reaction product of diphenylmethanediisocyanate, toluenediisocyanate ( reaction mass of isomers: 65 % 2,4- and 35 % 2,6-diisocyanate), octylamine, oleylamine and 4-ethoxyaniline (molar ratio 3.88:1:6.38:0.47:2.91)

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:

1999-01-26 to 1999-05-19

Reliability:

1 (reliable without restriction)

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)

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material:
The test substance was directly weighed into the test flasks.

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

The test substance was directly weighed into the test flasks.

Test organisms (species):

activated sludge

Details on inoculum:

- Preparation of inoculum for exposure: 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 resuspended in tap water at a concentration of 4 g dry material per litre and was fed daily with 50 mL synthetic sewage feed per litre, starting 2 days prior to use. The sludge was kept at room temperature under continuous aeration until use. Immediately before use, the dry weight of the activated sludge was determined, and diluted to 4 g dry material/L with tap water. The pH of the activated sludge was pH 7.4.

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

18-21 °C

Dissolved oxygen:

at least 6.0 mg/L

Nominal and measured concentrations:

10, 32, 100, 320 and 1000 mg/L

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 (replicates): one replicate
- No. of vessels per control (replicates): 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 the respiration rate was measured

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3.2

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

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

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: The 3-hour EC50 was calculated to be 5 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 62.2 % at the lowest nominal concentration of 10 mg/L. At the nominal concentrations of 32 and 100 mg/L, the respiration rate was inhibited by 89.1 % and 93.8 %, respectively.

Validity criteria fulfilled:

yes

Conclusions:

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

Executive summary:

The influence of the test substance on the activity of activated sludge was evaluated by measuring the respiration rate under defined conditions. The respiration rate (oxygen consumption) of an aerobic activated sludge fed with a standard amount of synthetic sewage was measured in the presence of various concentrations of the test substance after an incubation period of 3 hours. In comparison to the inoculum controls the respiration rate of the activated sludge was not or only slightly inhibited (-4.1 % to 8.4 %) up to the highest tested concentration of nominal 1000 mg test substance/L. Test substance concentrations exceeding 1000 mg/L were not tested. From the determined inhibition rates, the 3-hour EC 20 and EC 50 could not be quantified because up to the highest nominal test concentration of 1000 mg/L the respiration rate was not significantly inhibited. Nevertheless, the 3-hour EC 20 and EC 50 are clearly higher than 1000 mg/L under the present test conditions.

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.

Key value for chemical safety assessment

EC50 for microorganisms:

1 000 mg/L

EC10 or NOEC for microorganisms:

1 000 mg/L

Additional information

The influence of the test substance UREA 6 on the activity of activated sludge was evaluated by measuring the respiration rate under defined conditions according to EU-method C.11, OECD guideline 209 and OPPTS-method 850.6800. The respiration rate (oxygen consumption) of an aerobic activated sludge fed with a Standard amount of synthetic sewage was measured in the presence of various concentrations of the test substance after an incubation period of 3 hours. In comparison to the inoculum controls the respiration rate of the activated sludge was not or only slightly inhibited (-4.1 % to 8.4 %) up to the highest tested concentration of nominal 1000 mg test substance/L. Test substance concentrations exceeding 1000 mg/L were not tested. From the determined inhibition rates, the 3-hour EC 20 and EC 50 could not be quantified because up to the highest nominal test concentration of 1000 mg/L the respiration rate was not significantly inhibited. Nevertheless, the 3-hour EC 20 and EC 50 are clearly higher than 1000 mg/L under the present test conditions.