Pyrazole

Toxicity to microorganisms

Administrative data

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

- guideline study (no GLP) - Documentation of the older study falls short of today´s requirements, but corresponds to the standards at the time they were conducted; the quality of the study performance is nevertheless not influenced. Sufficient data suitable for assessment.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1990

Report date:

1990

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Pyrazole

EC Number:

206-017-1

EC Name:

Pyrazole

Cas Number:

288-13-1

Molecular formula:

C3H4N2

IUPAC Name:

1H-pyrazole

Details on test material:

- Batch number: LJ27/90
- Molecular formula: C3H4N2
- Molecular weight [g/mol]: 68.08
- Aggregate state: solid
- Colour: white-colourless
- Purity of the test substance: 100% (GC)
- Impurities: no
- Homogeneity: yes

Sampling and analysis

Analytical monitoring:

no

Test solutions

Details on test solutions:

- Method: Stock solution has been prepared; concentration: 1.25 g/L. Dilution series from stock solutions was prepared.

Test organisms

Test organisms (species):

activated sludge, domestic

Details on inoculum:

- Activated sludge from the municipal wastewater treatment plant of Edenkoben/Rheinland-Pfalz, Germany from 1990-02-13.
- Preparation of inoculum for exposure: The inoculum was washed twice.
- Biomass concentration: 1.5 g/L dry weight

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

180 min

Test conditions

Nominal and measured concentrations:

- Dilution series from a stock solution (1.25 g/L nominal) resulted in the following concentrations: 0, 0.02, 0.05, 0.2, 0.5, 1.0 g/L (nominal).

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Results and discussion

Effect concentrations

Duration:

180 min

Dose descriptor:

other: EC20

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

Expert judgement: The originally calculated EC20 (180 min) of 250 mg/L was corrected
- Inhibition effects (per cent inhibition) were calculated by using the mean of the two values determined for the controls (35.6 and 31.5 mg O2/[L h])
- The resulting inhibition effects [%] were: -17, -17, -12, -22, -12 for nominal concentrations of 0.02, 0.05, 0.2, 0.5, 1.0 g/L, respectively.
- Hence with the highest concentration of 1 g/L an inhibition effect of -12% was determined and only in one case the threshold of 20% was exceeded insignificantly.

Results with reference substance (positive control):

- Results with reference substance valid? Yes.
- Relevant effect levels: EC50 (180 min) between 5 and 30 mg/L

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Remarks:

The control respiration rates (blanc) are within 15 % of each other. The EC50 (180 min) of the reference control is in the accepted range 5 to 30 mg/L .