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Key value for chemical safety assessment

Additional information

No data is available on genetic toxicity for the test substance. However, reliable data from several in vitro studies and one in vivo study performed with CAS 16470-24-9; a close structural analogue, is available.

 

In vitro data:

An Ames test according to OECD TG 471 was performed with CAS 16470-24-9 (88.1% pure) to assess the mutagenic properties of the test substance. S. typhimurium TA 1535, TA 1537, TA 1538, TA 98 and TA 100 were treated with 10 - 5000 µg/plate of the test substance in bidest. water in the presence or absence of a metabolic activation system in a plate incorporation test. One pre-test and one experiment with triplicates per condition were performed. No increase of the mutation frequency was observed in any tester strain at any concentration. No toxicity was observed up to the maximum dose of 5000 mg/kg bw and weak precipitation occurred at the highest dose. The controls were valid and were within the historical control data. The use of 2-aminoanthracene as a sole indicator for the efficacy of the metabolic activation system is not recommended in the actual OECD TG 471 (adopted 1997), but was supposed not to affect the validity of the test. Although, no S. typhimurium TA 102 or E. coli strain was tested, as recommended in the actual guideline, the study is considered reliable and suitable for assessment and the substance is not proposed to be mutagenic in the Ames test (CIBA-GEIGY Ltd., 1987).

Supporting data is available from another Ames test performed according to a protocol similar to OECD TG 471 with CAS 16470-24-9 (80% pure). S. typhimurium TA 1535, TA 1537, TA 98 and TA 100 were treated with 4 – 2500 µg/plate of the test substance in DMSO in a plate incorporation assay with duplicates for each condition. All doses were tested with S9-mix in all strains and only the highest dose was tested additionally without S9-mix. No increase in mutation frequency was observed and no cytotoxicity occurred (Bayer AG, 1979a).

 

In a second in vitro test, performed according to OECD TG 473 and in compliance with GLP, the test substance (CAS 16470-24-9; 88.1% pure) was investigated on its ability to induce chromosome aberrations. Chinese hamster lung fibroblasts (V79) were treated with concentrations from 0.1 to 5.0 mg/mL for 4 hours with and without metabolic activation. Two cultures per conditions were evaluated. 5, 15.5 and 25.5 h after start of treatment (7, 18 and 28 h preparation interval, respectively) colcemid was added and the cells were harvested 2 h (7 h interval) or 2.5 h (18 and 28 h interval) for slide preparation. 2 slides per culture were prepared and100 metaphases per slide were analysed for chromosomal aberrations. Cytotoxicity was evaluated by colony forming ability and the mitotic index in a range-finding pre-experiment. A cytotoxic effect was seen at the highest concentration and an increase in chromosomal aberration was observed at 5.0 mg/mL (7 h interval, with S9). As only one slide could be evaluated because of the low number of cells in one slide, a second experiment was performed. The positive result could not be confirmed, thus, the test substance was not considered to induce structural chromosomal aberrations under the conditions chosen in this study. No polyploidy was detected. Appropriate solvent and positive controls were included and showed the expected results (CIBA-GEIGY Ltd., 1991).

 

In vivo data:

Induction of micronuclei in vivo was investigated in a reliable test performed according to OECD TG 474. 6 NMRI mice (10-week old) per group were treated with CAS 16470-24-9 (88.1% pure) at a dose of 5000 mg/kb bw per oral gavage. Polychromatic erythrocytes from femurs of all animals (5 per time point) were evaluated at 24, 48 and 72 h after treatment. 1000 polychromatic erythrocytes (PCE) were analysed per animal for micronuclei and no increase in the number of micronuclei was observed at any time point. Cytotoxicity was evaluated by the ratio between polychromatic and normochromatic erythrocytes and expressed in normochromatic erythrocytes per 1000 the PCEs. No toxic effect was observed. Cyclophosphamide was used as positive control and gave the expected increase in the number of micronuclei (CIBA-GEIGY Ltd., 1991).

A supporting study is available performed with CAS 16470-24-9 (78.7% pure). In a dominant lethal assay performed according to OECD TG 478 under GLP conditions, 50 male NMRI mice per group were once treated with 2500 and 5000 mg/kg bw of the test substance per oral gavage. The test showed absence of dominant lethal mutations (Bayer AG, 1995).

All available tests consistently yielded negative results indicating that the test substance has no mutagenic potential. Besides these negative findings on mutagenicity the test substance and structural related compounds are unlikely to be bioavailable after oral, dermal and inhalation exposure and therefore have not to be classified as germ cell mutagens. No carcinogenic properties were identified in rats.


Short description of key information:
In vitro:
Gene mutation (Bacterial reverse mutation assay/Ames): negative with and without metabolic activation in TA 1535, 1537, 1538, 98, and 100 (OECD 471); RA from CAS 16470-24-9
Chromosome aberration (OECD 473), V79: negative with and without metabolic activation; RA from CAS 16470-24-9
In vivo:
Chromosome aberration (micronucleus assay), mice: negative (OECD 474); RA from CAS 16470-24-9
Dominant Lethal Assay (OECD 478), mice: negative; RA from CAS 16470-24-9

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

The available data on genetic toxicity is reliable and suitable for classification. Based on this data, classification for genetic toxicity according to 67/584/EEC and EC/1272/2008 is not warranted.