0, 125, 250 and 500 mg/kg bw/day. Following a 56 day
treatment each male was housed with two virgin female rats per week for
two weeks. The females were sacrified thirteen days after mating for
determination of dominant lethal effects. The treatment had no adverse
effects with respect to clinical signs, mortality rate, body weight
gain, or organ weights of adult rats. The treatment also had no effect
on pregnancy, early foetal death, implantation, or pre-implantation
losses in female rats; whereas treatment with the positive control
triethylenmelamine produced the expected dominant lethal effects.
The findings of the study indicated that the test substance MBS was not
mutagenic to the germ cells of male rats under the test conditions
No classification is required according to the classification criteria
67/548/EWG and regulation no. 1272/2008 (GHS).
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