1,2-dimethylimidazole

Biodegradation in water and sediment: simulation tests

Administrative data

Endpoint:

biodegradation in water: sediment simulation testing

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because the substance is readily biodegradable

Justification for type of information:

JUSTIFICATION FOR DATA WAIVING
According to Regulation (EC) 1907/2006, Annex IX, Section 9.2.1.4, Column 2, sediment simulation testing does not need to be conducted if the substance is readily biodegradable.
The substance is not readily biodegradable according to OECD criteria. However, it is biodegradable based on an enhanced ready biodegradability test passing the test level of 60% CO2/ThCO2 but not meeting the 10-day window (OECD 301B, prolonged duration; BASF SE, 2012; see IUCLID Ch 5.2.1). In accordance with REACH Guidance document R.11 (ECHA, 2017: Table R.11-4, Figure R.11-3), substances which meet the pass level for ready biodegradability in enhanced ready biodegradation testing without the 10-day window are regarded as not P/vP. Further information for the assessment of non-persistence or persistence is not required. As this is the case for 1,2-dimethylimidazole, no sediment simulation study will be provided.

Cross-reference

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

exposure period: 2012-07-18 to 2012-09-18

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Deviations:

yes

Remarks:

prolonged test duration of 60 days

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

- Name of test substance: 1,2-Dimethylimidazole
- Test substance No.: 12/0074-1
- Batch identification: B 420
- CAS No.: 1739-84-0
- Purity: 99.1 g/100 g,
- Homogeneity: homogeneous
- Storage stability: The exposure period was guaranteed by the sponsor and the sponsor holds this responsibility.

- Molecular formula: C5H8N2
- Molecular weight: 96.13 g/mol
- Appearance: Liquid /yellow
- Water solubility: Completely soluble
- Storage conditions: Storage at room temperature, avoid temperatures >35°C
- Total Organic Carbon: 624 mg/g (calculated by molecular formula, purity 100%)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Municipal activated sludge from the wastewater treatment plant of Mannheim, Germany
- Laboratory culture: none
- Method of cultivation:
- Storage conditions: The inoculum was collected from the aeration tank of the plant and aerated in the laboratory until use. A suitable aliquot of the activated sludge suspension was sieved by a finely woven mesh with a mesh size about 1 mm. To reduce the content of inorganic carbon in the blank controls the activated sludge was aerated with carbon dioxide free air for about 72 hours at 22 ± 2° C,
- Preparation of inoculum for exposure: At the day of exposure the suspension was washed one time with tap water. Therefore the aeration was stopped and the sludge was allowed to settle. After settling the supernatant was discarded and the remaining sludge suspension was filled up with tap water and the concentration of the sludge was adjusted to 6.0 g/L dry weight.
- Pretreatment: none
- Concentration of sludge: Aliquots of 7.5 mL were added to the test vessels to obtain an activated sludge concentration of 30 mg/L dry weight.

Duration of test (contact time):

60 d

Initial conc.:

20 mg/L

Based on:

other: Total Organic Carbon (TOC)

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: according to guideline
- Solubilising agent (type and concentration if used): no
- Test temperature: 22+/- 2°C
- pH adjusted: adjusted to 7.4 ± 0.2
- Suspended solids concentration: 30 mg/L dry weight

TEST SYSTEM
- Culturing apparatus: 2L incubation vessels
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: aeration with carbon dioxide free air
- Measuring equipment: The determination of total carbon in solids is performed using a solid sample module SSM-5000A connected with a TOC-analyzer (Shimadzu TOC-5000A).
- Test performed in closed vessels: yes
- Test performed in open system: no
- Details of trap for CO2 and volatile organics if used: The test vessels were connected with an aeration unit and aerated by bubble aeration with carbon dioxide free air. The exposure phase was started by connection of the several test vessels with the absorption units. Usually once or twice per week, the TIC-content in the adsorption solutions and the DOC content of each test assay were determined. For TIC-measurement samples of the first carbon dioxide traps were taken and the TIC values were determined and used for the calculation of the amount of produced carbon dioxide. After each sampling the second trap was moved forward and the new trap with fresh sodium hydroxide solution was placed into the second position. Each trap was analyzed separately.

SAMPLING
- Sampling frequency: every 3-7 days

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Inhibition control: yes
- Toxicity control: yes

Reference substance:

aniline

Parameter:

% degradation (CO2 evolution)

Value:

ca. 6

Sampling time:

28 d

Remarks on result:

other: lag phase approx 28 days

Parameter:

% degradation (CO2 evolution)

Value:

ca. 42

Sampling time:

32 d

Parameter:

% degradation (CO2 evolution)

Value:

ca. 67

Sampling time:

60 d

Details on results:

Due to the long lag phase, biodegradation started after day 28. The following biodegradation curve was sigmoid indicating biodegradation (see attached document).

Table: Biodegradation degree; [CO2/ThCO2]

Test duration [d]	RS	IH	TS1	TS2	TS mv
0	0	0	0	0	0
3	16	1	1	-1	0
5	42	22	1	-1	0
11	75	35	1	-3	-1
14	84	39	1	-4	-2
18	88	41	0	-5	-3
21	90	41	0	-5	-3
25	91	47	0	-4	-2
28	92	65	3	9	6
32		73	43	40	42
35		77	57	47	52
39		80	67	53	60
42		81	71	56	64
49		82	75	59	67
53		83	76	59	68
55		83	76	58	67
60		83	75	59	67

RS: Reference substance

 

Table: DOC values [mg/L]; determined after centrifugation

		BC1	BC2	BC mv	IH	TS1	TS2	TS mv
At begin of exposure	a	0.3	0.3	0.3	38.4	19.0	19.4
	b	0.4	0.2		38.5	18.8	19.7
At the end of exposure	a	0.4	0.4	0.4	1.2	1.1	1.1
	b	0.4	0.5		1.2	1.2	1.3
Degree of DOC in the test assay [%]					98	96	96	96

BC: Blank control; IH: Inhibition control; TS: Test substance; mv: mean value

 

Further details on TIC measurement, calculation of formed CO2 and degradation curves can be found in the attached file: 1739-84-0_BASF 2012 OECD 301B_Additional inf_2022-02-14.pdf

 

Validity criteria

- Measured DIC-concentrations in the blank controls at begin of exposure (mean value): 0.8 mg/L
- Amount of produced CO2 in the blank controls at the end of exposure (mean value): 43.2 mg/L
- Deviation of the degree of biodegradation of the test substance in the plateau phase should be <20%: yes
- The degree of biodegradation of the reference substance should be >60% CO2/ThCO2 after 14 days: yes
- The degree of biodegradation in the inhibition control should be>25 % CO2/ThCO2 after 14 days: yes
- The content of DIC in the blank control at start of exposure at the test concentration of 20 mg/L TOC should be <1.0 mg/L: yes
- The amount of produced CO2 in the inoculum blank (“blank controls”) at the end of exposure (mean value) should be <70 mg/L: yes

Validity criteria fulfilled:

yes

Interpretation of results:

inherently biodegradable, not fulfilling specific criteria

Conclusions:

Due to the results it can be assumed, that the substance is inherently biodegradable without fulfilling specific criteria.