Reaction mass of 2-ethylhexyl (6-isocyanatohexyl)-carbamate and bis(2-ethylhexyl) 1,6-hexan-1,6-diylbiscarbamate

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

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:

equivalent or similar to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

activated sludge, domestic

Details on inoculum:

TEST ORGANISM:
- mixed population of aquatic microorganisms, origin of an aeration tank  of a domestic sewage treatment plant (Municipal STP Cologne-Stammheim,  Germany);
- pre-treatment: aeration
- daily feed: with synthetic medium
- pH-value: 7.5

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Hardness:

No data

Test temperature:

21.9 °C (concerning the highest concentration of 320 mg/L)

pH:

7.7 (concerning the highest concentration of 320 mg/L)

Dissolved oxygen:

oxygen (mg/L): O2-start 5.7; O2-end 5.5 (concerning the highest concentration of 320 mg/L)

Salinity:

n.a.

Conductivity:

No data

Nominal and measured concentrations:

- 32, 56, 100, 180, 320 mg/L (nominal)
- 10000 mg/L (Test item concentration in physico-chemical oxygen consumption control)

Details on test conditions:

PRETREATMENT:
- test item has been added to 130 mL deionized water, stirred for 2 hours (equilibration phase)

TEST CONDITIONS:
- type of application: direct weighing
- test concentration of the activated sludge: 840 mg/L  suspended solids
- temperature: 20 +/- 2 °C
- stirring period before start of incubation time: 17 h
- test concentration: 5 (32, 56, 100, 180, 320 mg/L)
- test item in physico-chemical oxygen consumption control:  1000 mg/L
- test parameter: respiration rate
- aeration: permanent
- reference substance: 3,5-Dichlorphenol (2.5, 5, 10, 20, 40 mg/L)

Reference substance (positive control):

yes

Remarks:

3.5 Dichlorophenol (Aldrich)

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

64 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

Test concentrations are given as nominal concentrations and have not been confirmed by analytical methods.

Respiration inhibition (Test item):
- 32 mg/L: 33.3 %
- 56 mg/L: 41.7 %
- 100 mg/L: 66.7 %
- 180 mg/L: 76.7 %
- 320 mg/L: 83.3 %

Results with reference substance (positive control):

- 2.5 mg/L: 8.3 % respiration inhibition
- 5 mg/L: 11.1 % respiration inhibition
- 10 mg/L: 50.0 % respiration inhibition
- 20 mg/L: 88.9 % respiration inhibition
- 40 mg/L: 94.4 % respiration inhibition

The physico-chemical oxygen consumption has been determined at 10000 mg/L test item concentration. As no physico-chemical oxygen consumption was observed at that test item concentration this observation also holds true for the lower test item concentrations.

Validity criteria fulfilled:

yes

Remarks:

(respiratory rates of the 2 controls differ less than 15 % from each other; the EC50 of the reference compound 3,5-dichlorophenol is in the range 5–30 mg/L)

Conclusions:

The substance showed 83.3 % respiration inhibition of activated sludge at a test item concentration of 320 mg/L. A 3 h-EC50 of 64 mg/L was determined. Test concentrations are given as nominal concentrations and have not been confirmed by analytical methods.

Executive summary:

In order to test the toxicity to microorganism of the substance, activated sludge from predominantly domestic sewage plant was exposed to the test solution of five nominal concentrations of the substance (32, 56, 100, 180, 320 mg/L), blank control solution and solution with positive reference substance for a period of 3 hours. Dissolved oxygen was recorded and respiration rates were claculated. 83.3 % respiration inhibition was observed at the highest concentration of test substance. The physico-chemical oxygen consumption has been determined at 10000 mg/L test item concentration. As no physico-chemical oxygen consumption was observed at that test item concentration this observation also holds true for the lower test item concentrations. The substance showed 83.3 % respiration inhibition of activated sludge at a test item concentration of 320 mg/L. A 3 h-EC50 of 64 mg/L was determined. Test concentrations are given as nominal concentrations and have not been confirmed by analytical methods.

This toxicity study is classified as acceptable and satisfies the guideline requirements for the toxicity study to microoragnisms.

Description of key information

The substance showed 83.3 % respiration inhibition of activated sludge at a test item concentration of 320 mg/L. A 3 h-EC50 of 64 mg/L was determined. Test concentrations are given as nominal concentrations and have not been confirmed by analytical methods (Neuhahn, 2006).

Key value for chemical safety assessment

EC50 for microorganisms:

64 mg/L

Additional information

The physico-chemical oxygen consumption has been determined at 10000 mg/L test item concentration. As no physico-chemical oxygen consumption was observed at that test item concentration this observation also holds true for the lower test item concentrations.