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Administrative data

Key value for chemical safety assessment

Additional information

Genetic toxicity in vitro

In a reverse mutation assay using 4 strains ofS.typhimurium(TA1535, TA1537, TA98 and TA100) with and without metabolic activation (rat liver S9 homegenates), 2,3 dichloro-1,3 butadiene (99% pure) was mutagenic in strains TA1535 with metabolic activation and in strains TA100 and TA98 with and without metabolic activation.

Although the cytogenicity of 2,3 dichloro-1,3 butadiene has not been assessed in vitro, negative responses were obtained a rat bone marrow micronucleus study and it is not considered necessary to repeat the investigation using an in vitro assay.

An HRPT assay of 2,3 dichloro-1,3 butadiene for gene mutation was negative.

Genetic toxicity in vivo

2,3 dichloro-1,3 butadiene showed no clastogenic activity in vivo after whole body exposures of rats to vapour concentrations of up to 200 ppm (1020 mg/m3). Clear evidence of bone marrow and systemic toxicity were observed at 200 ppm. No statistically significant increases in micronucleated polychromatic erythrocytes in rat bone marrow where observed in micronucleus assay in which rats were exposed by whole body inhalation to 2,3 dichloro-1,3 butadiene at 0, 50, 100 and 200 ppm for 6 hours/day on two consecutive days.


Short description of key information:
The genetic toxicity of 2,3 dichloro-1,3 butadiene has been investigated in standard and non-standard studies in vitro and in vivo. 2,3 dichloro-1,3 butadiene was found to be mutagenic in bacteria in the presence and absence of metabolic activation in a series of in vitro Ames tests but was not found to be clastogenic in a bone marrow micronucleus assay in which rats were exposed by inhalation to 2,3 dichloro-1,3 butadiene vapours up to 200 ppm. Additionally a guideline conform mammalian cell gene mutation assay (HPRT) test 2,3 dichloro-1,3 butadiene was negative.

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

Positive results obtained in bacterial mutagenicity tests suggest that 2,3 dichloro-1,3 butadiene may have some genotoxic potential in vitro, with or without metabolic activation. However, negative results were obtained in an in vivo bone marrow micronucleaus assay in which rats were exposed to 2,3 dichloro-1,3 butadiene by inhalation. An HPRT assay of 2,3 -dichlorobutadiene for gene mutation was also negative.

Overall, based on a weight-of-evidence consideration 2,3 dichloro-1,3 butadiene is judged as negative, and a classification of

2,3 dichloro-1,3 butadiene is not recommend.