Registration Dossier
Registration Dossier
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EC number: 246-377-7 | CAS number: 24636-31-5
Toxicity to aquatic algae and cyanobacteria
Administrative data
Link to relevant study record(s)
Description of key information
72 hour ErC50: 20.2 mg/l; ErC10: 4.78 mg/l; NOEC: 2.13 mg/l (geometric mean measured concentrations); effects of the hydrolysis products on growth rate of Psuedokirchneriella subcapitata.
Key value for chemical safety assessment
- EC50 for freshwater algae:
- 20.2 mg/L
- EC10 or NOEC for freshwater algae:
- 4.78 mg/L
Additional information
A 72 hour EC50 value of >20.2 mg/l, an EC10 value of 4.78 mg/l and a NOEC value of 2.13 mg/l (geometric mean measured concentrations) has been determined for the effects of the hydrolysis products of the test substance on growth rate of Pseudokirchneriella subcapitata, in compliance with OECD Guideline 201 (Alga, Growth Inhibition Test).
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 growth rate effects in the test. The use of the E(L)C50 value as a measurement of intrinsic toxicity represents a conservative interpretation of the test findings.
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