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Key value for chemical safety assessment

Additional information

Reverse gene mutation assay

A key study was identified (Reynolds, 1991). In a reverse gene mutation assay in bacteria performed according to the OECD test guideline No. 473 and in compliance with GLP, strains TA 1535, TA 97, TA 98 and TA 100 of S. typhimurium were exposed to Cis-2-pentenenitrile (99.97% pure) in DMSO at concentrations of 0, 500, 1000, 2000, 3000, 4000 and 5000 µg/plate in the presence and absence of mammalian metabolic activation (S-9 mix from male Crl:CD rat injected i.p. with Aroclor 1254). There was no evidence of induced mutant colonies over background in this study. Three other studies with reliability 2 showing negative results with and without metabolic activation were considered as supporting studies (Taylor, 1978 ; Seifried, 2005 ; Zeiger, 1992). In an other study (Reynolds, 1990) a weak positive trend was noted in TA97 and TA98 and was confirmed in strain TA98 without activation. Since this positive trend may be due to a contaminant and because 2-Pentenenitrile did not meet the criteria for a positive finding it is classified as ambiguous. This study was not considered as relevant since the results may due to a contaminant.

In vitro cytogenicity study in mammalian cells

In an in vitro chromosome aberration test performed according to the OECD guideline No. 473 and in compliance with GLP (Donner, 2004), Chinese hamster ovary cells were exposed to cis-2-Pentenenitrile at concentrations of 0, 324.2, 648 and 810.5 µg/mL without metabolic activation and 0, 60.79, 121.6 and 162.1 µg/mL with metabolic activation (rat liver homogenate metabolising system). Cis-2-pentenenitrile was tested up to limit concentration (10 mM).Two treatment conditions were used for the study: 4-hour exposure followed by a 16-hour expression period (with and without S9) and 20-hour exposure (without S9 only). In the 4- and 20-hour non-activated test systems, the percentage of cells with structural aberrations in the test substance-treated groups was not significantly increased above that of the solvent control at any concentration. In the 4-h S9 activated test system, the percentage of cells with structural aberrations in the 121.6 and 162.1 µg/mL test substance-treated groups was statistically significant (p<0.05, Fisher's exact test and Cochran-Armitage test). Under the test conditions, cis-2-Pentenenitrile was considered to be clastogenic to hamster ovary cells in vitro.

In vitro gene mutation study in mammalian cells

In a mammalian cell gene mutation assay (Seifried et al., 2005) performed similarly to OECD 476, cis-2-pentenenitrile diluted in water was tested in the agar version of L5178Y mouse lymphoma assay. The test substance was tested in the mutagenesis assay over a range of concentrations from 0.10 to 1.0 µL/mL for the non-activated cultures, and from 0.004 to 0.040 µL/mL for the S-9 activated cultures. Both the nonactivated and S-9 activated cultures produced significant increases in mutant frequency over that of the solvent control cultures. Under the test conditions employed in this study, cis-2-pentenenitrile induce mutation at the tk locus of L5178Y mouse lymphoma cells.

In vivo genotoxicity

In a Swiss CFLP mouse bone marrow micronucleus assay, 10 males/dose were treated by oral gavage with cis-pentene-2-nitrile commercial (purity unknown) at doses of 0, 2 x 0.02 and 2 x 0.1 mL/kg bw. Bone marrow cells were harvested at 6 hours post-treatment. The vehicle was arachis oil. Cis-pentene-2-nitrile commercial was tested at an adequate dose (based on a preliminary study results). The positive control induced the appropriate response. There was not a significant increase in the frequency of micronucleated polychromatic erythrocytes in bone marrow after treatment. However, there are relevant methodological deficiencies in this study: only male mice were tested, the administrated volume was higher than recommended. Moreover, animals were sacrificed 6 hours after the last administration instead of 18-24 hours corresponding to a suitable time for the test substance absorption, metabolism and/or cell cycle kinetic interactions.

Regarding the whole studies, in vitro tests showed a clastogenic effect of the cis-pentene-2-nitrile in CHO cells while no mutation wasn't induce neither in the bacteria nor in mammalian cells (CHO). However, cis-2-pentenenitrile induce mutation at thetk locus of L5178Y mouse lymphoma cells

Thus, it is not possible to draw any conclusion based on the in vitro genotoxicity of the cis-pentene-2 -nitrile even if the results of mutagenicity tests are generally of higher significance. According to the REACH guidelines, animals tests are, in general, be needed for the clarification of the relevance of positive findings. However, the in vivo micronucleus study performed with the test substance is not considered as reliable considering animal sacrifice time (see above) and leads to inconclusive results.

Short description of key information:
Bacterial reverse mutation assay / Ames test: S. typhimurium TA 1537, TA 97, TA 98 and TA 100: negative with and without metabolic activation.
In vitro cytogenicity study / Chromosome aberration test: clastogenic to hamster ovary cells.
In vitro gene mutation / Mouse lymphoma assay: mutagenic
In vivo gene mutation / Micronucleus assay: no significant increase in the frequency of micronucleated polychromatic erythrocytes. However, animals were sacrificed 6 hours after the last administration instead of 18-24 hours.

Endpoint Conclusion:

Justification for classification or non-classification

Based on results of the above studies, the genotoxic potential of cis-2 -pentenenitrile is inconclusive. Therefore, a further assessment is needed to estimate this potential (in vivo test). However, such test is not required for isolated transported intermediates under strictly controlled conditions.