Registration Dossier
Registration Dossier
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EC number: 201-127-6 | CAS number: 78-62-6
PBT assessment
Administrative data
PBT assessment: overall result
- Name:
- Diethoxy(dimethyl)silane 000078-62-6
- Type of composition:
- boundary composition of the substance
- State / form:
- liquid
- Reference substance:
- Diethoxy(dimethyl)silane 000078-62-6
- PBT status:
- the substance is not PBT / vPvB
- Justification:
Persistence Assessment
Diethoxy(dimethyl)silane (CAS 78-62-6) rapidly hydrolyses in the environment (half-life = 5.5 h at 20-25 °C and pH 7) and dimethylsilanediol and ethanol are formed. According to the Guidance on Information Requirements and Chemical Safety Assessment Chapter R.11: PBT/vPvB assessment (2017) hydrolysis is considered as primary degradation, and the formation of stable degradation products with PBT/vPvB properties should be considered for PBT assessment.
Since no data on the biodegradation of Diethoxy(dimethyl)silane (CAS 78-62-6) were available, good quality data from the analogue substance, trimethylsilanol (CAS 1066-40-6), were read across. The percentage biodegradation of trimethylsilanol (CAS 1066-40-6) was found to be 0% after 28 days. Therefore trimethylsilanol can be regarded as not biodegradable. Based on the results of the analogue substance, Diethoxy(dimethyl)silane is not assumed to be readily biodegradable. The other hydrolysis product ethanol is readily biodegradable (OECD 2004). Therefore, Diethoxy(dimethyl)silane (CAS 78-62-6) is considered to meet the criteria for persistence (P and vP).
Bioaccumulation Assessment
A log Kow value of 3 was predicted for the parent substance and a log Kow value of -0.4 was predicted for the silanol hydrolysis product using an appropriate calculation method. The other hydrolysis product, ethanol is also negligible with regard to bioaccumulation with its log Kow of -0.3.
Based on these information, Diethoxy(dimethyl)silane (CAS 78-62-6) and its hydrolysis products do not meet the criteria for bioaccumulation and are not B and not vB.
Toxicity Assessment
Studies with aquatic organisms of three different trophic levels did not show any short term toxicity effects up to the highest tested concentration of 100 mg test item/L. Long-term toxicity data available for algae, showed that the substance and its hydrolysis product exhibit EC10/NOEC > 0.01 mg/L and are therefore not considered as T for the environment.
Furthermore, neither the substance nor its hydrolysis products are classified for specific target organ toxicity, carcinogenicity, mutagenicity and is not toxic for reproduction and development towards mammals. The criteria for “T” based on mammalian effects are therefore not met.
In conclusion the substance is not PBT/vPvB.
Reference
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