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EC number: 257-473-3
CAS number: 51851-37-7
Reliable short-term toxicity
tests results are available for freshwater fish (Cyprinus carpio),
invertebrates (Daphnia magna) and algae (Scenedesmus
subspicatus) for [2-(perfluorohexyl)ethyl]triethoxysilane (CAS
51851-37-7, EC 257-37-7). The relevant short-term values are:
Fish: LC50 (96
h): >3.1 mg/l (highest concentration tested)
Daphnia: EC50 (48
h): >9 mg/l (highest concentration tested)
Algae: ErC50 (72
h): >7.1 mg/l; NOErC ≥7.1 mg/l (highest concentration
Test solution preparation
for the fish, invertebrate and algal tests involved making a stock
solution and stirring this for 18 hours prior to adding the test
organisms. The pH during the fish test was measured as 8.5 to 9, during
the invertebrate test as 7.9 to 8.0 and the pH at the start of the algae
test was 7.6 to 8.0. By the end of the algae test, the pH had risen to
9.4 to 9.6. [2-(Perfluorohexyl)ethyl]triethoxysilane will hydrolyse in
water under dilute conditions (half-life rates have been measured at
20°C as 1.44 hours at pH 4, 12.5 hours at pH 7 and 5.18 hours at pH 9).
Given that the rate of hydrolysis is expected to be slowest at around pH
7 and increase as the pH is raised or lowered, it is possible that pH
could influence the exposure of the organisms to
[2-(perfluorohexyl)ethyl]triethoxysilane and its hydrolysis product,
[2-(perfluorohexyl)ethyl]silanetriol. However, due to the hydrolysis
rate of 12.5 hours at pH 7 and the fact that the very low water
solubility of the parent substance can limit hydrolysis, the chemical
safety assessment is based on the properties of the parent substance.
The amount of silanol present in the test solution is dependent on how
much of the parent substance was dissolved. The water solubility of the
parent is extremely low and the test results show values above the limit
of solubility. Measurements of test substance in solution were made by
dissolved organic carbon analysis (DOC). With DOC it is not possible to
differentiate dissolved forms of the test substance and it is therefore
unclear how much of the parent substance, silanol hydrolysis product or
oligomer were dissolved in the test solution. However, there were no
effects seen during the tests and so it can be concluded that no effects
were seen at the limit of solubility of the test substance.
The presence of fluorocarbon
chains means that the parent substance, silanol and condensation
products have the potential for some surface activity. This is proven
for the silanol based on measured and read-across data. The effective
limits of solubility of both the parent substance and monomeric silanol
hydrolysis products are very low because of the tendency to condense to
oligomers which are of very low solubility. All forms of the substance
may have a tendency to enrich at surfaces rather than forming stable
evenly dispersed solutions. These phenomena may limit the extent of
hydrolysis under conditions at which the solubility of either parent or
oligomer is exceeded. The substance is extremely difficult to test and
so best use has been made of the existing studies.
Refer to IUCLID Section 6
endpoint summary (CSR Section 7.0) for further discussion of the
approach to chemical safety assessment.
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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