Dipentaerythritol hexaesters of 3,5,5-trimethylhexanoic and n-heptanoic acids

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

In accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5 a read across from the structurally similar analogue substance Dipentaerythritol with fatty acids, C5 and C9iso was conducted to fulfil the data requirements according to Annex VII of Dipentaerythritol hexaesters of 3,5,5-trimethylhexanoic and n-heptanoic acids (CAS 1379424-11-9) in regards to biodegradation behaviour.

This read-across is justified in detail in the overall summary (IUCLID section 5) and within the analogue justification in IUCLID section 13. Both substances have got the same alcohol component (dipentaerythritol) and similar fatty acid chain lengths (C7 and C9iso for the target substance compared to C5 and C9iso for the source substance).
An study following OECD 301B under GLP conditions (Mead, 2000) is available for the source substance. The study was conducted using activated sludge from a wastewater treatment plant as inoculum. Microorganisms were exposed to a test substance concentration of 14.7 mg/L under aerobic conditions for 28 days. The results indicated that the test substance reached a mean degradation of 14% after 28 days. Therefore, the test substance is not readily biodegradable according to the OECD criteria.

Based on the result from the structurally related source substance, in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5), it can be concluded that the target substance Dipentaerythritol hexaesters of 3,5,5-trimethylhexanoic and n-heptanoic acids (CAS 1379424-11-9) is not readily biodegradable according to the OECD criteria.

Reason / purpose for cross-reference:

read-across source

Key result

Parameter:

% degradation (CO2 evolution)

Value:

14

Sampling time:

28 d

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

The target substance Dipentaerythritol hexaesters of 3,5,5-trimethylhexanoic and n-heptanoic acids (CAS 1379424-11-9) is considered to be not readily biodegradable, based on the results obtained for the source structural analogue Dipentaerythritol hexaesters with nC5 and iC9 (EC 444-000-2) (OECD 301B under GLP conditions).

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

16 Mar - 14 Apr 1999

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)

Version / remarks:

adopted 1992

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:

The Department of Health of the Government of the United Kingdom, date of inspection 23 March 1998

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): A mixed population of activated sludge microorganisms was obtained on 15 Mar 1999 from the aeration state of the Severn Trent Water Plc sewage treatment plant at Belper, Derbyshire, UK which treats predominantly domestic sewage.
- Storage conditions: The sample of sludge was maintained on continuous aeration.
- Preparation of inoculum for exposure: The activated sludge was washed three times by settlement and resuspension. Approx. 24 h prior to the start of the test the inoculated culture medium was aerated overnight.
- Concentration of sludge: 30 mg suspended solids/L

Duration of test (contact time):

28 d

Initial conc.:

10 mg/L

Based on:

other: TOC

Initial conc.:

14.7 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: according to guideline OECD 301 A
- Solubilising agent (type and concentration if used): granular silica gel, final concentration 33.3 mg/L
- Test temperature: 21 °C in temperature controlled room
- Aeration: CO2 free air at approx. 40 mL/min, continuous stirring
- Suspended solids concentration: 30 mg/L
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 5 L glass culture vessels each containing 3 L of solution
- Number of culture flasks/concentration: 2
- Measuring equipment: Samples were analysed for CO2 using an Ionics 1555B TOC analyser and a Dohrmann DC-190 TOC analyser.
- Details of trap for CO2: The CO2 produced by degradation was collected in two 500 mL Dreschel bottles containing 350 mL of 0.05 M NaOH. The CO2 absorbing solutions were prepared using purified degassed water.

SAMPLING
- Sampling frequency for the first absorber vessel: on days 0, 1, 2, 3, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 27, 28 and 29
- Sampling frequency for the second absorber vessel: on days 0 and 29
- Sample storage before analysis: instant analysis
- Other: On day 28, 1 mL of concentrated HCl was added to each vessel to drive off any inorganic carbonates formed. The vessels were resealed, aerated overnight and the final samples taken from both absorber vessels on day 29.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, 2 vessels
- Toxicity control: yes, 1 vessel
- Reference control: yes, 2 vessels

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (CO2 evolution)

Value:

14

Sampling time:

28 d

Results with reference substance:

Sodium benzoate attained 100% degradation after 28 days confirming the suitability of the inoculum and test conditions.

The toxicity control attained 41% degradation after 28 days confirming that the test material was not toxic to the microflora in the sewage.

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

Not readily biodegradable: 14% (DOC) in 28 days (OECD 301B)

Description of key information

Not readily biodegradable: 14% (CO2 evolution) after 28 days (OECD 301B).

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater