2,4,6-trimethyl-2,4,6-tris(3,3,3-trifluoropropyl)cyclotrisiloxane

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

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution 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): Wareham Waste Water Treatment Plant, Wareham, Massachusetts

- Preparation of inoculum for exposure: passed through a 2-mm sieve, recombined, and centrifuged at 1000 rpm for 10 minutes. The supernatant was discarded, the sludge was washed with mineral salt medium and the contents were centrifuged at least once again and the supernatant was discarded.

Duration of test (contact time):

28 d

Initial conc.:

10 mg/L

Based on:

DOC

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS

- Solubilising agent (type and concentration if used): Since the test substance is insoluble, a stock solution was not prepared. Instead, approximately 0.0883 g (equivalent to 0.0300 g carbon; 34.0% carbon) of 2,4,6-trimethyl-2,4,6-tris(3,3,3-trifluoropropyl)cyclotrisiloxane was weighed onto small glass dishes and then the test substance was completely rinsed into each respective test or toxicity control vessel.

- Test temperature: 22 ± 2 ºC

- Aeration of dilution water: Yes

- Continuous darkness: yes


TEST SYSTEM
- Culturing apparatus: 4-L glass bottle with a rubber stopper into which one stainless steel needle with a Luer-Lok connection and two pieces of glass tubing were inserted.

- Number of culture flasks/concentration: Two

SAMPLING
On test days 1, 3, 6, 9, 14, 19 and 23, a 7-mL sample was removed from the first KOH carbon dioxide trap on each test system and analysed for CO2 evolution. On day 28, 1 mL of concentrated HCl was added to each test vessel after pH measurement to terminate biological activity. Aeration was continued overnight to drive any residual inorganic carbon from the test vessels. After overnight aeration, 7-mL samples for analysis of CO2 evolution were removed from the first and second traps.
The amount of evolved CO2 in each trap was determined using a Shimadzu TOC V-CPH Carbon Analyzer.

CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes

- Toxicity control: Yes

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (CO2 evolution)

Value:

0

Sampling time:

28 d

Details on results:

Toxicity control indicated no inhibition.

Results with reference substance:

The reference substance achieved 78.79% degradation by day 6 and approximately 85% degradation by day 14

Table 1:CO₂evolved (mg/l) and calculated % biodegradation for inoculum blank, test substance, reference substance and toxicity control

Type of suspension	1d		3d		6d		9d		14d		19d		23d		28d
	CO2evolved (mg/l)	(%) biodeg	CO2evolved (mg/l)	(%) biodeg	CO2evolved (mg/l)	(%) biodeg	CO2evolved (mg/l)	(%) biodeg	CO2evolved (mg/l)	(%) biodeg	CO2evolved (mg/l)	(%) biodeg	CO2evolved (mg/l)	(%) biodeg	CO2evolved (mg/l)	(%) biodeg
Inoculum Blank (mean of two replicates)	3.58	-	6.81	-	11.56	-	14.28	-	17.65	-	20.24		21.04		25.04
Test substance (mean of two replicates)	3.65	0.19	6.74	-0.20	10.15	-3.83	12.33	-5.30	16.33	-3.59	19.44	-2.18	20.28	-2.08	23.82	-3.33
Reference substance	13.71	27.62	29.61	62.16	40.45	78.79	44.85	83.39	48.82	84.99	52.18	87.09	51.66	83.50	54.92	81.49
Toxicity control	3.89	0.43	26.02	26.19	36.06	33.41	39.95	35.01	43.12	34.73	45.66	34.66	45.75	33.69	46.73	29.58

 

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

Biodegradation of 0% in 28 days (CO2 evolution) 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 (CO₂ evolution).

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater

Additional information

Biodegradation of 0% in 28 days (CO₂ evolution) was determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.