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Key value for chemical safety assessment

Additional information

In vitro gene mutation study in bacteria (Ames test):

In the key study (Bowles 2010) Salmonella typhimuriumstrains TA1535, TA1537, TA98, TA100 and Escherichia coli strain WP2uvrA-were treated with suspensions of the test material using both the Ames plate incorporation and pre-incubation methods at five dose levels, in triplicate, both with and without the addition of a rat liver homogenate metabolising system (10% liver S9 in standard co-factors). The dose range was determined in a preliminary toxicity assay and was 50 to 5000 µg/plate in the first experiment.The experiment was repeated on a separate day (pre-incubation method) using the same dose range as Experiment 1, fresh cultures of the bacterial strains and fresh test material formulations.No toxicologically significant increases in the frequency of revertant colonies were recorded for any of the bacterial strains, with any dose of the test material, either with or without metabolic activation or exposure method. The test material was therefore considered to be non-mutagenic under the conditions of the test.

In vitro cytogenicity study in mammalian cells (chromosome aberration test):

In the key study (Morris 2010) duplicate cultures of human lymphocytes, treated with the test material, were evaluated for chromosome aberrations at three dose levels, together with vehicle and positive controls. Three treatment conditions were used for the study, i.e. 4 hours exposure in the absence of metabolic activation (S9) with a 20-hour expression period, 4 hours in the presence of an induced rat liver homogenate metabolising system (S9), at a 2% final concentration with cell harvest after a 20-hour expression period and a 24 hours continuous exposure in the absence of metabolic activation.

The test material was non-toxic and did not induce any statistically significant increases in the frequency of cells with aberrations, in any of the exposure conditions, using a dose range that included a dose level that was the lowest precipitating dose level.

In vitro gene mutation study in mammalian cells (mouse lymphoma assay):

In the key study (Flanders 2010) one main experiment was performed. In this main experiment, L5178Y TK +/- 3.7.2c mouse lymphoma cells (heterozygous at the thymidine kinase locus) were treated with the test material at six dose levels in duplicate, together with vehicle (R0 medium) and positive controls. The exposure groups used were as follows: 4-hour exposures both with and without metabolic activation, and 24–hour exposure without metabolic activation. The dose range of test material was selected following the results of a preliminary toxicity and was 2.5 to 40 μg/ml for all three of the exposure groups. The test material did not induce any toxicologically significant dose-related increases in the mutant frequency at any dose level, either with or without metabolic activation, in any of the three exposure groups.

Short description of key information:
Kieselguhr soda ash flux calcined was tested for genotoxicity in an Ames (OECD TG 471) , chromosome aberration (OECD TG 473) and a mouse lymphoma assay (OECD TG 476). Results were negative in all three tests.

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

Results were negative in a full set of reliable in vitro genotoxicity studies and therefore no classification is warranted