Benzoic acid, 2-hydroxy-5-[[4-[[4-[[8-hydroxy-7-[[4-[(8-hydroxy-3,6-disulfo-1-naphthalenyl)azo]-2-methoxy-5-methylphenyl]azo]-3,6-disulfo-1-naphthalenyl]amino]-6-(phenylamino)-1,3,5-triazin-2-yl]amino]phenyl]azo]-, pentasodium salt

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:

From March 14 to April 3, 2007

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

Version / remarks:

1984

GLP compliance:

no

Remarks:

in accordance with ISO/IEC 17025

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

Test medium: synthetic sewage feed prepared with tap water: 16 ml of 100-fold sewage concentrate per 500 ml of final test mixture

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- inoculum: activated sludge from aeration tank of a municipal biological waste water treatment plant, non adapted, non pre-conditioned
- source: ARA Werdhölzli, CH-8048 Zürich (28 March 2007, 11 a.m.)
- concentration: 1.6 g/l dry matter in the final mixture

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

22 ± 0.5 °C

pH:

7.5 ± 0.5

Nominal and measured concentrations:

Nominal concentrations: 125, 250, 500, 1000 and 2000 mg/l.

Details on test conditions:

TEST SYSTEM
- Test vessel: 1000 ml flask
- Fill volume: 500 ml
- Aeration: yes
- No. of vessels per concentration: 1
- No. of vessels per control: 2
- Sludge concentration: 1.6 g/l dry matter
- Nutrients provided for bacteria: synthetic sewage feed

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: tap water

OTHER TEST CONDITIONS
- Adjustment of pH: to 7.5 ± 0.5 with NaOH or H2SO4, if necessary

EFFECT PARAMETERS MEASURED: oxygen consumption

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2
- Range finding study: no

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 2 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

No significant toxic effects to activated sludge were noted; respiration rates were in the same range as detremined for the 2 blank controls.
Variations between 2 controls was ± 5 %.

Results with reference substance (positive control):

EC50 (3h) = 4.6 mg/l

nominal concentration (mg/l)	O2 consumption rates (mg O2/l/h)	respiration inhbition (%)
0	31.0	-
0	34.2	-
125	32.9	-0.9
250	32.6	0.0
500	32.9	-0.8
1000	31.9	2.3
2000	30.8	5.7
reference
3	19.4	40.4
10	10.6	67.4
30	4.8	85.3

Validity criteria fulfilled:

yes

Conclusions:

EC50 (3h) > 2000 mg/l

Executive summary:

Method

Inhibitory effect of test substance on oxygen consumption of activated sludge microorganisms of a municipal treatment plant was tested under aerobic static conditions after 3 h of exposure. The inhibitory effect may include the effect on respiration and nitrification.

Nominal concentrations tested were 125, 200, 500, 1000 and 2000 mg/l, prepared by dilution of stock solution. No chemical analysis of test concentrations was conducted.

Results

No significant toxic effects were noted upon 3 h of exposure. Respiration rates were in the same range as determined for 2 blank controls. EC20, EC50 and EC80 > 2000 mg/l.

Description of key information

Respiration rate: EC50 (3h) > 2000 mg/l.

Additional information

TThe substance was tested according to OECD guideline 209.

Toxicity to microorganisms was evaluated by considering oxygen consumption upon 3 h of static exposure at concentrations between 125 and 2000 mg/l.

Two further studies were available, dated 1975 and 1982 and lacking of details on procedures and results. In both cases, no toxic effect were noted at the tested concentrations of 300 mg/l and 10000 mg/l, respectively.