1-(3,5-Dichloro-4-fluoro-phenyl)-2,2,2-trifluoro-ethanone

Toxicity to microorganisms

Administrative data

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2020

Report date:

2020

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation))

Version / remarks:

2010

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

1-(3,5-dichloro-4-fluorophenyl)-2,2,2-trifluoroethan-1-one

EC Number:

829-719-5

Cas Number:

1190865-44-1

Molecular formula:

C8H2Cl2F4O

IUPAC Name:

1-(3,5-dichloro-4-fluorophenyl)-2,2,2-trifluoroethan-1-one

Test material form:

liquid

Sampling and analysis

Analytical monitoring:

no

Test solutions

Vehicle:

no

Test organisms

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Source: aerobic activated sewage sludge from the aeration stage of the local wastewater treatment plant, ARA Birs (Birsfelden / Switzerland).
The aerobic activated sewage sludge was washed three times by centrifugation, decantation of the supernatant liquid phase and resuspension of the solid material in chlorine free tap water. Aliquots of the homogenized final sludge suspension were weighed, thereafter dried and the dry weight of the suspended solids was determined.
Based on this determination, a calculated amount of wet sludge was suspended in chlorine free tap water to obtain a concentration equivalent to 3 g dry material per liter. During the holding period of one day prior to use, the sludge was fed once with 50 mL synthetic sewage feed per liter and was kept at room temperature under continuous aeration until use. Before use the pH of the activated sludge inoculum was adjusted from pH 6.8 to pH 7.5 with a 1M NaOH solution.

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test conditions

Test temperature:

20 to 21 °C

pH:

Control: 7.3 to 7.4 at start and 7.7 to 7.8 at end of experiment
Test substance: 7.2 to 7.4 at start and 7.7 to 8.0 at end of experiment
Positive control: 7.3 at start and 7.8 to 8.0 at end of experiment

Dissolved oxygen:

Not less than 60 to 70% of saturation
Control: 8.3 to 8.5 mg/L at start and 7.0 to 8.2 mg/L at end of experiment
Test substance: 8.2 to 8.5 mg/L at start and 7.2 to 8.6 mg/L at end of experiment
Positive control: 8.5 to 8.6 mg/L at start and 7.1 to 8.7 mg/L at end of experiment

Details on test conditions:

Deionized water, containing less than 1 mg/L DOC (dissolved organic carbon) was used. The synthetic sewage feed was mixed to contain 16 g/L peptone, 11 g/L meat extract, 3 g/L urea, 0.7 g/L NaCl, 0.4 g/L CaCl2 x 2 H2O, 0.2 g/L MgSO4 x 7 H2O and 2.8 g/L K2HPO4.
2-L beakers were used containing 500 mL of incubation mixture. Magnetic stirrers and followers covered with inert material were used to ensure the aeration and mixing during incubation. The dissolved oxygen content was determined using an oxygen meter (Oxi 7310P from WTW GmbH, Weilheim, Germany).
The substance was tested with three replicates per concentration. Six blank controls containing activated sludge and synthetic medium were included. The positive control substance was tested with one replicate per concentration at 3.2, 10 and 32 mg/L.
At the start of the test, 16 mL synthetic sewage feed were made up to 250 mL with deionized water and then 250 mL activated sludge inoculum with a sludge concentration of nominally 3 g/L (dry weight) were added to this first control vessel. Thereafter, in time intervals of about fifteen minutes (an arbitrary but convenient interval) the procedure was repeated, except that the 16 mL synthetic sewage feed were added to the appropriate amounts of reference item or test item in deionized water to obtain a volume of 250 mL, followed by the addition of 250 mL inoculum.

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

52 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks on result:

other: 95% confidence limits of 44 and 62 mg/L

Effect concentrations 2

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

4.9 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

The test is regarded as valid since:
- the specific respiration rate of the blank controls was in the range of 34 to 42 mg oxygen per gram dry weight of sludge per hour and therefore, higher than 20 mg O2/gh.
- the coefficient of variation of oxygen uptake rate in control replicates was 7% and therefore, less than 30%.
- the 3-hours EC50 of the reference item 3,5-dichlorophenol was 5.9 mg/L and therefore, in the range of 2 to 25 mg/L.

Results with reference substance (positive control):

The 3-hour EC50 of the reference item 3,5-dichlorophenol (positive control) was calculated to be 5.9 mg/L with 95% confidence limits from 3.7 to 8.8 mg/L. The 3-hour EC50 is within the guidelines-recommended range of 2 to 25 mg/L, confirming the suitability of the activated sludge used.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The 3-hour EC50 was calculated to be 52 mg/L with 95%-confidence limits of 44 – 62 mg/L. The 3-hour NOEC was determined to be 4.9 mg/L.

Executive summary:

The inhibitory effect of the test item on the respiration rate of aerobic wastewater micro-organisms of activated sludge was investigated under GLP in a 3-hour respiration inhibition test according to the OECD TG 209 (2010). Based on the results of range-finding test a definitive test was performed at 4.9, 15.6, 50, 160 and 512 mg/L, with three replicates per concentration. As a positive control with 3,5-dichlorophenol was tested under identical test conditions, at concentrations of 3.2, 10 and 32 mg/L (all single replicates). Six blank controls, containing an equal volume of activated sludge and synthetic medium but no test or reference item, were included in the definitive test. The test vessels were kept at a constant temperature of 20 to 21 °C under normal laboratory light, and continuous aeration of the vessels was applied to ensure an oxygen saturation of at least 60 to 70%. A clear concentration-effect on the inhibition of the respiration rate of the sludge by exposure to the substance was observed, with a 3-hour EC50 value of 52 mg/L (95% confidence limits of 44 and 62 mg/L) and a 3-hour NOEC of 4.9 mg/L. The results of the blank and positive control treatments confirmed the suitability of the activated sludge and the method used. All the validity criteria were fulfilled.