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Ecotoxicological information

Toxicity to terrestrial plants

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Key value for chemical safety assessment

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There are no data describing the long-term toxicity of the registered substance to terrestrial plants. However, an OECD TG 208 toxicity to terrestrial plants study is proposed for the structural analogue, silsesquioxanes, phenyl. The need for this study will be re-assessed once the results of the OECD TG 222 with silsesquioxanes, phenyl are available. If there is no indication of risk from the OECD TG 222 study, the OECD TG 208 will not be conducted.

In the interim period, before the data with phenyl silsesquioxanes become available, data are available for the siloxane decamethylcyclopentasiloxane (D5, CAS: 541-02-6) with terrestrial plants. A short-term (14-day) IC50 value of 209 mg/kg dry weight has been determined for the effects of the test substance on root dry mass of Hordeum vulgare. IC50/EC50 values 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 EC50 values 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 is proposed for the registration substance. The need for this study will be re-assessed once the results of the OECD TG 222 with the registration substance are available. If there is no indication of risk from the OECD TG 222 study, the OECD TG 208 will not be conducted.

Read-across of the terrestrial toxicity data for D5 to 1,3,5-trimethyl-1,1,3,5,5-pentaphenyltrisiloxane CAS 3390-61-2 is considered to be suitable to derive an interim hazard and risk assessment under REACH for the registration substance.

Refer to Section 6.3 for further discussion.