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EC number: 239-311-3
CAS number: 15267-95-5
Valid short term measured data for the
registered substance are available for fish and algae.
A 96-hour LC50value of >100 mg/l
and NOEC value of 100 mg/l have been determined for the effects of the
test substance on mortality of Oncorhynchus mykiss and a 72-hour
ErC50value of >100 mg/l and NOEC value of 50 mg/l have been
determined for the effects of the test substance on Pseudokirchneriella
subcapitata, both results based on nominal concentration of the
As the substance is subject to rapid
hydrolysis, it is therefore likely that the test organisms were
primarily exposed to hydrolysis product retained in the test media.
The hydrolysis half-life of
(chloromethyl)triethoxysilane (CAS No. 15267-95-5) is approximately 2.5
h at 20-25°C and pH 7; the substance will therefore undergo rapid
hydrolysis in contact with water to form (chloromethyl)silanetriol and
REACH guidance (ECHA 2016, R.16) states that
“for substances where hydrolytic DT50 is less than 12
hours, environmental effects are likely to be attributed to the
hydrolysis product rather than to the parent itself”. TGD guidance,
(European Commission, 2003) and R.16 (ECHA, 2016) also suggests that
when the hydrolysis half-life is less than 12 hours, the breakdown
products, rather than the parent substance, should be evaluated for
aquatic toxicity. Therefore, the environmental hazard assessment,
including sediment and soil compartments due to water and moisture being
present, is based on the properties of the silanol hydrolysis product in
accordance with REACH guidance. As described in Section 1, condensation
reactions of the silanols are possible.
In order to reduce animal testing read-across
is proposed to fulfill up to REACH Annex IX requirements for the
registered substance from substances that have similar structure and
physicochemical properties. Ecotoxicological studies are conducted in
aquatic medium or in moist environments; therefore the hydrolysis rate
of the substance is particularly important since after hydrolysis occurs
the resulting product has different physicochemical properties and
In moist medium,
(chloromethyl)triethoxysilane hydrolyses rapidly (half-life 2.5 h at
20-25°C and pH 7) to (chloromethyl)silanetriol. The non-silanol
hydrolysis product ethanol is not expected to contribute to any adverse
effects at the relevant dose levels. This is discussed further below.
In the following paragraphs the read-across
approach for (chloromethyl)triethoxysilane is assessed for each
surrogate substance taking into account structure, hydrolysis rate and
Read-across from triethoxy(methyl)silane
(CAS No. 2031-67-6) to (chloromethyl)triethoxysilane (CAS No.
Measured data was not available for
chloromethyl)triethoxysilane (CAS No. 15267-95-5) therefore read across
from the comparable substances, triethoxy(methyl)silane (CAS No.
2031-67-6) was used to fill the data gap for invertebrates.
The registration and read-across substances are structurally
similar;the only difference is switching a Cl for a H on the methyl
group. The substances hydrolyse rapidly to produce the structurally
analogue silanol hydrolysis products, (chloromethyl)silanetriol and
The registered substances are part of an analogue group of
chloroalkoxysilane substances containing chloroalkyl and alkoxy groups
(III-15). The read-across substances is part of an analogue group of
triethoxysilanes hydrolysing rapidly at pH 7 (I-2-T-Et-H) and is
selected asthe most appropriate based
on chemical structure and similar physic-chemical properties. Both
substances have similarlog Kowvalues (2.5and
2.2, respectively) and comparable molecular weights. A similar
environmental behavior of the silanol hydrolysis products is also
expected, as their molecular weights and log Koware
comparable and due to the fast hydrolysis, the hydrolysis products of
these substances are also of relevance in the chemical safety assessment.
For the following endpoints read-across data
from the structural related substance triethoxy(methyl)silane were used
for the assessment of the aquatic toxicity. Reliable short-term toxicity
test result with freshwater organisms is available for invertebrates. A
48-hour EC50value of >500 mg/l and NOEC of ≥500 mg/l have
been determined for the effects of the test substance on mobility of Daphnia
magna based on nominal concentration of the substance. However, it
is likely that the test organisms were primarily exposed to the
hydrolysis products of the substance.
information is given in a supporting reports PFA (2016)
attached in Section 13 of the IUCLID dossier.
Key physicochemical parameters and ectoxicological data for the
registered and surrogate substances.
Si hydrolysis product
Molecular weight (parent)
Molecular weight (hydrolysis product)
log Kow(silanol hydrolysis product)
Water sol (parent)
1100 mg/l at 20°C
2900 mg/l at 20°C
Water sol (silanol hydrolysis product))
1E+06 mg/l at 20°C
1E+061 mg/l at 20°C
Vapour pressure (parent)
6.5 Pa at 25°C
100 Pa at 25°C
Vapour pressure (hydrolysis product)
2.1E-03 Pa at 25°C (QSAR)
5.20E-02 Pa at 25°C
Hydrolysis t1/2at pH 7 and 20°C-25°C
Hydrolysis t1/2at pH 4 and 25°C
Hydrolysis t1/2at pH 9 and 25°C
Short-term toxicity to fish (LC50)
Short-term toxicity to aquatic invertebrates (EC50)
Algal inhibition (ErC50and NOEC)
Long-term toxicity to aquatic invertebrates (NOEC)
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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