8-Chloro-6-(trifluoromethyl)imidazo[1,2-a]pyridine-2-carboxylic acid

Toxicity to microorganisms

Administrative data

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2016

Report date:

2016

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Test guideline 3

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

Test material

Test material information

1

Reference substance name:

8-chloro-6-(trifluoromethyl)imidazo[1,2-a]pyridine-2-carboxylic acid

Cas Number:

353258-35-2

Molecular formula:

C9H4ClF3N2O2

IUPAC Name:

8-chloro-6-(trifluoromethyl)imidazo[1,2-a]pyridine-2-carboxylic acid

Specific details on test material used for the study:

Test substance: IN-QEK31-011
Batch No.: SG0312574
Purity: 98.2%

Sampling and analysis

Analytical monitoring:

no

Test solutions

Vehicle:

no

Remarks:

The test item was directly dosed into each test flask and pure water was added.

Test organisms

Test organisms (species):

activated sludge of a predominantly domestic sewage

Study design

Test type:

not specified

Water media type:

other: pure water

Total exposure duration:

3 h

Test conditions

Test temperature:

20 ± 2°C during pre-incubation (3 hours) and evaluation period

pH:

pH of the activated sludge was 6.7

Nominal and measured concentrations:

Nominal: 10, 32, 100, 320 and 1000 mg/L

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: total and nitrification respiration

Effect concentrations 2

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

320 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: heterotrophic respiration

Effect concentrations 3

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

406.7 mg/L

95% CI:

>= 295 - <= 550.8

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: total respiration

Effect concentrations 4

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

550.1 mg/L

95% CI:

>= 459.5 - <= 663.7

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: heterotrophic respiration

Effect concentrations 5

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

211.9 mg/L

95% CI:

>= 90.8 - <= 493.5

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: nitrification respiration

Results with reference substance (positive control):

The 3-hour EC50 for total respiration was found to be 4.3 mg/L (lower cl: 2.3 mg/L, higher cl: 7.8 mg/L) thus lying in the range of 2 - 25 mg/L recommended by the test guidelines. The 3-hour EC50 for heterotrophic respiration was found to be 11.5 mg/L (lower cl: 8.1 mg/L, higher cl: 16.5 mg/L) thus lying in the range of 5 - 40 mg/L recommended by the test guidelines. For the oxygen uptake due to nitrification the 3-hour EC50 was 1.0 mg/L (lower cl: 0.3 mg/L, higher cl: 3.7 mg/L) lying in the range of 0.1 - 10 mg/L recommended by the test guidelines. The result confirms the suitability of the activated sludge used.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The NOEC could be established to be 100 mg/L for total and nitrification respiration and 320 mg/L for heterotrophic respiration. The 3-hour EC50 was found to be 406.7 mg/L (lower cl: 295.0 mg/L, higher cl: 550.8 mg/L, total respiration), 550.1 mg/L (lower cl: 459.5 mg/L, higher cl: 663.7 mg/L, heterotrophic respiration) and 211.9 mg/L (lower cl: 90.8 mg/L, higher cl: 493.5 mg/L, nitrification respiration).

Executive summary:

The effects of the test item on activated sludge were determined in a 3-hour exposure laboratory study conducted under OECD Guideline 209 (2010). Activated sludge from the aeration tank of a municipal sewage treatment plant was exposed to the test item at concentrations of 10, 32, 100, 320 and 1000 mg/L and 6 untreated controls. The same test design was repeated with the nitrification inhibitor N-allylthiourea.

The respiration rate (oxygen consumption) (total respiration, heterotrophic respiration and nitrification) of an aerobic activated sludge fed with a standard amount of synthetic sewage was measured in the presence of various concentrations of the test item after an incubation period of 3 hours. The test item was directly dosed into each test flask, which was subsequently filled with pure water. The test item was dissolved into the pure water as homogeneously as possible.

The test item had no inhibiting toxic effects on activated sludge up to a concentration of 100 mg/L, a test item concentration of 1000 mg/L caused an almost complete inhibition of respiration of activated sludge bacteria. The NOEC was established to be 100 mg/L for total respiration and respiration by nitrifying bacteria. The inhibition was 31% and 98% at test item concentrations of 320 mg/L and 1000 mg/L for total respiration. The heterotrophic respiration of the activated sludge was not inhibited up to concentrations of 320 mg/L and almost complete inhibited at 1000 mg/L.

The NOEC could be established to be 100 mg/L for total and nitrification respiration and 320 mg/L for heterotrophic respiration. The 3-hour EC50 was found to be 406.7 mg/L (lower cl: 295.0 mg/L, higher cl: 550.8 mg/L, total respiration), 550.1 mg/L (lower cl: 459.5 mg/L, higher cl: 663.7 mg/L, heterotrophic respiration) and 211.9 mg/L (lower cl: 90.8 mg/L, higher cl: 493.5 mg/L, nitrification respiration).