D,L-DIETHYL TARTRATE

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From June 30 to July 30, 2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

This study was performed according to OECD Guideline 301 D with GLP statement. River water was used as inoculum and ammonium chloride was omitted from the medium to prevent oxygen consumption due to nitrification (omission does not result in nitrogen limitation as shown by the biodegradation of the reference compound). This study is considered reliable without restriction.

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

Deviations:

yes

Remarks:

Ammonium chloride was omitted from the medium to prevent oxygen consumption due to nitrification; river water instead of an effluent/extract/mix. These deviations have no impact on the quality of this study.

Principles of method if other than guideline:

Not applicable

GLP compliance:

yes

Specific details on test material used for the study:

No additional information

Oxygen conditions:

aerobic

Inoculum or test system:

other: River water without particles was used as inoculum

Details on inoculum:

- Source of inoculum/activated sludge: River water was sampled from the Rhine near Heveadorp, The Netherlands (25-06-2015).
The nearest plant (Arnhem-Zuid) treating domestic wastewater biologically was 3 km upstream. The river water was aerated for 7 days before use to reduce the endogenous respiration (van Ginkel and Stroo, 1992). River water without particles was used as inoculum. The particles were removed by sedimentation after 1 day while moderately aerating.

Duration of test (contact time):

28 d

Initial conc.:

4 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: The river water used in the Closed Bottle test was spiked per liter of water with 8.5 mg KH2PO4, 21.75 mg K2HPO4, 33.4 mg Na2HPO4·2H2O, 22.5 mg MgSO4·7H2O, 27.5 mg CaCl2, 0.25 mg FeCl3·6H2O. Ammonium chloride was not added to the river water to prevent nitrification.
- Test temperature: 22-24 °C
- Continuous darkness: Yes
- Deionized water containing no more than 0.01 mg/L Cu (Sterlab certified; non-GLP analysis) was prepared in a water purification system.

TEST SYSTEM
- Culturing apparatus: Test was performed in 0.3 L Biological oxygen demand (BOD) bottles with glass stoppers
- Number of culture flasks/concentration: 10 bottles containing only river water, 6 bottles containing river water and sodium acetate, 10 bottles containing river water with test substance.
- Method used to create aerobic conditions: No data
- Method used to create anaerobic conditions: Not applicable
- Measuring equipment: The dissolved oxygen concentrations were determined electrochemically using an oxygen electrode (WTW TrioXmatic EO 200) and meter (WTW OXI 530) (Retsch, Ochten, The Netherlands). The pH was measured using a Eutech Cyberscan pH11 pH meter (Eutech Instruments, Nijkerk, The Netherlands). The temperature was measured and recorded with a sensor connected to a data logger.
- Test performed in closed vessels: Yes
- Test performed in open system: No

CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes

OTHERS:
- Each of the prepared solutions was dispensed into the respective group of BOD bottles so that all bottles were completely filled without air bubbles. The zero time bottles were immediately analyzed for dissolved oxygen using an oxygen electrode. The remaining bottles were closed and incubated in the dark. Two duplicate bottles of all series were withdrawn for analyses of the dissolved oxygen concentration at day 7, 14, 21, and 28.
- The biological oxygen demand (BOD) mg/mg of the test compound was calculated by dividing the oxygen consumption by the concentration of the test substance and sodium acetate in the closed bottle, respectively. The biodegradation was calculated as the ratio of the biochemical oxygen demand (BOD) to the theoretical oxygen demand (ThOD).

Reference substance:

acetic acid, sodium salt

Preliminary study:

See details in "Any other informaton on materials and methods incl. tables".

Test performance:

No data

Key result

Parameter:

% degradation (O2 consumption)

Value:

85

Sampling time:

28 d

Remarks on result:

other: Over 60% biodegradation was achieved in a period of approximately 8 days immediately following the attainment of 10% biodegradation.

Details on results:

- Theoretical oxygen demand (ThOD): The calculated theoretical oxygen demand (ThOD) of the test substance is 1.3 mg/mg.
- Toxicity: Inhibition of the degradation of a well-degradable compound, e.g. sodium acetate by the test substance in the Closed Bottle test was not determined because possible toxicity of the test substance to microorganisms degrading acetate is not relevant. Inhibition of the endogenous respiration of the inoculum by the test substance at day 7 was not detected. Therefore, no inhibition of the biodegradation due to the "high" initial test substance concentration is expected.
- Test conditions: The pH of the media was 8.0 at the start of the test. The pH of the medium at day 28 was 8.0 (control), and 7.9 (test and reference). Temperatures were within the prescribed temperature range of 22-24 °C.

Results with reference substance:

The ThOD of sodium acetate is 0.8 mg/mg. Sodium acetate was degraded by 85% of its theoretical oxygen demand after 14 days.

Table 5.2.1/1: Dissolved oxygen concentrations (mg/L) in the closed bottles

Time (days)	Oxygen concentration (mg/L)
	Oc	Ot	Oa
0	8.7	8.7	8.7
	8.7	8.7	8.7
Mean (M)	8.7	8.7	8.7
7	7.9	5.3	4.1
	7.8	4.9	3.9
Mean (M)	7.9	5.1	4.0
14	7.6	3.5	3.0
	7.6	3.5	2.9
Mean (M)	7.6	3.5	3.0
21	7.5	3.4	-
	7.5	3.2	-
Mean (M)	7.5	3.3	-
28	7.4	3.1	-
	7.5	3.0	-
Mean (M)	7.5	3.1	-

 

O_cRiver water with nutrients

O_tRiver water with nutrients, test material (4.0 mg/L)

O_aRiver water with nutrients and sodium acetate (6.7 mg/L).

 

Table 5.2.1/2: Oxygen consumption (mg/L) and the percentages biodegradation of the test substance, the test substance (BOD/ThOD) and sodium acetate (BOD/ThOD) in the Closed Bottle test

 

Time (days)	Oxygen consumption (mg/L)		Biodegradation (%)
	Test substance	Acetate	Test substance	Acetate
0	0.0	0.0	0	0
7	2.8	3.9	54	72
14	4.1	4.6	76	85
21	4.2		81
28	4.4		85

 

Validity of the test:

The validity of the test is demonstrated by an endogenous respiration of 1.2 mg/L at day 28. Furthermore, the differences of the replicate values at day 28 were less than 20%.

The biodegradation percentage of the reference compound, sodium acetate, at day 14 was 85. Finally, the validity of the test is shown by oxygen concentrations >0.5 mg/L in all bottles during the test period.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

The test substance was biodegraded by 85% at day 28 in the Closed Bottle test. Over 60% biodegradation was achieved after approximately 8 days immediately following the attainment of 10% biodegradation. The test substance therefore fulfilled the 14-day time window criterion for ready biodegradable substances (14-day time window can be applied to the Closed Bottle test where measurements are limited to prevent the test becoming too unwieldy). Hence, the test substance is classified as readily biodegradable.

Executive summary:

A ready biodegradability test was performed according to the OECD Guideline 301 D, to determine the biodegradability of the test substance by the Closed Bottle Test. Before definitive test, a screening test was conducted with the test substance (4 mg/L) exposed to river water and activated sludge for 7, 14, 21, 28 and 42 days.

 

The test substance was exposed to river water at a concentration of 4 mg/L with culture medium in closed bottles in the dark at 22-24 °C for 7, 14, 21 and 28 days. The degradation of the test material was assessed by the measurement of oxygen consumption. 

The test is valid as shown by an endogenous respiration of 1.2 mg/L and by the total mineralization of the reference compound, sodium acetate. Sodium acetate was degraded by 85% of its theoretical oxygen demand after 14 days. Finally, the most important criterion was met by oxygen concentrations >0.5 mg/L in all bottles during the test period.

 

The test substance did not cause a reduction in the endogenous respiration. The test substance is therefore considered to be non-inhibitory to the inoculum.

 

The test substance was biodegraded 85% at day 28 in the Closed Bottle test. Over 60% biodegradation was achieved in a period of approximately 8 days immediately following the attainment of 10% biodegradation. The test substance therefore fulfilled the 14-day time window criterion for ready biodegradable substances (14-day time window can be applied to the Closed Bottle test where measurements are limited to prevent the test becoming too unwieldy). Hence, the test substance is classified as readily biodegradable.

Reference 2

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:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
[further information is included as attachment to Iuclid section 13]

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
This read-across is based on the hypothesis that source and target substances have similar physico-chemical, (eco)toxicological and environmental fate properties because of their structural similarity.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The target and source substances are structurally related, in that both are diethyl tartrate. As two asymmetric (chiral) carbon atoms are present in this chemical structure, the chemical exists as 2 forms: D and L forms. The target substance is a reaction-mass of both forms (D and L) whereas the source substance is only L-form.
The target and source substances are typically very pure. No impurities that may contribute to the classification of the substances were identified. Therefore, it is concluded that the impurities will not affect the validity of the read-across.

3. ANALOGUE APPROACH JUSTIFICATION
Based on composition/structural similarity, both substances are not expected to have significantly different biodegradation profile in biodegradation testing.
The ready biodegradability test, performed on the source substance, was conducted according to OECD Test Guideline 301D and the test material was clearly identified. The biodegradation was 85% after 28 days, and as the 14-day window was fulfilled, the substance was considered readily biodegradable. The result of the study is adequate for the purpose of prediction.
Therefore, based on the considerations above, it can be concluded that the result of the biodegradation test conducted with the source substance is likely to predict the properties of the target substance and is considered as adequate to fulfil the information requirement of Annex VII, 9.2.1.1 of the REACH regulation.

4. DATA MATRIX
See attached document in Iuclid section 13.

Reason / purpose for cross-reference:

read-across source

Key result

Parameter:

% degradation (O2 consumption)

Value:

85

Sampling time:

28 d

Remarks on result:

other: Over 60% biodegradation was achieved in a period of approximately 8 days immediately following the attainment of 10% biodegradation.

Interpretation of results:

readily biodegradable

Conclusions:

According to the experimental study performed on the source substance, the biodegradation of the target substance can be determined at 85% after 28 days, within the 14-day window. Hence, the target substance is classified as readily biodegradable.

Executive summary:

No ready biodegradability test is available on the target substance, therefore good quality data for a related source substance have been read across for this endpoint. The target and source substances are structurally related, in that both are diethyl tartrate. As two asymmetric (chiral) carbon atoms are present in this chemical structure, the chemical exists as two forms: D and L forms. The target substance is a reaction-mass of both forms (D and L) whereas the source substance is only L-form.

In addition to the composition/structural similarity, no significant difference on the biodegradability potential is anticipated between the L-form (the source substance) and the racemic D,L-form (the target substance). Micro-organisms will degrade the organic matter in the same way. Therefore, isomerism is not expected to significantly influence the biodegradation profile between the target and source substances.

A ready biodegradability test was performed according to the OECD Guideline 301 D, to determine the biodegradability of the test substance (the source substance) by the Closed Bottle Test. Before definitive test, a screening test was conducted with the test substance (4 mg/L) exposed to river water and activated sludge for 7, 14, 21, 28 and 42 days. The test substance was exposed to river water at a concentration of 4 mg/L with culture medium in closed bottles in the dark at 22-24 °C for 7, 14, 21 and 28 days. The degradation of the test material was assessed by the measurement of oxygen consumption. The test is valid as shown by an endogenous respiration of 1.2 mg/L and by the total mineralization of the reference compound, sodium acetate. Sodium acetate was degraded by 85% of its theoretical oxygen demand after 14 days. Finally, the most important criterion was met by oxygen concentrations >0.5 mg/L in all bottles during the test period. The test substance did not cause a reduction in the endogenous respiration. The test substance is therefore considered to be non-inhibitory to the inoculum. The test substance was biodegraded 85% at day 28 in the Closed Bottle test. Over 60% biodegradation was achieved in a period of approximately 8 days immediately following the attainment of 10% biodegradation. The test substance therefore fulfilled the 14-day time window criterion for ready biodegradable substances (14-day time window can be applied to the Closed Bottle test where measurements are limited to prevent the test becoming too unwieldy). Hence, the test substance is classified as readily biodegradable.

Description of key information

Read-across, OECD Guideline 301 D, GLP, key study, validity 1:

85% biodegradation after 28 days, within the 14-day window.

Readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

No ready biodegradability test is available on the registered substance to assess the biodegradation potential of the registered substance. Therefore good quality data for a related source substance have been read across for this endpoint. The target and source substances are structurally related, in that both are diethyl tartrate. As two asymmetric (chiral) carbon atoms are present in this chemical structure, the chemical exists as two forms: D and L forms. The target substance is a reaction-mass of both forms (D and L) whereas the source substance is only L-form. In addition to the composition/structural similarity, no significant difference on the biodegradability potential is anticipated between the L-form (the source substance) and the racemic D,L-form (the target substance). Micro-organisms will degrade the organic matter in the same way. Therefore, isomerism is not expected to significantly influence the biodegradation profile between the target and source substances.

In this valid study, the ready biodegradability of the source substance has been determined by the Closed Bottle Test according to the OECD Guideline 301D with GLP statement. The test substance was exposed to river water at a concentration of 4 mg/L with culture medium in closed bottles in the dark at 22-24 °C for 7, 14, 21 and 28 days. The degradation of the test material was assessed by the measurement of oxygen consumption. The test substance was biodegraded 85% at day 28. Over 60% biodegradation was achieved in a period of approximately 8 days immediately following the attainment of 10% biodegradation. The test substance therefore fulfilled the 14-day time window criterion for ready biodegradable substances (14-day time window can be applied to the Closed Bottle test where measurements are limited to prevent the test becoming too unwieldy). In conclusion, the source substance, and by read-across the target substance, are classified as readily biodegradable. In addition, the test substance did not cause a reduction in the endogenous respiration. The source and target substances are therefore considered to be non-inhibitory to the inoculum.