Carbamic acid,N,N'-[1,3-phenylenebis[methyleneiminocarbonylimino(methyl-3,1-phenylene)]]bis-di-C11-14-isoalkylesters, C13-rich

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:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

The culture of Desmodesmus subspicatus was obtained in Jan. 2013 by MBM Sciencebridge GmbH (Institut für Pflanzenphysiologie of Universität Göttingen). The algae are kept as stock culture on solid agar at 7 °C. From the stock culture, a permanent culture was prepared. From an aliquot of the permanent culture, the pre-culture was prepared.

Test type:

not specified

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Test temperature:

22-24 °C

pH:

7.8 - 8.5

Details on test conditions:

Experimental Conditions
Date: 23. – 26. Jul. 2013
Treatments tested: 100 mg/L
Number of replicates: six replicates for the control
six replicates for the treatment
Vessels: glass flasks nominal volume 65 mL
Duration: 72 hours
Temperature: 22 – 24 °C
Lighting: 5800 Lux
Control: deionised water with nutrient medium and alga
Treatments: test solution and alga

Reference substance (positive control):

yes

Remarks:

K2Cr2O7

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

other: DOC values

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

other: DOC values

Basis for effect:

growth rate

Details on results:

Parameter Value 95%-confidence-interval
NOEL (Growth Rate) 72 h 100 mg/L not determinable
NOEL (AUC) 72 h 100 mg/L not determinable
NOEL (Yield) 72 h 100 mg/L not determinable
LOEL (Growth Rate) 72 h > 100 mg/L not determinable
LOEL (AUC) 72 h > 100 mg/L not determinable
LOEL (Yield) 72 h > 100 mg/L not determinable
72h ErL10 > 100 mg/L not determinable
72h EbL10 > 100 mg/L not determinable
72h EyL10 > 100 mg/L not determinable
72h ErL50 > 100 mg/L not determinable
72h EbL50 > 100 mg/L not determinable
72h EyL50 > 100 mg/L not determinable

Results with reference substance (positive control):

Parameter Value 95%-confidenceinterval
Range of interlaboratory
test (EU C.3)
NOEC 72 h < 0.16 mg/L not determinable none stated
LOEC 72 h 0.16 mg/L not determinable none stated
72h ErC50 0.73 mg/L not determinable 0.60 – 1.03 mg/L
72h EbC50 0.48 mg/L not determinable 0.20 – 0.75 mg/L
72h EyC50 0.42 mg/L not determinable none stated

Reported statistics and error estimates:

For the treatment with the nominal loading 100 mg/L, it was tested whether the differences between treatment and control were significant. The values for the area under the curve, Yield and the growth rate were used for the assessment of observed effect levels. In order to select a suitable test for significance, it was checked whether equality of variance was given.
Equality of variance was tested using the following equation:
2
2
2
1
s
s
F 
with s1 being the greater variance and s2 the smaller one.
The calculated value F was compared with the F-test table (level of significance 95%). If
the calculated value was smaller than the tabular value, equality of variance was given.
With the t-test, it was checked whether the differences are significant. Significance is given
if the calculated t-value is bigger than the limit of significance (t-value taken from the table
with grade of freedom: n1 + n2 – 2, level of significance 95 %).
For the endpoints μ, AUC and Yield, the differences between the nominal loading
100 mg/L and the control can be considered as not significant (level of significance:
97.5 %) as the calculated t-values were smaller than the limit of significance. Therefore,
the nominal loading 100 mg/L is stated as NOEL for these endpoints.

Validity criteria fulfilled:

yes

Conclusions:

All validity criteria were met.
The test item solutions were shaken for 24 hours before usage in the test to guarantee that the saturation concentration of the test item was reached. Significant inhibition of algal growth was not observed at the nominal loading of 100 mg/L. At the start and at the end of the test, the content of the test item in the test solutions was determined using DOC analysis. At the start of the test, the measured concentrations lay in the range of the limit of determination. This was caused by the very low solubility of the test item in the test medium. At the end of the test, the measured concentrations lay in the range of the blank control. Measured DOC values were biased by the presence of the test organism in the test solution. Therefore, the determination of the results was based on the nominal loadings. The EC50s of potassium dichromate were determined in a separate reference test (GLP
study no. 201301R301). For the estimation of the EC50s of the positive control, the fits showed sufficient statistical correspondence of the data with the dose-response-equation. The values were within the normal range of the laboratory. No observations were made which might cause doubts concerning the validity of the study outcome. The result of the test can be considered valid.

Executive summary:

The study was performed as a limit test using the nominal concentration 100 mg/L. Incubation time (test system Desmodesmus subspicatus) was 72 hours. The cell concentration of

each replicate was determined by measuring the absorption of the solutions at 440 nm every 24 hours with a spectral photometer. The cell density of the cultures was calculated

based on the correlation curve between the adsorption and the cell density of the cultures determined by microscope counts. Growth rate μ, area under the growth curve (AUC1) and the yield2 were determined from the cell densities at the respective observation times. Significant inhibition of algal growth was not observed. At the start and at the end of the test, the content of the test item in the test solutions was determined using DOC analysis. At the start of the test, the measured concentrations lay in the range of the limit of determination. This was caused by the very low solubility of the test item in the test medium. At the end of the test, the measured concentrations lay in the range of the blank control. Measured DOC values were biased by the presence of the test organism in the test solutions. Therefore, the determination of the results was based on the nominal loadings.

The EC50s of potassium dichromate were tested in a separate reference test. The values lay within the normal range of the laboratory. The following results for the test item Addukt TI 65 - MXDA were determined:

Endpoint NOEL LOEL EL10 EL50

Growth Rate 100 mg/L > 100 mg/L > 100 mg/L > 100 mg/L

AUC 100 mg/L > 100 mg/L > 100 mg/L > 100 mg/L

Yield 100 mg/L > 100 mg/L > 100 mg/L > 100 mg/L

Description of key information

Significant inhibition of algal growth was not observed at the nominal loading of 100 mg/L

Key value for chemical safety assessment

EC50 for freshwater algae:

100 mg/L