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EC number: 221-066-9
CAS number: 2996-92-1
Trimethoxyphenylsilane (CAS No. 2996 -92 -1) hydrolyses rapidly in
contact with water (DT50 = 0.4 h at
25°C and pH 7) to produce phenylsilanetriol
(CAS No. 3047 -74 -3) and methanol (CAS No. 67 -56 -1).
Methanol is considered non-hazardous at the concentrations at which it
would be present in the studies assessed. The ECHA guidance R.16
states that “for substances where hydrolytic DT50 is less than 12 h,
environmental effects are likely to be attributed to the hydrolysis
product rather than to the parent itself” (ECHA, 2016). The ECHA
guidance R.16 also suggests that in case the hydrolysis half-life is
less than 12 h, the breakdown products, rather than the parent
substance, should be evaluated for aquatic toxicity. Therefore,
the hazard assessment for the environment, including sediment and soil
compartments, is based on the properties of the hydrolysis product phenylsilanetriol,
in accordance with REACH guidance.
Experimental (supporting) studies for the
aquatic toxicity of the target substance trimethoxyphenylsilane (CAS No.
2996 -92 -1) are available for all three trophic levels, which were
conducted according to standard OECD guidelines and GLP. The studies for
the short-term toxicity to fish and aquatic invertebrates were performed
as limit tests with a maximum nominal test item concentration of 0.2
mg/L. The study for the toxicity to aquatic algae tested 5
concentrations up to a nominal test item concentration of 0.2 mg/L.
No effects were observed at the nominal test concentration of 0.20
mg/l for Oncorhynchus mykiss (OECD 203), Daphnia magna (OECD
202) and Pseudokirchnerella subcapitata (OECD 201). The results
are expressed relative to nominal test substance concentration. The
corresponding mean measured concentration of the substance in the
treated test medium over the course of the test was 0.074 mg/L for fish
study and 0.0029 mg/L in the Daphnia study. In the algae study,
analysis of the test media showed that measured concentrations of the
parent substance declined to below the Limit of Quantification (LOQ) of
the analytical method in all treatments within 24 hours of the start of
The maximum concentration tested in these studies (0.2 mg/L) were
slightly above the functional solubilities of the substance in the
respective test media, which had been determined in preliminary
solubility trials. However, the highest tested concentration is also
well below the predicted solubility of the substance (1700 mg/L).
Therefore, it was considered appropriate to read-across from reliable
and good quality data for the structurally analogous source substance
trichloro(phenyl)silane (CAS No. 98 -13 -5) as both the target and
source substance hydrolyse rapidly in contact with water (half-lives < 1
h) and form a common silanol hydrolysis product, namely
phenylsilanetriol (CAS No 3047 -74 -3). The other hydrolysis products
being methanol (target) and hydrochloric acid (source), respectively,
are not expected to be hazardous at the concentrations relevant to the
The effect concentrations derived for methanol in standard guideline
studies are all well above 100 mg/L (OECD SIDS, 2004). Thus, methanol is
not considered to contribute to the overall aquatic toxicity of the
target substance. In consequence, data for methanol are not presented
specifically for each environmental toxicity endpoint within this
By means of the read-across approach, experimental data are
available for the short-term toxicity of trimethoxyphenylsilane to all
three trophic levels, i.e. fish, invertebrates and algae. All studies
were performed according to accepted standard OECD guidelines and GLP
and the experimental study design favored exposure to the hydrolysis
No short-term aquatic toxicity was observed towards aquatic organisms of
all three trophic levels up to the highest concentration tested, i.e.
100 mg/L (nominal). Furthermore, an activated sludge respiration
inhibition test according to OECD guidelines and GLP indicates no
effects towards microorganisms of activated sludge.
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.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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