Hexanoic acid, 3,5,5-trimethyl-, 1,1'-[2-ethyl-2-[[(3,5,5-trimethyl-1-oxohexyl)oxy]methyl]-1,3-propanediyl] ester

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:

2012-08-07 to 2012-09-18

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP Guideline study

Qualifier:

according to guideline

Guideline:

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

Qualifier:

according to guideline

Guideline:

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

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.3110 (Ready Biodegradability)

GLP compliance:

yes (incl. QA statement)

Remarks:

19-21 July 2011

Oxygen conditions:

aerobic

Inoculum or test system:

sewage, predominantly domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Aeration stage of Severn Trent Water Plc sewage treatment plant, Loughborough, Leicestershire, UK on 06-08-2012
- Storage conditions: Washed twice by settlement and resuspension in mineral medium, maintained on continuous aeration at 21°C.
- Storage length: Used on day of collection
- Preparation of inoculum for exposure: As above
- Pretreatment: None
- Concentration of sludge: 30 mg suspended solids/L
- Initial cell/biomass concentration: Suspended solids concentration = 4.0 g/L prior to use
- Water filtered: no

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
- Composition of medium: as per OECD Guideline
- Additional substrate: No
- Solubilising agent (type and concentration if used): dispersed in mineral medium
- Test temperature: 21- 23°C
- pH: 7.4 - 7.7
- pH adjusted: yes to pH 7.4 prior to inoculm inclusion if needed.
- Suspended solids concentration: 30 mg ss/L
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 5L test culture vessels
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: CO2 free air bubbled through solution at rate of 30 to 100 mL/min per vessel
- Measuring equipment: See analytical method
- Details of trap for CO2 and volatile organics if used: two 500 mL Dreschel bottles containing 350 mL of 0.05M NaOH, prepared using purified de-gassed water

SAMPLING
- Sampling frequency:
Ist absorber: Days 0, 2, 4, 6, 8, 10, 14, 21, 28 and 29
2nd absorber: Days 0 and 29
- Sample storage before analysis: No

CONTROL AND BLANK SYSTEM
- Inoculum blank: inoculated mineral medim (x2)
- Abiotic sterile control: No
- Toxicity control: test item plus reference item in incoculated medium to give concentration of 20 mg C/L (x1)


STATISTICAL METHODS:

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (CO2 evolution)

Value:

0

Sampling time:

2 d

Parameter:

% degradation (CO2 evolution)

Value:

28

Sampling time:

6 d

Parameter:

% degradation (CO2 evolution)

Value:

69

Sampling time:

14 d

Parameter:

% degradation (CO2 evolution)

Value:

106

Sampling time:

21 d

Parameter:

% degradation (CO2 evolution)

Value:

114

Sampling time:

28 d

Details on results:

See attached document for IC values and biodegradation curve.

Results with reference substance:

The toxicity control attained 68% degradation after 14 days and 114% degradation after 28 days thereby confirming the test item was not toxic to sewage treatment micro-organisms.

See attached document for IC values and biodegradation curve.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

The test item attained 104% degradation after 28 days and satisfied the 10-day window validation criterion. The test item can therefore be considered to be readily biodegradable under the terms and conditions of the Guideline.

Executive summary:

Test Guidance

OECD Guideline 301B, EC Method C.4 -C and US EPA OPPTS 835.3110

Method

The test item at a concentration of 10 mg C/L was exposed to activated sewage sludge micro-organisms with a mineral medium in sealed culture vessels in the dark at 21 to 23°C for 28 days.

The degradation of the test item was assessed by the determination of carbon dioxide produced. Control solutions with inoculum and the reference item, sodium benzoate, together with a toxicity control were used for validation purposes.

Results

The test item attained 104% degradation after 28 days and satisfied the 10-day window validation criterion.

Conclusions

The test item can therefore be considered to be readily biodegradable under the terms and conditions of the Guideline.

Description of key information

The substance is readily biodegradable according to OECD criteria.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

In the key study performed to OECD Guideline 301B, EC Method C.4 -C and US EPA OPPTS 835.3110 the test item at a concentration of 10 mg C/L was exposed to activated sewage sludge micro-organisms with a mineral medium in sealed culture vessels in the dark at 21 to 23°C for 28 days. The degradation of the test item was assessed by the determination of carbon dioxide produced. The test item attained 104% degradation after 28 days and satisfied the 10-day window validation criterion. The test item can therefore be considered to be readily biodegradable.

 

Read-across to the environmental fate properties of fatty acid polyols (Fatty acids, C5-9, esters with pentaerythritol (EC 270-290-3, CAS 68424-30-6) and Decanoic acid, ester with 2-ethyl-2-(hydroxymethyl)-1,3-propanediol octanoate (EC 234-392-1, CAS 11138-60-6)) and their analogues is applicable based on the similarity in structure and physico-chemical properties. The justification for read-across is presented in Section 13 Assessment reports- Read-across justification.

 

Two studies, investigating the ready biodegradability of Decanoic acid, ester with 2-ethyl-2-(hydroxymethyl)-1,3-propanediol octanoate (EC

234-392-1, CAS-No 11138-60-6) according to OECD 301B (CO2 Evolution Test), are available. In both studies domestic activated sludge (non-adapted) was used as inoculum. In the key study (Häner, 2007) a mean degradation of 72% after 28 days could be observed and in the supporting study (Muckle, 2008) the test substance was degraded to 78.9% after 29 days. In both studies the 10-day-window was reached. The test substance can be classified as readily biodegradable according to OECD criteria.

 

A supporting study investigating the ready biodegradability of Fatty acids, C5-9 esters with pentaerythritol (EC 270 -290 -3, CAS-No. 68424-30-6) according to OECD 301B (CO2 Evolution), is available. In this study (Defleur, 1999) the biodegradation was tested in a CO2 Evolution test according to OECD 301B using domestic activated sludge as inoculum. At test termination after 28 days the substance had degraded 63.1%, but did not fulfil the 10 -day-window criteria. As the test substance is a mixture of constituents with different chain-lengths, sequential biodegradation of the individual structures is taking place. Due to a degradation of > 60% within 28 days Fatty acids, C5-9 esters with pentaerythritol (CAS-No. 68424-30-6) can be regarded as readily biodegradable. The 10 -day window validity criteria for ready biodegradation should not be applied to this substance (Annex I, OECD Guideline for The Testing of Chemicals 'Revised introduction to the OECD guidelines for testing of chemicals, section 3', OECD, March 2006).