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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:
12.06.2017 – 15.06-2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
Experimental test result using OECD guidelines
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Principles of method if other than guideline:
The freshwater algal growth inhibition test was carried out on Desmodesmus subspicatus with the substance 1-phenylazo-2-naphthol (CAS No.- 842-07-9) according to OECD Guideline 201.
GLP compliance:
no
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: No data
- Expiration date of the lot/batch: No data
- Purity test date: No data

RADIOLABELLING INFORMATION (if applicable)
- Radiochemical purity: No data
- Specific activity: No data
- Locations of the label: No data
- Expiration date of radiochemical substance: No data

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: No data
- Stability under test conditions: No data
- Solubility and stability of the test substance in the solvent/vehicle: No data
- Reactivity of the test substance with the solvent/vehicle of the cell culture medium: No data

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: No data
- Preliminary purification step (if any): No data
- Final dilution of a dissolved solid, stock liquid or gel: No data
- Final preparation of a solid: No data

FORM AS APPLIED IN THE TEST (if different from that of starting material) No data

OTHER SPECIFICS: No
Analytical monitoring:
no
Details on sampling:
No data
Vehicle:
yes
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
The stock solution 1.0 g/L was prepared by dissolving dark reddish-orange powder in acetone. Test solutions of required concentrations were prepared by mixing the stock solution of the test sample with OECD growth medium and inoculum culture. It was not possible to test higher substance concentration due to formation of precipitate.

- Controls: OECD medium as specified in OECD 201, used as a control and for dilution of the stock solution.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Strain: 86.81 SAG
- Source (laboratory, culture collection): Institute of botany of the ASCR
- Age of inoculum (at test initiation): 9.8 x 10E3 cells/ml
- Method of cultivation: No data

ACCLIMATION
- Acclimation period: No data
- Culturing media and conditions (same as test or not): No data
- Any deformed or abnormal cells observed: No data
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Remarks on exposure duration:
±1 hour
Post exposure observation period:
No data
Hardness:
No data
Test temperature:
23°C ± 2°C
pH:
The sample at concentration 10.0 mg/L: pH = 8.2 changed to pH = 7.8 during the test,
Control: pH = 8.1 changed to pH = 7.6 during the test.
Control+acetone: pH = 7.9 changed to pH = 7.4 during the test.
Dissolved oxygen:
No data
Salinity:
No data
Conductivity:
No data
Nominal and measured concentrations:
0, 0, 0.6, 1.2, 2.5, 5.0, 10.0 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: 50ml glass vessel
- Type : closed (with air-permeable stopper)
- Material, size, headspace, fill volume: 15 ml
- Aeration: No data
- Type of flow-through (e.g. peristaltic or proportional diluter): No data
- Renewal rate of test solution (frequency/flow rate): No data
- Initial cells density: 9.8x10E3 cells/mL
- Control end cells density: No data
- No. of organisms per vessel: No data
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): No data
- No. of vessels per vehicle control (replicates): No data

GROWTH MEDIUM
- Standard medium used: Yes

OTHER TEST CONDITIONS
- Adjustment of pH: Without adjustment
- Photoperiod: Continuous
- Light intensity and quality: 6000 lx - 8000 lx

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell counting: electronic particle counter.
- Chlorophyll measurement: No
- Other: ErC50 was calculated using non-linear regression by the software Prism 4.0
Reference substance (positive control):
yes
Remarks:
Potassium dichromate (K2Cr2O7)
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
41.8 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL: 18.8 - 92.6 mg/L
Details on results:
No data
Results with reference substance (positive control):
- Results with reference substance valid
- ErC50: 0.75 mg/L K2Cr2O7
Reported statistics and error estimates:
No data
Validity criteria fulfilled:
yes
Conclusions:
The median effective concentration (EC50) for the test substance, 1-phenylazo-2-naphthol, in a freshwater algae Desmodesmus subspicatus was determined to be 41.8 mg/L on the basis of effects on growth rate in a 72 hour study with 95% CL of 18.8 - 92.6 mg/L.
Executive summary:

The freshwater algal growth inhibition test was carried out on Desmodesmus subspicatus with the substance 1-phenylazo-2-naphthol (CAS No.- 842-07-9) according to OECD Guideline 201.

 

The stock solution 1.0 g/L was prepared by dissolving dark reddish-orange powder in acetone. Test solutions of required concentrations were prepared by mixing the stock solution of the test sample with OECD growth medium and inoculum culture and tested at the concentrations 0, 0, 0.6, 1.2, 2.5, 5.0, 10.0 mg/L. Effects on the growth rate of the organism were studied. The test was performed under static conditions in a static fresh water system at a temperature of 23± 2°C. Initial cell density of test organism used was 9.8x10(3) cells/ml. Determination of cell counting involve the use of electronic particle counter. ErC50 was calculated using non-linear regression by the software Prism 4.0.

The median effective concentration (EC50) for the test substance, 1-phenylazo-2-naphthol, in a freshwater algae Desmodesmus subspicatus was determined to be 41.8 mg/L on the basis of effects on growth rate in a 72 hour study with 95% CL of 18.8 - 92 .6 mg/L and also the substance was found to be not rapidly degradable. Thus considering the CLP Criteria for aquatic classification of the substance, it is concluded that 1-phenylazo-2-naphthol exhibits toxicity to aquatic algae (Desmodesmus subspicatus) in the chronic 3 classification category.

Description of key information

The freshwater algal growth inhibition test was carried out on Desmodesmus subspicatus with the substance 1-phenylazo-2-naphthol (CAS No.- 842-07-9) according to OECD Guideline 201. The median effective concentration (EC50) for the test substance, 1-phenylazo-2-naphthol, in a freshwater algae Desmodesmus subspicatus was determined to be 41.8 mg/L on the basis of effects on growth rate in a 72 hour study with 95% CL of 18.8 - 92.6 mg/L and also the substance was found to be not rapidly degradable. Thus considering the CLP criteria for aquatic classification of the substance, it is concluded that the substance ‘1-phenylazo-2-naphthol (CAS No. 842-07-9)’ exhibits toxicity to aquatic algae in the chronic 3 classification category.

Key value for chemical safety assessment

EC50 for freshwater algae:
41.8 mg/L

Additional information

Various studies including experimental data following OECD guideline and predicted results from validated model for toxicity to aquatic algae with the target substance 1-phenylazo-2-naphthol (CAS No. 842-07-9) were summarized as follows:

The freshwater algal growth inhibition test was carried out by SSS (2017) on Desmodesmus subspicatus with the substance 1-phenylazo-2-naphthol (CAS No.- 842-07-9) according to OECD Guideline 201. 

The stock solution 1.0 g/L was prepared by dissolving dark reddish-orange powder in acetone. Test solutions of required concentrations were prepared by mixing the stock solution of the test sample with OECD growth medium and inoculum culture and tested at the concentrations 0, 0, 0.6, 1.2, 2.5, 5.0, 10.0 mg/L. Effects on the growth rate of the organism were studied. The test was performed under static conditions in a static fresh water system at a temperature of 23± 2°C. Initial cell density of test organism used was 9.8x10(3) cells/ml. Determination of cell counting involve the use of electronic particle counter. ErC50 was calculated using non-linear regression by the software Prism 4.0.

The median effective concentration (EC50) for the test substance, 1-phenylazo-2-naphthol, in a freshwater algae Desmodesmus subspicatus was determined to be 41.8 mg/L on the basis of effects on growth rate in a 72 hour study with 95% CL of 18.8 - 92 .6 mg/L and also the substance was found to be not rapidly degradable.

Moreover, another study was predicted using OECD QSAR toolbox version 3.4 (2017) with respect to the descriptor log Kow; to assess the toxicity effect of 1-phenylazo-2-naphthol in aquatic algae in a 72 hours of exposure. The median effective concentration (EC50) for the test substance, 1-phenylazo-2-naphthol, in algae (Desmodesmus subspicatus) on a growth rate effect was estimated to be 30.77 mg/L in a 72 hour study and also the substance was found to be not rapidly degradable.

Thus, based on the above experimental and predicted studies, the effective concentration (EC50) value was found to be in the range of 30.77 mg/L to 41.8 mg/L and also the substance was found to be not rapidly degradable. Thus considering the CLP criteria for aquatic classification of the substance, it is concluded that the substance ‘1-phenylazo-2-naphthol (CAS No. 842-07-9)’ exhibits toxicity to aquatic algae in the chronic 3 classification category.

Although this value suggests classification of the substance in Aquatic chronic category 3, since it is classified in Aquatic chronic category 4 as per the Harmoni sed classification - Annex VI of Regulation (EC) No 1272/2008 (CLP Regulation), the same has been considered for the dossier.

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