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Ecotoxicological information

Toxicity to terrestrial plants

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Description of key information

Toxicity to terrestrial higher plants: IC50 (14-day): 209 mg/kg dry weight for effects on root dry mass in Hordeum vulgare, read-across from an analogous substance, decamethylcyclopentasiloxane (D5, CAS 541-02-6) within the Reconsile Siloxanes Category.

EC50 (14-day): >4054 mg/kg dry weight for effects on seedling emergence, root and shoot length and root and shoot dry mass in Trifolium pratense, read-across from an analogous substance, decamethylcyclopentasiloxane (D5, CAS 541-02-6) within the Reconsile Siloxanes Category.

Key value for chemical safety assessment

Short-term EC50 or LC50 for terrestrial plants:
209 mg/kg soil dw

Additional information

There are no data describing the long-term toxicity of the registered substance to terrestrial plants. However, data are available for the siloxane decamethylcyclopentasiloxane (D5, CAS: 541-02-6). A short-term (14-day) IC50value of 209 mg/kg dry weight has been determined for the effects of the test substance on root dry mass of Hordeum vulgare. IC50/EC50values for effects on seedling emergence, root and shoot length and shoot dry mass determined in the same test were ≥248 mg/kg dry weight. 14-day EC50values of >4054 mg/kg dry weight have been determined for the effects of the test substance on seedling emergence, root and shoot length and root and shoot dry mass of Trifolium pratense. NOECs were not determined in the tests.

An OECD TG 208 toxicity to terrestrial plants study has already been proposed for a structurally-similar substance within the Siloxanes Category, Silsesquioxanes, Phenyl (CAS 70131-69-0). The need for this study will be re-assessed once the results of the OECD TG 222 with Silsesquioxanes, Phenyl (CAS 70131-69-0) are available. If there is no indication of risk from the OECD TG 222 study, the OECD TG 208 will not be conducted.

The approach to chemical safety assessment for octaphenylcyclotetrasiloxane will be reconsidered once further data becomes available.

Read-across of the terrestrial toxicity data for D5 to octaphenylcyclotetrasiloxane is considered to be suitable as an interim approach for the purpose of chemical safety assessment.

Refer to Section 6.3 for further discussion.