6'-(dibutylamino)-3'-methyl-2'-(phenylamino)spiro[isobenzofuran-1(3H),9-(9H)-xanthen]-3-one

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:

1991-02-22

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

yes

Remarks:

1 % Tween 80-acetone.

Test organisms (species):

sewage, domestic

Details on inoculum:

- Name and location of sewage treatment plant where inoculum was collected: The aeration stage of the HRC Ltd. sewage treatment plant treating predominantly domestic sewage.
- Method of cultivation: The sample was maintained at 20 ± 2 °C with continuous aeration and used within 24 hours of collection. The pH was 7.1 and the suspended solids level of the sample was 4.3 g/L. Consequently, no adjustment of these characteristics was considered necessary.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Hardness:

350 mg/L (CaCO3)

Test temperature:

21 °C

pH:

6.0 - 8.5

Details on test conditions:

TEST SYSTEM
- Test vessel: conical flasks
- Type: open
- Material, size, fill volume: glass, 500 mL, 500 mL
- Aeration: Compressed air via narrow bore glass tubes.
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Laboratory tap water, dechlorinated by sodium thiosulphate.

OTHER TEST CONDITIONS
- Adjustment of pH: No
- Photoperiod: 3 h light
- Light intensity: Normal laboratory lighting.

EFFECT PARAMETERS MEASURED: BOD, after 30 min and 3 h

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Key result

Duration:

3 h

Dose descriptor:

IC50

Effect conc.:

> 4 mg/L

Nominal / measured:

nominal

Key result

Duration:

0 h

Dose descriptor:

NOEC

Effect conc.:

4 mg/L

Nominal / measured:

nominal

Details on results:

- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: No
- Effect concentrations exceeding solubility of substance in test medium: Yes, 4 mg/L was the highest test concentration that could be prepared due to the limited solubility of the test substance in water. A satisfactory dispersion of the test substance in water could not be achieved at concentrations in excess of this level.

Results with reference substance (positive control):

- Results with reference substance valid? Yes

Table 1: Summary of te results

Treatment	Conc., mg/L	O2 consumption rates, mgO2/L/min	% inhibition
30 min
Control	-	0.45	-
		0.43	-
Test Item	4.0	0.46	<5>
		0.47	<7>
Pos. Control	3.2	0.41	7
	10.0	0.37	16
	32.0	0.08	82
3 h
Control	-	0.39	-
		0.39	-
Test Item	4.0	0.40	<3>
		0.40	<3>
Pos. Control	3.2	0.37	5
	10.0	0.16	59
	32.0	0.06	85
<increase>

Validity criteria fulfilled:

not specified

Conclusions:

In this study on toxicity to microorganisms, a 3h-IC50 of above 4 mg/L was determined. The respective NOEC was set to above or equal 4 mg/L.

Executive summary:

In a 3 hour acute toxicity study, cultures of activated sludge were exposed to the test substance at a nominal concentration of 4 mg/L under aerobic conditions in accordance with OECD guideline 209 (Huntingdon, 1991). 4 mg/L was the highest test concentration that could be prepared due to the limited solubility of the test substance in water. A satisfactory dispersion of the test substance in water could not be achieved at concentrations in excess of this level. A 3h-IC50 of above 4 mg/L was determined. The respective NOEC was set to above or equal 4 mg/L.

Description of key information

In an activated sludge respiration inhibition test an IC50 of above 4 mg/L was determined after 3 hours.

Additional information

Key study

In a 3 hour acute toxicity study, cultures of activated sludge were exposed to the test substance at a nominal concentration of 4 mg/L under aerobic conditions in accordance with OECD guideline 209 (Huntingdon, 1991). 4 mg/L was the highest test concentration that could be prepared due to the limited solubility of the test substance in water. A satisfactory dispersion of the test substance in water could not be achieved at concentrations in excess of this level. A 3h-IC50 of above 4 mg/L was determined. The respective NOEC was set to above or equal to 4 mg/L.