Isopropylcyclohexane

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:

2012-02-23 to 2012-03-22

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline Study

Qualifier:

according to guideline

Guideline:

OECD Guideline 310 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test)

Deviations:

no

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Municipal sewage treatment plant, D-31137 Hildesheim, Germany
- Pretreatment/Concentration of sludge: The activated sludge was washed twice with autoclaved tap water. After the second washing the settled sludge was resuspended in mineral salts medium and was maintained in an aerobic condition by aeration for 2-4 hours. Thereafter the sludge was homogenized with a blender. The supernatant was decanted and maintained in an aerobic condition by aeration with Co2 free air for 6 days.
10 mL/L were used to initiate inoculation.
- Initial cell/biomass concentration: 6.9 * 10E10 CFU/L corresponding to 6.9 * 10E8 CFU/L in the test vessel

Duration of test (contact time):

28 d

Initial conc.:

15 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: Mineral salts medium acc. to OECD 310 / 80 mL
- Test temperature: 20-25 °C
- pH adjusted: no
- Continuous darkness: no, low light conditions (brown glass bottles)

TEST SYSTEM
- Culturing apparatus: Headspace flasks / 120 mL
- Number of culture flasks/concentration: Triplicates
- Method used to create aerobic conditions: Shaker (150-200 rpm)
- Details of trap for CO2 and volatile organics if used: The CO2 production in the test vessels was determined by measuring the increase of the inorganic carbon (IC) concentration during the incubation.
- Other: The reference item was weighed out and was transferred into a measuring flask with demineralised water. The required volumes of mineral medium stock solutions and inoculum were added and the flask was filled up with demineralised water. 80 mL of this solution were placed in each test vessel of the reference item and toxicity control replicates.
1.5 µL test item (corresponding to 1.2 mg test item) was injected directly into the test solution through the septum of the closed test vessels of each test item and toxicity control replicate.

SAMPLING
The CO2 production in the test vessels was determined by measuring the increase of the inorganic carbon (IC) concentration during the incubation.
Determination of CO2 was carried out by IC analysis with a carbon analyser according to DIN EN 1484.
Analysis was carried out at test start, twice in the first three weeks and on day 28.
The TIC of the sodium hydroxide solution (blind value) was determined at each sampling time.

CONTROL AND BLANK SYSTEM
- Inoculum blank: Test medium without test and reference item
- Abiotic sterile control: No
- Toxicity control: Test item and reference item in test concentration

STATISTICAL METHODS:
The amount of TIC produced was calculated by correcting the results of the test item and reference item for endogenous TIC production of the control groups and the blind value of the sodium hydroxide solution.
The biodegradation was calculated from the ratio theoretical TIC concentration at test start (ThIC = TOC) to net TIC production.
The 95 % confidence interval for the mean percentage biodegradation after 28 days was calculated for the test item and functional control using the software SigmaPlot (Windows), SPSS CORPORATION.

Reference substance:

benzoic acid, sodium salt

Remarks:

30 mg/L

Preliminary study:

Not performed

Parameter:

% degradation (CO2 evolution)

Value:

1

Sampling time:

28 d

Details on results:

The maximum amount of total inorganic carbon (TIC) produced in the inoculum controls until the end of the test was 0.62 mg C/L. The validity criterion for the inoculum controls at the end of the test according to the guidelines (< 3 mgC/L) was met.
The adaptation phase of the functional control changed after 1 day into the degradation phase (degradation  10 %). The course of the degradation phase was rapid and the pass level of 60 % was reached after 3 days. The biodegradation came to 91 % after 28 days. The validity criterion degradation > 60 % after 14 d is fulfilled. The 95 % confidence interval on day 28 was
90 - 93 %
The test item replicate did not reach the 10 % level and the biodegradation remained at 1 % until 28 days. The 95 % confidence interval on day 28 was 0 - 4 %

Results with reference substance:

The biodegradation of the toxicity control reached 32 % within 14 days and it came to 38 % after 28 days. The biodegradation of the reference item was not inhibited by the test item in the toxicity control. The 95 % confidence interval on day 28 was 34 - 42 %

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

The test item is classified as not readily biodegradable in the 10-d-window and after 28 days.

Executive summary:

The ready biodegradability of the test item Hydrocumene (batch no.: 3347/ 27372) was determined with a non adapted activated sludge over a test period of 28 days in the Headspace Test. The study was conducted according to OECD 310 and EN ISO 14593 at Dr.U.Noack-Laboratorien. The test item was tested at a concentration of 15 mg/L in triplicates (test end: 5 replicates), corresponding to a carbon content of 12.9 mg C/L. The biodegradation of the test item was followed by TIC analyses of the quantity of CO₂ produced by the respiration of bacteria. The amount of TIC produced was calculated by correcting the results of the test and reference item for endogenous TIC production of the control groups and the blind value of the sodium hydroxide solution. The biodegradation was calculated for each sampling time.

The test item replicate did not reach the 10 % level and the biodegradation remained at 1 % until 28 days. The 95 % confidence interval on day 28 was 0 - 4 %.

Description of key information

The ready biodegradability of the test item was determined with a non adapted activated sludge over a test period of 28 days in

the Headspace Test. The study was conducted according to OECD 310 and EN ISO 14593 at Dr.U.Noack-Laboratorien. The test item was tested at a concentration of 15 mg/L in triplicates (test end: 5 replicates), corresponding to a carbon content of 12.9 mg C/L. The biodegradation of the test item was followed by TIC analyses of the quantity of CO2 produced by the respiration of bacteria. The test item replicate did not reach the 10 % level and the biodegradation remained at 1 % until 28 days.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed