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Ecotoxicological information

Toxicity to microorganisms

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Administrative data

Link to relevant study record(s)

activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
according to guideline
other: Commission Directive 88/302/EEC; Official Journal of the EC L 133, Part C
Principles of method if other than guideline:
corresponds for the most parts to the test method OECD 209

GLP compliance:
Analytical monitoring:
Details on test solutions:
The test substance has been added to about 130 ml deionized water, treated 3-4 h by ultrasound and stirred overnight before testing (equilibration phase).
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- type: mixed population of different microorganisms
- origin: aeration tank of a waste water plant treating predominantly domestic sewage (Wupper area water authority, Germany)
- pretreatment: none
- pH-value: 6.7
Test type:
Water media type:
Limit test:
Total exposure duration:
3 h
No data
Test temperature:
the values varied between 21.0 and 21.2 °C

the values varied between 8.0 and 8.1

Dissolved oxygen:
oxygen (mg/l) at O2-start: the values varied between 6.4 and 6.5
oxygen (mg/l) at O2-end: the values varied between 4.4 and 5.2

No data
Nominal and measured concentrations:
Test concentrations are given as nominal concentrations and have not been confirmed by analytical methods.
Details on test conditions:
- type of application: direct weighing
- test concentration of the activated sludge: 320 mg/l
- incubation time: 3 hours
- aeration: permanent
- temperature: 20 + 2 °C
- test concentration: 5 (56, 100, 180, 320, 560 mg/l)
- test parameter: respiration rate
Reference substance (positive control):
3,5-Dichlorophenol (purity 97 % )
3 h
Dose descriptor:
Effect conc.:
191 mg/L
Nominal / measured:
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
respiration rate
Details on results:
The EC values are determined by statistical methods (probit analysis).
Results with reference substance (positive control):
EC50: 14 mg/l (EC10 4.7 mg/l, EC90 39 mg/l)
The EC values are determined by statistical methods (probit analysis).
Validity criteria fulfilled:
Executive summary:

Concerning the acute toxicity of 4,4-methylenedicyclohexyl diisocyanate to activated sludge a study was conducted according to Directive 88/302/EEC Part C. The 3 h-EC50 determined by Probit analysis gave a value of 191 mg/l (Bayer AG, 2000).

Description of key information

Regarding the toxicity to microorganisms, an oxygen consumption inhibition test according to Commission Directive 88/302/EEC, Part C (corresponds to the OECD TG 209) with activated sewage sludge during 3 hours was performed and an EC50 of 191 mg/l was determined (Bayer AG, 2000e). Before testing a pre-treatment was performed with the test substance according to the recommendation mentioned in the OECD Guidance Document on aquatic toxicity testing of difficult substances and mixtures in order to accelerate the solution procedure. For that purpose 4,4’-methylenedicyclohexyl diisocyanate was treated in water by ultrasound for 3 - 4 hours and stirred overnight.

Key value for chemical safety assessment

EC50 for microorganisms:
191 mg/L

Additional information