Registration Dossier

Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

Administrative data

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

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2018
Report Date:
2018

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
no
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid

Test organisms

Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Results and discussion

Effect concentrationsopen allclose all
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 5.1 mg/L
Nominal / measured:
meas. (initial)
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Basis for effect:
growth rate

Applicant's summary and conclusion

Conclusions:
Two experiments were performed. In the 1st experiment a limit test at the concentration
1000 mg/L (nominal), clear inhibition of algal growth was observed. Therefore, a full test
was performed.
The study was performed using 5 concentrations ranging from 10 to 1000 mg/L (experiment
I: 1000 mg/L). Incubation time (test system Desmodesmus subspicatus) was
72 hours. The test solutions were shaken for 24 hours to guarantee that the saturation
concentration of the test item was reached.
Significant inhibition of algal growth was observed at all concentrations. Inhibition at the
concentrations 10 – 320 mg/L was in a similar range.
At the start and at the end of the test, the content of the test item in the test solutions was
estimated by calculation based on the organic carbon content of the test item and measurement
of the dissolved organic carbon (DOC) content in the test solutions using a carbon
analyser.
In the second experiment the measured test item concentration at the end of the test was
slightly lower than at the beginning, especially at the lower test item concentration. At the
lowest concentration no test item was detectable at the end of the test. That means the
measurable test item concentration was affected by the presence of the algal cells. From
this follows that test item was present in the test solution, but partly not measurable because
of adsorption or ingestion onto the algal cells. Therefore, the biological results were
based on the measured start concentration. This is in agreement with the requirements of
the OECD guideline (see point 40 on page 6 in the guideline).
Results are also provided for nominal concentrations.
Since the test item is a poorly soluble UVCB, extrapolation of the ECx values in the statistical
evaluation is not possible. Extrapolation would lead to incorrect results due to the limited
solubility of the test item. Therefore, the EC50 values (growth rate) and the EC10 values
(Yield) are given as ranges or as “not determinable”, respectively.
The 72h-EC50 values of potassium dichromate were determined in a separate reference
test. For the estimation of the 72h-EC50 values of the positive control, the fits showed sufficient
statistical correspondence of the data with the dose-response-equation. The values
were within the range of the laboratory.
The pH of the blank control should not fluctuate by more than 1.5 units. The change was
0.1 units (experiment II) and respectively 0.8 units (experiment I) in the blank control.
All validity criteria were met.
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:

Two experiments were performed. In the 1st experiment a limit test at the concentration

1000 mg/L (nominal), clear inhibition of algal growth was observed. Therefore, an additional

full test was performed. The results of the 1st experiment were not statistically evaluated.

The second experiment was performed using 5 concentrations ranging from 10 to 1000

mg/L (nominal). Incubation time (test system Desmodesmus subspicatus) was 72 hours.

The cell concentration of each replicate was determined by measuring the cell numbers

every 24 hours with an electronic particle counter. Growth rate μ and the yield1 were determined

from the cell number at the respective observation times.

Significant inhibition of algal growth was observed at all concentrations. Inhibition at the

concentrations 10 – 320 mg/L was in a similar range.

At the start and at the end of the test, the content of the test item in the test solutions was

estimated by calculation based on the organic carbon content of the test item and measurement

of the dissolved organic carbon (DOC) content in the test solutions using a carbon

analyser.

In the second experiment the measured test item concentration at the end of the test was

lower than at the beginning, especially at the lower test item concentration. At the lowest

concentration no test item was detectable at the end of the test. That means the measurable

test item concentration was affected by the presence of the algal cells. From this follows

that test item was present in the test solution but partly not measurable because of

adsorption or ingestion onto the algal cells. Therefore, the biological results were based on

the measured start concentration. This is in agreement with the requirements of the OECD

guideline (see point 40 on page 6 in the guideline).

Results are also provided for nominal concentrations. Since the test item is a poorly soluble

UVCB, extrapolation of the ECx values in the statistical evaluation is not possible. Extrapolation

would lead to incorrect results due to the limited solubility of the test item.

Therefore, the EC50 values (growth rate) and the EC10 values (Yield) are given as ranges

or as “not determinable”, respectively.

The 72h-EC50 values of potassium dichromate (K2Cr2O7, CAS No. 7778-50-9) were determined

in a separate reference test. The values lay within the range of the laboratory

(growth rate 0.73 - 1.10 mg/L, yield 0.21 – 0.66 mg/L).

The following results for the test item Palmitoyl grapevine shoot extract were determined: