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activated sludge respiration inhibition testing
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
Please refer to the justification for grouping of substances provided in IUCLID Section 13.
Reason / purpose for cross-reference:
read-across source
3 h
Dose descriptor:
Effect conc.:
> 100 mg/L
Nominal / measured:
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
An activated sludge respiration inhibition 3h-EC10 value of >100 mg/l (loading rate) was determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP. The source substance is the hydrolysis product of the target substance. Since the hydrolysis half life is < 1 h, the results derived for the source substance describe additionally the effects of the the target substance.

Description of key information

The inhibition of the degradation activity of activated sludge is not anticipated.

Key value for chemical safety assessment

Additional information

Experimental data for dimethoxydimethylsilane (CAS 1112-39-6) are not available. However, since dimethoxydimethylsilane hydrolyses rapidly to dimethylsilanediol and methanol (DT50 < 0.6 h) the hydrolysis products rather than the parent substance should be considered for the assessment, read-across data for the hydrolysis product, dimethylsilanediol, are considered appropriate for the assessment.

No studies are available to assess the toxicity to microorganisms of dimethoxydimethylsilane (CAS 1112-39-6), however, data are available for the structural analogue substance trimethoxy(methyl)silane (CAS 1185-55-3). Details on read-across can be found in the attached justification attached in IUCLID Section 13.

The study with the analogue substance was performed according to OECD 209 (GLP) with a limit concentration of 100 mg/L. Activated sludge of a predominantly domestic sewage was used as inoculum. No inhibition of growth was recorded after 3 h of incubation resulting in an EC10 (3 h) of >100 mg/L.

Based on the result of the analogue substance, Dimethoxydimethylsilane (CAS 1112-39-6) is not assumed to be harmful to activated sludge microorganisms and an inhibition of degradation in sewage treatment plants is not anticipated.