2-[[4-[(2-cyanoethyl)ethylamino]phenyl]azo]-5-nitrobenzonitrile

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:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study without detailed documentation

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

GLP compliance:

not specified

Test organisms (species):

activated sludge

Details on inoculum:

- Inoculum: a mixed population of activated sewage sludge microorganisms.
- Source: the aeration Stage of Severn Trent PLC Sewage Treatment Plant, Belper, Derbyshire.
- Preparation: the sample was maintained at 21 °C with continuous aeration and used on the day of collection.
- pH: the pH was buffered to pH 7.0 with sodium hydroxide solution.
- Suspended solids level: adjusted to 3.9 g/l prior to use.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Nominal and measured concentrations:

1000 mg/l

Details on test conditions:

TEST SYSTEM
- No. of vessels per concentration: 3 replicates
- No. of vessels per control: 2 replicates

RANGE FINDING STUDY
- No. of vessels per concentration: 1 replicates
- No. of vessels per control: 2 replicates
- Concentrations: 10, 100 and 1000 mg/l
- Results: at the highest tested dose, the inhibition of respiration was of 11 %; variation between controls was of ± 4 %.

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Duration:

3 h

Dose descriptor:

IC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Results with reference substance (positive control):

IC50 (3h): 9.2 mg/l

MAIN STUDY

Vessel	O2 consumption rate mg/O2/l/min	% inhibition
Control 1	0.42	-
Control 2	0.48	-
Variation	± 7 %	-
Test item 1000 mg/l	0.44	2
Test item 1000 mg/l	0.44	2
Test item 1000 mg/l	0.44	2
Reference 3.2 mg/l	0.37	18
Reference 32 mg/l	0.06	87

RANGE FINDING STUDY

Vessel	O2 consumption rate mg/O2/l/min	% inhibition
Control 1	0.29	-
Control 2	0.27	-
Test item 10 mg/l	0.31	<11>
Test item 100 mg/l	0.26	7
Test item 1000 mg/l	0.25	11
Reference 3.2 mg/l	0.26	7
Reference 32 mg/l	0.03	39

Conclusions:

IC10 (3h) > 1000 mg/l (nominal)

Executive summary:

The inhibitory effect of test item on the oxygen consumption of activated sludge microorganisms was investigated under aerobic static conditions. The exposure time of the test substance on the activated sludge was 3 hours. A preliminary range finding test was conducted at the nominal concentrations of 10, 100 and 1000 mg/l. Due to absence of significant impact, 1000 mg/l was chosen as limit concentration for the main study. In the main experiment, 3 replicates were assayed for the test item and 2 replicates were run as control. 3,5-dichlorophenol was used os reference control.

At the applied test concentration (i.e. 1000 mg/l), the test substance showed no significant toxic effects to the activated sludge: the substance caused an inhibition of the 2 %. Positive reference substance showed an inhibition effect in the historical range.

Conclusion

IC10 (3h) > 1000 mg/l (nominal)

Description of key information

IC10 (3h) > 1000 mg/l (nominal)

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

1 000 mg/L

Additional information

The inhibitory effect of test item on the oxygen consumption of activated sludge microorganisms was investigated under aerobic static conditions, following the a method and procedures comparable to those described into the OECD guideline 209. At the applied test concentration (i.e. 1000 mg/l), the test substance showed no significant toxic effects to the activated sludge: the substance caused an inhibition of the 2 %. Positive reference substance showed an inhibition effect in the historical range.

A second experiment, conducted on a less pure lot, confirmed the outcomes obtained in the key study. The inhibitory effect of the test item was investigated in a respiratory test. Only a slight inhibition (19.8 %) of the respiration rate was recorded. The IC50 (3h) was determined higher than 100 mg/l.