Registration Dossier
Registration Dossier
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EC number: 238-518-6 | CAS number: 14513-34-9
Endpoint summary
Administrative data
Description of key information
There are no reliable aquatic toxicity data available for the registration substance, therefore good quality data for the structurally-related substance, 3-(chlorodimethylsilyl)propyl methacrylate (CAS 24636-31-5), have been read across.
Reliable short-term toxicity tests results are available for freshwater invertebrates (Daphnia magna) and algae (Pseudokirchneriella subcapitata) for the read-across substance 3-(chlorodimethylsilyl)propyl methacrylate (CAS 24636-31-5). The relevant short-term values are:
Daphnia: EC50 (48 h): 0.573 mg/l (expressed in terms of geometric mean measured concentration of the hydrolysis products, sum of 3-[hydroxy(dimethyl)silyl]propyl methacrylate (monomeric silanol) and 1,1,3,3-tetramethyldisiloxane-1,3-diyl)dipropane-1,3-diyl dimethacrylate (CAS 18547-93-8, EC 242-419-3) (siloxane dimer))
Algae: EC50 (72 h): 20.2 mg/l; ErC10 4.78 mg/l (expressed in terms of geometric mean measured concentration of the hydrolysis products, sum of 3-[hydroxy(dimethyl)silyl]propyl methacrylate (monomeric silanol) and 1,1,3,3-tetramethyldisiloxane-1,3-diyl)dipropane-1,3-diyl dimethacrylate (CAS 18547-93-8, EC 242-419-3) (siloxane dimer))
The very rapid hydrolysis of the tested substance (half-life <5 min at pH 7 and 20-25 °C) is consistent wth the analytical evidence that the test organisms in each test were exposed primarily to the hydrolysis products, 3-[hydroxy(dimethyl)silyl]propyl methacrylate (monomeric silanol) and 1,1,3,3-tetramethyldisiloxane-1,3-diyl)dipropane-1,3-diyl dimethacrylate (CAS 18547-93-8, EC 242-419-3) (siloxane dimer).
In view of the test media preparation method, pH adjustment and exposure regime it is likely that the test organisms were exposed predominantly to the hydrolysis products (monomeric silanol) and both dissolved and undissolved condensation products (siloxane dimer) of the tested substance. The study was supported by analysis of these hydrolysis products which demonstrates the complete hydrolysis of the chlorosilane group and shows that under the conditions of the test a high proportion of the hydrolysis products are present in the form of dimeric siloxane (at a concentration well in excess of its predicted limit of solubility).
It is to be expected that at higher concentrations, dimeric siloxane condensation products can form from aqueous solutions of the monomeric silanol. There is some evidence of undissolved material (precipitated products) in the study report for this test, and therefore physical effects may have contributed to some extent to the effects in these tests. The use of the E(L)C50 values as a measurement of intrinsic toxicity represents a conservative interpretation of the test findings.
Refer to IUCLID Section 6 endpoint summary for further discussion of the approach to chemical safety assessment and justification for read across.
Additional information
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