Disodium 2-(2,4,5,7-tetraiodo-6-oxido-3-oxoxanthen-9-yl)benzoate

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

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:

no

Details on test solutions:

The stock solution 100 mg/L was prepared 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.

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
- Age of inoculum (at test initiation): 5x10e3 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:

72 h ±1 hour

Test temperature:

23°C ± 2°C

pH:

The sample at concentration 100 mg/L : pH = 8.0 changed to pH = 7.1 during the test,
control : pH = 8.2 changed to pH = 7.6 during the test

Nominal and measured concentrations:

Nominal concentrations: 0, 8, 15, 29, 55 and 100 mg/L, respectively

Details on test conditions:

TEST SYSTEM
- Test vessel: 50ml glass vessel
- Type : Closed (with air permeable stopper)
- Material, size, headspace, fill volume: 7.5 ml per replicate in 50 ml glass vessel
- 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
- No. of vessels per concentration (replicates): 3

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 concentrations 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:

other: ErC50

Effect conc.:

34.1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95% CI is 21.4-54.2 mg/l

Results with reference substance (positive control):

- Results with reference substance valid
- ErC50: 0.69 mg/L K2Cr2O7

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 due to the exposure of test chemical, the EC50 value was determine to be 34.1 mg/L.

Executive summary:

An acute study was conducted to determine the effect of test chemical on the growth of green algae when exposed for 72 hours. Test conducted according to the OECD Guideline 201 (Alga, Growth Inhibition Test). Desmodesmus subspicatus (previous name: Scenedesmus subspicatus) was used as a test organism. The stock solution 100 mg/L was prepared 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. Various nominal concentrations 0, 8, 15, 29, 55 and 100 mg/L, respectively were used in the study. Test conducted under the static system. 50 ml Glass vessel filled with 15 ml of test solution were used in the study, in which 5x10e3 cells/ml were added. Test performed using 3 replicates. Temperature maintained at 23±2°C and pH value 8 changed to 7.1 in sample, whereas for control 8.2 changes to 7.6 during test. 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 green algae Desmodesmus subspicatus (previous name: Scenedesmus subspicatus) due to the exposure of test chemical for 72 hours, the ErC50 value was determined to be 34.1 mg/l with 95 % CI of 21.4 to 54.2 mg/l. Thus, based on the ErC50 value, test chemical considered to be toxic 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 and Chlorella vulgaris, due to the test chemical exposure for 72 hours, the EC50 value was determine to be 34.1 mg/L and > 200 mg/l. As the toxicity were observed on the growth of algae Desmodesmus subspicatus after exposure period of test chemical for 72 hours, chemical consider to be toxic and can be consider to be classified in aquatic chronic category 3 as per the CLP classification criteria.

Key value for chemical safety assessment

EC50 for freshwater algae:

34.1 mg/L

Additional information

Summarized result from the various experimental sources for the determination of effect of test chemical on the growth of algae are as mentioned below:

 

An acute study was conducted to determine the effect of test chemical on the growth of green algae when exposed for 72 hours. Test conducted according to the OECD Guideline 201 (Alga, Growth Inhibition Test). Desmodesmus subspicatus (previous name: Scenedesmus subspicatus) was used as a test organism. The stock solution 100 mg/L was prepared 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. Various nominal concentrations 0, 8, 15, 29, 55 and 100 mg/L, respectively were used in the study. Test conducted under the static system. 50 ml Glass vessel filled with 15 ml of test solution were used in the study, in which 5x10e3 cells/ml were added. Test performed using 3 replicates. Temperature maintained at 23±2°C and pH value 8 changed to 7.1 in sample, whereas for control 8.2 changes to 7.6 during test. 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 green algae Desmodesmus subspicatus (previous name: Scenedesmus subspicatus) due to the exposure of test chemical for 72 hours, the ErC50 value was determined to be 34.1 mg/l with 95 % CI of 21.4 to 54.2 mg/l. Thus, based on the ErC50 value, test chemical considered to be toxic and classified in aquatic chronic category 3 as per the CLP classification criteria.

 

Above study further supported by the second study from experimental source. The principle of this study was to determine the effect of test substance on the growth of fresh water green algae. The study was conducted following OECD guideline 201- Alga growth inhibition test. Chlorella vulgaris was used as test organism.The test solution was prepared by adding 70mg of test chemical in 350 ml of BBM to get the final concentration of 200 mg/L. The remaining test solutions were prepared by dilution from the above stock solution. To have a better growth and visibility of cells, the initial cell density of the culture was kept 1 X 10e4cells/ml.The test concentrations chosen for the study 6.25mg/l, 12.5mg/l, 25mg/l, 50 mg/l, 100mg/l and 200 mg/l were prepared using stock solution of the test substance using de-ionized water and the study conducted under the static system. For the assessment of algal growth, the test was conducted in replicates. The control flask was maintained in triplicates as recommended in the OECD guideline and the test concentration were selected in geometric series which were maintained in duplicates. To obtain a quantitative concentration-response relationship by regression analysis, a linearizing transformation of the response data into probit was performed. Using the same, effective concentration (EC) were determined. Algal growth was calculated daily by counting the cells microscopically with the help of haemocytometer. For microscopic observations the cultures were observed daily with the help of a microscope to verify a normal and healthy appearance of the algal culture and also to observe any abnormal appearance of the algae (as may be caused by the exposure of the test item). Apart from this, the cell count of each test vessel was also noted with the help of a microscope and haemocytometer. The test is considered to be valid as met all the standard parameters. The green algae 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 test substance. EC50 calculated through probit analysis was observed to be > 200 mg/L. Thus based on the effects observed on the growth rate of algae, chemical consider to be nontoxic and not classified as per the CLP classification criteria. 

 

As the toxicity were observed on the growth of algae Desmodesmus subspicatus after exposure period of test chemical for 72 hours, chemical consider to be toxic and can be consider to be classified in aquatic chronic category 3 as per the CLP classification criteria.