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EC number: 208-765-4 | CAS number: 541-05-9
Long-term toxicity to aquatic invertebrates
Administrative data
Link to relevant study record(s)
- Endpoint:
- long-term toxicity to aquatic invertebrates
- Type of information:
- experimental study planned
- Study period:
- After approval by ECHA
- Justification for type of information:
- Experimental study planned: the substance is registered at Annex X. Testing for long-term toxicity to aquatic invertebrates is an Annex IX requirement and, currently, no long-term toxicity to invertebrates data are available.
The parent substance hexamethylcyclotrisiloxane (D3, CAS 541-05-9; EC No. 208-765-4) hydrolyses rapidly (23 minutes at pH 7 and 25°C) to an initial intermediate hydrolysis product, 1,1,3,3,5,5-hexamethyltrisiloxane-1,5-diol (L3-diol; CAS 3663-50-1; EC No. 222-920-3), followed by further hydrolysis (>200 hours at pH 7 and 25°C) to the ultimate hydrolysis product dimethylsilanediol (DMSD, CAS 1066-42-8; EC No. 213-915-7). The L3-diol is the relevant chemical species for assessment of aquatic toxicity.
A long-term toxicity to Daphnia magna study with L3-diol, in accordance with OECD TG 211, is therefore proposed.
The L3-diol has relatively high water solubility (1700 mg/l) therefore the test organisms should be exposed to L3-diol at the maximum test concentration required by the guideline, i.e., 10 mg/l, depending on the results of preliminary range-finding studies. - Qualifier:
- according to guideline
- Guideline:
- OECD Guideline 211 (Daphnia magna Reproduction Test)
- Endpoint:
- long-term toxicity to aquatic invertebrates
- Type of information:
- experimental study
- Adequacy of study:
- supporting study
- Study period:
- 2017-08-28 - 2017-09-13
- Reliability:
- 1 (reliable without restriction)
- Rationale for reliability incl. deficiencies:
- guideline study
- Qualifier:
- according to guideline
- Guideline:
- OECD Guideline 211 (Daphnia magna Reproduction Test)
- GLP compliance:
- yes (incl. QA statement)
- Analytical monitoring:
- yes
- Details on sampling:
- Bulk test solution sampled on days 0, 2, 7, 14 and 19
Pooled replicate solutions were sampled on days 2, 5, 9, 16 and 21 - Vehicle:
- no
- Details on test solutions:
- The highest (limit) test concentration was prepared by direct addition, solutions were renewed every Monday, Wednesday and Friday
- Test organisms (species):
- Daphnia magna
- Details on test organisms:
- in-house cultures, initially obtained from Aquatic BioSystems, Inc., Fort Collins, Colorado
Feed: Day 1-6: 0.4 mL Raphidocelis subcapitata and 0.1 mL yeast, wheat grass and finfish food suspension
Day 7-20: 0.5 mL Raphidocelis subcapitata and 0.1 mL yeast, wheat grass and finfish food suspension - Test type:
- semi-static
- Water media type:
- freshwater
- Limit test:
- yes
- Total exposure duration:
- 21 d
- Hardness:
- 54-64 mg CaCO3/ L
- Test temperature:
- 20-21 °C
- pH:
- 7.4-8.0
- Dissolved oxygen:
- 7.4-8.9 mg/L
- Conductivity:
- 157-200 uS/cm
- Nominal and measured concentrations:
- Nominal concentration: 12 mg/L
Measured concentration (time-weighted mean, averaging measured concentration): 12.6 mg/L - Details on test conditions:
- TEST SYSTEM
- Material, size, headspace, fill volume: 125 mL glass jars with 90 mL medium
- Renewal rate of test solution (frequency): Monday, Wednesday, Friday
- No. of organisms per vessel: 1
- No. of vessels per concentration (replicates): 10
- No. of vessels per control (replicates): 10
- Biomass loading rate: 0.2 mg C/daphnid/day
TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Lake Huron water: flocculated with ferric chloride, sand filtered, carbon filtered, UV-irradiated
OTHER TEST CONDITIONS
- Adjustment of pH: with gaseous CO2
- Photoperiod: 16 h light
- Light intensity: 1042-1484 lux
EFFECT PARAMETERS MEASURED (with observation intervals, if applicable) : mortality, daily
TEST CONCENTRATIONS
- Results used to determine the conditions for the definitive study: Limit test with 12 mg/L based on short term test with EC > 117 mg/L - Reference substance (positive control):
- no
- Key result
- Duration:
- 21 d
- Dose descriptor:
- NOEC
- Effect conc.:
- >= 12.6 mg/L
- Nominal / measured:
- meas. (TWA)
- Conc. based on:
- test mat.
- Basis for effect:
- other: survival, reproduction and growth
- Duration:
- 21 d
- Dose descriptor:
- EC50
- Effect conc.:
- > 12.6 mg/L
- Nominal / measured:
- meas. (TWA)
- Conc. based on:
- test mat.
- Basis for effect:
- other: survival, reproduction and growth
- Validity criteria fulfilled:
- yes
- Conclusions:
- A 21 day NOEC value of ≥ 12.6 mg/L and EC50 value of > 12.6 mg/L (based on Time Weighted Average Measured concentrations) have been determined for the effects of the test substance on survival, reproduction and growth of Daphnia magna.
Referenceopen allclose all
Nominal conc. (mg/L) |
Time weighted mean measured conc. (mg/L) |
Percent survival | Average Cumulative Offspring Per surviving Adult (mean ± SD) | Length in milimeter (mean ± SD) | Dry weight in Milligrams (mean ± SD) |
| 0 (water control) | 0 (<LLQ) | 90 | 120.7 ± 9.9 | 4.19 ± 0.06 | 0.53 ± 0.15 |
| 12 | 12.6 | 90 | 118.2 ± 11.6 | 4.17 ± 0.07 | 0.44 ± 0.07 |
| NOEC (mg/L) | 12.6 | 12.6 | 12.6 | 12.6 | |
| LOEC (mg/L) | > 12.6 | > 12.6 | > 12.6 | > 12.6 | |
| MATC (mg/L) | > 12.6 | > 12.6 | > 12.6 | > 12.6 |
Description of key information
Key value for chemical safety assessment
Additional information
No long-term toxicity to aquatic invertebrates data are currently available with the registered substance, hexamethylcyclotrisiloxane (D3, CAS 541-05-9; EC No. 208-765-4). D3 hydrolyses rapidly (23 minutes at pH 7 and 25°C) to an initial intermediate hydrolysis product, 1,1,3,3,5,5-hexamethyltrisiloxane-1,5-diol (L3-diol; CAS 3663-50-1; EC No. 222-920-3), followed by further hydrolysis (>200 hours at pH 7 and 25°C) to the ultimate hydrolysis product dimethylsilanediol (DMSD, CAS 1066-42-8; EC No. 213-915-7).
The initial hydrolysis product, the L3-diol, is the relevant chemical species for assessment of aquatic toxicity.
A long-term toxicity to Daphnia magna study with L3-diol, in accordance with OECD TG 211, is therefore proposed.
The L3-diol has relatively high water solubility (1700 mg/l) therefore the test organisms should be exposed to L3-diol at the maximum test concentration required by the guideline, i.e., 10 mg/l, depending on the results of preliminary range-finding studies.
Dimethylsilanediol:
A 21-day NOEC value of ≥12.6 mg/l and EC50 value of >12.6 mg/l (Time Weighted Average measured concentrations, limit test) have been determined for the effects of the ultimate hydrolysis product dimethylsilanediol (DMSD, CAS 1066-42-8; EC No. 213-915-7) on survival, reproduction and growth of Daphnia magna. The data are used to derive indicative sediment and soil PNECs for the ultimate hydrolysis product, using the Equilibrium Partitioning Method.
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