4-tert-butylcyclohexanone

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2002-07-25 to 2002-07-28

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2002

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Test guideline 2

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

4-tert-butylcyclohexanone

EC Number:

202-678-5

EC Name:

4-tert-butylcyclohexanone

Cas Number:

98-53-3

Molecular formula:

C10H18O

IUPAC Name:

4-tert-butylcyclohexan-1-one

Sampling and analysis

Analytical monitoring:

yes

Test solutions

Vehicle:

no

Details on test solutions:

Pretreatment of the test substance:
A stock solution was prepared to give the desired series of test concentrations. To achieve this 125.2 mg of the test substance were added to 1 litre of dilution water and treated for 1 h in an ultrasonic bath and afterwards stirred for 24 h on a magnetic stirrer. Finally undissolved particles of the test substance were removed by filtration using a folded filter of pore size 7-1.2 µm.

Test organisms

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

source: 'The collection of algal cultures', Institute of Plant Physiology, University Goettingen, Germany

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test conditions

Test temperature:

21-25°C

Details on test conditions:

cell density at test start: ca. 10E4 cells/mL;
light intensity: 60-120 µE/(m2 * s) (equivalent to about 4000-8000 lux);
treatment groups: 6 test item concentrations (with 3 replicates each) plus 1 control (6 replicates);
nominal test item concentrations: 100, 50, 25, 13, 6.3, 3.2 mg/L

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

45 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: 95% CL: 40-50 mg/L

Effect concentrations 2

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

60 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 3

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

21.1 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Effect concentrations 4

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

39.5 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

biomass

Effect concentrations 5

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

12.1 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 6

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

21.1 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

All results are expressed in terms of mean measured concentrations. Measured concentrations ranged from 68 - 108% of nominal values at 0 hours, and from 58 - 85% of nominal values at 72 hours, respectively.

Calculation/Expression of results
- Cell density measurements in the test and control cultures are tabulated according to the concentration of test substance and the time of measurement. Growth curves are plotted for each test concentration and control.
The area under the growth curve [b] is calculated for each test culture (equation given in study report).
- The growth rate [r] is calculated for each test culture (equation given in study report).
- The percentage inhibition of both, growth [b] and growth rate [r] is calculated for each test concentration (equation given in study report).
EC 50 values for both, growth [b] and growth rate [r] were calculated by probit analysis.
- NOEC and LOEC of both, growth [b] and growth rate [r] were determined by a multisample comparison (according to DUNNETT)

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

A study was performed to assess adverse effects of p-tert.-Butylcyclohexanon rein on the growth (= increase in cell density) and the growth rate (= rate of increase in cell density with time) of the planktonic freshwater algal species Desmodesmus subspicatus over several generations.
The study was conducted in accordance with EEC Methods for Determination of Ecotoxicity Annex to Directive 92/69/EEC (O.J. No. L383A, 29.12.92) Part C, Method 3 'Algal inhibition test' which is in most parts equivalent to the OECD Guideline for Testing of Chemicals No. 201 'Alga, Growth Inhibition Test'.
Exponentially growing algal cells were exposed for a period of 72 hours to a range of concentrations (i.e. 3.2, 6.3, 13, 25, 50 and 100 mg) of p-tert.-Butylcyclohexanon rein dissolved in water. Auxiliaries used to prepare the test media were an ultrasonic bath, a magnetic stirrer and a folded filter.
The cell densities were measured at 24 hour intervals. Inhibition of the algal population was measured as reduction in growth (index b) and growth rate (index r), relative to control cultures grown under identical conditions. Growth and growth rates were used to calculate a No Observed Effect Concentration and a Lowest Observed Effect Concentration according to DUNNETT (1955, 1964). The following values were determined:
Results [mg/L]
EbC 50 (72 h): 45
ErC 50 (72 h): 60
NOEC [b]: 21.1
LOEC [b]: 39.5
NOEC IrJ: 12.1
LOEC [r]: 21.1
All results are expressed in terms of mean measured concentrations. Measured concentrations ranged from 68 - 108% of nominal values at 0 hours, and from 58 - 85% of nominal values at 72 hours, respectively.