Pyrazolo[5,1-b]quinazolin-9(1H)-one, 2-methyl-

Toxicity to microorganisms

Administrative data

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2000-01-11 - 2000-02-24

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP and guideline compliant study.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2000

Report date:

2000

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Version / remarks:

1993

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

18 Nov 1987

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

ISO 8192 (Water quality - Test for inhibition of oxygen consumption by activated sludge for carbonaceous and ammonium oxidation)

Version / remarks:

1986

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

2-methyl-1H,9H-pyrazolo[3,2-b]quinazolin-9-one

EC Number:

616-079-5

Cas Number:

74336-55-3

Molecular formula:

C11 H9 N3 O

IUPAC Name:

2-methyl-1H,9H-pyrazolo[3,2-b]quinazolin-9-one

Sampling and analysis

Analytical monitoring:

not specified

Test solutions

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
Handling of a poorly water-soluble test substance:
The test substance was added in the required amount to the test vessel with about 180 mL deionized water. The mixture was stirred for 22 ± 2 hours to obtain an optimal solution. Then synthetic medium was added, the pH-value was adjusted to 7.5 ± 0.5, the inoculum was added and the test started.

Test organisms

Test organisms (species):

activated sludge, domestic

Details on inoculum:

The inoculum was washed, brought to a concentration of 5 g/L dry substance and aerated for about 24 hours. 50 mL were added to a total volume of 250 mL to obtain a concentration of 1 g/L dry substance in the test.

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

180 min

Test conditions

pH:

before correction: 6.8
after correction: 7.2

Salinity:

Not applicable

Nominal and measured concentrations:

nominal concentration: 0, 10, 100 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Erlenmeyer vessel (nominal volume 250 mL)

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: 8 mL/vessel 100-fold concentrated OECD medium

OTHER TEST CONDITIONS
- Adjustment of pH: Yes

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 10

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

180 min

Dose descriptor:

other: EC20

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Effect concentrations 2

Duration:

180 min

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Effect concentrations 3

Duration:

180 min

Dose descriptor:

other: EC80

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

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

Results with reference substance (positive control):

- Results with reference substance valid? yes
- Relevant effect levels: EC50 = 5.4 mg/L

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

EC50 (180 min) > 100 mg/L (nominal)

Executive summary:

The determination of the inhibition of oxygen consumption of activated sludge by the test substance was assessed according to OECD guideline 209 and EU method C.11. (BASF, 2000). Activated sludge from a laboratory wastewater plant treating municipal sewage served as inoculum. Samples of activated sludge were exposed to 100 mg/L of the test substance (nominal concentration). The respiration rate of samples of activated sludge fed with synthetic sewage was measured in Erlenmeyer vessels after a contact time of 3 hours. The pH value of the media was adjusted before the inoculum was added. All validity criteria were met.

The respiration rate of the inoculum was not affected by the test substance therefore an EC50 of greater than 100 mg/L was determined after a three hour exposure.