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Diss Factsheets

Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Administrative data

Link to relevant study record(s)

Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
For details please refer to Read Across Justification Document, Section 13.2

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
For details please refer to Read Across Justification Document, Section 13.2

3. ANALOGUE APPROACH JUSTIFICATION
For details please refer to Read Across Justification Document, Section 13.2

4. DATA MATRIX
For details please refer to Read Across Justification Document, Section 13.2
Reason / purpose for cross-reference:
read-across source
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:
The measured concentrations lay between 92 % and 95 % of the nominal concentrations at the beginning of the test and between 81 % and 102 % of the nominal concentrations at the end of the test. Therefore, the determination of the biological results was based on the nominal concentrations.
At the start of the test, a new calibration was performed. Therefore, at the start of the test, the QC sample was only measured after the measurement of the samples from the test item solutions. The mean QC recovery rate at the start and the end of the test lay in the demanded range and was not taken into account.
Results with reference substance (positive control):
- Results with reference substance valid? yes
- ErC50 (72h): 0.64 mg/L; 95% confidence interval: 0.58 – 0.71 mg/L
- EyC50 (72h): 0.32 mg/L; 95% confidence interval:0.31 – 0.33 mg/L
Reported statistics and error estimates:
Calculation of results was performed with the help of validated software (Microsoft Excel®).
Because algal growth in the concentration of 100 mg/L (nominal) was higher than in the blank control, no statistically evaluation was performed and the EC50 for growth rate and yield was stated as being higher than the highest tested concentration.

Cell number measured

Nominal Concentration in mg/L Cell Number/mL
0 h 72 h
Blank control 114 27404
114 31861
114 36819
114 42458
114 37719
114 32520
1 114 40101
114 41509
114 42126
10 114 47332
114 40926
114 39487
100 114 39009
114 39211
114 40059

Non-GLP pre-test results (72h)

Nominal Concentration in mg/L Inhibition in %
Growth rate Yield
Blank control 0 0
1 -3,14 -18,59
10 -3,65 -22,45
100 -2,36 -13,35

Negative inhibition values indicate a stimulation of algal growth compared to the blank control.

Validity criteria fulfilled:
yes
Remarks:
- The cell concentration in the blank control increase: > factor 16 in 72 h - Mean coefficient of variation of daily growth rates in the blank controls: max. 35 % -Coefficient of variation of average growth rate during the whole test period: < 7%
Conclusions:
ErC50 (72h) > 100 mg/l (nominal)
ErC10 (72h) > 100 mg/l (nominal)
NOEC (growth rate, 72h) ≥ 100 mg/l (nominal)
Executive summary:

This study evaluated the toxicity of the test item towards Desmodesmus subspicatus according to the OECD 201 and EU Method C.3. This freshwater green alga is chosen as a typical species of phytoplankton.


The resulting endpoints are the NOEC, LOEC and, if applicable, the EC10and EC50for growth rate and yield.If there is a negative inhibition at the end of the test in the highest tested concentration, all values is given in a range.


A positive control was tested in a separate study to assure that the test conditions are reliable.


 


The test concentrations for the main study were chosen based on the results of the range finding test. Algae were exposed to 0 -1 -10 -100 mg/l of the substance and the cells were counted at 24, 48 and 72 hours. The growth rate and yield inhibition percentage were determined at 72 hours. No inhibition of growth rate or yield was observed at any of the tested concentrations. The EC50 at 72 h from the dose range finding test is therefore > 100 mg/l, while the NOEC at 72 h could be ≥ 100 mg/l.


In the main study algae were exposed to the substance under static conditions for 72 hours at 4.6, 10, 22, 46 and 100 mg/L nominal. The test concentrations were measured at the beginning and at the end of the study.  A positive control was tested in parallel. The cell concentrations were tested every 24 hours with an electronic particle counter. The pH value in treatments and blank control was measured at the beginning and start of the test. At the end of the test, the treatments were examined microscopically in order to assess the appearance of the algae and detect abnormalities (e.g. caused by the exposure to the test item).


The measured concentrations lay between 92 % and 95 % of the nominal concentrations at the beginning of the test and between 81 % and 102 % of the nominal concentrations at the end of the test. Normal and Healthy Appearance of the Algae was noted.


No inhibition of the growth was noted in any of the test solutions and control.


ErC50 (72h) > 100 mg/l (nominal)
ErC10 (72h) > 100 mg/l (nominal)
NOEC (growth rate, 72h) ≥ 100 mg/l (nominal)


 


 


 

Description of key information

ErC50 (72h) > 100 mg/l (nominal)
ErC10 (72h) > 100 mg/l (nominal)
NOEC (growth rate, 72h) ≥ 100 mg/l (nominal)

Key value for chemical safety assessment

EC50 for freshwater algae:
100 mg/L
EC10 or NOEC for freshwater algae:
100 mg/L

Additional information

Data from Similar Substance 01 were considered for the evaluation of the potential of the substance to cause toxic effects to aquatic algae. Justification for Read Across is given in Section 13.


The toxic potential of the substance to green algae was evaluated after 2 hours of exposure to different concentrations of the substance (ranging from 40 -1800 mg/l). Fluorescence parameters were measured on 2 ml algal suspension after 1 and 2 h of exposure. The ΕC50 (2h) was determined to be 1098.1 ± 13.7 mg/l.


 


A second study is performed.


This study evaluated the toxicity of the test item towards Desmodesmus subspicatus according to the OECD 201 and EU Method C.3 and under GLP conditions. This freshwater green alga is chosen as a typical species of phytoplankton. The test concentrations for the main study were chosen based on the results of the range finding test. Algae were exposed to 0 -1 -10 -100 mg/l of the substance and the cells were counted at 24, 48 and 72 hours. The growth rate and yield inhibition percentage were determined at 72 hours. No inhibition of growth rate or yield was observed at any of the tested concentrations. The EC50 at 72 h from the dose range finding test is therefore > 100 mg/l, while the NOEC at 72 h could be ≥ 100 mg/l.


In the main study algae were exposed to the substance under static conditions for 72 hours at 4.6, 10, 22, 46 and 100 mg/L nominal. The test concentrations were measured at the beginning and at the end of the study.  A positive control was tested in parallel. The cell concentrations were tested every 24 hours with an electronic particle counter. The pH value in treatments and blank control was measured at the beginning and start of the test. At the end of the test, the treatments were examined microscopically in order to assess the appearance of the algae and detect abnormalities (e.g. caused by the exposure to the test item).


The measured concentrations lay between 92 % and 95 % of the nominal concentrations at the beginning of the test and between 81 % and 102 % of the nominal concentrations at the end of the test. Normal and Healthy Appearance of the Algae was noted.


No inhibition of the growth was noted in any of the test solutions and control.


ErC50 (72h) > 100 mg/l (nominal)
ErC10 (72h) > 100 mg/l (nominal)
NOEC (growth rate, 72h) ≥ 100 mg/l (nominal)