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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:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
Experimental test result performed using standard test guideline
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Principles of method if other than guideline:
Objective of this study was to observe the action of test chemical when it exposed with the Desmodesmus subspicatus (previous name: Scenedesmus subspicatus) for 72 hrs. Test conducted in accordance with OECD Guideline 201 (Alga, Growth Inhibition Test).
GLP compliance:
no
Analytical monitoring:
no
Vehicle:
yes
Remarks:
Acetone
Details on test solutions:
The stock solution 100 mg/l was prepared by dissolving white 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.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Common name:
- 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
- Acclimation period:
- Culturing media and conditions (same as test or not):
- Any deformed or abnormal cells observed:
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
23±2°C
pH:
Test at highest concentration 100 mg/l: pH 7.9 changes to 7.4 during test
Control: 8.1 changes to 7.7
Control + acetone: pH 8 changes to 7.6 during test
Nominal and measured concentrations:
0, 0, 6, 12, 24, 50 and 100 mg/l nominal concentration were used in the study
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.:
17.5 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95 % CI was 14.2 mg/l to 21.6 mg/l.
Results with reference substance (positive control):
- Results with reference substance valid
- ErC50: 0.69 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 algae Desmodesmus subspicatus (previous name: Scenedesmus subspicatus) due to the exposure of chemical the ErC50 was determine to be 17.5 mg/l.
Executive summary:

Objective of this study was to observe the action of test chemical when it exposed with the Desmodesmus subspicatus (previous name: Scenedesmus subspicatus) for 72 hrs. Test conducted in accordance with OECD Guideline 201 (Alga, Growth Inhibition Test). The stock solution 100 mg/l was prepared by dissolving white 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. 0, 0, 6, 12, 24, 50 and 100 mg/l nominal concentration were used in the study.

With the test substance one positive control Potassium dichromate (K2Cr2O7) was also run simultaneously. After the exposure of chemical, effect concentration ErC50 was calculated using nonlinear regression by the software Prism 4.0. Effect on the growth of algae was determine after an exposure period of 72 hrs. Based on the growth rate inhibition of algae Desmodesmus subspicatus (previous name: Scenedesmus subspicatus) due to the exposure of chemical, the ErC50 was determine to be 17.5 mg/l. Based on the ErC50 value, it can be conclude that the substance is likely to be hazardous to aquatic algae and classified in aquatic chronic category 3 as per the CLP classification criteria.

Description of key information

Based on the growth rate inhibition of algae Desmodesmus subspicatus (previous name: Scenedesmus subspicatus) due to the exposure of chemical the ErC50 was determine to be 17.5 mg/l.

Key value for chemical safety assessment

EC50 for freshwater algae:
17.5 mg/L

Additional information

Various short term studies available for the test chemical and read-across chemical were reviewed to determine the toxic nature of test chemical on the growth of algae. The studies are as mentioned below

 

Objective of this experimental key study was to observe the action of test chemical when it exposed with the Desmodesmus subspicatus (previous name: Scenedesmus subspicatus) for 72 hrs. Test conducted in accordance with OECD Guideline 201 (Alga, Growth Inhibition Test). The stock solution 100 mg/l was prepared by dissolving white 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. 0, 0, 6, 12, 24, 50 and 100 mg/l nominal concentration were used in the study. With the test substance one positive control Potassium dichromate (K2Cr2O7) was also run simultaneously. After the exposure of chemical, effect concentration ErC50 was calculated using nonlinear regression by the software Prism 4.0. Effect on the growth of algae was determine after an exposure period of 72 hrs. Based on the growth rate inhibition of algae Desmodesmus subspicatus (previous name: Scenedesmus subspicatus) due to the exposure of chemical, the ErC50 was determine to be 17.5 mg/l. Based on the ErC50 value, it can be conclude that the substance is likely to be hazardous to aquatic algae and classified in aquatic chronic category 3 as per the CLP classification criteria.

 

Above study was supported by the second study from experimental report the effect of test chemical was studied on the growth of fresh water green alga Chlorella vulgaris. The study was conducted following OECD guideline 201- Alga, growth inhibition test. The test concentration chosen for the study were 2.63 mg/L,3.95 mg/L,5.92 mg/L,8.88 mg/L,13.33 mg/L,20 mg/L. The test concentrations were prepared using stock solution of the test item 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 item. EC50 calculated graphically through probit analysis was observed to be 10.560 mg/L. Thus based on this value, it can be concluded that the substance can be considered as toxic to aquatic organisms and thus can be classified in aquatic chronic category 3 as per the CLP classification criteria.

Above study supported by read-across chemical, toxicity to green algae study was carried out for assessing the effect of the test chemical at 22°C. The study was conducted for 48 hrs. For the test chemical, based on effect on growth rate of the test organism, the 48hr LOEC was determined to be  32mg/l.

 

Thus on the basis of both experimental study reports, it was concluded that the test chemical exhibit toxicity to aquatic algae and classified in aquatic chronic category 3 as per the CLP classification criteria.