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EC number: 204-066-3
CAS number: 115-11-7
in vitro and in vivo data available for the butenes category indicates
that category members are not genotoxic.
bacterial mutation studies (Ames tests) on all isomers (butene,
but-1-ene, 2-butene and 2-methylpropene) are provided by Araki (1994)
and a key study on 2-butene is provided by Safepharm (1992a). Supporting
studies on 2-methylpropene are provided by Cornet et al (1992), NTP
(1998) and Shimizu et al (1985). In all studies, category members were
not mutagenic in the presence or absence of metabolic activation; the
results from positive control compounds indicate that the assay and
metabolic activation system were functioning within the acceptable range.
was tested in vitro for clastogenic (Safepharm 1992b) and mutagenic
(Envigo 2015) properties in the presence or absence of metabolic
activation in rat lymphocytes and L5178Y mouse lymphoma cells,
respectively. Both studies produced negative results, and metabolic
activation had no effect. 2-Methylpropene also gave negative results in
vitro; a micronucleus assay in human lymphocytes (Jorritsma et al 1995)
and a mouse lymphoma mutation assay (IRI 1981a) were both negative. In
addition, a mammalian cell transformation assay with 2-methylpropene
(IRI 1981b) was also negative in the presence or absence of metabolic
activation. In all cases, positive control compounds gave the expected
results, demonstrating that the studies were robust.
in vivo genotoxicity of 2-methylpropene was examined in a key bone
marrow micronucleus assay (Exxon 1990), in which mice were exposed to
concentrations up to 10,000 ppm (22,948 mg/m3) for 2 days. No
statistically significant increase in micronucleus formation in the bone
marrow was observed; therefore 2-methylpropene was not clastogenic in
this assay. A peripheral blood micronucleus test was also conducted
during a repeat dose toxicity test with 2-methylpropene, in which mice
were exposed via inhalation for 14 weeks at 500, 1000, 2000, 4000 and
8000 ppm (1147, 4589, 18,359 mg/m3). No increases in the frequency of
micronucleated normochromatic erythrocytes were seen in peripheral blood
samples in either sex (NTP 1998).
of the overall database on genotoxicity data for all the butene isomers
within this category, together with the negative rat and mouse
carcinogenicity studies conducted on 2-methylpropene, indicate that
there is minimal likelihood that butenes category members present a
of the butenes category are not genotoxic and therefore do not warrant
classification under GHS/CLP.
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