reaction product of diphenylmethanediisocyanate, octylamine, 4-ethoxyaniline and ethylenediamine (1:0,37:1,53:0,05)

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:

1998-10-23 to 1999-02-15

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.6800 (Modified Activated Sludge, Respiration Inhibition Test for Sparingly Soluble Chemicals)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

The test substance was directly weighed into the test flasks.

Test organisms (species):

activated sludge, domestic

Details on inoculum:

- Method of cultivation: The Sludge was washed by centrifugation and the supernatant liquid phase was decanted. The solid material was resuspended in tap water and again centrifuged. The latter procedure was repeated twice. The washed sludge was diluted with tap water and to this mixture, 50 mL synthetic sewage feed per litre was added daily, starting two days prior to use. The sludge was kept at room temperature under continuous aeration until use. Immediately before use of an aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge (g) to its dry weight (g) determined. Based on this ratio, a calculated aliquot of washed sludge suspension, corresponding to 4 g dry material per litre, were made up with tap water. The pH of the activated sludge was determined to be pH 7.2.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Post exposure observation period:

No

Hardness:

Not specified

Test temperature:

18 °C during the incubation period

pH:

7.2 to 8.3

Dissolved oxygen:

at least 7.9 mg/L

Salinity:

Not applicable

Conductivity:

Not specified

Nominal and measured concentrations:

10, 32, 100, 320, 1000 mg/L (nominal concentrations)

Details on test conditions:

TEST SYSTEM
- Test vessel: glass flasks of approximately 1 litre volume and Karlsruher flasks of 250 mL volume
- Aeration: with compressed air (approximately 0.6 litre per minute)
- No. of vessels per concentration: one replicate
- No. of vessels per control: two replicates
- Biomass loading rate: 4 g dw

TEST MEDIUM / WATER PARAMETERS
- in accordance to the guideline

OTHER TEST CONDITIONS
- Adjustment of pH: no

EFFECT PARAMETERS MEASURED: after 3 hours of incubation measurement of oxygen concentration.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3.2

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Key result

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

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Results with reference substance (positive control):

- Results with reference substance valid? yes
- Relevant effect levels: 3-hour EC50 was calculated to be 6.4 mg/L (95 % confidence limits could not be calculated).
- Other: The following nominal concentrations of the positive control substance 3,5-Dichlorophenol were tested on the same activated sludge and under identical conditions as the test article: 100, 32 and 10 mg/L. In comparison to the controls the respiration rate of the activated sludge was inhibited by 58.6 % at the lowest nominal concentration of 10 mg/L. A t the nominal concentrations of 32 and 100 mg/L, the respiration rate was inhibited by 86.3 and 93.5 %, respectively.

Reported statistics and error estimates:

Not specified

Validity criteria fulfilled:

yes

Conclusions:

No toxicity was observed up to a nominal concentration of 1000 mg/L after 3 hours of exposure.

Executive summary:

The inhibitory effect of UREA 4 on the respiration rate of aerobic waste water micro organisms of activated sludge was investigated in a 3-hour respiration test. This study examined five different nominal test substance concentrations in the range from 10 to 1000 mg/L, two inoculum controls and three different concentrations of the reference substance 3,5 - Dichlorophenol in the range from 10 to 100 mg/L. In comparison to the inoculum controls the respiration rate of the activated sludge was not inhibited (-0.2 to 2.0 %) at all tested concentrations up to nominal 1000 mg/L. Test substance concentrations exceeding 1000 mg/L nominal were not tested. From these inhibition rates, the 3-hour EC20 and 3-hour EC50 could not be quantified because up to the highest nominal test concentration of 1000 mg/L no inhibition of the respiration rates was noted after three hours contact time. Nevertheless, the 3-hour EC20 and 3-hour ECSO are clearly higher than 1000 mg/L nominal under the present test conditions. The 3-hour EC50 for the positive control 3,5-Dichlorophenol, which was tested in the same way as the test article, was found to be 6.4 mg/L and is within the range of 5 - 30 mg/L recommended by the test guidelines; thus, confirming suitability o f the activated sludge.

Description of key information

The toxicity to microorganisms was assessed at nominal concentrations of 10, 32, 100, 320 and 1000 mg/L for 3 hours. The EC50 was > 1000 mg/L (nominal, limit concentration). The NOEC was greater or equal 1000 mg/L.

Additional information

The inhibitory effect of UREA 4 on the respiration rate of aerobic waste water micro organisms of activated sludge was investigated in a 3-hour respiration test according to EU-method C.11, OECD guideline 209 and OPPTS-method 850.6800. This study examined five different nominal test substance concentrations in the range from 10 to 1000 mg/L, two inoculum controls and three different concentrations of the reference substance 3,5 - Dichlorophenol in the range from 10 to 100 mg/L. In comparison to the inoculum controls the respiration rate of the activated sludge was not inhibited (-0.2 to 2.0 %) at all tested concentrations up to nominal 1000 mg/L. Test substance concentrations exceeding 1000 mg/L nominal were not tested. From these inhibition rates, the 3-hour EC20 and 3-hour EC50 could not be quantified because up to the highest nominal test concentration of 1000 mg/L no inhibition of the respiration rates was noted after three hours contact time. Nevertheless, the 3-hour EC20 and 3-hour ECSO are clearly higher than 1000 mg/L nominal under the present test conditions. The 3-hour EC50 for the positive control 3,5-Dichlorophenol, which was tested in the same way as the test article, was found to be 6.4 mg/L and is within the range of 5 - 30 mg/L recommended by the test guidelines; thus, confirming suitability o f the activated sludge.