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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
Study period:
2018-05-22 - 2018-05-25 (experimental phase)
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
under GLP
Qualifier:
according to
Guideline:
OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)
Version / remarks:
OECD Guideline for the Testing of Chemicals No. 201, adopted 23. Mar. 2006, An-nex 5 corrected: 28 July 2011 “Freshwater Alga and Cyanobacteria, Growth Inhibition Test”
Deviations:
yes
Remarks:
but not affecting the integrity and validity of the study
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Version / remarks:
Regulation (EU) No. 2016/266 amending Regulation (EC) No. 440/2008, Annex IV, Method C.3: “FRESHWATER ALGAE AND CYANOBACTERIA, GROWTH INHIBI-TION TEST,” adopted 07. December 2015
Deviations:
yes
Remarks:
but not affecting the integrity and validity of the study
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
The test item was stored in a closed vessel at 20 ± 5°C
Analytical monitoring:
yes
Details on sampling:
- Concentrations: 0 / 4.6 / 10 / 22 / 46 / 100 mg/L nominal concentration
- Sampling method: After the test, samples for the analytical determination were taken.
- Sample storage conditions before analysis: No storage mentioned, the concentration of the test item in the test vessels was measured at the start and at the end of the test.
Vehicle:
no
Remarks:
algal medium
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: A stock solution containing 100.6 mg/L test item in algal medium (demineralised water enriched with minerals but without algae) was prepared. Lower test concentrations were prepared by dilution of the stock solution in algal medium.
- Controls: no treatment resp. potassium dichromate
- Evidence of undissolved material (e.g. precipitate, surface film, etc.): none
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Common name: Unicellular freshwater green alga
- Strain: Desmodesmus subspicatus, SAG Strain Number 86.81
- Source (laboratory, culture collection): The culture of Desmodesmus subspicatus was obtained in January 2016 by MBM Sciencebridge GmbH (Institut für Pflanzenphysiologie of Universität Göttingen).
- Method of cultivation: The algae are kept as stock culture on solid agar at 2 - 8 °C. From the stock culture, a permanent culture was prepared. From an aliquot of the permanent culture, the pre-culture was prepared.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Post exposure observation period:
none
Test temperature:
20.4 – 23.1 °C
pH:
7.8 - 8.3
Nominal and measured concentrations:
nominal: 0 / 4.6 / 10 / 22 / 46 / 100 mg/L
measured, t=0h: < LOQ / 4.83 / 10.62 / 21.86 / 46.62 / 105.05 mg/L
measured, t=72h: < LOQ / 4.66 / 9.81 / 23.32 / 50.17 / 106.35 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: glass flasks
- Type (delete if not applicable): open (covered with perforated plastic foil acting as a stopper)
- Material, size, headspace, fill volume: glass flasks, total volume 65 mL, fill volume 45 ± 2 ml
- Renewal rate of test solution (frequency/flow rate): none
- Initial cells density: 2000 cells / mL
- Control end cells density: 272767 cells / mL
- No. of vessels per concentration (replicates): 3 replicates for each treatment
- No. of vessels per control (replicates): 6 replicates for the blank control

GROWTH MEDIUM
- Standard medium used: yes

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: no
- Photoperiod: continuous
- Light intensity and quality: 5000 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: electronic particle counter
Appearance of the algae was checked at the end of the test.
Reference substance (positive control):
yes
Remarks:
Potassium dichromate K2Cr2O7 (CAS No. 7778-50-9) was used as positive control in a separate reference test.
Duration:
72 h
Dose descriptor:
NOEC
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:
biomass
Remarks:
yield
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Remarks:
yield
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:
EC10
Effect conc.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Remarks:
yield
Key result
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:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Remarks:
yield
Details on results:
- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test): none
- Any stimulation of growth found in any treatment: no
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: no
- Effect concentrations exceeding solubility of substance in test medium: none
Results with reference substance (positive control):
- Results with reference substance valid? Yes
- EC50:
Parameter Value 95% confidence interval
72h ErC50 0.90 mg/L 0.77 – 1.1 mg/L
72h EyC50 0.42 mg/L 0.35 - 0.51 mg/L
Validity criteria fulfilled:
yes
Conclusions:
The study was conducted under GLP according to OECD guideline 201 and EU method C.3 on the registered substance itself. The method is to be considered scientifically reasonable with no deficiencies in documentation or deviations from the guidelines, the validity criteria were met. Hence, the results can be considered as reliable to assess the toxicity of PPSOH towards algae.
The measured concentrations lay between 99 % and 106 % of the nominal concentrations at the beginning of the test and between 98 % and 109 % of the nominal concentrations at the end of the test. Therefore, the determination of the results was based on the nominal concentrations.
No significant inhibition of algal growth was observed in the highest concentrated treatment, i.e. 100 mg/L, so the EC50 (growth rate) was determined to be >100 mg/L. Hence, PPSOH does not need to be classified as hazardous to the environment, neither acutely nor chronic, according to Regulation 1272/2008 and amendments.
Executive summary:

The study was conducted under GLP according to OECD guideline 201 and EU method C.3 on the registered substance itself.

One valid experiment was performed.

The study was performed using 5 concentrations ranging from 4.6 to 100 mg/L. 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 yield were determined from the cell number at the respective observation times.

The inhibition values in the treatments were scattering but no significant inhibition of algal growth was observed in the highest concentrated treatment. This was in agreement with the result of a non-GLP pre-test.

In the treatments 4.6 mg/L and 46 mg/L a not explainable inhibition of algal growth was observed.

The test solutions were prepared by dilution of a stock solution of the test item and the measured test item concentrations in all treatments was in the expected range.

That means that the solutions were not incorrectly prepared and the inhibition of algal growth was not caused by the test item.

The measured concentrations lay between 99 % and 106 % of the nominal concentrations at the beginning of the test and between 98 % and 109 % of the nominal concentrations at the end of the test. Therefore, the determination of the results was based on the nominal concentrations.

Because of the scattering inhibition values, only the highest concentration 100 mg/L was used for statistical evaluation.

The 72h-EC50values 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 item1-(2-hydroxy-3-sulphonatopropyl)pyridinium, inner salt (PPSOH)were determined:

 

Table Results of the test item

Endpoint

NOEC

LOEC

EC10

EC50

Growth Rate

≥ 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

 

PPSOH does not need to be classified as hazardous to the environment, neither acutely nor chronic, according to Regulation 1272/2008 and amendments.

Description of key information

Toxicity to algae: EC50(72h) > 100 mg/L, NOEC(72h) ≥ 100 mg/L, both growth rate and yield, for Desmodesmus subspicatus (OECD 201, GLP)

Key value for chemical safety assessment

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

Additional information