Dimethyl azelate

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:

2017-09-06 to 2017-12-08

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

GLP study performed according to OECD Guideline No. 301 D. All validity criteria were fulfilled

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)

Deviations:

no

Principles of method if other than guideline:

Not applicable

GLP compliance:

yes (incl. QA statement)

Remarks:

10 January 2017

Specific details on test material used for the study:

None

Oxygen conditions:

aerobic

Inoculum or test system:

natural water / sediment: freshwater

Details on inoculum:

- Origin: River water was sampled from “La Mourachonne”, situated downstream of a plant treating domestic wastewater (Pegomas, France).
- Pre-conditioning: The river water was aerated for about 7 days before use as inoculum at the test temperature to reduce endogenous respiration.

Duration of test (contact time):

28 d

Initial conc.:

2 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Test water: Mineral medium (reconstituted water), as prescribed by the OECD Guideline No. 301D
- Composition of medium: The mineral medium was prepared by adding one mL of each of the following stock solutions (a to d) to each litre of ultrapure water: a) 8.5 mg KH2PO4, 21.75 mg K2HPO4, 33.40 mg Na2HPO4•2H2O, 0.50 mg NH4Cl. The pH of this solution was approximately 7.5; b) 36.40 mg CaCl2•2H2O, c) 22.50 mg MgSO4•7H2O and d) 0.25 mg FeCl3•6H2O.). This reconstituted water was aerated for at least 20 min and thereafter set aside at the test temperature for about 20 h before use.
- Test temperature: Temperatures recorded continuously and situated between 20.7 and 21.3°C throughout the test (average value: 21.1°C), and complied with the requirements as laid down in the study plan (22°C ± 2°C, constant within 1°C).
- Continuous darkness: Yes

TEST SYSTEM
- Culturing apparatus: All-glass sealed with ground glass stoppers BOD (Biological Oxygen Demand) bottles of approximately 300 mL capacity. Each test vessel was uniquely identified with study code, replicate number, date of the start of the biodegradability test (=J0) and type of series.
- Inoculum: A concentration of inoculum of approximately 6.10^4 cells.L-1 was used.
- Number of culture flasks/concentration: 20 bottles containing test item, inoculum, mineral medium and silica gel (test suspension)

SAMPLING
- Sampling frequency: Determinations of the concentration of dissolved oxygen using an oxygen electrode in duplicate vessels taken from each group (except the procedure and toxicity control) were made at day 0, 7, 14, 21 and 28, and only at the start of the test and after 7 and 14 days of incubation for the procedure and toxicity control.
- Temperature: Measured continuously in the growth chamber.

CONTROL AND BLANK SYSTEM
- Inoculum blank: 20 bottles containing inoculum, mineral medium and silica gel (inoculum blank with silica gel); 20 bottles containing inoculum and mineral medium (inoculum blank without silica gel)
- Test suspension: 20 bottles containing test item, inoculum, mineral medium and silica gel
- Procedure control: 6 bottles containing reference substance, inoculum and mineral medium
- Toxicity control: 6 bottles containing test item, reference substance, inoculum and mineral medium

Reference substance:

benzoic acid, sodium salt

Remarks:

2 mg/L

Preliminary study:

None

Key result

Parameter:

% degradation (O2 consumption)

Value:

108

Sampling time:

7 d

Remarks on result:

other: The plateau was reached at day 7

Details on results:

Test item DIMETHYL AZELATE was biodegraded by 108% (mean) at day 7, when the plateau was reached. Therefore, the pass level of 60% was reached after less than 7 days of incubation and the 10-day window criterion was successful.

Calculated ThOD of the test item: 2.07 mg O2/mg, based on a MW of 216 g/mol (C11 H20 O4)

Results with reference substance:

Calculated ThOD of the reference substance: 1.67 mg O2/mg, based on a MW of 144.1 g/mol (C7 H5 O2 Na). The biodegradation percentage of the reference substance, sodium benzoate, was 76% at day 7 and 80% at day 14, thus confirming the suitability of the inoculum used.

Table 5.2.1/1: Percentage biodegradation of the test item, the reference substance and of the toxicity control throughout the test

		Time (days)
		0	7	14	21	28
Test Suspension (2 mg test item.L^-1)	Replicate 1	0.00	112.32	77.78	104.59	97.22
	Replicate 2	0.00	103.14	76.33	73.43	106.16
	Mean	0	108	77	89	102
Procedure Control (2 mg reference substance.L^-1)	Replicate 1	0.00	76.35	80.84	N.A.	N.A.
	Replicate 2	0.00	75.75	79.34	N.A.	N.A.
	Mean	0	76	80	N.A.	N.A.
Toxicity Control (2 mg reference substance.L^-1 + 2 mg test item.L^-1)	Mean	0	32	58	N.A.	N.A.

* % biodegradation_{tox. Control}=  (BOD tox. cont / ThODref. subst.) * 100

with BOD tox. cont = (mTox(o) - mTox(n)) - (ma(o) - ma(n)) / mg test ref susbst.L^-1in vessel

and where:

 n = number of days after the start of the test

mTox(0) = mean toxicity control value at day 0

 mTox (n) = mean toxicity control value at day n

 ma(0) = mean test suspension value at day 0

 ma(n) = mean test suspension value at day n.

Table 5.2.1/2: Dissolved oxygen concentrations (mg.L^-1) throughout the test

	Time (days)
	0	7	14	21	28
Inoculum Blank + silica gel	8.84	8.11	7.90	7.88	7.38
	8.92	8.15	7.66	7.76	7.43
Mean	8.88	8.13	7.78	7.82	7.41
Test Suspension (2 mg test item.L^-1)	8.87	3.47	4.55	3.48	3.37
	8.87	3.85	4.61	4.77	3.00
Mean	8.87	3.66	4.58	4.13	3.19
Inoculum Blank (without silica gel)	8.69	8.12	7.98	8.09	7.70
	8.66	8.13	7.95	7.85	7.70
Mean	8.68	8.13	7.97	7.97	7.70
Procedure Control(2 mg reference substance.L^-1)	8.61	5.51	5.20	N.A.	N.A.
	8.56	5.48	5.20	N.A.	N.A.
Mean	8.59	5.50	5.20	N.A.	N.A.
Toxicity Control (2 mg reference substance.L^-1 + 2 mg test item.L^-1)	8.59	1.97	2.75	N.A.	N.A.
	8.62	2.66	2.00	N.A.	N.A.
Mean	8.61	2.32	2.38	N.A.	N.A.

Validity criteria of the test:   

Inoculum blank: Oxygen depletion in the inoculum blank did not exceed 1.5 mg dissolved oxygen/L after 28 days.

Residual [O₂]: Oxygen concentrations were > 0.5 mg/L in all bottles during the test period.

Replicate values: The differences of the replicate (test suspension) values at day 7 when the plateau was reached were less than 20 %.

Reference substance: The biodegradation percentage of the reference substance, sodium benzoate, was 76% at day 7 and 80% at day 14, thus confirming the suitability of the inoculum used.

Moreover, in the toxicity control containing both the test item and the reference item sodium benzoate, 32% biodegradation was noted at day 7 and 58% biodegradation at day 14 of the test. According to the test guideline, the test item can be assumed to be not inhibitory to the microbial inoculum because degradation was greater than 25% within 14 days (based on total ThOD).

Thus all validity criteria of the test have been fulfilled in the present study.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

Under the test conditions and according to the requirements of the test guideline, DIMETHYL AZELATE can be considered as readily biodegradable.

Executive summary:

A ready biodegradability study was performed to assess the biotic degradation of the test item DIMETHYL AZELATE according to the OECD Guideline 301 D (Closed bottle test) and in compliance with GLP.

BOD bottles were filled with mineral medium inoculated with river water and test item added at a nominal concentration of 2 mg/L with the help of silica gel. In the meantime, two series blanks (with and without silica gel) were filled with inoculated mineral medium. Furthermore, bottles containing reference substance sodium benzoate (2 mg/L) were tested in order to check the procedure. A toxicity control, containing both the test item and the reference substance, was also performed in order to check the absence of test item effect onthe microbial inoculum.The concentrations of dissolved oxygen in duplicate bottles from each group incubated at 22°C ± 2°C in darkness were measured at the start of the test and thereafter once a week until the end of the test.

The validity of thetest was demonstratedby an endogenous respiration < 1.5 mgO2/L and by a biodegradation of the reference substance of 80% of its ThOD after 14 days of incubation. Moreover,the differences of the replicate values at day 7 when the plateau was reached were less than 20%andoxygen concentrations were > 0.5 mg/L ^{in all bottles during the test period}. Furthermore,the toxicity control showed that the test item had no inhibitory effect on the activity of the microbial inoculum.

According to the OECD 301 guidelines, substances are considered to be readily biodegradable in the closed bottle test if the degradation of the test item is equal to or greater than 60% (based on ThOD) in the ten-day window within the 28-day period of the test (the 10-day window begins when the degree of biodegradation has reached 10% of the ThOD). The test item DIMETHYL AZELATE was biodegraded by 108% (mean) at day 7, when the plateau was reached. Therefore, the pass level of 60% was reached after less than 7 days of incubation and the 10-day window criterion was successful.

Under the test conditions and according to the requirements of the test guideline, DIMETHYL AZELATE can be considered as readily biodegradable.

Description of key information

The test item DIMETHYL AZELATE was biodegraded by 108% (mean) at day 7, when the plateau was reached. Therefore, the pass level of 60% was reached after less than 7 days of incubation and the 10-day window criterion was successful. Under the test conditions and according to the requirements of the test guideline, DIMETHYL AZELATE can therefore be considered as readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

For that endpoint, an experimental study on the registered substance was available. This study was performed to assess the biotic degradation of the test item DIMETHYL AZELATE according to the OECD Guideline 301 D (Closed bottle test) and in compliance with GLP.

BOD bottles were filled with mineral medium inoculated with river water and test item added at a nominal concentration of 2 mg/L. In the meantime, two series blanks (with and without silica gel) were filled with inoculated mineral medium. Furthermore, bottles containing reference substance sodium benzoate (2 mg/L) were tested in order to check the procedure. A toxicity control, containing both the test item and the reference substance, was also performed in order to check the absence of test item effect onthe microbial inoculum. The concentrations of dissolved oxygen in duplicate bottles from each group incubated at 22°C ± 2°C in darkness were measured at the start of the test and thereafter once a week until the end of the test.

According to the OECD 301 guidelines, substances are considered to be readily biodegradable in the closed bottle test if the degradation of the test item is equal to or greater than 60% (based on ThOD) in the ten-day window within the 28-day period of the test (the 10-day window begins when the degree of biodegradation has reached 10% of the ThOD). The test item DIMETHYL AZELATE was biodegraded by 108% (mean) at day 7, when the plateau was reached. Therefore, the pass level of 60% was reached after less than 7 days of incubation and the 10-day window criterion was successful. Therefore, under the test conditions and according to the requirements of the test guideline,DIMETHYL AZELATE can be considered as readily biodegradable.

The validity criteria of the study were respected. The study satisfies guidelines requirements for ready biodegradability studies and was therefore considered as acceptable for that endpoint.