(E)-1-(2,4,4-trimethyl-2-cyclohexen-1-yl)-2-buten-1-one

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:

From 2022-06-16 to 2022-08-15

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Version / remarks:

1992

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Municipal sewage treatment plant, Hildesheim, Germany.
- Pretreatment: The activated sludge was washed twice with chlorine free tap water. After the second washing the settled sludge was resuspended in mineral salts medium and was maintained in an aerobic condition by aeration with CO2 free air until test start (3 days) at the test temperature. The amount of inoculum used to initiate inoculation was 4.76 mL/L (25.0 mg/L dw).

Duration of test (contact time):

60 d

Initial conc.:

19 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: Mineral salts medium according to OECD 301 F
- Test temperature: Nominal: 20 - 24 ± 1 °C; Actual: 22.1 – 22.5°C
- Photoperiod: Dark

TEST SYSTEM
- Culturing apparatus: Closed bottles
- Number of culture flasks/concentration: Total number of replicates of test item 2, total number of replicates of inoculum control 4, total number of replicates of functional control 2, total number of replicates of toxicity control 1.
- Measuring equipment: The oxygen consumption was determined in the incubation vessels by the OxiTop® measuring system at 360 measuring points during the 60 d incubation period.

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (O2 consumption)

Value:

41

Sampling time:

60 d

Details on results:

Degradation kinetics (%):
-Day 14: Rep1: 1%, Rep2: 0%
-Day 28: Rep1: 1%, Rep2: 12%
-Day 42: Rep1 6%, Rep2: 28%
-Day 60: Rep1: 28%, Rep2 53%
The biodegradation of the test item begins with a certain lag time (approx. 24 -36 days). Because of the late start of the biodegradation, special bacterial cultures are probably required, which consequently generate a deviation between the test item replicates. Since the two test item replicates show an identical increase in percentage biodegradation and the first replicate only starts with a delay, the deviations between the two test item replicates are considered to be acceptable.

Toxicity control after 14 days: 39% (it is assumed that the test item is not inhibitory). After 28 days: 50%. After 60 days: 82%.

Results with reference substance:

Biodegradation:
- Day 14: Rep1: 80%, Rep2: 90%
- Day 28: Rep1: 90%, Rep2: 100%
- Day 42: Rep1: 93%, Rep2: 100%
- Day 60: Rep1: 93%, Rep2: 100%

Validity criteria fulfilled:

yes

Remarks:

see details on results

Interpretation of results:

not readily biodegradable

Conclusions:

The study showed that the test item is not readily and not inherently, ultimately biodegradable as it did not reach the respective pass pass levels (60% of biodegradability).

Executive summary:

The present study was conducted in order to evaluate the biodegradability of the test item by measuring its percentage of biodegradation with inoculum in a period of 60 days. The test method was performed following the OECD Test Guideline 301F and GLP. The test item concentration was 19 mg/L. Benzoic acid was used as reference substance in the functional control as well as in the toxicity control.

The biodegradation of the test item begins with a certain lag time (approx. 24 -36 days). Because of the late start of the biodegradation, special bacterial cultures are probably required. The two test item replicates show an identical increase in percentage biodegradation, but the first replicate starts with a delay (10% reached on day 46, compared to 10% reached on day 27 for replicate 2). After the 60-d period the mean biodegradation of the test item was calculated to be 41% without achieving a plateau (replicate 1: 28%; replicate 2: 53%). The study shows that the test item degradation starts after a long-lag phase (> 26 days) and would degrade even more over a longer time. Nevertheless, the test item has to be regarded as not readily and not inherent, ultimately biodegradable, but can be classified as inhernt, primarily biodegradable.

Description of key information

Not readily biodegradable: 41% after 60d (OECD 301)

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Additional information

The present study was conducted in order to evaluate the biodegradability of the test item by measuring its percentage of biodegradation with inoculum in a period of 60 days. The test method was performed following the OECD Test Guideline 301F and GLP. The test item concentration was 19 mg/L. Benzoic acid was used as reference substance in the functional control as well as in the toxicity control.

The biodegradation of the test item begins with a certain lag time. Because of the late start of the biodegradation, special bacterial cultures are probably required. The two test item replicates show an identical increase in percentage biodegradation, but the first replicate starts with a delay (10% reached on day 46, compared to 10% reached on day 27 for replicate 2). After the 60-d period the mean biodegradation of the test item was calculated to be 41% without achieving a plateau (replicate 1: 28%; replicate 2: 53%). The study shows that the test item degradation starts after a long-lag phase and would degrade even more over a longer time. Nevertheless, the test item has to be regarded as not readily and not inherent, ultimately biodegradable, but can be classified as inhernt, primarily biodegradable.