2-(2,4-dichlorophenyl)-2-(1H-imidazol-1-ylmethyl)-1,3-dioxolane-4-methanol

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:

2015-07-08 to 2015-07-24

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

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Qualifier:

according to guideline

Guideline:

ISO 8192 (Water quality - Test for inhibition of oxygen consumption by activated sludge for carbonaceous and ammonium oxidation)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

see study report

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material:
* batch: M14IB5308
* WIL Research test item number: 206568/B
- Expiration date of the lot/batch: 2016-02-03 (retest date)
- Purity test date: 2015-04-23

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: At room temperature
- Stability under test conditions: stable
- Solubility and stability of the test substance in the solvent/vehicle: solubility in water 0.26 g/L

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: The test item was not sufficiently souble to allow the preparation of a 10 g/L stock solution in water. Therefore, 1 L test bottles were filled with 200 mL of test item mixtures in Milli-RO water with initial loading rates of 2.5 times the final loading rate. These mixtures were stirred in closed dark brown bottles for 24 to 25 hours. Subsequently, 16 mL synthetic medium made up to 50 mL with Milli-RO water and 250 mL sludge were added resulting in the required concentrations (10, 100 and 1000 mg/L). Optimal contact was ensured applying continuous aeration and stirring.
- Controls:blank controls: test medium without test item and treated in the same way as the test item solutions.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Laboratory culture: predominantly domestic sewage treatment plant, "Waterschap Aa en Maas", 's-Hertogenbosch, The Netherlands.
- Preparation of inoculum for exposure: coarsely sieved (1 mm) and allowed to settle. The supernatant was removed and ISO-medium was added. A small amount of the sludge was weighed and dried overnight at ~105°C to determine the amount of suspended solids
- Pretreatment: The batch of sludge was used one day after collection; therefore 50 mL of synthetic medium was added per L of activated sludge at the end of the collection day. The sludge was kept aerated at test temperature until use.
- Initial biomass concentration: 3.0 g/L of sludge
- The pH was 7.7 and 7.5 on the day of testing for the combined limit/range-finding and limit test, respectively.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Post exposure observation period:

After 3h of exposure, oxygen consumption was recorded for approximately 10 minutes.

Test temperature:

Range finding test: 20-22°C
Limit test: 18-22°C

pH:

Before addition of sludge: 7.5-7.6
After the 3-h exposure period: 7.4-8.4

Dissolved oxygen:

The aeration was adjusted in such a way that the dissolved oxygen concentration at the start was above 60-70% saturation (60% of air saturation is > 5 mg/L at 20°C) and to maintain the sludge flocs in suspension.

Salinity:

not applicable

Nominal and measured concentrations:

Nominal concentrations:
- Range-finding test: Control, 10, 100, 1000 mg/L
- Limit test: Control, 1000 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: All glass open bottles/vessels
- Aeration: The aeration was adjusted in such a way that the dissolved oxygen concentration at the start was above 60-70% saturation (60% of air saturation is > 5 mg/L at 20°C) and to maintain the sludge flocs in suspension..
- Number of replicates: 3 (limit test)
- Number of control replicates: 6
- Biomass loading rate: initial loading ca. 3.0 g dw/L
g dw/L

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: adjusted ISO medium, formulated using RO-water (tap water purified by reverse osmosis)

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Determination of oxygen was performed with multiple oxygen probes connected to a BlueBox (GO-Systemelektronik GmbH, Germany), a multichannel measuring and controlling system. Oxygen consumption was monitored for approximately 10 min after the 3-h exposure period. Respiration rate was calculated from the measurements.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: none (limit test)
- Range finding study
- Test concentrations: 10, 100, 1000 mg/L
- Results used to determine the conditions for the definitive study: yes

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Key result

Duration:

3 h

Dose descriptor:

other: ELR50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Key result

Duration:

3 h

Dose descriptor:

other: NOELR

Effect conc.:

1 000 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 data
- Effect concentrations exceeding solubility of substance in test medium: no data
- Blank controls oxygen uptake rate: 30 and 25 mg oxygen per one gram of activated sludge for the combined limit/range-finding and limit test, respectively
- Coefficient of variation of oxygen uptake rate in control replicates: 7% and 26% for the combined limit/range-finding and limit test, respectively

Results with reference substance (positive control):

3-h EC50 = 5.8 and 2.3 mg/L (for the range-finding and limit test respectively).
This is within the recommended range of 2-25 mg/L confirming suitability of the activated sludge used.

Reported statistics and error estimates:

The 3-h EC50 values were based on Probit Analysis.
The NOEC determination was based on the Two-sample t-test Procedure, alpha=0.05, one-sided, smaller.

Validity criteria fulfilled:

yes

Conclusions:

An activated sludge respiration inhibition test (according OECD guideline 209) with activated sludge from a predominantly domestic sewage treatment plant resulted in a 3-h ELR50 > 1000 mg T001159/L. The results of the study can be considered reliable without restriction.

Description of key information

The study of Desmares-Koopmans (2016), investigating the acute toxicity of T001159 to microorganisms according to OECD guideline 209, was considered as the key study for endpoint coverage.  The 3-h ELR50 was >1000 mg/L.

The 3-h NOELR was 1000 mg/L.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

1 000 mg/L