diethyl 1-(2,4-dichlorophenyl)-5-methyl-4,5-dihydro-1H-pyrazole-3,5-dicarboxylate

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:

01 Jul 1994

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

GLP compliance:

yes

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: No stock solution, the test product was directly weighed into the test vessels due to the low solubility in water; 100 ml purest water were added and the solution ultrasonicated for 15 min.

Test organisms (species):

activated sludge, domestic

Details on inoculum:

- Laboratory culture: No, Activated sludge from the municipal sewage treatment plant at Frankfurt-Sindlingen was used.
- Preparation of inoculum for exposure: Preparation was performed in accordance with the cited EC Directive.
- Pretreatment: Prior to the test, the inocolum had not been acclimatised to the test substance or reference substance.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

20 ± 2°C

pH:

7.2 ± 0.2

Reference substance (positive control):

yes

Remarks:

3, 5-dichlorophenol

Duration:

3 h

Dose descriptor:

other: EC20

Effect conc.:

615.3 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Findings

The respiration rate in the test vessels containing the test item showed a slight dose-dependent decrease at all test

concentrations, indicating the test item to be slightly harmful to activated sludge microorganisms. However, even

at the highest concentration 1000 mg/L, the inhibition did not exceed 25.2%. The 3-hour EC20 was calculated to

be 615.3 mg/L and the 3-hour EC50 was > 1000 mg/L test item. The 3-hour EC50 of the toxic standard 3, 5 DCP

was within the tolerable range of 5 to 30 mg/L, thus verifying the sensitivity of the testing system used. The

respiration rates of the three untreated control replicates showed only minor (5 %) deviations from the mean

value. Thus, the criteria of validity specified in the testing guideline were fulfilled in this study.

Conclusion:

The 3h EC50 and EC20 of the test item for respiratory inhibition of activated sludge fed with synthetic sewage

was > 1000 mg/L and 615.3 mg/L, respectively. The test item is therefore of non-toxic to activated sludge

microorganisms.

Description of key information

EC50 (3 h) > 1000 mg/L with activated sludge (OECD 209)

Additional information

The respiration inhibition of the test item was tested during an OECD Guideline 209 Activated Sludge Respiration Inhibition Test. The 3h EC50 and EC20 values of the test item for respiratory inhibition of activated sludge fed with synthetic sewage were > 1000 mg/L and 615.3 mg/L, respectively. The test item is therefore of low toxicity to activated sludge microorganisms and the inhibition of degradation activity of activated sludge is not anticipated.