4,4'-methylenedicyclohexyl diisocyanate

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:

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:

yes

Analytical monitoring:

no

Vehicle:

no

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:

TEST ORGANISM:
- 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:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Hardness:

No data

Test temperature:

the values varied between 21.0 and 21.2 °C

pH:

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

Salinity:

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:

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):

yes

Remarks:

3,5-Dichlorophenol (purity 97 % )

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

191 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

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:

yes

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