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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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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 (Alga, Growth Inhibition Test)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
yes
Details on sampling:
- Concentrations:
- Sampling method: Samples were taken from the control and each test group at 0 and 72 hours for quantitative analysis. Duplicate samples were taken at 0 and 72 hours.
- Sample storage conditions before analysis: Duplicate samples were stored at approximately -20°C for further analysis if necessary.
Vehicle:
no
Details on test solutions:
For the purposes of the definitive test, the test material was dissolved directly in culture medium.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
The test was carried out using Desmodesmus subspicatus strain CCAP 276/20. Liquid cultures of Desmodesmus subspicatus were obtained from the Culture Collection of Algae and Protozoa (CCAP), Dunstaffnage Marine Laboratory, Oban, Argyll, Scotland.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
Temperature was maintained at 24±1°C throughout the test.
pH:
The pH values of the test flask were observed to increase from 7.0 - 7.2 at 0 hours to 7.5 - 7.8 at 72 hours.
Nominal and measured concentrations:
Based on the results of the range-finding test the following test concentrations were assigned to the definitive test: 6.25, 12.5, 25, 50 and 100 mg/L.
Reference substance (positive control):
yes
Remarks:
potassium dichromate
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
23 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC20
Effect conc.:
42 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
120 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
12.5 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
6.25 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
9.1 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
EC20
Effect conc.:
13 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
33 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Remarks on result:
other: 95% Confidence Limits 27 - 39 mg/L
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
12.5 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
6.25 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
8.3 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
cell number
Duration:
72 h
Dose descriptor:
EC20
Effect conc.:
11 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
cell number
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
29 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
cell number
Remarks on result:
other: 95% Confidence Limits 24 - 34 mg/L
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
12.5 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
cell number
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
6.25 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
cell number
Details on results:
Analysis of the test preparations at 0 and 72 hours showed measured test concentrations range from 91% to 103% of nominal and so the results are based on nominal test concentrations only.
All test and control cultures were inspected microscopically at 72 hours. There were no abnormalities detected in any of the control or test cultures at 72 hours.
Results with reference substance (positive control):
The following results were determined from data from the positive control substance (potassium dichromate):

EC50 (72 hr): 0.49 mg/L [95% Confidence Limits 0.43 - 0.55 mg/L]
EC50 (72 hr): 0.22 mg/L [95% Confidence Limits 0.19 - 0.24 mg/L]
EC50 (72 hr): 0.23 mg/L [95% Confidence Limits 0.21 - 0.27 mg/L]

NOEC [Growth Rate]: 0.125 mg/L
NOEC [Yield (cell number)]: 0.0625 mg/L
NOEC [Biomass]: 0.0625 mg/L

LOEC [Growth Rate]: 0.25 mg/L
LOEC [Yield (cell number)]: 0.125 mg/L
LOEC [Biomass]: 0.125 mg/L

The results from the positive control with potassium dichromate were within the normal range for this reference material.
Validity criteria fulfilled:
yes
Conclusions:
The effect of the test material on the growth of Desmodesmus subspicatus has been investigated over a 72 hour period and gave a 72 hour EC50 of 120 mg/L based on growth rate, a 72 hour EC50 of 29 mg/L (95% Confidence Limits: 24 - 34 mg/L based on cell number, and a 72 hour EC50 of 33 mg/L (95% Confidence Limits: 27 - 39 mg/L) based on biomass. The LOEC based on growth rate, cell number and biomass was 12.5 mg/L, and the NOEC based on growth rate, cell number and biomass was 6.25 mg/L.
Executive summary:

The acute toxicity of the test substance to aquatic algae was determined in accordance with the OECD Guideline for Testing of Chemicals 201. Following a preliminary range-finding test, Desmodesmus subspicatus was exposed to an aqueous solution of the test material at concentrations of 6.25, 12.5, 25, 50 and 100 mg/L (three replicate flasks per concentration) for 72 hours. A positive control conducted approximately every six months used potassium dichromate as the reference material. The effect of the test material on the growth of Desmodesmus subspicatus has been investigated over a 72 hour period and gave a 72 hour EC50 of 120 mg/L based on growth rate, a 72 hour EC50 of 29 mg/L (95% Confidence Limits: 24 - 34 mg/L) based on cell number, and a 72 hour EC50 of 33 mg/L (95% Confidence Limits: 27 - 39 mg/L) based on biomass. The LOEC based on growth rate, cell number and biomass was 12.5 mg/L, and the NOEC based on growth rate, cell number and biomass was 6.25 mg/L. The validity criteria of the test were fulfilled.

Description of key information

 The registered substance is not considered acutely toxic to aquatic algae, based on the EU Classification, Labelling and Packaging (CLP) criteria. The key study gave a 72 hour EC50 of 120 mg/L based on growth rate on BPA 1-4.5EO. The supporting study gave a 72 hour EC50 of 17.1 mg/L based on growth rate on BPA 2EO.

Key value for chemical safety assessment

EC50 for freshwater algae:
120 mg/L

Additional information

Two studies were conducted to assess the acute toxicity of the test substance to aquatic algae. Both studies were considered reliable as they were conducted on the registered substance according to OECD Testing Guideline 201. The key study conducted on Desmodesmus subspicatus gave a 72 hour EC50 of 120 mg/L based on growth rate, a 72 hour EC50 of 29 mg/L based on cell number, and a 72 hour EC50 of 33 mg/L based on biomass on BPA 1-4.5EO. The supporting study conducted on Pseudokirchnerella subcapitata gave a 72 hour EC50 of 3.22 mg/L based on yield and a 72 hour EC50 of 17.1 mg/L based on growth rate on BPA 2EO.

The 72 hour EC50 values obtained in these studies do not lead to the registered substance being classified as acutely toxic to aquatic algae, based on the EU Classification, Labelling and Packaging (CLP) criteria.