[1R-(1α,2β,5α)]-1-(isopropyl)-2-methoxy-4-methylcyclohexane

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

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)

Remarks:

Staatliches Gewerbeaufsichtsamt, Hildesheim, Germany

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Municipal sewage treatment plant
- Initial cell/biomass concentration: 3.8 x 10E+7 Colony Forming Units (CFU)/L in the final test solution
- Pretreatment: Activated sludge was washed twice with chlorine free tap water; settled sludge resuspended in mineral salts medium; maintained under aerobic condition by aeration for 2.5 hours; homogenized with a blender; after sedimentation the supernatant decanted and maintained under aerobic conditions by aeration with CO2-free air for 5 days; 10 mL/L used to initiate inoculation

Duration of test (contact time):

28 d

Initial conc.:

17 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: 20 - 24 °C
- pH: 7.75 - 8.01
- pH adjusted: no
- Dispersion treatment: Continuous stirring
- Continuous darkness: yes

TEST SYSTEM
- Measuring equipment: OxiTop system
- Test performed in closed vessels: yes
- Details of trap for CO2 and volatile organics if used: Soda lime

SAMPLING
- Sampling frequency: Continuous measurement (360 measuring points during the 28 days; every 112 minutes one measurement)

CONTROL AND BLANK SYSTEM
- Inoculum control: yes (with 2 replicates)
- Toxicity control: yes
- Functional control: yes

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (O2 consumption)

Value:

14

Sampling time:

28 d

Details on results:

In the toxicity control (17 mg/L test item and 45 mg/L sodium benzoate) the biodegradation achieved 55% after 14 days. After 28 days the biodegradation came to 63%. The validity criterion that the test item should not inhibit the biodegradation of the reference item was fulfilled.

Results with reference substance:

The adaptation phase changed to degradation phase within 1 day (degradation > 10%) and the biodegradation came to a maximum of 100% on day 18. The pass level for ready biodegradation (> 60% degradation) was reached within 2 days. Therefore the validity criterion that the degradation should be > 60% after 14 d was fulfilled.

Table 1: Degradation of test substance, functional- and toxicity control

Biodegradation (%)
	Day 7	Day 14	Day 21	Day 28
Replicate 1 Test Item 17 mg/L Replicate 2	1	1	4	12
	4	4	10	15
Functional Control 45 mg/L	87	96	100	100
Toxicity Control 17 mg/L Test Item + 45 mg/L Reference Item	50	55	59	63

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

Not readily biodegradable: 14% after 28 d (OECD 301F)

Description of key information

The substance is not readily biodegradable within 28 days (14% based on O2 consumption, OECD 301 F).

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

One GLP guideline study is available, which assessed the ready biodegradability of the test substance according to OECD guideline 301 F. Activated sludge, composed of a mixed bacterial population of aquatic microorganisms, was collected from the aeration tank of a local municipal sewage treatment plant treating predominantly domestic sewage and was continuously aerated until test start. The non-adapted activated sludge was inoculated with a nominal concentration of 17 mg/L, corresponding to a ThOD of 51.2 mg O2/L per test vessel during 28 d in the dark. The oxygen was depleted by the respiration of bacteria and the degradation was followed by measuring the oxygen concentration. The biodegradation rate is therefore expressed as the percentage BOD and was calculated for each study day. The 1st test item replicate reached the 10% level (beginning of biodegradation) on day 24 and the 2nd test item replicate on day 20. Both test item replicates were oscillating at this level and did not reach the pass level of 60% until test end. The mean biodegradation on day 28 was 14%. The biodegradation of the functional control reached a maximum of 100% degradation on day 18. The toxicity control showed no toxic effects on bacteria at the tested concentration. Therefore, the test substance is considered to be not readily biodegradable.