2-ethylhexyl 3,5,5-trimethylhexanoate

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:

30 July - 10 December 2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.3110 (Ready Biodegradability)

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

The study was performed with aerobic activated sludge from a wastewater treatment plant (ARA Ergolz II, Füllinsdorf, Switzerland) treating predominantly domestic wastewater. The sludge was washed twice with tap water by centrifugation and the supernatant liquid phase was decanted. A homogenized aliquot of the final sludge suspension was weighed, thereafter dried and the ratio of wet to dry weight was calculated.

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Initial conc.:

>= 289 - <= 291 other: mgO2/L

Based on:

ThOD/L

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

Light conditions: darkness
Test temperature: 22 °C, maintained with a built-in thermostat and checked once per week.
pH: Prior to test start, the pH was measured in each test flask before the addition of the activated sludge inoculum (Table 3). At the end of incubation, the pH was measured again in each test flask.

Reference substance:

benzoic acid, sodium salt

Remarks:

Lot No. BCBB4145, Purity 99.7%

Preliminary study:

none

Test performance:

Validity of the Test
The results are considered valid since the following criteria are met:
- The oxygen demand of the inoculum control (medium and inoculum) was 19 mg O2 /L within 28 days (criterion: normally 20 - 30 mg O2 /L but not greater than 60 mg O2 /L).
- The degradation rates of the replicate test flasks containing the test item, test water and inoculum deviated by about 10% at the end of the test (criterion: not more than 20% deviation at the time the plateau is reached, at the end of the test or at the end of the 10-day window).
- The percentage degradation of the reference item reached the level for ready biodegradability (at least 60% of ThOD in a 10-day window) by Day 3. (criterion: at least 60% of ThOD in a 10-day window by Day 14 for the reference item).

Key result

Parameter:

% degradation (O2 consumption)

Value:

59

Sampling time:

28 d

Details on results:

The percent biodegradation of the test item was calculated based on the theoretical oxygen demand (ThOD) of 2.90 mg O2/mg test item.
The biochemical oxygen demand (BOD) of the test item in the test media significantly increased from exposure day 9 until test termination after 28 days. At the end of the 28-day exposure period, the mean biodegradation of 2-ethylhexyl 3,5,5-trimethylhexanoate amounted to 59% .
Consequently, the test item was found to be inherently biodegradable under the test conditions within 28 days.
However, the pass level for ready biodegradability, i.e. biodegradation of at least 60% of the ThOD in a 10-day window within the 28-day period of the test, was not reached.

Results with reference substance:

The percent biodegradation of the reference item sodium benzoate was calculated based on the theoretical oxygen demand of 1.67 mg O2/mg.
In the procedure controls, the reference item sodium benzoate was degraded by an average of 84% by exposure day 14, and reached an average biodegradation of 90% by the end of the test (Day 28), thus confirming suitability of the activated sludge.

Biodegradation in the toxicity control:

The percent biodegradation in the toxicity control, containing both test item and sodium benzoate, was calculated based on the sum of the ThOD of the test item and the reference item (see Sections 3.3.2 and 3.4). In the toxicity control, the run of the curve of the oxygen consumption over the 28-day exposure period correlated very well with the oxygen demand of the two added substances, i.e. test item and reference item. Within 14 days of exposure, biodegradation amounted to 37%. Thus, according to the test guidelines, the test item had no inhibitory effect on activated sludge microorganisms at the tested concentration of 100 mg/L because biodegradation in the toxicity control was >25% within 14 days.

Validity criteria fulfilled:

yes

Interpretation of results:

inherently biodegradable

Conclusions:

Based on a biodegradation rate of 59% within 28 days the substance is considered as inherently biodegradable.

Executive summary:

The test item was investigated for its ready biodegradability in a manometric respirometry test over 28 days according to the OECD Guideline for Testing of Chemicals No. 301F (1992), the Commission Regulation (EC) No 440/2008, C.4-D and the US EPA Draft Ecological Effects Test Guidelines OPPTS 835.3110 (Paragraph (q)).

The study was performed with aerobic activated sludge from a wastewater treatment plant (ARA Ergolz II, Füllinsdorf, Switzerland) treating predominantly domestic wastewater. The sludge was washed twice with tap water by centrifugation and the supernatant liquid phase was decanted.

The biochemical oxygen demand (BOD) in the test media significantly increased from exposure day 9 until test termination after 28 days. At the end of the 28-day exposure period, the mean biodegradation of the test item amounted to 59%.

The test item was found to be inherently biodegradable under the test conditions within 28 days. However, the pass level for ready biodegradability, i.e. biodegradation of at least 60% of the ThOD in a 10-day window within the 28-day period of the test, was not reached. According to the test guidelines, the test item had no inhibitory effect on activated sludge microorganisms at the tested concentration of 100 mg/L.

Description of key information

59% in 28 days in a OECD 301F (test substance is considered as inherently biodegradable according to guidance on information requirements and chemical safety assessment, Chapter R.7b.

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable

Type of water:

freshwater

Additional information

The test item was investigated for its ready biodegradability in a manometric respirometry test over 28 days according to the OECD Guideline for Testing of Chemicals No. 301F (1992), the Commission Regulation (EC) No 440/2008, C.4-D and the US EPA Draft Ecological Effects Test Guidelines OPPTS 835.3110 (Paragraph (q)).

The study was performed with aerobic activated sludge from a wastewater treatment plant treating predominantly domestic wastewater. The sludge was washed twice with tap water by centrifugation and the supernatant liquid phase was decanted.

The biochemical oxygen demand (BOD) in the test media significantly increased from exposure day 9 until test termination after 28 days. At the end of the 28-day exposure period, the mean biodegradation of the test item amounted to 59%.

The test item was found to be inherently biodegradable under the test conditions within 28 days. However, the pass level for ready biodegradability, i.e. biodegradation of at least 60% of the ThOD in a 10-day window within the 28-day period of the test, was not reached. According to the test guidelines, the test item had no inhibitory effect on activated sludge microorganisms at the tested concentration of 100 mg/L.