Registration Dossier
Registration Dossier
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EC number: 222-123-0 | CAS number: 3353-69-3
Toxicity to microorganisms
Administrative data
Link to relevant study record(s)
Description of key information
Toxicity to microorganisms: ASRI 3 hr EC50 >1000 mg/l, NOEC ≥1000 mg/l (OECD 209), read-across from a structurally-related substance. The NOEC is equivalent to > 742 mg/l when expressed in terms of the silanol hydrolysis product of the tested substance.
Key value for chemical safety assessment
- EC10 or NOEC for microorganisms:
- 742 mg/L
Additional information
There are no reliable microorganism toxicity data available for the registered substance 1,2-bis[dichloro(methyl)silyl]ethane (CAS 3353-69 -3), therefore good quality data for the structurally-related substance, 1,6 -bis(trimethoxysilyl)hexane (CAS 87135-01-1), have been read-across. Both substances have a structurally similar silanol hydrolysis products: 1,2-bis[dihydroxy(methyl)silyl]ethane and 1,6 -bis(trihydroxysilyl)hexane, respectively. In view of the very rapid hydrolysis, it is the silanol hydrolysis product that is relevant for environmental risk assessment.
The other hydrolysis products are hydrogen chloride and methanol, for the registered substance and for the read-across substance, respectively.
Hydrogen chloride is not expected to have adverse effects on microorganisms in a sewage treatment plant, where the pH is maintained within a favourable range.
Methanol does not have adverse effects on microorganims (OECD, 2004).
In the study with 1,6 -bis(trimethoxysilyl)hexane (CAS 87135-01-1), an activated sludge respiration inhibition 3h EC50 value of >1000 mg/l (loading rate) and NOEC of ≥1000 mg/l was determined in a reliable study conducted according to an appropriate test protocol and in compliance with GLP. This indicates that the test substance was not toxic to waste water (activated sludge) bacteria at a loading rate of 1000 mg/l. The results may be expressed in terms of concentration of the hydrolysis product of the tested substance, 1,6-bis(trihydroxysilyl)hexane, by applying a molecular weight correction: (MW of silanol = 242.38 / MW of parent = 326.54) * >1000 = > 742 mg/l.
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