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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:
key study
Study period:
12.12.2016 – 15.12.2016
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:
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 according to OECD Guideline 201.
GLP compliance:
no
Analytical monitoring:
no
Details on sampling:
No data
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
The solution 100 mg/L was prepared by dissolving white powder in OECD growth medium.

- 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): 5x1000 cells/ml

Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Remarks on exposure duration:
±1 hour
Test temperature:
23°C ± 2°C
pH:
The sample at concentration 100 mg/L : pH = 7.9 changed to pH = 7.5 during the test,
Control : pH = 8.1 changed to pH = 7.7 during the test
Dissolved oxygen:
No data
Salinity:
No data
Conductivity:
No data
Nominal and measured concentrations:
No data
Details on test conditions:
TEST SYSTEM
- Test vessel: 50ml glass vessel
- Type: Closed (with air-permeable stopper)
- Material, size, headspace, fill volume: 15 ml
- No. of vessels per concentration (replicates): 6

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): Growth rate inhibition
- Determination of cell counting: Electronic particle counter.
- Chlorophyll measurement: No
- Other: EC50 was calculated
Reference substance (positive control):
yes
Remarks:
Potassium dichromate (K2Cr2O7)
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: No significant difference p = 0.395
Details on results:
After the exposur period of 72 hrs, only 0.5 % inhibition were observed on algae
Results with reference substance (positive control):
- Results with reference substance valid
- ErC50: 0.69 mg/L K2Cr2O7
Reported statistics and error estimates:
The differences in means of control and sample were estimated by the test t-test for independent groups at a 95% confidence level, all individual replicates were used. Statistically significant differences are for p < 0.05.
Validity criteria fulfilled:
yes
Conclusions:
The median effective concentration (EC50) for the test substance in a freshwater algae Desmodesmus subspicatus was determined to be >100 mg/L on the basis of effects on growth rate in a 72 hour study. After the exposur period of 72 hrs, only 0.5 % inhibition were observed on algae.
Executive summary:

The freshwater algal growth inhibition test was carried out on Desmodesmus subspicatus with the substance. Test conducted in accordance to OECD Guideline 201. The solution 100 mg/L was prepared by dissolving white powder in OECD growth medium. A limit test at sample concentration of 100 mg/L was performed. 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 5x1000 cells/ml. Determination of cell counting involve the use of electronic particle counter. The median effective concentration (EC50) for the test substance in a freshwater algae Desmodesmus subspicatus was determined to be >100 mg/L on the basis of effects on growth rate in a 72 hour study. After the exposure period of 72 hrs, only 0.5 % inhibition were observed on algae. Thus on the basis of this EC50 value and according to the CLP Criteria for aquatic classification of the substance, it is concluded that test chemical does not exhibit toxicity to aquatic algae.

Description of key information

The freshwater algal growth inhibition test was carried out on Desmodesmus subspicatus with the substance. Test conducted in accordance to OECD Guideline 201. The solution 100 mg/L was prepared by dissolving white powder in OECD growth medium. A limit test at sample concentration of 100 mg/L was performed. 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 5x1000 cells/ml. Determination of cell counting involve the use of electronic particle counter. The median effective concentration (EC50) for the test substance in a freshwater algae Desmodesmus subspicatus was determined to be >100 mg/L on the basis of effects on growth rate in a 72 hour study. After the exposure period of 72 hrs, only 0.5 % inhibition were observed on algae. Thus on the basis of this EC50 value and according to the CLP Criteria for aquatic classification of the substance, it is concluded that test chemical does not exhibit toxicity to aquatic algae.

Key value for chemical safety assessment

EC50 for freshwater algae:
100 mg/L

Additional information

Based on the effects observation on growth rate inhibition of algae by the chemical exposure, studies were reviewed from various experimental sources for test chemical were studied and mention as below:

In the first experimental report toxicity were studied. The freshwater algal growth inhibition test was carried out on Desmodesmus subspicatus with the substance. Test conducted in accordance to OECD Guideline 201. The solution 100 mg/L was prepared by dissolving white powder in OECD growth medium. A limit test at sample concentration of 100 mg/L was performed. 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 5x1000 cells/ml. Determination of cell counting involve the use of electronic particle counter. The median effective concentration (EC50) for the test substance in a freshwater algae Desmodesmus subspicatus was determined to be >100 mg/L on the basis of effects on growth rate in a 72 hour study. After the exposure period of 72 hrs, only 0.5 % inhibition were observed on algae. Thus on the basis of this EC50 value and according to the CLP Criteria for aquatic classification of the substance, it is concluded that test chemical does not exhibit toxicity to aquatic algae.

 

Similarly in the second study from secondary sources (1991) a phytotoxicity test was performed to determine the effect of test chemical on the marine alga Skeletonema costatum. Cultures were incubated at 20 degrees Celsius (°C) under approximately 2,000 lux illumination. Culture were exposed to 500 & 1000 mg/l (ppm) concentration of test chemical. Concentrations for the definitive test were based on the results of a 96-hour range-finding test. Concentrations of test chemical ≤ 1000 mg/L did not appear to adversely affect the growth of Skeletonema costatum. After 96 h of exposure, increase of in vivo chlorophyll a was 8% in cultures exposed to 500ppm and 14% in those exposed to 1000 mg/l. Cell numbers in cultures exposed to 500 mg/l increased 4% while cultures exposed 1000 mg/l were similar to the control. Thus, the no observed effect concentration (NOEC) of test chemical on the marine alga Skeletonema costatum on a growth rate effect was considered to be ≤ 1000 mg/L in a 96 hour study.

 

Thus based on the both studies experimental data from report and secondary source, it was concluded that the chemical was nontoxic and not classified as per the CLP classification criteria.