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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:
other: Experimental test result performed using standard test guideline
Justification for type of information:
Data is from experimental report.
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
no
Analytical monitoring:
no
Vehicle:
yes
Remarks:
Acetone
Details on test solutions:
The stock solution (200 g/L) was prepared by dissolving colourless liquid in acetone. Test solutions 200 mg/l was prepared by dissolving stock solution in OECD growth medium and it was kept in ultrasonic bath for 20 min.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Common name: Freshwater algae
- Strain: 86.81 SAG
- Source (laboratory, culture collection): Institute of botany of the ASCR
- Initial biomass concentration: 5x10(3) cells /ml
- Method of cultivation: No data available

ACCLIMATION - No data available
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Test temperature:
23±2°C
pH:
Test at highest concentration: 7.9 (Change to 7.7 during tests)
Control: 8.0 (changed to 7.9 during test)
Nominal and measured concentrations:
200 mg/l nominal concentration
Details on test conditions:
TEST SYSTEM
- Test vessel: 50 ml Glass vessel
- Type: closed (with air permeable stopper)
- Sample volume: 15 ml
- Initial cells density: 5x10(3) cells/ml
- No. of vessels per concentration (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes

OTHER TEST CONDITIONS
- Adjustment of pH: No
- Photoperiod: Continuous
- Light intensity and quality: 6000-8000 lx

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: microscope with counting chamber Cyrus I or electronic particle counter.
- 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.:
> 200 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 1.5 % growth inhibited at 200 mg/l
Remarks:
Nontoxic
Results with reference substance (positive control):
Results with reference substance valid
- EC50: 0.69 mg/L
Reported statistics and error estimates:
The differences in means of control and sample were estimated by the t-test for independent groups at a 95 % confidence level, all individual replicates were used (STATISTICA CZ – data analysis software system, version 9.0, StatSoft, Inc.). Statistically significant differences are for p < 0.05.
Validity criteria fulfilled:
yes
Conclusions:
The EC50 value for the test substance, on Desmodesmus subspicatus was determined to be greater than 200 mg/L on the basis of effects on growth rate in a 72 hour study.
Executive summary:

The Study was conducted to determine the effect of test chemical on fresh water algae, D. subspicatus, (86.81 SAG). All the parameters were followed as mentioned in the OECD guidelines 201. Initial stock solution was prepared by dissolving 200g/L in acetone.Further test solution of 200 mg/L was prepared by dissolving stock solution in OECD medium, and kept it in ultrasonic bath for 20 min to obtain homogenous solution. Algae were exposed to 200 mg/L concentration for the period of 72 hours. Simultaneously, to increase reliability of experiment, another study was conducted on algae using K2Cr2O7 (reference compound) under same conditions.Algal growth rate was counted at every regular interval of 24 hours, till the end of exposure period. On the basis of growth rate, median effective concentration (EC50) of test chemical was >200 mg/L. By considering EC50 value it can be concluded that test chemical is non toxic to aquatic algae, and cannot be classified as per CLP regulation.

Description of key information

The EC50 value for the test substance, on Desmodesmus subspicatus was determined to be >200 mg/L on the basis of effects on growth rate in a 72 hour study. Based on the EC50 it can be concluded that the chemical was nontoxic and can be consider to be not classified as per the CLP classification criteria.

Key value for chemical safety assessment

EC50 for freshwater algae:
200 mg/L

Additional information

Based on the experimental data for the target as well as read-across analogues which are extracted by using mechanistic approach and functionally and structurally similar to the target chemical, toxicity of test chemical were determined on the basis of growth inhibition of freshwater algae. The studies are summarized as below:

 

The Study was conducted to determine the effect of test chemical on fresh water algae, D. subspicatus, (86.81 SAG). All the parameters were followed as mentioned in the OECD guidelines 201. Initial stock solution was prepared by dissolving 200g/L in acetone.Further test solution of 200 mg/L was prepared by dissolving stock solution in OECD medium, and kept it in ultrasonic bath for 20 min to obtain homogenous solution. Algae were exposed to 200 mg/L concentration for the period of 72 hours. Simultaneously, to increase reliability of experiment, another study was conducted on algae using K2Cr2O7 (reference compound) under same conditions.Algal growth rate was counted at every regular interval of 24 hours, till the end of exposure period. On the basis of growth rate, median effective concentration (EC50) of test chemical was >200 mg/L. By considering EC50 value it can be concluded that test chemical is non toxic to aquatic algae, and cannot be classified as per CLP regulation.

 

Again, the study was conducted following OECD guideline 201- (Alga, growth inhibition test), for determininig the toxicty of test chemical on green algae. The test chemical was prepared by adding 50 mg of test chemical in 250 ml of BBM to get the final concentration of 200 mg/L. This stock solution was kept for stirring for 2 hours to obtain a homogenous solution for the experiment. The test concentration chosen for the study were 6.25 mg/L, 12.5 mg/L, 25 mg/L,50 mg/L,100 mg/L, 200 mg/L. The test chemical concentrations were prepared using stock solution of the test chemical using mineral media. The green alga was exposed to the test concentration for a period of 72 hours to observe average specific growth rate and % growth inhibition under the effect of the test chemical. The median effective concentration (EC50) of test chemical was 129.652 mg/L. Thus based on this value, it can be concluded that the substance can be considered as non-toxic to aquatic organisms and thus cannot be classified as hazardous as per the CLP classification criteria.

Further, the third study was conducted to assess the toxic effects of the test compound on the green alga Chlorella vulgaris, in compliance with the OECD guideline 201 (Alga, Growth Inhibition Test). The test substance was prepared by adding 50 mg of test substance in 100 ml of BBM to get the final concentration of 500 mg/L. The test concentration chosen for the study were 3.125 mg/l, 6.25 mg/l, 12.5 mg/l, 25 mg/l, 50 mg/l and 100 mg/l, which were prepared using stock solution of the test substance using de-ionized water. The test was conducted in replicates. Algal growth was calculated daily by counting the cells microscopically with the help of haemocytometer. After 72 hours of exposure to test chemical to various nominal test concentrations, EC50 was determine to be 204.70 mg/l. Based on the EC50, it can be concluded that the chemical was nontoxic and can be consider to be not classified as per the CLP classification criteria.

Thus, based on the above EC50 values, it can be concluded that the chemical was nontoxic and can be consider to be not classified as per the CLP classification criteria.