1-Ethoxy-2,3-difluoro-4-(trans-4-propylcyclohexyl)-benzene

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:

Jun 06 - Dec 02, 2016

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 (Carbon and Ammonium Oxidation))

Version / remarks:

July, 2010

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

The test substance was insufficiently soluble to permit addition via aqueous solution. Individually weighed quantities of test substance were added directly to the appropriate test vessels.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

The activated sludge inoculum was collected from the sludge return line at Pool or Burley Menston sewage treatment works (West Yorkshire, UK), which has a predominantly domestic catchment. The point of collection was to ensure that the activated sludge sample was relatively free of exogenous material.
Preparation and Maintenance
The sludge was transported to the test facility in a closed container with an adequate headspace to prevent the sample becoming anoxic. On arrival at the test facility, the sludge was aerated with a compressed air supply delivered through a suitable distribution device.
The suspended solids concentration was determined gravimetrically following homogenisation and adjusted using dechlorinated tap water to 3 g/L (± 0.3 g/L). The sludge was maintained at 20 ± 2 °C with aeration. During storage it was maintained at 20 ± 2 °C and fed with synthetic sewage concentrate at a rate of 50 mL/L.
An activated sludge sample that provided the test inoculum for the range-finder test was collected on 7 June 2016, the activated sludge sample that provided the test inoculum for the definitive limit test was collected on 20 July 2016.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Test temperature:

20 ± 2 °C

pH:

7.01 - 7.25

Dissolved oxygen:

saturated

Nominal and measured concentrations:

Range Finder: 1, 10, 100 and 1000 mg/L
Definitive Limit: 1, 10, 100 and 1000 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: ca 250 mL glass conical flask
- Type (delete if not applicable): open
- Aeration:compressed air supply
- No. of vessels per concentration (replicates): range finder: 2, definitive: 3
- No. of vessels per control (replicates): range finder: 1, definitive: 1
- No. of vessels per vehicle control (replicates): range finder: 4, definitive: 1
- Sludge concentration (weight of dry solids per volume): 3 g/L
- Weight of dry solids per volume of reaction mixture per unit of time:
- Nutrients provided for bacteria: no
- Nitrification inhibitor used (delete if not applicable): N-allylthiourea
- Biomass loading rate:
TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: dechlorinated tap water

OTHER TEST CONDITIONS
- Adjustment of pH: yes

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 10
- Justification for using fewer concentrations than requested by guideline: n.a.
- Range finding study yes
- Test concentrations: 1, 10, 100, 1000 mg/L
- Results used to determine the conditions for the definitive study: range finding results

Reference substance (positive control):

yes

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of heterotrophic respiration

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of respiration due to nitrification

Results with reference substance (positive control):

3,5-DCP:
Total Respiration: 10.1 mg/L
Nitrification Respiration: 3.3 mg/L

Validity criteria fulfilled:

yes

Conclusions:

There was no statistically significant inhibition of respiration observed during the test. The EC50 for the test item was greater than 1000 mg/L under these test conditions. The NOEC value was determined to be 1000 mg/L, the highest concentration tested.

Executive summary:

The aim of this study was to determine the no observable effect concentration (NOEC) and estimate the effect concentration for an x% effect (ECx) for activated sludge exposed to the test substance, where possible. The study was undertaken according to OECD Guideline 209, Activated Sludge, Respiration and Inhibition Test (Carbon and Ammonium Oxidation), adopted July, 2010.

The activated sludge inoculum for the limit test was collected from the sludge return line at Pool Sewage Treatment Works (West Yorkshire, U.K.), which has a predominantly domestic catchment. The point of collection was to ensure that the activated sludge sample was relatively free of exogenous material.

A range-finder test, employing nominal test material concentrations of 1, 10, 100 and 1000 mg/L, was undertaken to determine the appropriate concentration levels for a definitive test. The range-finder test showed no inhibition of total, or heterotrophic respiration, but did show inhibition of nitrification respiration at 100 mg/L and 1000 mg/L.

Based on the results of the range-finding test, a definitive limit test was conducted at concentrations of 1, 10, 100 and 1000 mg/L. Blank controls were also included.

The results of the definitive test showed no inhibition of total or heterotrophic respiration at all concentrations up to, and including, 1000 mg/L. A limited effect was observed on nitrification respiration at 100 mg/L (24 % inhibition) but this was not statistically significant.

As only limited inhibition was observed, determination of EC50 was not possible and is therefore reported to be greater than 1000 mg/L (the highest concentration tested under these conditions). The NOEC for the test item is reported to be 1000 mg/L.

Description of key information

There was no statistically significant inhibition of respiration observed during the test. The EC50 for the test item was greater than 1000 mg/L under these test conditions. The NOEC value was determined to be 1000 mg/L, the highest concentration tested.

Additional information

The aim of this study was to determine the no observable effect concentration (NOEC) and estimate the effect concentration for an x% effect (ECx) for activated sludge exposed to the test substance, where possible. The study was undertaken according to OECD Guideline 209, Activated Sludge, Respiration and Inhibition Test (Carbon and Ammonium Oxidation), adopted July, 2010.

The activated sludge inoculum for the limit test was collected from the sludge return line at Pool Sewage Treatment Works (West Yorkshire, U.K.), which has a predominantly domestic catchment. The point of collection was to ensure that the activated sludge sample was relatively free of exogenous material.

A range-finder test, employing nominal test material concentrations of 1, 10, 100 and 1000 mg/L, was undertaken to determine the appropriate concentration levels for a definitive test. The range-finder test showed no inhibition of total, or heterotrophic respiration, but did show inhibition of nitrification respiration at 100 mg/L and 1000 mg/L.

Based on the results of the range-finding test, a definitive limit test was conducted at concentrations of 1, 10, 100 and 1000 mg/L. Blank controls were also included.

The results of the definitive test showed no inhibition of total or heterotrophic respiration at all concentrations up to, and including, 1000 mg/L. A limited effect was observed on nitrification respiration at 100 mg/L (24 % inhibition) but this was not statistically significant.

As only limited inhibition was observed, determination of EC50 was not possible and is therefore reported to be greater than 1000 mg/L (the highest concentration tested under these conditions). The NOEC for the test item is reported to be 1000 mg/L.