2-fluoro-6-trifluoromethylpyridine

Toxicity to microorganisms

Link to relevant study record(s)

Reference

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

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.6800 (Modified Activated Sludge, Respiration Inhibition Test for Sparingly Soluble Chemicals)

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Substance ID: F6TF
Purity: 99.56%

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Activated sludge from Shenyang North Sewage Treatment Plant was normally used as the microbial inoculum for the test. On return to the laboratory the sludge was washed with tap water. After centrifuging the supernatant was decanted. This procedure was repeated three times. A small amount of the washed sludge was weighed and dried. From this result the amount of wet sludge was calculated which must be suspended in water in order to obtain an activated sludge with a mixed liquor suspended solids level of 4 g/L (±10 percent).

The sludge was not used on the day of collection, synthetic sewage was added to each litre of the activated sludge prepared as described above; this was then aerated overnight at 20 ±2ºC. It was then kept aerated for use during the day before being used. Before use the pH was checked and the value was in the range of 6.0 to 8.0. The mixed liquor suspended solids was determined as described in the preceding paragraph. In the test period, the same batch of sludge was to be used on subsequent days; a further synthetic sewage feed was added at the end of each working day.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Test temperature:

20 ±2ºC

pH:

7.3

Salinity:

freshwater

Nominal and measured concentrations:

Nominal: 300 mg/L

Details on test conditions:

Test conditions:

(i) Duration/contact time: 3 h, during which aeration takes place.
(ii) Water: Drinking water
(iii) Air supply: Clean oil-free. Air flow 0.5 to 1 L/min.
(iv) Temperature: 20 ±2 °C

The experimental procedure which followed for the 3-h contact period was given below:

Four vessels, 1 L beakers
1. At time "0" 16 mL of the synthetic sewage feed was made up to 300 mL with water. Microbial inoculum (200 mL) was added and the total mixture (500 mL) poured into a first control vessel. Aeration at 0.5 to 1 L/min was commenced using a Pasteur pipette as aeration device.
2. At time "20 min" 16 mL of the synthetic sewage feed was made up to 300 mL with 284 mL of the test substance solution and microbial inoculum (200 mL) was added to make a volume of 500 mL (identified as Test 1).
3. This process was repeated at 20-minutes to give a replicate of the test substance treatment (Test 2).
4. After 20 min the second control was prepared.

After 3 hours the contents of the first vessel was poured into the measuring apparatus and the respiration rate was measured over a period of up to 10 min. This determination was repeated on the contents of each vessel at 20-min intervals, in such a way that the contact time in each vessel was three hours . Oxygen consumption was measured and recorded after an aeration time of 3 hours contact time.

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 300 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Results with reference substance (positive control):

EC50 of the reference substance (3-5, dichlorophenol) was 10 mg/L.

The two control respiration rates were within 15% of each other and the EC50 (3-h) of reference substance was in the acceptance range of 5-30 mg/L. These indicated that the test was valid.

Table 1. Respiration Rate and Percent Inhibition for Test Substance

 

Test Vessel	Respiration Rate (mg/L * min)	Percent Inhibition
Control 1	0.18	x
Test 1	0.19	-2.7
Test 2	0.18	2.7
Control 2	0.19	x

 

 

Table 2. Respiration Rate and Percent Inhibition for Reference Substance (3,5-dichlorophenol)

 

Test Vessel	Respiration Rate (mg/L * min)	Percent Inhibition
Control 1	0.25	x
Reference (1 mg/L)	0.24	2.0
Reference (2.7 mg/L)	0.2	18.4
Reference (7.1 mg/L)	0.17	30.6
Reference (18.8 mg/L)	0.07	71.4
Reference (50 mg/L)	0.03	87.8
Control 2	0.24	x

 

 

Validity criteria fulfilled:

yes

Conclusions:

The 3-hour EC50 and EC0 were greater than 300.0 mg/L (nominal concentration).

Executive summary:

The test assessed the effect of the test substance on micro-organisms in an aerobic aqueous medium by measuring the respiration rate under defined conditions according to OECD 209. The definitive test was conducted using a limit test concentration of 300.0 mg/L (nominal concentration). Two controls without test substance were included in the test design, one at the start and the other at the end of the test series. The two control respiration rates were within 15% of each other. The EC50 of the reference substance (3-5, dichlorophenol) was 10 mg/L. These results indicate that the test is valid.

 The percent inhibition of the test substance on aerobic micro-organisms was 0% and the 3-hours EC50 and EC0 were greater than 300.0 mg/L (nominal concentration).

Description of key information

Based on nominal concentrations:
3-hour EC50 > 300 mg/L

Key value for chemical safety assessment

EC50 for microorganisms:

300 mg/L