4-tert-pentylcyclohexanone

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

activated sludge respiration inhibition testing

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: read-across from a guideline study

Justification for type of information:

Toxicity to microorganisms is based on read-across from p-tert-butylcyclohexanon. The documentation is presented in the Endpoint summary of Aquatic toxicity.

Reason / purpose for cross-reference:

read-across source

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

517 mg/L

Basis for effect:

inhibition of total respiration

Key result

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

103 mg/L

Basis for effect:

inhibition of total respiration

Validity criteria fulfilled:

yes

Reference 2

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

04 Feb 2002 to 06 Feb 2002

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

The substance has been added to about 130 mL deionized water and stirred overnight before testing (equilibration phase) and was subsequently directly weighed into the test vessels.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Type: mixed population of aquatic microorganisms (activated sludge)
- Origin: aeration tank of a waste water treatment plant treating predominantly domestic sewage (Wupper area water authority)
- Pretreatment: aeration of the activated sludge; daily feed with synthetic medium
- pH of the suspension before application: 7.3

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

20.7 - 21.6 °C

pH:

7.3 - 8.3

Dissolved oxygen:

- Dissolved O2 at start of the test: 5.3 - 7.4 mg/L
- Dissolved O2 at termination of the test: 2.6 - 7.2 mg/L

Nominal and measured concentrations:

- Nominal concentrations: 0 (control), 320, 560, 1000, 1800 and 3200 mg/L
- Nominal concentrations reference substance: 2.5, 5.0, 10.0, 20.0 and 40.0 mg/L

Details on test conditions:

TEST SYSTEM
- Aeration: yes, permanent (3 hours)
- No of replicates: not specified
- No vessels per control (replicates): 2
- Test concentration of the activated sludge: 360 mg/L suspended solids (because of strong respiration of the activated sludge).

TEST PARAMETERS MEASURED
- Respiration rate: The respiration rate of an activated sludge is measured after a contact time of 3 hours.
- Other parameters: The oxygen concentration was measured in all vessels at the starting and termination of the test. Furthermore, the pH and temperature were determined.

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

517 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Key result

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

103 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

Inhibition was observed from the lowest test substance concentration (31.7%) and increased in a dose-dependent manner up to 90.7% inhibition at 3200 mg/L. See 'Any other information on results incl. tables'.

Results with reference substance (positive control):

The 3-h EC50 value for the reference substance was determined to be 8.2 mg/L. See 'Any other information on results incl. tables'.

Reported statistics and error estimates:

Probit analysis

Table: results test substance / controls

Nominal test concentrations   [mg/L]	Respiratory rate test substance  [mg/L · h]	Phys.-chem. O2 consumption   [mg/L · h]	Respiratory rate phys.-chem. O2 consumption [mg/L · h]	Inhibition     [%]
320	25.0	0.0*	25.0	31.7
560	15.4	0.0*	15.4	57.9
1000	12.0	0.0*	12.0	67.2
1800	4.8	0.0*	4.8	86.9
3200	3.4	0.0*	3.4	90.7
Control, mean	36.6
Control 1	36.0
Control 2	37.2

* The physico-chemical oxygen consumption has been determined at 10000 mg/L test substance concentration. As no physico-chemical oxygen consumption was observed at that test substance concentration, this observation also holds true for the lower test substance concentrations

Table: results for the reference substance 3,5 -dichlorophenol

Nominal test concentration [mg/L]	Respiratory rate [mg/l·h]	Inhibition [%]
2.5	28.8	21.3
5	27.4	25.1
10	15.0	59.0
20	7.2	80.3
40	4.3	88.3

ADDITIONAL TEST RESULTS TEST SUBSTANCE

- EC25: 221 mg/L

- EC75: 1210 mg/L

- EC90: 2600 mg/L

Validity criteria fulfilled:

yes

Remarks:

See 'Any other information on materials and methods incl. tables'

Conclusions:

The 3-h EC50 and EC10 values for microorganisms in activated sludge are 517 and 103 mg/L, respectively.

Executive summary:

The toxicity of the substance to microorganisms was investigated in an activated sludge respiration inhibition study according to OECD TG 209 and in compliance with GLP criteria. In this study activated sludge from a predominantly domestic sewage was exposed to nominal test substance concentrations of 0 (control), 320, 560, 1000, 1800 and 3200 mg/L for 3 hours. Test concentrations were not analytically verified. The effects on microorganisms was determined by measuring total respiration rates and comparing these to an unexposed control. Inhibition was observed from the lowest test substance concentration (31.7%) and increased in a dose-dependent manner up to 90.7% inhibition at 3200 mg/L. Based on these results, 3-h EC50 and EC10 values of 517 and 103 mg/L were derived, respectively.

Description of key information

No data is available for Orivone. Therefore read-across is performed to the close structural analogue p-tert-butylcyclohexanone (CAS 98-53-3). Its toxicity of the substance to microorganisms was investigated in an activated sludge respiration inhibition study according to OECD TG 209 and in compliance with GLP criteria. In this study activated sludge from a predominantly domestic sewage was exposed to nominal test substance concentrations of 0 (control), 320, 560, 1000, 1800 and 3200 mg/L for 3 hours. Test concentrations were not analytically verified. The effects on microorganisms was determined by measuring total respiration rates and comparing these to an unexposed control. Inhibition was observed from the lowest test substance concentration (31.7%) and increased in a dose-dependent manner up to 90.7% inhibition at 3200 mg/L. Based on these results, 3-h EC50 and EC10 values of 517 and 103 mg/L were derived, respectively. There is no need to convert the toxicity of the source chemical data towards Orivone, because of the comparable properties of the substances.

Key value for chemical safety assessment

EC50 for microorganisms:

517 mg/L

EC10 or NOEC for microorganisms:

103 mg/L