3-ETHYL-5,5-DIMETHYL-GAMMA BUTYROLACTONE

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:

From 15 July 2009 to 12 August 2009

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

All validity criteria were fulfilled. However, this study is considered reliable with restrictions for the following reasons: lag phase very long (15 days), correlation between replicates was not satisfactory (as one measurement [day 21, test 1] showed a degradation value above the pass level which could not be confirmed after 28 days), the linearity of degradation in time is not good (lower degradation at 23 days than 21 days in both replicates, also between 28 and 26 days).

Qualifier:

according to guideline

Guideline:

OECD Guideline 310 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test)

Version / remarks:

2006

Deviations:

no

Qualifier:

according to guideline

Guideline:

ISO 14593:1999 (Water quality - Evaluation of ultimate aerobic biodegradability of organic compounds in aqueous medium - Method by analysis of inorganic carbon in sealed vessels (CO2 headspace test))

Version / remarks:

2005

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Date of inspection: 27 and 28 November 2006 / Date of signature: 12 January 2007

Specific details on test material used for the study:

- Appearance: Trouble liquid, possible formation of crystals

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Remarks:

activated sludge from a biological sewage treatment plant was used. The chosen plant is treating mostly household sewage.

Details on inoculum:

- Source of inoculum/activated sludge: The sludge was taken from the activation basin of the ESN (Stadtentsorgung Neustadt) sewage treatment plant, Im Altenschemel, NW-Lachen-Speyerdorf. Date of collection: 15 July 2009
- Pretreatment: The sludge was filtrated through a cloth, then washed with tap water twice, with test medium once and resuspended in test medium. It was then aerated. The dry matter was determined with 4260 mg suspended solids/L. Dosage of inoculum was adapted to the dry matter.

Duration of test (contact time):

28 d

Initial conc.:

32.2 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

- Composition of medium: same as guidelines

- Test vessels: All glassware is cleaned with the laboratory cleaning agent Mucasol and then rinsed with tap water (thrice), diluted HCl (once), tap water (thrice) and deionised water (thrice). 250 mL narrow-neck-flasks were used as test vessels. These are made from DURAN 3.3, closed with lids and silicon septa. In the lid is a small hole, through which the NaOH 7-m can be dosed using a needle.

- Experimental parameters: The test was conducted with a volume of 150 mL in each test vessel. Seven points of measurement were made. Two controls, two flasks containing aniline as positive control, two flasks containing test item, one flask containing test item and 0.05 g HgCl2/L, but no inoculum (testing for abiotic degradation) and one flask containing test item and aniline (testing for toxic effects) were tested at each point of measurement.
The test was performed at room temperature (22+/-2°C) without direct lighting.
The emitted CO2 in the headspace and test solution was absorbed with NaOH and the increase of the IC content was determined. Sampling dates (days 0, 2, 12, 21, 23, 26 and 28) were derived from the degradation behaviour of the test item. During the exponential degradation phase, samples were taken every two or three days, else every five or six days. At the end of the test (day 28), six vessels (test series control, positive control, test) resp. three vessels (test series blank, abiotic control, toxicity control) were measured.

- Sampling: To each vessel to be measured, 1.5 mL of NaOH 7-m was added by syringe and needle and the vessel was shaken for one hour again. After settling down, a sample of 2 mL was pipetted into TOC-vials which were closed.
- CO2 determination: Analyses of the emitted CO2 were made by IC measurement. Each sample was measured at least 3 times. The carbon analyser was calibrated with freshly prepared reference solutions (containing a mixture of Na2CO3 and NaHCO3) weekly, quality control samples were measured daily.

Reference substance:

aniline

Test performance:

- Lag phase: 15 days
- Degradation phase: 16 days
- 10-day window: 15-25 days
- Degradation at the end of 10-day window: 48 %
- Degradation at the end of the test: 52 %

Key result

Parameter:

% degradation (CO2 evolution)

Value:

52

Sampling time:

28 d

Details on results:

The test item must be classified as not readily biodegradable since the pass level of 60% at the end of the 10-day window as well as at the end of the test was missed.
The test item showed no ultimate biological degradation. The lag phase was very long (15 days), and degradation during the 10-day window took place slowly. Correlation between replicates was not satisfactory, as one measurement (day 26, test 1) showed a degradation value above the pass level which could not be confirmed. It must be kept in mind that although all vessels are filled from the same flask, dosage with test item was performed individually, and therefore, variation within flasks may be greater than normal.
Abiotic degradation was not observed.

Results with reference substance:

Degradation behaviour of positive control and toxicity control was normal. The positive control showed ready biodegradation (63% biodegradation after only 2 days); the replicates showed very good correspondence. Degradation in the toxicity control was 93% at the end of the test, the test item can be stated as not toxic towards the inoculum in a concentration of 32.2 mg/L.

Table 5.2.1/1: Degradation values in %

Day	Positive control 1	Positive control 2	Positive control (mean)	Test 1	Test 2	Test (mean)	Abiotic control	Toxicity control
2	55.9	71.2	63.5	4.2	-4.0	0.1	0.6	2.2
12	90.3	93.9	92.1	3.5	0.7	2.1	1.5	44.7
21	88.9	88.0	88.5	54.4	23.5	38.9	2.0	54.9
23	87.0	84.6	85.8	38.1	11.1	24.6	1.4	60.1
26	85.0	87.1	86.1	78.9	43.4	61.1	-10.3	84.0
28	104.5	98.5	101.5	58.4	45.5	52.0	-1.0	93.2

Validity criteria fulfilled:

yes

Remarks:

Degradation of positive control: 63% after 2 days. Mean net IC content of controls at the end of the test: 2.15 mg/L.

Interpretation of results:

not readily biodegradable

Conclusions:

52% biodegradation (mean value) was determined after 28 days. The test substance is not considered readily biodegradable.

Executive summary:

The test item was tested using a concentration of 32.2 mg test substance/L in test medium following ISO 14593:2005 resp. OECD 310.

Aniline was chosen as positive control. Activated sludge from a sewage treatment plant was used as inoculum (concentration 4 mg suspended solids/L). The test was left running for 28 days.

All validity criteria were met. Degradation of the positive control was 63% after two days.

The following data were determined for the test item:

- 10-day window: day 15 -  day 25

- degradation at the end of 10-day window: 48 %

- degradation at the end of the test: 52 %

Therefore, the test substance is not readily biodegradable.

Description of key information

OECD Guideline 310, ISO Guideline 14593:2005, GLP, Key study, validity 2:

52% biodegradation (mean value) after 28 days.

Not readily biodegradable. However, a biodegradation between 20% and 60% suggest partial and primary degradation of the test substance.

 

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater

Additional information

To assess the biodegradation potential of the registered substance, one experimental study is available.

This study (LAUS, 2009) was performed on the registered substance according to OECD Guideline 310, ISO Guideline 14593:2005 with GLP compliance. The test substance was exposed to activated sludge at a concentration of 32.2 mg test substance/L in test medium, during 28 days. According to the results of this study, all validity criteria were met. The test substance was biodegraded by 52% at day 28 (mean value) and should therefore not be classifed as readily biodegradable. However, a biodegradation between 20% and 60% suggest partial and primary degradation of the test substance.