bis(2-ethylhexyl) 4,4’-{6-[4-tert-butylcarbamoyl)anilino]-1,3,5-triazine-2,4-diyldiimino}dibenzoate

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

Study period:

2008

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

Qualifier:

according to guideline

Guideline:

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

GLP compliance:

yes (incl. QA statement)

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

A mixed population of activated sewage sludge micro-organisms was obtained for the range-finding test and for the definitive test from the aeration stage of the Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK .

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Hardness:

Laboratory tap water dechlorinated
140 mg/L as CaCO3

Test temperature:

about 21 °C

pH:

8.1 at the start of the experiment
8.5 at the end of the experiment

Reference substance (positive control):

yes

Remarks:

3.5 -dichlorophenol

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Basis for effect:

inhibition of total respiration

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

1 000 mg/L

Nominal / measured:

nominal

Basis for effect:

inhibition of total respiration

Range-finding Test
No significant effect on respiration was observed at either test concentration employed. Based on this information, a single test concentration, in triplicate, of 1000 mg/L was selected for the definitive test. The test material was insoluble in water and it was justifiable to conduct the definitive test at a single concentration of 1000 mg/L in excess of the water solubility level of the test material.

Definitive test
It was considered unnecessary and unrealistic to test at concentrations in excess of 1000 mg/L. The initial and final dissolved oxygen concentrations were below those recommended in the test guidelines (6.5 and 2.5 mg O2/L respectively). This was considered to have had no adverse effect on the results of the study given that in all cases the oxygen consumption rate was determined over the linear portion of the oxygen consumption trace. The validation criteria for the control respiration rates have been satisfied. Observations made showed that at the test concentration of 1000 mg/L at 0 hours and 30 mins contact time there was a dark brown dispersion with particles of test material on the surface and dispersed throughout. A pale brown dispersion with particles of test material dispersed homogenously throughout was observed at 3 hours contact time.

Validity criteria fulfilled:

yes

Conclusions:

The effect of the test material on the respiration of activated sewage sludge micro-organisms gave a 3-h EC50 > 1000 mg/L. The NOEC after 3 h exposure was 1000 mg/L.

Description of key information

3-h NOEC = 1000 mg/L (nominal concentrations), activated sludge, respiration inhibition, OECD TG 209 and EU method C.11, 2008

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

1 000 mg/L

Additional information

A GLP limit study on the respiration inhibition of activated sewage sludge is available for this endpoint. The study followed the OECD TG 209 and the EU method C.11 (Reliability 1). The activated sludge was exposed in triplicate to a control and a nominal test concentration of 1000 mg/L for 3 hours. In addition, 3,5-dichlorophenole was used as a positive control. The test conditions were: temperature about 21 °C, pH 8.1-8.5. The 3-h test substance NOEC was determined to be 1000 mg/L based on nominal concentrations.