5-bromo-1,3-dichloro-2-fluorobenzene

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

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:

2010

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

The test substance was directly pipetted into each test flask. The weight was recorded and filled up with pure water.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Name and location of sewage treatment plant where inoculum was collected: Bensheim, Germany
- Method of cultivation: the activated sludge was used as collected, but coarse particles were removed by settling for a short period (15 minutes) and then the upper layer decanted. During holding prior to use for one day (dose-response study) or two days (pre-test), the sludge was fed daily with 50 mL synthetic sewage feed per litre and kept aerated at room temperature until use

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

20 ± 3 °C

pH:

Control: 6.9 to 7.1 at start and 7.5 to 7.9 at end
Positive control: 6.9 at start and 7.7 to 7.8 at end
Test solutions: 6.8 to 7.0 at start and 7.2 to 7.4 at end

Dissolved oxygen:

Control: 6.1 to 6.8 mg O2/L at start and 5.8 to 7.7 mg O2/L at end
Positive control: 6.3 to 6.5 O2/L at start and 7.7 to 8.3 mg O2/L at end
Test solutions: 6.4 to 7.0 mg O2/L at start and 6.6 to 7.2 mg O2/L at end

Nominal and measured concentrations:

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

Details on test conditions:

TEST SYSTEM
- Test vessel: all
- Type: open
- Material, size, headspace, fill volume: Glass flasks of approximately 1 L volume, final test volume of 500 mL per flask
- Aeration: during the holding period and during the 3 hours of the respiration inhibition test, the sludge was aerated with compressed air (1.017 L/minute)
- No. of vessels per concentration (replicates): 5
- No. of vessels per control (replicates): 6
- No. of vessels per positive control (replicates): 5
- No. of vessels per abiotic control (replicates): not applicable
- Sludge concentration (weight of dry solids per volume): 3 g/L
- Nutrients provided for bacteria: synthetic sewage was prepared by mixing 80 g peptone, 55 g meat extract, 15 g urea, 3.5 g NaCl, 2.0 g CaCl2 x 2 H2O, 1.0 MgSO4 x 7 H2O, 14 g K2HPO4 filled up with 5 L of deionised water
- Nitrification inhibitor used: N-allylthiourea

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: deionised water
- Particulate matter: not reported
OTHER TEST CONDITIONS
- Adjustment of pH: no
- Details on termination of incubation: For the measurement of the respiration rate a well-mixed sample of test medium from each flask was poured into a Karlsruher flask after exactly 3 hours incubation time and was not further aerated during measurement. The oxygen concentration was then measured with an oxygen electrode and recorded for about ten minutes. During measurement, the samples were continuously stirred on a magnetic stirrer.
EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3
- Range finding study
- Test concentrations: 10, 100 and 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:

EC10

Effect conc.:

85.8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

100 mg/L

Nominal / measured:

nominal

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:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of heterotrophic respiration

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

909.7 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):

Total respiration EC50 = 2.5 mg/L
Heterotrophic respiration EC50 = 14.8 mg/L
Nitrification respiration EC50 = 0.9 mg/L

Validity criteria fulfilled:

yes

Conclusions:

Based on total respiration, the test substance had no effects on activated sludge micro-organisms up to a concentration of 100 mg/L and significant dose-response related effects on total respiration at concentrations of 320 and 1000 mg/L. Therefore, the NOEC for respiration inhibition was 100 mg/L, and the EC50 was >1000 mg/L.

Executive summary:

A respiration inhibition study with activated sludge from a sewage treatment plant receiving domestic waste water was conducted in accordance with OECD TG 209 under GLP. The 3-hour toxicity test had the purpose to evaluate the influence of the test substance on the activity of the activated sludge by measuring the respiratin rate under defined conditions. The effects on the activated sludge were studied in a pre-test and a main test. For each replicate, a test solution with a final volume of 500 mL was tested in a 1 L glass flask: 16 mL of synthetic sewage feed and an adequate volume of the test substance or of the stock solution of the reference substance was directly pipetted into each test flask, which was then filled up with pure water to 250 mL. At the start of the test, 250 mL of activated sludge inoculum with a sludge concentration of 3.0 g/L suspended solids was added. The

Description of key information

Respiration inhibition: 3-hour NOEC = 100 mg/L, 3-hour EC50 >1000 mg/L in activated sludge (GLP, OECD TG 209)

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

100 mg/L

Additional information

The result of the key study was confirmed in a new study conducted to meet the data requirements for registration of the substance in a non-EEA country, which gave an EC50 value for the inhibition of total respiration of >1000 mg/L.