4-Ethyl-2',3'-difluor-4''-propyl-1,1':4',1''-terphenyl

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:

Apr 14 - Dec 09, 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)

Specific details on test material used for the study:

Purity: 99.93%

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.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Test temperature:

20 ± 2°C

pH:

7.08 - 7.14

Dissolved oxygen:

saturated

Nominal and measured concentrations:

0, 1, 10, 100 and 1000 mg/L
highest concentration was conducted in triplicate

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): 2, except highest cooncentration: 3
- No. of vessels per vehicle control (replicates): range finder: 6
- 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
- Particulate matter:
OTHER TEST CONDITIONS
- Adjustment of pH: yes

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
TEST CONCENTRATIONS
- Spacing factor for test concentrations: 10
- Justification for using fewer concentrations than requested by guideline: n.a.
- Test concentrations: 1, 10, 100, 1000 mg/L

Reference substance (positive control):

yes

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

1 000 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

1 000 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

inhibition of heterotrophic respiration

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

1 000 mg/L

Nominal / measured:

meas. (initial)

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: 4.6 mg/L
Nitrification Respiration: 1.1 mg/L

Validity criteria fulfilled:

yes

Conclusions:

There were no statistically significant effects on respiration observed during the test. The EC50 for 4-Ethyl-2',3'-difluor-4''-propyl-1,1':4',1''-terphenyl was greater than 1000 mg/L under the test conditions.

Executive summary:

 

 

Purpose

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.

 

Study Design

The study was undertaken according to OECD Guideline 209, Activated Sludge, Respiration and Inhibition Test (Carbon and Ammonium Oxidation), adopted July, 2010.

 

Methods

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.

 

Results

A range-finder/limit test, employing nominal concentrations of 1, 10, 100 and 1000 mg/L, was undertaken to determine the appropriate concentration levels for a definitive test. The range-finder/limit test showed no inhibition of total, nitrification or heterotrophic respiration. As there were sufficient control replicates at the start and end of each exposure period and the highest concentration (1000 mg/L) was conducted in triplicate, as per the OECD 209 guideline, it was not therefore necessary to carry out any further testing.

Determination of EC50 was not possible and is therefore reported to be greater than 1000 mg/L (the highest concentration tested under these conditions). As there were slight enhancement effects noted (observed as negative inhibition), the endpoint for this is reported as No Observed Adverse Effect Concentration (NOEAC). The NOAEC is therefore reported to be 1000 mg/L.

 

The validity criteria applied to this study type were met and therefore the data are considered valid.

 

Conclusion

There were no statistically significant effects on respiration observed during the test. The EC50 was greater than 1000 mg/L under the test conditions.

Description of key information

OECD 209 study (Reliability 1): NOEC = 1000 mg/L

Key value for chemical safety assessment

EC50 for microorganisms:

1 000 mg/L

EC10 or NOEC for microorganisms:

1 000 mg/L