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Key value for chemical safety assessment

Additional information

OBSH was shown to be mutagenic in two reliable reverse mutation assays (OECD 471) with Salmonella typhimurium and Escherichia coli with and wihtout S9.

Further a reliable a mammalian chromosome aberation test (OECD 473) was positive with and without S9 and further a hepatocyte DNA repair test was positive in rat as well as mouse heaptocytes.

The genetic toxicity of OBSH in vivo was evaluated in a mammalian erythrocyte micronucleus test (OECD 474). It was concluded that OBSH did not induce micronuclei in mouse erythrocytes.

Although no structural anomalies were found in this vivo test OBSH must be suspeced to be a mutagen due to the clear positive in vitro tests showing direct mutagenic response, clastogenic response and response on DNA repair.


Short description of key information:
In in vitro bacterial reverse mutation tests (OECD TG 471), OBSH showed positive results in Salmonella typhimurium strains TA 98, TA 100, TA 1535 and/or Escherichia coli (WP2 uvrA) with or without S9 mix. In a chromosomal aberration test (OECD TG 473) with CHL cells and in a DNA repair test with rat and mouse hepatocytes, OBSH elicited positive results. However, in an in vivo mammalian erythrocyte micronucleus assay (OECD TG 474), OBSH did not exhibit mutagenic effects in mouse bone marrow cells at doses ranging from 375 to 1,500 mg/kg bw.

Endpoint Conclusion: Adverse effect observed (positive)

Justification for classification or non-classification

In summary, OBSH was shown to be mutagenic in two reliable reverse mutation assays (OECD 471) with Salmonella typhimurium and Escherichia coli with and wihtout S9.

Further a reliable a mammalian chromosome aberation test (OECD 473) was positive with and without S9 and also a hepatocyte DNA repair test was positive in rat as well as mouse heaptocytes.

In an in vivo OECD 474 OBSH did not induce micronuclei and chromosome aberations in mouse erythrocytes. Although no structural anomalies were found in this vivo test, OBSH with its reactive hydrazide structure most still be highly suspected to be a mutagen due to the clear positive in vitro tests showing direct mutagenic response, clastogenic repsonse and impact on DNA repair.

Based on this it is considered most appropriate to assign a classification with Muta 2 H341 to OBSH, as further more targeted in vivo testing on the direct mutagenic properties is considered superfluous as positive response is considered to be the most probable outcome.