Octamethyltrisiloxane

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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

The study was conducted according to an appropriate OECD test guideline, and in compliance with GLP.

Qualifier:

according to guideline

Guideline:

OECD Guideline 310 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test)

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Activated sludge was collected from the Cambridge Wastewater Treatment Facility, Cambridge, Maryland on March 30, 2009. The Cambridge facility treats predominantly residential wastes.

- Preparation of inoculum for exposure: The sludge was sieved using a 2-mm screen and then aerated at test temperature until its adjustment. The activated sludge was diluted in test medium to approximately 30 mg total suspended solids/L and aerated with CO2-free air until its adjustment. The inoculated medium used in the test was prepared by diluting the preconditioned activated sludge in test medium to 4 mg total suspended solids/L.

Duration of test (contact time):

28 d

Initial conc.:

20 mg/L

Based on:

DOC

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST SYSTEM
- Culturing apparatus: glass serum bottles with a nominal volume of 160 mL. The chambers were sealed with butyl rubber septa and crimp caps.


SAMPLING
- Sampling frequency: Replicate chambers from the control, reference and treatment groups were removed for IC analysis once a week over the test period. Replicate chambers from the toxicity control group were removed for IC analysis on Days 1 and 28. Three replicate test chambers from each group were analysed at each respective sacrifice interval, except for the last interval (5 replicates each).

- Sampling method: Samples for analysis were prepared by converting CO2 to carbonate. One millilitre of 7M NaOH was injected into the test chambers, which were subsequently shaken for at least 1 hour at test temperature. After mixing, the chambers were removed from the shaker table, allowed to settle and then samples were removed for IC analysis.

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (CO2 evolution)

Value:

0

Sampling time:

28 d

Details on results:

Test substance: -3.7% in 28 days
Reference substance: 96.5% in 28d (>60% in 7 days)
Toxicity control: 46.2% in 28d

Table 1: Inorganic carbon concentration (mg C/l) and calculated % biodegradation for inoculum blank, reference substance, test substance and toxicity control

Type of suspension	1d		7d		14d		21d		28d
	Inorg. C (mgC/l)	(%) biodeg	Inorg. C (mgC/l)	(%) biodeg	Inorg. C (mgC/l)	(%) biodeg	Inorg. C (mgC/l)	(%) biodeg	Inorg. C (mgC/l)	(%) biodeg	Cumulative average(%) biodeg(Day 28)
Inoculum Blank	-	-	0.3; 0.1; 0.4	-	2.3; 2.4; 1.8	-	2.9; 2.8; 3.1	-	2.8; 2.8; 3.1; 2.6; 3.1	-	-
Reference substance	-	-	16.9; 16.8; 17.4	83.8; 83.4; 86.1	18.8; 19.5; 19.1	84.1; 87.4; 85.4	20.5; 20.4; 20.4	88.4; 88.2; 88.2	22.1; 22.0; 22.2; 21.9; 21.9	96.7; 96.3; 97.5; 96.1; 95.8	96.5
Test substance	-	-	0.1; 0.0; 0.0	-0.7; -1.3; -1.5	1.9; 2.3; 1.5	-1.5; 0.4; -3.2	2.4; 2.3; 2.4	-2.9; -3.2; -2.6	2.2; 2.2; 2.4; 2.1; 2.0	-3.5; -3.7; -2.6; -3.9; -4.6	-3.7
Toxicity control	13.4; 13.6; 13.6	33.7; 34.3; 34.4	-	-	-	-	-	-	21.3; 21.1; 21.1; 21.4; 20.9	46.6; 46.0; 45.9; 46.8; 45.5	46.2

 

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

Biodegradation of 0% in 28 days was determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.

Description of key information

Biodegradation in water: screening tests: 0% in 28 days (OECD 310)

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

Biodegradation of 0% in 28 days was determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.