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EC number: 219-137-4 | CAS number: 2370-88-9
Ecotoxicological Summary
Administrative data
Hazard for aquatic organisms
Freshwater
- Hazard assessment conclusion:
- PNEC aqua (freshwater)
- PNEC value:
- 34 mg/L
- Assessment factor:
- 1 000
- Extrapolation method:
- assessment factor
- PNEC freshwater (intermittent releases):
- 340 mg/L
Marine water
- Hazard assessment conclusion:
- PNEC aqua (marine water)
- PNEC value:
- 3.4 mg/L
- Assessment factor:
- 10 000
- Extrapolation method:
- assessment factor
STP
- Hazard assessment conclusion:
- PNEC STP
- PNEC value:
- 3.2 mg/L
- Assessment factor:
- 10
- Extrapolation method:
- assessment factor
Sediment (freshwater)
- Hazard assessment conclusion:
- PNEC sediment (freshwater)
- PNEC value:
- 122 mg/kg sediment dw
- Extrapolation method:
- equilibrium partitioning method
Sediment (marine water)
- Hazard assessment conclusion:
- PNEC sediment (marine water)
- PNEC value:
- 12.2 mg/kg sediment dw
- Extrapolation method:
- equilibrium partitioning method
Hazard for air
Air
- Hazard assessment conclusion:
- no hazard identified
Hazard for terrestrial organisms
Soil
- Hazard assessment conclusion:
- PNEC soil
- PNEC value:
- 4.5 mg/kg soil dw
- Extrapolation method:
- equilibrium partitioning method
Hazard for predators
Secondary poisoning
- Hazard assessment conclusion:
- no potential for bioaccumulation
Additional information
PNECwater
HD4 was not toxic at a loading rate of 100 mg/l in short-term studies with Daphnia and algae. In addition the substance hydrolyses very rapidly in water (half-life for degradation of parent 2.2 minutes at pH 7 and 25°C). Therefore, it is not appropriate to derive PNECs for the parent substance.
Degradation to small molecule silanols is predicted to be rapid, full hydrolysis of the Si-H groups to give the final product methylsilanetriol is expected to be slower but still complete in approximately 1 day. Therefore, it is appropriate to derive PNECs for methylsilanetriol. L(E)C50’s for this substance have been calculated using an appropriate validated QSAR method (PFA 2013ag).
The PNECaquatic(freshwater)is therefore based on the lowest LC/EC50value (EC50: 34000 mg/l for algae) that has been determined for methylsilanetriol using the QSAR method.
Short-term data are available for three trophic levels; therefore, an assessment factor of 1000 is applied.
Therefore, PNECaquatic (freshwater)is 34000/1000 = 34 mg/l.
Since no data are available for marine species the PNECaquatic (marine water)is derived from the short-term freshwater species toxicity data. An additional assessment factor of 10 is applied to account for possible differences between marine and freshwater environments, giving an overall assessment factor of 10 000.
Therefore, PNECaquatic (marine water)is 34000/10000 = 3.4 mg/l.
Where freshwater releases are intermittent, it is appropriate to reduce the assessment factor to 100.
Therefore, PNECaqua (intermittent releases)is 34000/100 = 340 mg/l.
PNECsediment
There are no measured data for sediment-dwelling organisms.The PNEC values for the sediment compartment have therefore been derived from the PNECs for the aquatic compartment using the equilibrium partitioning approach in conjunction with the predicted log KOCof thehydrolysis product, methylsilanetriol (-2.8) and the Ksusp-watervalue of 0.9 as follows:
PNECsediment | = | Ksusp-water | * PNECaquatic(freshwater)* 1000 |
|
| RHOsusp |
|
For methylsilanetriol this is:
PNECsediment | = | 0.9 | * 34 * 1000 |
|
| 1150 |
|
|
|
|
|
| = | 26.6 mg/kg wwt | |
In the absence of measured data, it is not appropriate to use assessment factors to determine PNECsedimentvalues. The log Kowof the hydrolysis product is <3, therefore, no additional assessment factor is needed to account for possible uptake via sediment ingestion.
Hence a PNECsediment(freshwater)of 26.6 mg/kg wwt, equivalent to 122 mg/kg dwt, will be used for risk characterisation. The same equation is used to derive the PNECsediment(marine water) and substituting the PNECaquatic(freshwater)with the PNECaquatic(marine water)to determine a PNECsediment(marine water)of 2.66 mg/kg wwt and 12.2 mg/kg dwt.
PNECsoil
There are no measured data for soil-dwelling organisms.The PNEC value for the soil compartment has therefore been derived from the PNEC for the aquatic compartment using the equilibrium partitioning approach in conjunction with the predicted log KOCof the hydrolysis product, methylsilanetriol (-2.8) and the Ksoil-watervalue of 0.2 as follows:
PNECsediment | = | Ksoil-water | * PNECaquatic(freshwater)* 1000 |
|
| RHOsoil |
|
For methylsilanetriol this is:
PNECsediment | = | 0.2 | * 34 * 1000 |
|
| 1700 |
|
|
|
|
|
| = | 4 mg/kg wwt | |
In the absence of measured data, it is not appropriate to use an assessment factor to determine a PNECsoilvalue. The log Kowof the hydrolysis product is <3, therefore, no additional assessment factor is needed to account for possible uptake via sediment ingestion.
Hence a PNECsoilof 4 mg/kg wwt, equivalent to 4.5 mg/kg dwt, will be used for risk characterisation.
Conclusion on classification
It is proposed that the substance should not be classified for the environment on the basis of EC50s of >100 mg/l for daphnia and algae.
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