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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:
24.03.2017 – 31.03-2017
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 p-tolyl acetate (CAS No.- 140-39-6) 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 150.0 mg/L was prepared by dissolving colourless liquid in OECD growth medium. Test solutions of required concentrations were prepared by mixing the stock solution of the test sample with OECD growth medium and inoculum culture.

- 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): 5x103 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:
Sample at concentration 150.0 mg/L: pH = 7.2 changed to pH = 7.6 during the test
Control 1: pH= 8.3 changed to pH = 7.9 during the test.
Control 2: pH= 8.0 changed to pH = 7.6 during the test.
Dissolved oxygen:
No data
Salinity:
No data
Conductivity:
No data
Nominal and measured concentrations:
0, 0, 30.0, 45.0, 67.5, 100.0, 150.0 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: 5x103 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: microscope with counting chamber Cyrus I or 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.:
115.1 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL: 100.2 - 132.3 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, p-tolyl acetate , in a freshwater algae Desmodesmus subspicatus was determined to be 115.1 mg/L on the basis of effects on growth rate in a 72 hour study with 95% Cl of 100.2 - 132.3 mg/L.
Executive summary:

The freshwater algal growth inhibition test was carried out on Desmodesmus subspicatus with the substance p-tolyl acetate (CAS No.- 140-39-6) according to OECD Guideline 201.

 

The stock solution 150.0 mg/L was prepared by dissolving colourless liquid in OECD growth medium. 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, 30.0, 45.0, 67.5, 100.0, 150.0 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 5x10(3) cells/ml. Determination of cell counting involve the use of microscope with counting chamber Cyrus I or 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, p-tolyl acetate, in a freshwater algae Desmodesmus subspicatus was determined to be 115.1 mg/L on the basis of effects on growth rate in a 72 hour study with 95% CL of 100.2 - 132.3 mg/L. Thus, according to CLP Criteria for aquatic classification of the substance, it is concluded that p-tolyl acetate (CAS No.- 140-39-6) does not exhibit toxicity to aquatic algae (Desmodesmus subspicatus).

Description of key information

The median effective concentration (EC50) for the test substance, p-tolyl acetate, in a freshwater algae Desmodesmus subspicatus was determined to be 115.1 mg/L on the basis of effects on growth rate in a 72 hour study with 95% CL of 100.2 - 132.3 mg/L. Thus, according to CLP Criteria for aquatic classification of the substance, it is concluded that p-tolyl acetate (CAS No.- 140-39-6) does not exhibit toxicity to aquatic algae (Desmodesmus subspicatus).

Key value for chemical safety assessment

EC50 for freshwater algae:
115.1 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 p-tolyl acetate (CAS No.140-39-6) and to its read across substance tert-Butyl acetate (CAS no. 540-88-5) by considering its structure-activity relationships, were summarized as follows:

The freshwater algal growth inhibition test was carried out on Desmodesmus subspicatus with the substance p-tolyl acetate (CAS No.- 140-39-6) according to OECD Guideline 201.

The stock solution 150.0 mg/L was prepared by dissolving colourless liquid in OECD growth medium. 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, 30.0, 45.0, 67.5, 100.0, 150.0 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 5x10(3) cells/ml. Determination of cell counting involve the use of microscope with counting chamber Cyrus I or 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, p-tolyl acetate, in a freshwater algae Desmodesmus subspicatus was determined to be 115.1 mg/L on the basis of effects on growth rate in a 72 hour study with 95% CL of 100.2 - 132.3 mg/L. Thus, according to CLP Criteria for aquatic classification of the substance, it is concluded that p-tolyl acetate (CAS No.- 140-39-6) does not exhibit toxicity to aquatic algae (Desmodesmus subspicatus).

Also, based on the prediction done using the OECD QSAR toolbox version 3.4 with log kow as the primary descriptor and considering the five closest read across substances, the short term toxicity on aquatic algae and cyanobacteria was predicted for target substance p-tolyl acetate (CAS no. 140 -39 -6) (2017). EC50 value was estimated to be127.536 mg/l for Pseudokirchneriella subcapitata for 72 h duration. Based on this value it can be concluded that the substance p-tolyl acetate can be considered as non-toxic to aquatic environment and thus can be considered to be not-classified as per the CLP classification criteria.

Additional supporting study for the short term toxicity on aquatic algae and cyanobacteria of target chemical p-tolyl acetate(CAS No. 140-39-6) is predicted using the EPI Suite ECOSAR version 1.10 (EPI Suite, 2017), the 96 hours EC50 was estimated to be 41.938 mg/l on green algae for substance p-tolyl acetate(CAS no. 140 -39 -6) with growth inhibition effects. But the BCF value of p-tolyl acetatewas not >= 500 as well as the substance was found to be readily bio-degradable in water compartment. Thus, the chemical p-tolyl acetate can be considered as non-toxic to aquatic organisms and thus cannot be classified as hazardous as per the CLP criteria.

In another study of read across substance tert-Butyl acetate (CAS no. 540-88-5) from peer reviewed journal (G. BRINGMANN and R. KOH, 1980), short term toxicity to Entosiphon Sulcatum study was carried out for 72 hrs. The study was based on the effects on Entosiphon Sulcatum in a static fresh water system. Test chemical of known concentration was prepared in sterile double distilled water. For maintenance of the test strain of Entosiphon sulcatum, continuously inoculate the expected required number of stock cultures at 72 h or 96 h intervals. For this, mix 8 ml of stock solution and 8 ml of sterile double-distilled water in 300 -ml Erlenmeyer flasks stoppered with metal caps and add 2 ml of a stock culture and 2 ml of the adjusted bacterial suspension for Entosiphon stock cultures. Store stock cultures at 25°C. Before inoculation control the flasks containing the stock cultures by means of an inverse microscope. Escherichia coli was used as a feeding material of the test organism Entosiphon sulcatum.

Prepare two parallel dilution series in 300 -ml Erlenmeyer flasks stoppered with metal caps. The dilutions will contain 1 part v/v each of pollutant solution in 20 to 214 parts v/v of mixture. Test vessel contain the known conc. of chemical and test organism. Leave the test culture at 25ᵒC for 72 hrs. Before measurement, control each flask by means of an inverse microscope. Add 10% of a 1.1% NaNO3 solution in double-distilled water filtered through a membrane filter (pore size 0.2/µm), and determine the number of protozoa by means of a cell counter. Pollutant concentrations at which the onset of inhibitory action was observed have been obtained by mathematical evaluation of counts. The term counts corresponds to impulses indicated by the coulter counter. Based on the onset of the inhibitory effect on population of the test organism Entosiphon Sulcatum, the 72 hr LOEC value was determined to be 970 mg/l, respectively.

 

Based on the overall reported results for target chemical p-tolyl acetate and for its read across substance, it can be concluded that the test substance p-tolyl acetate can be considered as non-toxic to aquatic algae and thus cannot be classified as hazardous as per the CLP classification criteria.