N-[2-(4-oxo-4H-3,1-benzoxazin-2-yl)phenyl]naphthalene-2-sulphonamide

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 July 16th to November 02nd, 1990

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Version / remarks:

adopted on April 4, 1984

GLP compliance:

no

Details on test solutions:

The test article (0.5 g) was suspended with 100 mg Tween 80 and thereafter diluted up to 1000 ml in bidistiIled water.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Source: the tests were run with aerobic activated sludge from a domestic waste-water treatment plant (ARA, Sissach/Switzerland).
- Pre-treatment: the sludge was coarsely sleved, centrifuged, the supernatant liquid phase decanted, the solid material resuspended in tap water and again centrifuged. The procedure was repeated a further two times. An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge (ml) to its dry weight (g) determined.
- Preparation of inoculumn: based on the ratio, a volume of washed sludge suspension corresponding to 4.0 g dry material were made up with Soerensen buffer (pH = 7) to 1 litre.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

20-25 °C

Nominal and measured concentrations:

10 and 100 mg/l

Details on test conditions:

TEST SYSTEM
- Aeration: yes. The tests were carried out about 0.2 l/minute instead of 0.5 l/minute to prevent possible foam development.
- No. of vessels per concentration: 1 replicate
- No. of vessels per control: 3 replicates
- Activated sludge amount: 200 ml per vessel

TEST MEDIUM / WATER PARAMETERS
- Preparation of dilution water: OECD recommended synthetic sewage feed. Thereafter, the sludge was aerated at until use.
- pH: the pH measured was 7.6.

OTHER TEST CONDITIONS
- Photoperiod: light/dark cycle of 15 hours of artificial fluorescent light (about 500-1500 Lux) per day.

SAMPLES ANALYSIS
After 180 minutes of aeration at 22 °C, the first sampIe was taken for oxygen measurement over a period of up to 10 minutes. Thereafter, in 15 minutes intervals, the rest of the samples were submitted to measurement of oxygen concentration.
Sampling was started with the control 1. Thereafter, the measurements were continued with the positive controls and the test article samples. Finally, the oxygen consumption of control 2 was determined.

DETERMINATION OF OXYGEN CONCENTRATION
Oxygen consumption was measured over a period of 10 minutes. During measurement, the sample was not aerated but continuously stirred on a magnetic stirrer.
The apparatus used for oxygen measurements was the WTW OXI 91 (Wissenschaftlich- Technische Werkstaetten, Weilheim/Federal Republic of Germany).
The pH was determined with the pH 90 (WTW, Weilheim/FRG).

VALIDATION OF THE TEST
The tests are validated by testing a known standard, i.e. 3,5-dichlorophenol.
Its IC50-value should be in the range of 5 - 30 mg/I.
Furthermore, the variation between the two control samples (start, end) should not be greater than 15 %.

Reference substance (positive control):

yes

Remarks:

3,5-dichorophenol

Duration:

3 h

Dose descriptor:

IC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

The respiration rate of the sludge was not inhibited (-6.7 %) at the highest concentration of test item, i.e. 100 mg/I.

Results with reference substance (positive control):

At a concentration of the standard of 3.2 mg/l, no inhibit'lon of the respiration rate was observed (-5 %). Almost complete inhibition (92.4 %) was observed at 50 mg/I. The IC50 was found to be about 12.8 mg/I.

Test vessel	Oxygen consumption (mg O2/l min)	Inhibition (%)	pH
Control	1.16	-	7.7
Control	1.22	-	7.7
Control	1.58	-	7.7
Mean (control1 and 2)	1.19
Deviation (control1 and 2)	5.20%
Test item 100 mg/l	1.27	-6.7	7.7
Test item 10 mg/l	1.50	-26.1	7.7
3,5-dichlorophenol 50 mg/l	0.09	92.4	7.7
3,5-dichlorophenol 10 mg/l	0.56	52.9	7.7
3,5-dichlorophenol 3.2 mg/l	1.25	-5.0	7.7

Validity criteria fulfilled:

yes

Conclusions:

IC50 (3h) > 100 mg/l

Executive summary:

The toxicity of test item on aerobic waste-water bacteria in the respiration test, according to the method and procedures described into the OECD guideline 209.

The test article showed no inhibition (-6.7 %) of the respiration rate up to a concentration of 100 mg/l. The IC50 was determined to be higher than100 mg/l.

The IC50 for 3,5-dichlorophenol tested under the same conditions was about 12.8 mg/l.

Conclusion

IC50 (3h) > 100 mg/l

Description of key information

Not harmful/toxic to microorganisms

Additional information

The toxicity of test item on aerobic waste-water bacteria in the respiration test, according to the method and procedures described into the OECD guideline 209. The test article showed no inhibition (-6.7 %) of the respiration rate up to a concentration of 100 mg/l. The IC50 was determined to be higher than100 mg/l.