Reaction mass of 1,3-dimethyl-1,1,3,3-tetraphenyldisiloxane and 1,3,3,5-tetramethyl-1,1,5,5-tetraphenyltrisiloxane and 1,3,3,5,5,7-hexamethyl-1,1,7,7-tetraphenyltetrasiloxane

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

22 June - 2 August 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

The sludge was taken from the activation basin of the sewage treatment plant, In den Seewiesen, 67480 Edenkoben.
Date of collection: 29. Jun. 2018, batch no: 20180629
The sludge was filtrated, washed with test medium (2x) and re-suspended in test medium. It was then aerated until use. The dry matter was determined to contain 4060 mg of suspended solids/L.

Duration of test (contact time):

<= 28 d

Parameter followed for biodegradation estimation:

CO2 evolution

Reference substance:

aniline

Test performance:

The test item was tested using a concentration of nominally 20 mg organic carbon/L test item in test medium following OECD 301B and EU-Method C.4-C.
Aniline was chosen as positive control.
Activated sludge was used as inoculum (concentration in the test 25.0 mg dry matter/L). The test was left running for 28 days.

Key result

Parameter:

% degradation (CO2 evolution)

Value:

6.2

Sampling time:

28 d

Details on results:

Degradation values in %

Day Positive Positive Positive Test1 Test2 Test Abiotic Toxicity
Control 1 Control 2 Control Mean Control Control
Mean
2 1.0 -1.3 -0.1 -0.8 1.1 0.2 0.8 -0.7
4 6.1 10.0 8.1 1.0 -0.5 0.2 1.1 8.0
7 38.4 31.2 34.8 2.2 0.1 1.2 0.8 18.4
9 67.7 50.5 59.1 3.5 0.5 2.0 0.7 26.2
11 73.7 59.7 66.7 5.1 1.8 3.5 0.4 31.1
14 75.1 64.4 69.8 3.3 2.1 2.7 0.2 31.7
18 75.0 67.1 71.0 4.6 1.7 3.1 -0.2 33.5
23 81.9 77.1 79.5 4.9 4.6 4.7 0.4 34.8
29 78.7 73.7 76.2 4.0 8.3 6.2 0.1 35.7

Results with reference substance:

76.2% after 28 days

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

The degree of biodegradation reached 6 % after 28 days.

Executive summary:

The degree of biodegradation reached 6 % after 28 days. The 10-day-window was not detected.

Because the test item is a mixture, the 10-day window has not to be taken into account. Degradation missed 60 % within 28 days, too. Therefore, regardless of the 10-day-window the test item is considered as “not readily biodegradable"within 28 days”.

The abiotic degradation reached 0.1 %.

Description of key information

The degree of biodegradation reached 6 % after 28 days. Degradation missed 60 % within 28 days.

The test item is considered as “not readily biodegradable" within 28 days”.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater