Zinc EDDHA

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

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:

Please refer to Read Across Statement attached in Section 13

Reason / purpose for cross-reference:

read-across source

Preliminary study:

The test guideline recommends a test concentration of the test substance of 10 - 40 mg/L Dissolved Organic Carbon (DOC). A test concentration of 20 mg/L DOC was used. The selected test concentration of 20 mg DOC/L corresponds to approximately 62 mg/L Acetic acid, oxo-, sodium salt.
It is anticipated that the selected test concentration causes no toxic effects to the microorganisms. The selected test concentration was tested in an additional inhibition control test assay and no toxic effects to the microorganisms were observed.

Test performance:

No unusual observations during test or any other information affecting results were reported.

Parameter:

% degradation (DOC removal)

Value:

10 - 20

Sampling time:

28 d

Remarks on result:

other: mean value of two test assays

Details on results:

The test substance is considered as not readily biodegradable according to the OECD criteria.

Results with reference substance:

The reference substance (aniline) attained 91 % degradation after 14 days, based on DOC.

ACCOUNT OF TEST RESULTS

Test substance: Acetic acid.oxo-.sodium salt

Stock Solution, initial weight: 1233.7 mg/L

Dissolved Organic Carbon (DOC): 403 mg/L

DOC conc. at the test (nominal): 20 mg/L

Reference substance: aniline

Stock Solution, initial weight: 400.5 mg/L

Theoretical Organic Carbon (ThOC): 310 mg/L (calculated by initial weight)

DOC conc. at the test (nominal): 20 mg/L

 

Sample		BC1	BC2	RS	IH	PC	AC	TS1	TS2
Test substance concentration [mg/L] |		-	-	-	61.7	61.7	61.7	61.7	61.7
Inoculum conc. [mg/L dry matter]		30	30	30	30	-	30	30	30
Demineralized water [mL/vessel]		982	982	917	867	936	931	932	932
Mineral	solution A	10	10	10	10	10	10	10	10
medium	solution B	1	1	1	1	1	1	1	1
[mL/L]	solution C	1	1	1	1	1	1	1	1
	solution D	1	1	1	1	1	1	1	1
Stock Solution; test substance [mL]		-	-	-	50	50	50	50	50
Stock Solution; reference subst.[mL]		-	-	65	65	-	-	-	-
Mercury chloride sol.| [mL/vessel]		-	-	-	-	1	1	-	-
pH values before; after correction		7.8	7.8	7.8	7.7	7.7	7.7	7.7	7.8
		7.4	7.4	7.4	7.4	7.4	7.4	7.4	7.4
Inoculum (6 g/L) [mL/vessel]		5	5	5	5	-	5	5	5
Total test volume [mL]		1000	1000	1000	1000	1000	1000	1000	1000

 

Legend: BC = blank control; RS = reference substance; IH = inhibition control; PC = abiotic control; AC = adsorption control; TS = test substance

Removal of Dissolved Organic Carbon (DOC) [%]:

Test duration [days]	RS	IH	PC	AC	TS1	TS2	TS mv
0	0	0	0	0	0	0	0
1	-1	0	-5	3	-1	1	0
3	10	12	-3	7	7	5	6
7	96	53	1	7	9	10	10
10	92	52	-2		8	5	7
14	91	52	3		7	5	6
17	95	55	-3		12	12	12
21	93	54	1		8	6	7
24	95	57	6		13	13	13
27	98	59	3		17	16	17
28	97	57	4		11	10	11

Legend: BC = blank control; RS = reference substance; IH = inhibition control; PC = abiotic control; TS = test substance, AC = adsorption control; mv = mean value

Validity criteria fulfilled:

yes

Remarks:

All validity criteria are fulfilled according to the applied OECD Guideline.

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

The test material attained 10 - 20 % degradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline 301A. The study was conducted under certificated GLP compliance and a well documented study report is available. The same result is expected for the target substance because the core chemical structures of EDDHA-moiety-containing constituents are the same in the source and in the target substance. Thus the same biodegradation rates are expected.

Executive summary:

The DOC Die-Away Test is a batch test method to determine the ultimate aerobic biodegradability of a test substance in water. Mixtures of the test substance, a defined inorganic medium and a non pre-adapted inoculum (e.g. activated sludge or effluent from a municipal wastewater treatment plant) are incubated and aerated at a temperature of 22 +/- 2 °C for up to 28 days (Schwarz, 2010). Samples are taken at regular intervals to determine the Dissolved Organic Carbon concentration (DOC). The mean value of two test assays was used to determine the final biodegradation rate after the regulary exposure time. Thereby the test substance attained 10 - 20 % degradation. Based on the co-incubation with the reference substance anilin, it could be demonstrated that the test concentration used (20 mg/L DOC) was not toxic (inhibitory effect) on the sewage treatment bacteria flora. Anilin attained 91 % degradation after 14 days, indicating that the test system was suitable. In this experiment, the test substance was poorly biodegradable and is therefore considered as "not readily biodegradable" according to OECD criteria.

Description of key information

Read across: OECD 301A, not readily biodegradable - 10 - 20 % degradation after 28 days

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable

Type of water:

freshwater

Additional information

No experimental investigations concerning the biodegradability of the registered substance are available. Therefore, read-across from the structurally related substance Fe(Na)EDDHA (CAS 84539-55-9) was performed (BASF, 2010; Study No. 21G0753/093217). The DOC Die-Away Test is a batch test method to determine the ultimate aerobic biodegradability of the source substance Fe(Na)EDDHA in water. Mixtures of the test substance, a defined inorganic medium and a non pre-adapted inoculum (e.g. activated sludge or effluent from a municipal wastewater treatment plant) are incubated and aerated at a temperature of 22 +/- 2 °C for up to 28 days (Schwarz, 2010). Samples are taken at regular intervals to determine the Dissolved Organic Carbon concentration (DOC). The mean value of two test assays was used to determine the final biodegradation rate after the regular exposure time. Thereby the test substance attained 10 - 20 % degradation. Based on the co-incubation with the reference substance aniline, it could be demonstrated that the test concentration used (20 mg/L DOC) was not toxic (inhibitory effect) on the sewage treatment bacteria flora. Aniline attained 91 % degradation after 14 days, indicating that the test system was suitable. In this experiment, the test substance was poorly biodegradable and is therefore considered as "not readily biodegradable" according to OECD criteria.