Tripotassium propylsilanetriolate

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

No reliable information is available for tripotassium propylsilanetriolate, however, a reliable bacterial mutagenicity study is available for the structural analogue trimethoxypropylsilane, and reliable data are available for the structural analogue substance triethoxyisobutylsilane 17980-47-1 forin vitrocytogenicity and bacterial and mammalian gene mutation;in vivomicronucleus data are also available for triethoxyisobutylsilane.

In vitro:

Gene mutation (Bacterial reverse mutation assay / Ames test): read-across from structural analogue trimethoxypropylsilane: negative with and without metabolic activation inSalmonella typhimuriumstrains TA 98, TA, 100, TA 1535 and TA 1537 (according to OECD TG 471 1983) (Ebert, R (1996)).

Gene mutation (Bacterial reverse mutation assay / Ames test): read-across from structural analogue triethoxyisobutylsilane: negative with and without metabolic activation inSalmonella typhimuriumstrains TA 98, TA, 100, TA 1535, TA 1537 and TA 1538 (similar to OECD TG 471) (Hüls (1996)).

In vitrocytogenicity: read-across from structural analogue substance triethoxyisobutylsilane: negative with and without metabolic activation in CHO cells (according to OECD TG 473 1983) (May (1992)).

Mammalian gene mutation: read-across from structural analogue substance triethoxyisobutylsilane: negative with and without metabolic activation in Chinese hamster ovary (CHO cells (according to OECD TG 476 1984) (Ebert, R (1991)).

In vivo:

Micronucleus assay in mouse (oral gavage study): read-across from structural analogue triethoxyisobutylsilane: negative (OECD TG 474) (HRC (1988)).

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Description of key information

Micronucleus assay in mouse (oral gavage study): read-across from structural analogue triethoxyisobutylsilane: negative (OECD TG 474) (HRC (1988)).

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

Genetic tox data for potassium methylsilanetriolate added - to be discussed when cytogenicity result is available - if not agreed will need to be removed

No reliable information is available for tripotassium propylsilanetriolate, however, a reliable bacterial mutagenicity study is available for the structural analogue trimethoxypropylsilane (CAS 1067-25-0), and reliable data are available for the structural analogue substance triethoxyisobutylsilane (CAS 17980-47-1) forin vitrocytogenicity and bacterial and mammalian gene mutation;in vivomicronucleus data are also available for triethoxyisobutylsilane.

In addition, information from reliable bacterial and mammalian gene mutation assays is available for the related substance potassium methylsilanetriolate.

The structural analogue trimethoxypropylsilane hydrolyses rapidly (hydrolysis half-life 4.6 hour at 20°C) forming propylsilanetriol and methanol; the registered substance dissociates under aqueous conditions producing propylsilanetriolate and free potassium ions. Under comparable conditions of concentration and pH, propylsilanetriolate is equivalent to the parent acid propylsilanetriol. Potassium ions are ubiquitous in nature and important in metabolism and are not of concern for genetic toxicity. The second structural analogue, triethoxyisobutylsilane, hydrolyses to a similar organosilane, (2 -methylpropyl) silanetriol and ethanol. None of the functional groups of the substances or their hydrolysis products is associated with genetic toxicity (OECD, (2004a); OECD, (2004b)), and it is considered scientifically justified to read-across between these substances. Additional information is given in a supporting report (PFA, (2013aa)) attached in Section 13 of the IUCLID 5 dossier. Further discussion of read-across can be found in Section 1.4.

Trimethoxypropylsilane was chosen as read-across substance as it has the same propyl side-chain as the registered substance and it hydrolyses to propylsilanetriol which is equivalent to the registered substance under comparable conditions of pH and concentration. Triethoxyisobutylsilane was chosen as read-across substance as it has a similar side-chain, and hydrolyses to a structurally analogous silanetriol. None of the substances includes features that are structural alerts for genetic toxicity (Benigniet al.(2008)).

The structural analogue tripotassium propylsilanetriolate has been tested in a reliable bacterial mutagenicity assay conducted according to OECD 471and in compliance with GLP (Ebert, R (1996)). Both the original study and read-across to the registered substance are considered to be reliability 2. No mutagenic effect was observed for the test substance up to limit or cytotoxic concentration in any of the test strains in two independent experiments without and with metabolic activation. Appropriate positive and solvent controls were included and gave expected results. It is concluded that the test substance is negative for mutagenicity to bacteria under the conditions of the test.

Further evidence for lack of mutagenicity to bacteria is provided by the structural analogue triethoxyisobutylsilane, which has been tested for mutagenicity to bacteria, in a reliable study which was conducted according to the appropriate EU guideline, compliant with GLP (Hüls (1996)). Both the original study and read-across to the registered substance are considered to be reliability 2. No evidence of a test-substance related increase in the number of revertants was observed with or without activation in the initial or the repeat experiments usingSalmonella typhimuriumstrains TA 98, TA 100, TA 1535, TA 1537 and TA 1538. It is concluded that the test substance is negative for mutagenicity to bacteria under the conditions of the test.

No data are available for mutagenicity to a bacterial strain capable of detecting cross-linking or oxidising mutagens. In view of the lack of genetic toxicity demonstrated in studies on mammalian cells [andin vivo], and the absence of structural features that indicate that such mutagenicity is likely, testing in an appropriate 5th strain is not considered necessary. In addition, many of the organosilanes and organosiloxanes have been tested in an appropriate 5th strain, and the only one of these substances which has given a positive result in a bacterial strain capable of detecting cross-linking or oxidising mutagens contains an epoxy- side-chain (which is associated with cross-linking mutagenicity), and this substance was also positive inSalmonella typhimuriumstrains TA 100, TA 1535 as well as in E. coli WP2 uvrA, so it is not expected that testing in an appropriate fifth strain would add to the information on genetic toxicity of this substance.

The structural analogue triethoxyisobutylsilane has been tested in a reliable study conducted according to OECD 473 and under GLP (May (1992)). Both the original study and read-across to the registered substance are considered to be reliability 2. No increase in the number of cells with aberrations was observed either with or without metabolic activation. Cytotoxicity was not reported. Solvent and positive controls gave expected results. It is concluded that the test substance is negative for the induction of chromosome aberrations under the conditions of this study.

The structural analogue triethoxyisobutylsilane has been tested in a reliable study according to OECD 476 and in compliance with GLP (Ebert, R (1991)). Both the original study and read-across to the registered substance are considered to be reliability 2. No statistically and biologically significant increases in the mutant frequency were observed with or without activation in either the initial or the repeat experiment. Appropriate solvent and positive controls were included and gave expected results. It is concluded that the test substance is negative for mutagenicity to mammalian cells under the conditions of the test.

The structural analogue triethoxyisobutylsilane has been tested for the induction of micronuclei in mice according to OECD TG 471 and under GLP conditions (HRC (1988)). The original study was considered reliability 1. Read-across to the registered substance is considered scientifically justified and is reliability 2. No evidence was seen of a test substance induced increase in the incidence of micronucleated polychromatic erythrocytes in mice bone marrow. The ratio of normochromatic to polychromatic erythrocytes was not affected by the test substance indicating lack of toxicity to bone marrow cells. It is concluded that the test substance does not cause damage to chromosomes under the conditions of the test.

Justification for classification or non-classification

Based on the available read-across genetic toxicity data, tripotassium propylsilanetriolate is not classified for mutagenicity according to Regulation (EC) No 1272/2008.