4,4'-methylenedicyclohexyl diisocyanate

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

analytical monitoring was performed with DOC measurement. No substance specific analysis was performed.

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Version / remarks:

Cited as Directive 92/69/EEC, C.3

GLP compliance:

yes

Analytical monitoring:

yes

Vehicle:

no

Details on test solutions:

To accelerate the solution procedure a five fold amount (37.5 mg/1) of the maximum water solubility of the test substance in the
preliminary test (7.5 mg/1) was weighed into water, treated for 60 seconds at 8000 rpm.with an ultra-turrax and afterwards stirred
an a magnetic stirrer for 24 hours. To remove undissolved particles, the resulting emulsion was filtered using a folded filter of the
pore size 7-12 gm.

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM:
- stock culture: non-axenic strain obtained from the Institute of Plant Physiology at the University of Göttingen (Germany); exponentially-growing stock cultures maintained under constant temperature conditions (23 +/- 2 °C), light intensity (120 µE. x mE-2 x sE-1), cell density measured using a microcell counter

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

No data

Test temperature:

No data

pH:

pH value after 0 h : 8.1
pH value after 72 hrs: the values varied between 9.3 and 10.4

Dissolved oxygen:

No data

Salinity:

No data

Nominal and measured concentrations:

Nominal concentration of 0.08, 0.16, 0.31, 0.63, 1.3 and 2.5 mg/l: No TOC determination as the measured concentrations to be expected were below the detection limit of the TOC determination (2 mg/l)
Nominal concentration of 5 mg/l: Analytical value after 0 hour: 4 mg/l, after 72 hours: 6 mg/l, resp.

Details on test conditions:

TEST SYSTEM:
- test vessels: 300 ml Erlenmeyer flasks with stoppers
- culturing apparatus: light chamber with shaker
- dilution water: deionized water
- test cultures: final cell density 10 E+4 cells/ml
- method of administration: direct weighing
- test concentration: 7 (0.08, 0.16, 0.31, 0.63, 1.3, 2.5 and 5.0 mg/l) plus 1 control
- test parameter: growth and growth rate

MONITORING DATA:
- cell density measurements of growth (daily)
- analysis: twice, at test start and after 72 h
- pH-value: at test start, after 72 h

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.31 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other:

Remarks:

The study mentioned a NOEC of 0.31 mg/L based on growth rate. However there is no clear concentration-effect correlation. The effect values fluctuate between -18.2% amd +18.2 inhibition in the concentration range 0.08 to 5 mg/L. Although the statistical evaluation results in a NOEC, the biological significance is not given. It is therefore decided to evaluate the result of this study as "no effects to algae".

Details on results:

With the Dunett test the 72 h-NOEC and 72 h-LOEC for the growth rate were estimated.

Validity criteria fulfilled:

yes

Executive summary:

Concerning the algal toxicity, a test with Desmodesmus subspicatus in the presence of 4,4-methylenedicyclohexyl diisocyanate was performed according to the Directive 92/69/EEC, C.3 (Bayer AG, 2000).

The nominal values showed 72 h-EC50 values for the growth rate as well as biomass to be > 5 mg/l. With the Dunett test the 72 h-NOEC and 72 h-LOEC for the growth rate was estimated to be 0.31 mg/l and 0.63 mg/l resp..

The study mentioned a NOEC of 0.31 mg/L based on growth rate. However there is no clear concentration-effect correlation. The effect values fluctuate between -18.2% amd +18.2 inhibition in the concentration range 0.08 to 5 mg/L. Although the statistical evaluation results in a NOEC, the biological significance is not given. It is therefore decided to evaluate the result of this study as "no effects to algae".

Description of key information

Concerning the algal toxicity, a 72-hour test with Scenedesmus subspicatus was performed. According to Directive 92/69/EEC, C.3, the growth inhibition of the alga species was investigated with test substance concentrations in the range of 0.08 to 5 mg/l. The proceeding for preparation of the stock solution was in the same way as described above (7.1.1). A 72 h-ErC50 of > 5 mg/l was determined. As the test concentrations for the determination of the NOEC and LOEC were below the detection limit of the TOC determination (2 mg/l), the test results of the algal toxicity study refer to nominal concentrations. The arithmetic means of the TOC determination of the highest test concentration (5 mg/l) exhibited an expected recovery rate (90%) of the test substance based on organic C (Bayer AG, 2000d). As the reported NOErC is considered to be statistically significant but not biologically significant due to fluctuating effects values, it is decided to evaluate the result of this study as "no effects to algae".

Key value for chemical safety assessment

EC50 for freshwater algae:

5 mg/L

EC10 or NOEC for freshwater algae:

5 mg/L

Additional information

Should read >5.0 mg/L.