Dibutyl [[bis[(2-ethylhexyl)oxy]phosphinothioyl]thio]succinate

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:

7 August 2006 to 14 September 2006

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study without detailed documentation

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

not specified

Remarks:

Testing carried out under ISO17025.

Specific details on test material used for the study:

Sample description and concentration: The product is tested directly (+/- 20 mg C/l)
Total Organic Carbon content: 57.5%

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

Origin and concentration of the inoculum: Station Epuration Gembloux 2nd Stage; 04/08/2006; >10E6 CFU/mL (Verification with Merck Cult Dip Combi)

Duration of test (contact time):

28 d

Initial conc.:

>= 10 - <= 20 mg/L

Based on:

DOC

Remarks:

DOC or TOC

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST PRINCIPLE
A clearly chemically defined medium, without any other organic carbon sources, was mixed up to the substance to be examined. Then micro-organisms issued from mud were added. Finally the released CO2 is trapped under the BaCO3 compound. After comparison to the control results, the amount of CO2 product was determinated and expressed in percent of CO2 theoretically linked to the TOC and the amount of test substance put in experiment.

OUTLINE OF THE METHOD
Air free from carbon dioxide passes through the solutions using a flow of 50 to 100 mL/min. The released CO2 from biodegradation reacts with Ba(OH)2 and is trapped under Barium carbonate precipitate. Then the amount of CO2 is determined by back titration of the remaining Ba(OH)2 with HCl and phenolphthalein as indicator. In this procedure, every 2 days, the Ba(OH)2 solution flask closest to the test container has to be removed and an new one has to be added at the end of the queue (the first two flasks have been put closest to the test container). The titrations were carried out every two or three days from the first 10 days and every three to five days until the day 28
At day 28, the pH of the solution in the container was measured, then 1 mL of concentrated HCl was added to the container in order to purge the CO2 from the test solutions. The last titration was carried out the day 29.

Reference substance:

benzoic acid, sodium salt

Remarks:

20 mg C/l

Key result

Parameter:

% degradation (CO2 evolution)

Value:

12.1

Sampling time:

28 d

Details on results:

The released CO2 is determined from the remaining Ba(OH)2 in absorber flasks taken into account the CO2 released from the blank (inoculum).
Reactions are:
CO2 released from biodegradation
Ba(OH)2 + CO2 --> BaCO3 + H2O
Ba(OH)2 + 2 HCl --> BaCl2 + 2 H2O
Biodegradability is expressed in % versus CO2 or TOC

Results with reference substance:

Reference (benzoic acid, sodium salt) biodegradability = 90.6 % after 28 days; Blank control: 25.2 mg

An organic compound is considered readily biodegradable if:

- the result after 28 days reach 60 %,

- when biodegration start (at 10 % of biodegradability), the level of 60 % must be reached after 10 days

Validity criteria fulfilled:

yes

Remarks:

The reference biodegradability must be > 60 %. The blank control must be < 50 mg.

Interpretation of results:

not readily biodegradable

Conclusions:

The ready biodegradability of the test substance according to OECD guideline 301-B was determined to be 12.1% and is therefore not readily biodegradable.

Executive summary:

The biodegradability of the test substance was investigated according to OECD guideline 301-B over 28 days.

A clearly chemically defined medium, without any other organic carbon sources, is mixed up to the substance to be examined. Then micro-organisms issued from mud are added. Finally the released CO2 is trapped under the BaCO3 compound. After comparison to the control results, the amount of CO2 product is determinated and expressed in percent of CO2 theoretically linked to the TOC and the amount of test substance put in experiment.

The test substance showed a biodegradation of 12.1% after 28 days and is therefore not readily biodegradable.

Description of key information

The test item attained 12.1% biodegradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No. 301B.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater