Registration Dossier
Registration Dossier
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EC number: 943-282-9 | CAS number: -
PBT assessment
Administrative data
PBT assessment: overall result
- PBT status:
- the substance is not PBT / vPvB
- Justification:
Persistence assessment
Trimethyl(octadecyloxy)silane is readily biodegradable (failing 10-day window) and hydrolyses at a moderate rate (half-life 15 hours at pH7 and 25°C) in contact with water to trimethylsilanol and octadecan-1-ol. Octadecan-1-ol is considered to be inherently biodegradable but on the borderline between readily and inherently biodegradable. Therefore the registration substance and the non-silanol hydrolysis product are not considered to be persistent or very persistent in the environment.
The silanol hydrolysis product, trimethylsilanol, is not readily biodegradable, and therefore, this substance meets the screening criteria for persistence (P/vP).
Bioaccumulation assessment
Both the trimethyl(octadecyloxy)silane and octadecan-1-ol constituents have log Kow values >8, which means that the screening criteria for B and vB are met. However, octadecan-1-ol is a naturally occurring substance that is readily metabolised and so does not meet the criteria for B or vB. Trimethylsilanol has a low log Kow value (≤4.5) and, therefore, does not meet the screening criteria for B or vB.
Toxicity assessment
There are no ecotoxicity data available for the registration substance. However, based on low water solubility and high log Kow, long-term ecotoxicity effects are not expected. Therefore the substance is not T. Octadecan-1-ol is not T based on a 21-d NOEC of 0.98 mg/L reported in a long-term invertebrate study. Reliable short-term aquatic toxicity tests in fish, invertebrates and algae with trimethylsilanol indicate that the criteria for T are not met. Additionally, for the registration substance and transformation products, there is no evidence of chronic toxicity, as identified by the classifications: T, R48, or Xn, R48 according to Directive 67/548/EEC or specific target organ toxicity after repeated exposure (STOT RE category 1 or 2) according to Regulation EC No 1272/2008, and no classifications as carcinogenic (category 1 or 2), mutagenic (category 1 or 2), or toxic for reproduction (category 1, 2 or 3) according to Directive 67/548/EEC or carcinogenic (category 1A or 1B), germ cell mutagenic (category 1A or 1B), or toxic for reproduction (category 1A, 1B or 2) according to Regulation EC No 1272/2008. It can be concluded that the criteria for T are not met for either the registration substance or transformation products.
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