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The potential of yttrium oxide to induce genetic toxicity was assessed in three in vitro studies performed according to OECD Guidelines and in compliance with GLP. All studies are used as Key studies and scored Klimisch 1.

Ames test:

A reverse gene mutation assay in bacteria was conducted according to EU Method B.13/14 guideline and in compliance with GLP (Sokolowski A, 2006). This study was scored as reliability 1 according to Klimisch criteria.

Strains TA1535, TA1537, TA98, TA100 and TA102 of S. typhimurium were exposed to yttrium oxide (99.36 %), at concentrations of 0 - 5000 µg/plate in the presence and absence of mammalian metabolic activation [plate co-incubation and pre-incubation].

Yttrium oxide was tested up to limit concentration (5000 µg/plate). The positive controls induced the appropriate responses in the corresponding strains. There was no evidence of induced mutant colonies over background in each strain with and without metabolic activation.

Mammalian Cell mutation in vitro (HPRT):

This test was scored 1 according to Klimisch criteria as it was conducted according to OECD 476 and in compliance with GLP.

The test item Yttrium Oxide was assessed for its potential to induce mutations at the HPRT locus using V79 cells of the Chinese Hamster.

Experiment I with and without metabolic activation and experiment II with metabolic activation were performed as a 4 h short-term exposure assay. Experiment II without metabolic activation was performed as 20 h long time exposure assay.

The test item was investigated at the following concentrations as single cultures:

Experiment I

without metabolic activation:

0.00316, 0.0100, 0.0316, 0.100, 0.316, 1.0, 2.5, 5.0, 7.5 and 10 mM

and with metabolic activation:

0.00316, 0.0100, 0.0316, 0.100, 0.316, 1.0, 2.5, 7.5 and 10 mM

Experiment II

without metabolic activation:

0.00316, 0.0100, 0.0316, 0.100, 0.316, 1.0, 2.5, 5.0 and 7.5 mM

and with metabolic activation:

0.025, 0.05, 0.1, 0.2, 0.4, 0.8, 1.6, 3.2, 6.4 and 10 mM

Precipitation of the test item was noted in experiment I at concentrations of 1.0 mM and higher (with and without metabolic activation). In experiment II precipitation was found at concentrations of 1.0 mM and higher (without metabolic activation) and at concentrations of 0.8 mM and higher (with metabolic activation).

Biologically relevant growth inhibition was observed in experiment I and II without metabolic activation. Inexperiment I without metabolic activation the relative growth was 41.6% for the highest concentration (10 mM) evaluated. The highest biologically relevant concentration evaluated with metabolic activation was 10 mM with a relative growth of 90.0%. In experiment II without metabolic activation the relative growth was 10.8% for the highest concentration (7.5 mM) evaluated. The highest concentration evaluated with metabolic activation was 10 mM with a relative growth of 79.2%.

In both experiments no biologically relevant increase of mutants was found after treatment with the test item (with and without metabolic activation).

No dose-response relationship was observed.

Chromosomal aberration in vitro:

The test was conducted according to OECD 473 and with GLP compliance and was scored 1 according to Klimisch criteria.

Blood samples were obtained from healthy donors not receiving medication. For this study (in each experiment) blood was collected from two donors. Blood samples were drawn by venous puncture and collected in heparinized tubes.

The cultures were treated at each concentration. The following concentrations were used in the main experiments:

Experiment I: Without and with metabolic activation, 4 h treatment, 24 h preparation interval: 0.3, 0.6, 1.2, 2.5, 5.0, 8.0 and 10.0 mM

Experiment II:

Without metabolic activation, 24 h treatment, 24 h preparation interval:

0.6, 1.2, 2.5, 5.0, 7.5 and 10.0 mM

With metabolic activation, 4 h treatment, 24 h preparation interval:

0.5, 1.0, 2.0, 4.0, 7.0 and 10.0 mM

The cells were treated in experiment I (without and with metabolic activation) for 4 h with the test item. The metaphases were prepared 24 h after the treatment. In experiment II without metabolic activation the cells were treated for 24 h and prepared at the end of the treatment. In experiment II with metabolic activation the cells were treated for 4 h and prepared 24 h after the treatment. The dose group selection for microscopic analyses of chromosomal aberrations are based on the mitotic index in accordance with the guidelines.

In experiment I and II no biologically relevant decreases of proliferation index were observed.

In experiment I and II with and without metabolic activation, the number of aberrant cells found in the cultures treated with the test item did not show a biologically relevant increase compared to the corresponding negative control. In addition, no dose-response relationship was observed.

In experiment II with metabolic activation only 140 instead of 200 cells could be evaluated due to precipitation at a concentration of 2 mM. However, the assessment of genotoxicity was still possible as at the higher concentration of 4 mM 200 cells could be evaluated.

EMS (400 and 600 µg/mL, respectively) and CPA (5 µg/mL) were used as positive controls and induced distinct and biologically relevant increases in cells with structural chromosomal aberrations, thus proving the ability of the test system to indicate potential clastogenic effects.

No biologically relevant increase in the frequencies of polyploid cells was found after treatment with the test item.

 


Justification for selection of genetic toxicity endpoint
No study was selected since all in vitro studies were negative.

Short description of key information:
Reverse gene mutation assay in bacteria (Ames test): negative with and without metabolic activation.
Mammalian cell gene mutation assay (HPRT locus) in vitro: negative with and without metabolic activation.
Chromosomal aberration in vitro in human lymphocytes: negative with and without metabolic activation. .

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

Based on negative results of the three mentioned genetic toxicity tests in vitro, the substance does not need to be classified according to GHS (Regulation (EU) 1272/2008).