Hydrocarbons, C4, n-butene conc.

Endpoint summary

Additional information

There are no specific studies on the streams in the C4 low 1,3-butadiene category (CAS Numbers; 91052-98-1, 92045-23-3, 95465-89-7) but mutagenicity data are available on the component substances. Butane, isobutane and the butene isomers were all negative in genotoxicity tests under conditions where positive control substances gave the expected results. All streams within this category contain less than 0.1% w/w 1,3-butadiene and therefore the content of 1,3-butadiene has no impact on their genotoxicity. The available data therefore indicates that members of this category are not likely to be mutagenic in humans and therefore classification is not warranted under Dir 1999/45/EC or GHS/CLP.

 

 

Specific data are as follows:

 

Butane: In vitro, key bacterial mutation assays have been conducted in the presence and absence of metabolic activation. Butane was not mutagenic in this test system (Kirwin and Thomas 1980, NTP, 2005). An in vitro, key, mammalian cell cytogenetic assay has been conducted in the presence and absence of metabolic activation. Butane caused no increases in the frequencies of chromosome aberrations in this assay (Safepharm, 2008). No mammalian in vivo genotoxicity data are available for butane but it was negative in the Sex Linked Recessive Lethal assay in drosophila (NTP, 2005).

 

Isobutane: In vitro, a key bacterial mutation assay has been conducted in the presence and absence of metabolic activation. Isobutane was not mutagenic in this test system (Kirwin and Thomas, 1980). No in vivo genotoxicity data are available for isobutane.

 

Butene isomers (butenes): In vitro bacterial mutation tests on all isomers were negative in the presence and absence of metabolic activation Araki (1994) Safepharm (1992). 2-Butene has been tested in vitro in a chromosome aberration study (Safepharm 1992) where it was not clastogenic to rat lymphocytes in vitro in the presence and absence of metabolic activation. This result is also supported by other negative in vitro genetic toxicity studies on 2-methylpropene; a micronucleus assay in human lymphocytes (Jorritsma et al 1995), a mouse lymphoma mutation assay (IRI 1981a) and a mammalian cell transformation assay (IRI 1981b) were negative. In vivo, a key bone marrow micronucleus assay on 2-methylpropene (Exxon 1990), and a mouse peripheral blood micronucleus test (NTP 1998) were both negative.

 

 

There is no data on the genetic toxicity of the component substances in humans.

Short description of key information:
There are no specific genotoxicity studies on the streams in the C4 low 1,3-butadiene category (CAS Numbers; 91052-98-1, 92045-23-3, 95465-89-7, 95465-90-0 and 95465-91-1) but data on the component substances (butane, isobutane and butene isomers) indicate that members of this category are not genotoxic in vitro or vivo under conditions where positive control compounds gave the expected results. The streams within this category contain less than 0.1% w/w 1,3-butadiene and therefore this has no impact on their genotoxicity. The available data therefore indicates that members of this category are not likely to be mutagenic in humans.

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

There are sufficient data available on component substances to conclude that streams within the C4 low 1,3-butadiene category are not genotoxic therefore no classification is warranted under Dir 1999/45/EC or GHS/CLP.The genotoxic effects of this category will be not driven by the content of 1,3-butadiene as this is less than 0.1% w/w for all category members and therefore exempt from classification/hazard assessment based on this substance.