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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
Study period:
From FEB 2003 to MAR 2003
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
yes
Remarks:
For the preparation of the stock solution the test substance was not treated in an ultrasonic bath, because after short mixing in demiralized water a clear solution was obtained (minor deviation)
Qualifier:
according to guideline
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
yes
Remarks:
For the preparation of the stock solution the test substance was not treated in an ultrasonic bath, because after short mixing in demiralized water a clear solution was obtained (minor deviation)
GLP compliance:
yes
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: Schering AG, Bergkamen, Germany - Batch No. 61703003
- Purity test date: 99.5%

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Stability: Stable according to reanalysis no. 04205349

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing: The substance was dissolved in demineralized water
- Nominal concentration of the unfiltered solution: 125 mg/L

OTHER SPECIFICS:
Selected physio-chemical properties
Water solubility: S20-c > 546 g/L (according to Schering report A09525)
Vapor pressure: P25 < 10-3 Pa (according to Schering report A07301)
Hydrolytic stability: t½ > 1 year at 25°C (according to Schering report A0S 129
Analytical monitoring:
not specified
Vehicle:
yes
Remarks:
dernineralized water
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)

- Method: For the preparation of the test solutions 125 mg/L iotroxic acid, disodium salt, was dissolved in demineralized water. This solution was used for the preparation of the test solutions.

- Controls: A control solution was prepared with demineralized water without test material.

- Chemical name of vehicle (organic solvent, emulsifier or dispersant): Demineralized water

- Concentration of vehicle in test medium (stock solution and final test solution(s) or suspension(s) including control(s)): The highest concentration was a 1: 1.25 dilution obtained by adding nutrient solution and inoculum, the further concentrations were obtained by dilutions of 1 :2.5, 1 :5, 1: 10, 1 :20, and 1 :40 with demineralized water, nutrient solution and inoculum.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Source (laboratory, culture collection): Sammlung von Algenkulturen, Universitat Goettingen" (Collection of Algae Cultures, University Goettingen)
- Age of inoculum (at test initiation): The algae for the pre-culture were taken from a stock up to seven days old, approximately 72 hours before the start of the incubation in the test.

ACCLIMATION
- Acclimation period: The test vessels were incubated under intermittent stirring for approximately 72 hours in an incubating apparatus (Abimed AlgenTest XT) with continuous light (at approximately 6000-8000 lux) and controlled temperature (water bath).
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Post exposure observation period:
The algae were microscopically examined at the end of exposure. The algae of one test vessel of each test concentration group including the control were examined with regard to cell abnormalities
Test temperature:
The temperature was 23°C during the whole test period fulfilling the validity criterion.
pH:
The pH at the end of the test was between 10.1 and 10.3.
Nominal and measured concentrations:
Nominal concentration of iotroxic acid, disodium salt (mg/L): 0.0, 3.1, 6.3, 12.5, 25.0, 50.0, 100.0.
Reference substance (positive control):
no
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
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Details on results:
Fluorescence determination: As a parameter for the cell density, the chlorophyll fluorescence in the test and control solutions were determined at 0, 24, 48 and 72 hours of incubation. All measurements were made by means of a fluorescence photometer at a wavelength of 320 and 800 nm for agitation and measurement, respectively. Sampling volume and sampling time was electronically controlled. For statistical reasons, it is aimed that the coefficient of variation between replicates at 72 hours does not exceed 25%. The test is valid, when the fluorescence increase is at least 16-fold in the controls after 72 hours.

Calculation of results and statistical analysis: The values for the average area below the growth curves, specific growth rate, and the percentage inhibition were calculated by the computer program Abimed "AlgenTest XT 2.21 ". The program calculates the respective parameters according to the mathematical formulas given in the OECD guideline (1). The EbCso/72 hours (biomass) and the ErCso/72 hours (growth rate) as well as the 95% confidence limits are also calculated by the above referenced computer program on the basis of a probit analysis.

Inhibition of biomass and the growth rate(%) of Desmodesmus suhspicatus after 72 hours exposure to iotroxlc acid, disodium salt 

Nominal concentration
of iotroxic acid, disodium salt (mg/L) 
Inhibition in percent
Biomass (integral) Growth rate
0.0 (control)  0.0 0.0
3.1 -4.6 10.4
6.3 -11.0 6.3
12.5 -8.5 -9.4
25.0 -5.6 -10.7
50.0 -6.4 -1.1
100.0 -4.0 -7.2
Validity criteria fulfilled:
yes
Remarks:
The validity criteria recommended by the guideline (1 ), i.e. ≥ 16-fold increase of algae cells after 72 hours in the controls, were fulfilled.
Conclusions:
Iotroxic acid, disodium salt had no inhibitory effect on the growth of Desmodesmus subspicatus. The EbC50 (biomass) and the ErC50 (growth rate) was > 100 mg/L.
Executive summary:

In a 72 hour acute toxicity study, the freshwater aquatic vascular plants green algae Desmodesmus subspicatus were exposed to iotroxic acid, disodium salt at nominal concentrations of 0, 3.1, 6.3, 12.5, 25.0, 50.0, 100.0 mg a.i. /L under static or renewal conditions in accordance with the OECD 201 guideline. The 72 hour ErC50 and EbC50 values based on growth rate and biomass were > 100 and > 100 mg a.i./L, respectively.  The validity criteria recommended by the the OECD 201 guideline (i.e. > 16-fold increase of algae cells after 72 hour) in the controls, were fulfilled.

 

No changes in morphological structures or other abnormalities were observed except some oversized cells in the highest test concentration.

 

This toxicity study is classified as acceptable and satisfies the guideline requirement for OECD 201 Growth inhibition test of iotroxic acid, disodium salt on the green algae Desmodesmus subspicatus toxicity study.

 

Results Synopsis

 

Test Organism: Desmodesmus subspicatus

Test Type: Static

 

72 hour ErC50:  >100 mg a.i./L (growth rate)

72 hour EbC50:  >100 mg a.i./L (biomass)

Description of key information

Iotroxic acid, disodium salt had no inhibitory effect on the growth of Desmodesmus subspicatus. The EbC50 (biomass) and the ErC50 (growth rate) was > 100 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
100 mg/L

Additional information

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