Imidazolium compounds, 1-[2-(2-carboxyethoxy)ethyl]-1(or 3)-(2-carboxyethyl)-4,5-dihydro-2-norcoco alkyl

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:

June 28, 2019 - April 18, 2019

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:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

- Solid content: 99.7%.
- Carbon content: 60.15% (determined by Hydrotox with a total carbon analyzer) .

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of activated sludge: municipal wastewater treatment plant Breisgauer Bucht.
- Concentration of sludge: the dry solid content of the activated sludge was 4.2 g/L. It was determined by weight measurements after drying at 105°C for 4 hours (mean of triplicate measurements).
- Pretreatment: the activated sludge was washed twice with tap water by settling the sludge, decanting the supernatant and re-suspending the sludge.

Duration of test (contact time):

28 d

Initial conc.:

20 mg/L

Based on:

TOC

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

PRERATION OF THE SOLUTIONS:
Test item:
The test item was added directly into the test vessels. 49.2 – 50.6 mg of the test item were added into the test vessels corresponding to a concentration of 19.7 – 20.3 mg/L organic carbon.

Toxicity control:
49.5 mg of the test item and 5.15 mL of the reference stock solution (10 g/L) were added into the toxicity control vessel corresponding to a concentration of 39.8 mg/L organic carbon.

TEST CONDITIONS
- Composition of medium: Mineral medium as described in the OECD 301
- Test temperature: The temperature was 20.7 – 22.4°C throughout the whole study and therefore within the required range of 22 ± 2°C.
- pH adjusted: no
- Aeration: The aeration rate was kept at a rate of 30 - 100 mL / min (1.6 - 5.5 bubbles / second) and determined visually daily on working days. (counted bubbles: 2.5 – 5.3 bubbles/second).
- Suspended solids concentration: 30 mg/L dry solids.
- Continuous darkness: yes


TEST SYSTEM:
- Number of flasks: In total three reactors containing the test item with inoculum, three reactors containing only inoculum (blank), three reactors containing the reference compound with inoculum and one reactor containing the test item and reference compound with inoculum (toxicity control) were set up.
- Method used to create aerobic conditions: The CO2-free air production system consists of an air compressor, three 1000 mL gas wash bottles filled with dry soda lime in series followed by one bottle filled with 0.1 M NaOH (sodium hydroxide).
- Measuring equipment: The CO2 produced in the reactors was absorbed in two 250 mL gas wash bottles in series each
filled with 200 mL 0.2 M NaOH.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, 3 reactors containing only inoculum (blank)
- Toxicity control: yes, one reactor containing the test item and reference compound with inoculum (toxicity control) were set up.

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (CO2 evolution)

Value:

43.6

Sampling time:

28 d

Details on results:

TEST ITEM:
The degradation extent of the test item at the end of the test was 43.6% of ThCO2 at 28 d after acidification (mean of three replicates). See 'Any other information on results incl. tables'.

TOXICITY CONTROL:
The degradation extent in the toxicity control was 56.9% within 14 days. According to the guideline, the test substance had no inhibitory effect on the inoculum. See 'Any other information on results incl. tables'.

Ultimate biodegradation after x days [% of ThCO2]

Days	0	4	7	11	14	21	28	29
Test item flasks	0	12.5	20.0	26.9	30.0	38.6	43.1	45.1
	0	14.2	22.9	30.4	36.3	4.08	44.2	42.7
	0	16.8	24.4	30.4	33.8	36.8	43.3	43.1
Reference flasks	0	72.1	78.1	82.4	84.8	83.8	84.4	84.1
	0	71.7	72.9	80.0	81.6	85.1	85.9	87.3
	0	72.5	78.9	84.8	85.6	85.2	84.7	86.7
Toxicity control	0	40.4	49.5	55.1	56.9	62.1	64.8	64.8

Validity criteria:

- The IC content in the test vessel was less than 5% of the TOC introduced with the test item.

- The CO2 evolution in the inoculum blank at the end of the test was below 40 mg/L.

- The difference of extremes of replicate values of the test item at the end of the test was less than 20%.

- The biodegradation of the reference compound reached the pass level of 60% ThCO2 by day 4.

- The degradation extent in the toxicity control was above 25% in 14 days based on ThCO2.

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

The degradation of the test item at the end of the test was 43.6% of ThCO2 (28 d after acidification, mean of three replicates). Therefore, the test item did not reach the criteria for ready biodegradability (60% of ThCO2 within a 10-d window). The degradation of the toxicity control after 14 days was 56.9%. The test item had no inhibitory effect on the inoculum according to the criterion of the guideline.

Executive summary:

The ready biodegradability of the test item was investigated in a GLP-compliant study performed in accordance with OECD Guideline 301B. The degradation of the toxicity control after 14 days was 56.9%. Thus, the test item had no inhibitory effect on the inoculum according to the criterion of the guideline. The degradation of the test item at the end of the test was 43.6% of ThCO2 (28 d after acidification, mean of three replicates). Therefore, the test item did not reach the criteria for ready biodegradability (60% of ThCO2 within a 10-d window).

Description of key information

The ready biodegradability of the test item was investigated in a GLP-compliant study (Flach, 2018) performed in accordance with OECD Guideline 301B. The degradation of the toxicity control after 14 days was 56.9%. Thus, the test item had no inhibitory effect on the inoculum according to the criterion of the guideline. The degradation of the test item at the end of the test was 43.6% of ThCO2 (28 d after acidification, mean of three replicates). Therefore, the test item did not reach the criteria for ready biodegradability (60% of ThCO2 within a 10-d window).

Key value for chemical safety assessment

Type of water:

freshwater

Additional information

The aerobic biodegradability of the test item was investigated in GLP-compliant study (Flach, 2018) performed in accordance with standard methods, without deviations. The study is considered as reliable (Klimisch 1) and is selected as a key study for the endpoint.