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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:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
Experimental test result performed using standard test guideline
Qualifier:
according to guideline
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 10.0 g/l was prepared 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.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Common name: green 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:
no
Total exposure duration:
72 h
Test temperature:
23±2°C
pH:
the sample at concentration 10.0 mg.I'1: pH = 7.9 changed to pH = 7.8 during the test
control : pH = 8.1 changed to pH = 7.8 during the test
control + acetone: pH = 7.8 changed to pH = 7.6 during the test
Nominal and measured concentrations:
Npminal concentrations: 0, 0, 0.6 , 1.2 . 2.4 , 5.0 , 10.0 mg/l, respectively
Details on test conditions:
TEST SYSTEM
- Test vessel: 50 ml Glass vessel
- Type (delete if not applicable): closed (with air permeable stopper)
- Sample volume: 15 ml
- Initial cells density: 5x10(3) cells/ml
- No. of vessels per concentration (replicates): 3

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:
other: ErC50
Effect conc.:
9.8 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95 % CI 9.6 - 9.9 mg/l
Results with reference substance (positive control):
- Results with reference substance valid
- ErC50: 0.77 mg/L (24 hours)
Reported statistics and error estimates:
ErC50 was calculated using non linear regression by the software Prism 4.0
Validity criteria fulfilled:
yes
Conclusions:
Based on the growth rate inhibition of green algae Desmodesmus subspicatus (previous name: Scenedesmus subspicatus) due to the exposure of test chemical, the ErC50 value was determine to be 9.8 mg/l.
Executive summary:

Principle of this study was to evaluate the nature of test chemical when comes in contact with the test organism. Test was conducted according to the OECD guideline 201. Desmodesmus subspicatus (previous name: Scenedesmus subspicatus) was used as test organism. The stock solution 10.0 g/l was prepared 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. 0.6 , 1.2 . 2.4 , 5.0 , 10.0 mg/l, respectively concentrations were used. With the test substance one positive control Potassium dichromate (K2Cr2O7) was also run simultaneously. After the exposure of chemical, effect concentration EC50 was calculated using nonlinear regression by the software Prism 4.0. Effect on the growth of algae was determined after an exposure period of 72 hrs. The median effective concentration (EC50) of the test substance on algae was determined to be 9.8 mg/L with 95% CI of 9.6 mg/l to 9.9 mg/l on the basis of growth rate inhibition effects in a 72 hour study. Based on the ErC50 value, the substance chemical was consider likely to be hazardous to aquatic algae and can be consider to be classified in aquatic chronic 2 category as per the CLP classification criteria.

Description of key information

Principle of this study was to evaluate the nature of test chemical when comes in contact with the test organism. Test was conducted according to the OECD guideline 201. Desmodesmus subspicatus (previous name: Scenedesmus subspicatus) was used as test organism. The stock solution 10.0 g/l was prepared 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. 0.6 , 1.2 . 2.4 , 5.0 , 10.0 mg/l, respectively concentrations were used. With the test substance one positive control Potassium dichromate (K2Cr2O7) was also run simultaneously. After the exposure of chemical, effect concentration EC50 was calculated using nonlinear regression by the software Prism 4.0. Effect on the growth of algae was determined after an exposure period of 72 hrs. The median effective concentration (EC50) of the test substance on algae was determined to be 9.8 mg/L with 95% CI of 9.6 mg/l to 9.9 mg/l on the basis of growth rate inhibition effects in a 72 hour study. Based on the ErC50 value, the substance chemical was consider likely to be hazardous to aquatic algae and can be consider to be classified in aquatic chronic 2 category as per the CLP classification criteria.

Key value for chemical safety assessment

EC50 for freshwater algae:
9.8 mg/L

Additional information

Based on the various experimental studies from different sources including secondary databases, authoritative database and studies were reviewed for the evaluation of the effects of test chemical and structurally and functionally similar read across chemicals on the growth of algae. The studies are as mentioned below:

Principle of this study was to evaluate the nature of test chemical when comes in contact with the test organism. Test was conducted according to the OECD guideline 201. Desmodesmus subspicatus (previous name: Scenedesmus subspicatus) was used as test organism. The stock solution 10.0 g/l was prepared 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. 0.6 , 1.2 . 2.4 , 5.0 , 10.0 mg/l, respectively concentrations were used. With the test substance one positive control Potassium dichromate (K2Cr2O7) was also run simultaneously. After the exposure of chemical, effect concentration EC50 was calculated using nonlinear regression by the software Prism 4.0. Effect on the growth of algae was determined after an exposure period of 72 hrs. The median effective concentration (EC50) of the test substance on algae was determined to be 9.8 mg/L with 95% CI of 9.6 mg/l to 9.9 mg/l on the basis of growth rate inhibition effects in a 72 hour study. Based on the ErC50 value, the substance chemical was consider likely to be hazardous to aquatic algae and can be consider to be classified in aquatic chronic 2 category as per the CLP classification criteria.

Above study further supported by the seconfd study from authoritative database. Principle of this study was to determine the effect of test chemical on the growth of green algae. Chlorella vulgaris was used as a test organism. Test conducted under the static system for 96 hours. Effects were measured on the basis of growth rate inhibition of algae. Exponential growth phase algae were exposed with test chemical. Based on the growth rate inhibition of green algae Chlorella vulgaris, due to the test chemical exposure for 96 hours, the EC50 value was determined to be 9.7 mg/l.

Principle of this third study was to determine the effect of test chemical on the growth of aquatic algae. Anacystis aeruginosa (Blue green algae) was used as a test organism. Test conducted under the static system for 24 hours. After the exposure period of 24 hours, 0% survival of algae was observed. Based on the mortality rate of Blue green algae Anacystis aeruginosa, due to the test chemical exposure for 24 hours, the EC100 value was observed to be at 5 mg/l.

Thus based on the above all studies and effects observations, it was concluded that the test chemical was toxic and classified in aquatic chronic category 2 as per the CLP classification criteria.