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Key value for chemical safety assessment

Additional information

Read-across from strontium chloride and strontium nitrate to strontium hydroxide:

Based on the negative results in thein-vitro tests for the soluble strontium compounds (SrCl2: ca. 1000 - 2000 g/L, 0 - 40 °C and Sr(NO3)2: ca. 700 - 800 g/L, 25 °C) and assuming that the mutagenic/genotoxicity effects will be based on the cation concentration, read across to the soluble Sr(OH)2(ca. 20 g/L, 25°C) is considered to be justified and will likely lead to rather conservative no-effect levels.

Nevertheless, tests on the mutagenic potential of strontium compounds in bacteria are considered dispensable for principal considerations, since inorganic metal compounds are frequently negative in this assay due to limited capacity for uptake of metal ions (Guidance on information requirements and chemical safety assessment, Chapter R.7a, p. 387; HERAG facts sheet mutagenicity, Chapter 2.1).

It is concluded that strontium nitrate did not induce micronuclei in cultured human peripheral blood lymphocytes following treatments in the absence and presence of an Aroclor induced rat liver metabolic activation system (S-9 mix). Based on read-across the same is considered true for strontium hydroxide. Concentrations were tested and analysed up to 2116 µg/mL.

It is concluded that strontium nitrate did not induce mutation at the tk locus of L5178Y mouse lymphoma cells when tested under the conditions employed in this study . Based on read-across the same is considered true for strontium hydroxide.

These conditions included treatments up to precipitating concentrations in two independent experiments, in the absence and presence of a rat liver metabolic activation system (S-9 mix).

Further testing of in vivo genetic toxicity tests is not considered necessary.


Justification for selection of genetic toxicity endpoint
Three in vitro key studies are available addressing bacterial reverse mutation, in vitro gene mutation and chromosome aberration for strontium chloride and strontium nitrate respectively. Read-across between strontium chloride or strontium nitrate and strontium hydroxide is performed and fully justified (see discussion below). Due to the outcome of these tests strontium hydroxide could be regarded to have no mutagenic / genotoxic potential.

Short description of key information:
Strontium substances have been tested in bacterial reverse mutation assays, in vitro gene mutation and chromosome aberration test.
- in-vitro gene mutation in bacteria (OECD 471): negative (no data is available for Sr(OH)2, thus read-across from SrCl2 to Sr(OH)2 was performed)
- in-vitro gene mutation in mammalian cells (OECD 476): negative (no data is available for Sr(OH)2, thus read-across from Sr(NO3)2 to Sr(OH)2 was performed)
- in-vitro chromosome aberration (OECD 473): negative (no data is available for Sr(OH)2, thus read-across from Sr(NO3)2 to Sr(OH)2 was performed)

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

All available reliable studies showed no genetic toxicity for strontium chloride or strontium nitrate. Read-across between these two compounds and strontium hydroxide is performed. Thus, strontium hydroxide could be regarded to have no mutagenicity / genotoxicity effects, tested in vitro. Hence, no classification and labelling is required.