Cyclohexanemethanol, 4-(1-methylethyl)-

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

August 2, 2011 to September 6, 2012

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Version / remarks:

2010

Deviations:

yes

Remarks:

The initial and final dissolved oxygen concentrations were outside those recommended in the test guidelines. This was considered to have had no adverse effect on the results of the study.

GLP compliance:

yes (incl. QA statement)

Remarks:

Inspected on July 19-21, 2011 / Signed on August 31, 2011

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Purity test date: March 21, 2012

Analytical monitoring:

not required

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Preparation of inoculum for exposure: The activated sewage sludge sample was maintained on continuous aeration in the laboratory at a temperature of approximately 21ºC overnight prior to use in the test. On the day of collection the activated sewage sludge (10 litres) was fed synthetic sewage sludge (500 mL).

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Post exposure observation period:

No

Hardness:

Not reported

Test temperature:

20±2ºC

pH:

the pH of the synthetic sewage stock used to feed the activated sewage sludge was pH 7.1 and the pH of the synthetic sewage stock used for the definitive test was pH 7.8.

Dissolved oxygen:

5.3-7.0 mg O2/L

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal: 0 (control), 100, 180, 320, 560 and 1000 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 500 mL conical flask
- Aeration: yes
- No. of organisms per vessel: The suspended solids concentration was equal to 3.0 g/L prior to use in the inoculum. 250 ml inoculum was added to each vessel
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 5
- No. of vessels per vehicle control (replicates): 3

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: deionised reverse osmosis water
- Total organic carbon: less than 1 mg/L Dissolved Organic Carbon

OTHER TEST CONDITIONS
- Photoperiod: continuous
- Light intensity: normal laboratory lighting

EFFECT PARAMETERS MEASURED: Oxygen Consumption

TEST CONCENTRATIONS
- Range finding study: yes (10, 100 and 1000 mg/L)
- Results used to determine the conditions for the definitive study: yes

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Duration:

3 h

Dose descriptor:

other: EC20

Effect conc.:

120 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of nitrification rate

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

190 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: 95% CL=170-210

Duration:

3 h

Dose descriptor:

other: EC80

Effect conc.:

310 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: no
- Effect concentrations exceeding solubility of substance in test medium: no

Results with reference substance (positive control):

- Results with reference substance valid? yes (3h EC50 = 8.9 mg/L)

Validity criteria fulfilled:

yes

Remarks:

In some instances, initial and final dissolved oxygen concentrations were outside those recommended in the test guidelines. This was considered to have had no adverse effect on the results of the study.

Conclusions:

The 3 hour EC50 was determined to be 190 mg/L based on respiration rate.

Executive summary:

A study was performed, according to OECD Guideline 209, to assess the effect of the test item on the respiration of activated sewage sludge. Following a preliminary range-finding test, activated sewage sludge was exposed to an aqueous dispersion of the test item at concentrations of 100, 180, 320, 560 and 1000 mg/L (3 replicates for each test concentration) for a period of 3 hours at a temperature of 20 ± 2 °C with the addition of a synthetic sewage as a respiratory substrate. The rate of respiration was determined after 3 hours contact time and compared to data for the control and a reference item, 3,5-dichlorophenol. The coefficient of variation of oxygen uptake in the control vessels was 6.85% and the specific respiration rate of the controls was 31.33 mg oxygen per gram dry weight of sludge per hour. The validation criteria have therefore been satisfied. The validation criterion for the reference item EC50 value was also satisfied. In some instances, the initial and final dissolved oxygen concentrations were outside those recommended in the test guidelines (7.0 mg O2/L and 2.0 mg O2/L respectively). This was considered to have had no adverse effect on the results of the study given that in all cases the oxygen consumption rate was determined over the linear portion of the oxygen consumption trace. The dissolved oxygen concentrations in all vessels were above 60 to 70% of the dissolved oxygen saturation level of 8.9 mg O2/L. There was a higher oxygen consumption rate in the 180 mg/L replicate R1 test vessel compared to replicates R2 and R3. This resulted in a lower inhibition value for the 180 mg/L replicate R1 test vessel compared to replicates R2 and R3. However the EC values are calculated based on the mean degradation value for the three replicate vessels for each concentration so it is considered to have no effect on the study.

The effect of the test item on the respiration of activated sewage sludge micro-organisms gave a 3-Hour EC50 value of 190 mg/L, 95% confidence limits 170 - 210 mg/L.

Description of key information

The substance was reported to have low toxicity to microorganisms derived from activated sludge, with a 3-hour EC50 value for growth inhibition of 190 mg/L (nominal) in an OECD guideline study (Test No. 209).

Key value for chemical safety assessment

EC50 for microorganisms:

190 mg/L

Additional information

The inhibitory concentration of the substance on the respiration of aerobic waste water bacteria was determined in a mixed population of activated sewage sludge (Harland Laboratories, 2012). The test method followed the OECD Guidelines for Testing of Chemicals No. 209. 3,5-Dichlorophenol was used as the reference substance at concentrations of 3.2, 10, and 32 mg/L. In this study the oxygen consumption rates were measured after time of 3 hours at nominal concentrations of 100, 180, 320, 560, and 1000 mg/L. The inhibitory concentration (EC50) (3h contact time) for reference substance was 8.9 mg/L, while the EC50 value (3h contact time) for the test substance was 190 mg/L (mean measured), suggesting that the substance is not toxic to microorganisms.