N-(2-chloroethyl)-4-[(2,6-dichloro-4-nitrophenyl)azo]-N-ethyl-m-toluidine

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))

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

The batch of Disperse Brown 27 (4852-1501) tested was a brown powder with a purity of 99.7 %

Vehicle:

yes

Details on test solutions:

The test item was not sufficiently soluble to allow the preparation of a 10 g/L stock solution in water. Therefore, 1-litre test bottles were filled with 200 mL of test item mixtures in Milli-RO water (tap water purified by reverse osmosis; Millipore Corp., Bedford, Mass., USA), with initial loading rates of 2.5 times the final loading rate. These mixtures were stirred in closed dark brown bottles for approximately 15 minutes. Subsequently, 16 mL synthetic medium made up to 50 mL with Milli-RO water and 250 mL sludge were added resulting in the required loading rates

Test organisms (species):

activated sludge of a predominantly domestic sewage

Test type:

flow-through

Water media type:

other: Milli-RO water

Limit test:

yes

Total exposure duration:

3 h

Remarks on exposure duration:

Optimal contact between the test item and test organisms was ensured by applying continuous aeration and stirring.

Test temperature:

18-21 °C in compliance with study plan (20 ± 2 °C).

pH:

Before addition of sludge was between 7.5 and 7.6. After the 3 hour exposure period the pH was between 7.4 and 8.3.

Dissolved oxygen:

dissolved oxygen concentration at the start of the study was above 60-70% saturation (60% of air saturation is > 5 mg/L at 20°C) and to maintain the sludge flocs in suspension.

Details on test conditions:

The pH in all test vessels, before addition of sludge was between 7.5 and 7.6. After the 3 hour exposure period the pH was between 7.4 and 8.3.
The temperature continuously measured in the temperature control vessels ranged between 18 and 21°C during the test, and complied with the requirements as laid down in the study plan (20 ± 2°C).

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Key result

Duration:

3 h

Dose descriptor:

other: NOELR

Effect conc.:

ca. 1 000 mg/L

Nominal / measured:

not specified

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Key result

Duration:

3 h

Dose descriptor:

other: ELR50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

not specified

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

The combined limit/range-finding test showed -25%, 1% and an average of 12% inhibition of the respiration rate at loading rates of 10, 100 and 1000 mg/L (mean value), respectively. No statistical significant inhibition of the respiration rate was observed at a loading rate of 1000 mg/L. Therefore, the NOELR was considered to be the highest test concentration. The ELR50 was above the highest loading rate tested (1000 mg/L). There was no significant oxygen uptake from abiotic processes.

Results with reference substance (positive control):

The batch of activated sludge was tested for sensitivity with the reference item 3,5-dichlorophenol, and showed normal sensitivity.

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of this present test Disperse Brown 27 was not toxic to waste water bacteria (activated sludge) at a loading rate of 1000 mg/L (NOELR).
The ELR50 was above 1000 mg/L.

Executive summary:

The batch of Disperse Brown 27 tested was a brown powder with a purity of 99.7% (HPLC).

No correction was made for the purity/composition of the test item. The test item was not sufficiently soluble to allow the preparation of a 10 g/L stock solution

in water. Therefore, the test item – Milli-RO water mixtures were magnetically stirred for a period of approximately 15 minutes. Subsequently, synthetic medium, sludge and Milli-RO water were added resulting in the required loading rates. Optimal contact between the test item and test organisms was ensured by applying continuous aeration and stirring during the 3-hour exposure period. Thereafter, oxygen consumption was recorded for approximately 10 minutes.

In a combined limit/range-finding test loading rates of 10, 100 and 1000 mg/L were tested. The highest loading rate was tested in triplicate, lower loading rates consisted of one replicate. Furthermore, at 1000 mg/L an abiotic control (1 replicate) was tested. Responseswere compared to the controls. No statistical significant inhibition of the respiration rate was observed at a loading rate of 1000 mg/L. There was no significant oxygen uptake from abiotic processes.

The batch of activated sludge was tested for sensitivity with the reference item 3,5-dichlorophenol, and showed normal sensitivity.

The study met the acceptability criteria prescribed by the study plan and was considered valid.

Disperse Brown 27 was not toxic to waste water (activated sludge) bacteria at a loading rate of 1000 mg/L (NOELR). The ELR50 was above 1000 mg/L.

Description of key information

Under the conditions of this present test Disperse Brown 27 was not toxic to waste water bacteria (activated sludge) at a loading rate of 1000 mg/L (NOELR). The ELR50 was above 1000 mg/L.

Additional information

Under the conditions of this present test Disperse Brown 27 was not toxic to waste water bacteria (activated sludge) at a loading rate of 1000 mg/L (NOELR).

The ELR50 was above 1000 mg/L.