2-Naphthalenesulfonic acid, 7-amino-4-hydroxy-8-[2-[2-sulfo-4-[[2-(sulfooxy)ethyl]sulfonyl]phenyl]diazenyl]-, potassium sodium salt (1:?:?), coupled with diazotized 2-[(4-amino-5-methoxy-2-methylphenyl)sulfonyl]ethyl hydrogen sulfate

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:

Experiment start date - 14 May 2003; Experiment end date - 16 May 2003; Study completion date - 30 July 2003.

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

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Identity: FAT 40812/A
Batch: WP 8/03
Purity: approx. 75 %
Appearance: Solid, dark red-brownish powder
Expiration date: 23 April 2010
Storage: At room temperature at about 20 °C

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

- Stock solution: 2.00 g test item were weighed, dissolved, homogenised, and made up to 1000 mL with tap water.
- Test item concentrations: To obtain the nominal test concentrations of: 26, 64, 160, 400, and 1000 mg test item/L the following volumes were taken from the stock solution: 1.3, 3.2, 8.0, 20, and 50 mL, added to respective test vessels, then filled up to 100 mL with tap water after adding 3.2 mL synthetic sewage feed and 40 mL sludge. The test item solutions were prepared immediately before test start.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Test system: Activated sludge of a communal sewage treatment plant (ARA Therwil, Switzerland) collected on May 14, 2003.
- Sludge pre-treatment: The inoculum was prepared two days before test began. The freshly collected activated sludge was washed 3 times with tap water. Subsequently the sludge was aerated. The day the test started, a sample of the activated sludge was taken to determine the dry weight of the suspended solids. The final concentrations of the inoculum was about 4.3 g/L suspended solids. The pH of the inoculum was 6.4.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

18.5 °C

pH:

7.6 - 7.7

Nominal and measured concentrations:

- Nominal: 26, 64, 160, 400, and 1000 mg/L.

Details on test conditions:

- Sludge dry weight: 1.7g/L suspended solids.
- Test volume: 100 mL.
- Aeration: 0.1 - 0.2 L/min. by Pasteur pipette.
- Estimation technique: O2 - consumption, measured with an oxygen sensitive electrode system: OXI DIGI 530.

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:

growth inhibition

Details on results:

At all the test concentrations no significant inhibition of the respiration rate of the activated sludge was observed (% inhibition of the respiration rate <15 %).

Results with reference substance (positive control):

IC50(3h) of 3,5 Dichlorophenol = 10.3 mg/L.

Validity criteria fulfilled:

yes

Conclusions:

The 3-h EC50 value is >1000 mg/L in micro organisms.

Executive summary:

In a GLP-compliant 3-hour respiration inhibition test, performed according to OECD Guideline 209, the inhibitory effect of the test substance on the respiration rate of aerobic wastewater microorganisms of activated sludge was investigated. The nominal concentration were 26, 64, 160, 400, and 1000 mg/L. In addition, two controls and the reference item 3,5-dichlorophenol were tested. The results of these treatments confirmed the suitability of the activated sludge and the method used. The test substance had no significant inhibitory effect on the respiration rate of activated sludge after the incubation period of 3 hours. The 3-hour EC50 could not be calculated, but was clearly higher than 1000 mg/L.

Description of key information

In a GLP-compliant 3-hour respiration inhibition test, performed according to OECD Guideline 209, the inhibitory effect of the test substance on the respiration rate of aerobic wastewater microorganisms of activated sludge was investigated. The nominal concentration were 26, 64, 160, 400, and 1000 mg/L. In addition, two controls and the reference item 3,5-dichlorophenol were tested. The results of these treatments confirmed the suitability of the activated sludge and the method used. The test substance had no significant inhibitory effect on the respiration rate of activated sludge after the incubation period of 3 hours. The 3-hour EC50 could not be calculated, but was clearly higher than 1000 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:

1 000 mg/L