Registration Dossier
Registration Dossier
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EC number: 208-765-4 | CAS number: 541-05-9
Sediment toxicity
Administrative data
Link to relevant study record(s)
- Endpoint:
- sediment toxicity: long-term
- Type of information:
- experimental study planned
- Study period:
- After approval by ECHA
- Justification for type of information:
- No long-term toxicity to sediment organisms data are currently available with the registration substance, hexamethylcyclotrisiloxane (D3, CAS 541-05-9; EC No. 208-765-4).
D3 rapidly hydrolyses (23 min at pH 7 and 25 °C) to the intermediate hydrolysis products 1,1,3,3,5,5-hexamethyltrisiloxane-1,5-diol (CAS 3663-50 -1; L3-diol) and tetramethyldisiloxanediol (L2-diol), with the final product being dimethylsilanediol (DMSD, CAS 1066-42-8; EC No. 213-915-7). The L3-diol is the initial hydrolysis product. The half-life for the hydrolysis of the L3-diol and L2-diol is approximately 200 hours at pH 7 and 25 °C.
The environmental safety assessment focuses on L3-diol and DMSD.
L3-diol is soluble in water (1700 mg/l limited to 1000 mg/l by condensation reactions) but has a log Kow of 3.2. The assessment of effects in sediment dwelling organisms is therefore relevant and a long-term sediment toxicity test with L3-diol on an endobenthic, sediment-ingesting species is proposed. - Qualifier:
- according to guideline
- Guideline:
- OECD Guideline 225 (Sediment-Water Lumbriculus Toxicity Test Using Spiked Sediment)
Reference
Description of key information
Key value for chemical safety assessment
Additional information
No long-term toxicity to sediment organisms data are currently available with the registration substance, hexamethylcyclotrisiloxane (D3, CAS 541-05-9; EC No. 208-765-4).
D3 rapidly hydrolyses (23 min at pH 7 and 25°C) to the intermediate hydrolysis products 1,1,3,3,5,5-hexamethyltrisiloxane-1,5-diol (CAS 3663-50-1; EC No. 222-920-3; L3-diol) and 1,1,3,3-tetramethyldisiloxane-1,3-diol (CAS 1118-15-6; EC No. 214-258-9; L2-diol), with the final product being dimethylsilanediol (DMSD, CAS 1066-42-8; EC No. 213-915-7). The L3-diol is the initial hydrolysis product. The half-life for the hydrolysis of the L3-diol and L2-diol is approximately 200 hours at pH 7 and 25°C.
The environmental safety assessment focuses on L3-diol and DMSD.
L3-diol is soluble in water (1700 mg/l predicted, limited to 1000 mg/l by condensation reactions) but has a log Kow of 3.2. The assessment of effects in sediment dwelling organisms is therefore relevant and a long-term sediment toxicity test with an endobenthic, sediment-ingesting species is required. A long-term sediment toxicity test with L3-diol under OECD TG 225, Sediment-Water Lumbriculus Toxicity Test Using Spiked Sediment, is proposed.
No aquatic PNECs have been derived due to the absence of effects in the aquatic studies. Indicative aquatic PNECs have been determined for use in the equilibrium partitioning calculation to derive sediment and soil PNECs. These PNECs will be updated once the experimental data are available.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.
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