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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2 - 11 October 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2017
Report Date:
2017

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)
Version / remarks:
23 March 2006, Annex 5 corrected 28 July 2011
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Version / remarks:
20 May 2008, amended 7 December 2015, for the purpose of its adaptation to technical progress, by Commission Regulation (EU) 2016/266
Deviations:
no
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
impurity
Test material form:
solid: particulate/powder
Details on test material:
Batch No.: 10004539
Storage at room temperature approx. 20°C

Sampling and analysis

Analytical monitoring:
yes

Test solutions

Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
The following test flasks were set up:
- Test solution (Tn); containing test medium, test item and algae (six replicates)
- Blank control (Bn); containing test medium and algae (six replicates)
- Since the test item is soluble, the test solution was prepared by directly dissolving the test item in sterile-filtered Algal medium (pH adjusted at 8.0 ± 0.2). 100 ml of this test solution was added to the sterile test flasks and inoculated with an exponentially growing preculture of algae.
Pure Algal medium, handled as the test item solutions inoculated with the exponentially growing preculture of algae mentioned above, served as blank controls. For the incubation, the test flasks were then placed on an orbital shaker at a nominal shaking speed of about 130 revolutions per min.
- Evidence of undissolved material: Not relevant. Since the test item is soluble, the test solution was prepared by directly dissolving the test item in sterile-filtered Algal medium (pH adjusted at 8.0 ± 0.2)

Test organisms

Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Test organism: Axenic slope culture of Desmodesmus subspicatus 86.81SAG (Collection of Algal Cultures, Institute of Freshwater Ecology, University of Göttingen, D-37073 Göttingen, Germany
- Culture: 250 ml flask containing 100 ml of sterile OECD medium inoculated with cell material from an axenic slope culture
- Illumination: Continuous (2000–3000 lux) from Osram Fluora L18W77 and Osram Daywhite L18W840 (Osram AG, Winterthur, Switzerland)
- Temperature: 21 to 24°C, maintained at ± 2°C in a thermo-controlled room
- Control of sensitivity: twice per year, with potassium dichromate

Study design

Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h

Test conditions

Hardness:
not reported
Test temperature:
Min: 22.7; Max: 23.9; Mean: 23.4
pH:
7.8 - 8.2
Dissolved oxygen:
not reported
Salinity:
not reported
Conductivity:
not reported
Nominal and measured concentrations:
The concentrations of Adenosine in the test media were measured by HPLC analysis at the beginning and after 24, 48 h and 72 h of exposure. These analyses revealed that the concentrations were stable over the 72 h test period (95% of the initially measured concentration) and were within 80-120% of the nominal concentration. The initially measured concentration was 99.3 mg/l and the measured concentration after 72 h of exposure was 94.8 mg/l.
Therefore, the effective concentrations ErCx/EyCx were assessed based on nominal concentration of the test item.
Details on test conditions:
TEST SYSTEM
- Test vessel: 250 ml flasks, all-glass, with 100 ml of test medium, shaken (130 rpm)
- Test medium: Recommended OECD medium
- Preculture: Exponentially growing culture of Desmodesmus subspicatus
- Illumination: Source: continuous from Osram Fluora L 18W77 and Osram Daywhite L 18W840 (Osram AG, Winterthur, Switzerland)
- Light intensity: the light intensity amounts to about 3000 lux which corresponds to about 40 µE•m-2•s-2
- Homogeneity: the light intensity is maintained within ±15% from the average light intensity over the incubation area. The test vessels are repositioned every day within the incubation area to minimize variation.
- Temperature: 21 to 24°C, maintained at ± 2°C in a thermo-controlled room
- pH: Initially adjusted to 8 ± 0.2; the pH of the control medium should not increase by more than 1.5 units during the test
- Test type: Static exposure conditions over a period of 72 h
- Starting cell density: 0.5–0.85 µg/ml with respect to dry weight corresponding to about 2–5•103 cells/ml (i.e. OD680 of about 0.005 units)

RANGE FINDING STUDY
Prior to the definitive test a non-GLP range finding test with nominal concentrations of 1, 10 and 100 mg/l of Adenosine was performed. The results indicated that the test item is well soluble and that the test solutions can be prepared by respective dilutions of a stock solution. It also showed, that at a concentration of 100 mg/l the test item is rather stable in algal medium over 72 h. Based on the results of this non-GLP range finding test, the definitive test was performed as a limit test at the nominal concentration of 100 mg/l.

EFFECT PARAMETERS MEASURED
- Cell density: Cell concentrations were determined every 24 h using a spectrophotometer at 680nm wavelength (Shimadzu UV 1800, Shimadzu Schweiz GmbH, Römerstr. 3, CH-4153 Reinach). Aliquots of 5 ml were removed from each test flask under sterile conditions. Cell concentrations at time 0 h were only determined in the blank controls.
Reference substance (positive control):
not required
Remarks:
Control of sensitivity: None – the culture is re-purchased annually

Results and discussion

Effect concentrationsopen allclose all
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:
NOEC
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Details on results:
- Exponential growth in the control (for algal test): yes
- Any stimulation of growth found in any treatment: yes (growth rate and yield)
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: no

With respect to the endpoint growth rate, no significant effects were observed as compared to the blank controls.
Based on these effects and the nominal concentrations of the test item, the median effect concentration with respect to growth rate (ErC50/0–3 days) of Adenosine to Desmodesmus subspicatus was estimated to be >100 mg/l.
The no observed effect concentration (NOErC) with respect to growth rate was determined to be 100 mg/l.

With respect to the endpoint yield (biomass production), no significant effects were observed as compared to the blank controls.
Based on these effects and the nominal concentrations of the test item, the median effect concentration with respect to yield (EyC50/0–3 days) of Adenosine to Desmodesmus subspicatus was estimated to be >100 mg/l.
The no observed effect concentration (NOEyC) with respect to yield was determined to be 100 mg/l.
Reported statistics and error estimates:
Statistical analysis was performed with respect to the no observed effect concentrations. The statistical analysis was conducted with the software ToxRat® Standard Version 3.2.1.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Remarks:
In the control cultures: average specific growth rate of 1.56 (>0.92)/coefficient of variation of average specific growth rates: 7% (<=7%)/ mean coefficient of variation for section-by-section specific growth rates 16.3% (<=35%).
Conclusions:
The acute toxicity of Adenosine (CAS no. 58-61-7) to Desmodesmus subspicatus was determined in a 72 hour static test according to OECD guideline 201. The median effect concentration with respect to growth rate (ErC50/0–3 days) of Adenosine to Desmodesmus subspicatus was estimated to be >100 mg/l nominal concentration. The no observed effect concentration (NOErC) with respect to growth rate was determined to be 100 mg/l nominal concentration. The results of the test can be considered reliable without restriction.
Executive summary:

The growth inhibitory effects of Adenosine (CAS no.58-61-7) to the green alga Desmodesmus subspicatus were investigated according to test guideline OECD 201, over a period of 72 h.

The test item Adenosine is solid, 100% pure and has a high solubility (4.13 g/l at a pH of 7.0 to 7.6 and ca. 20°C). Consequently,the test solution was prepared by directly dissolving the test item in sterile-filtered Algal medium. 

The only nominal concentration was 100 mg/l. Six parallel test vessels were used for the test item and six for the blank controls.

The concentration of Adenosine in the test medium was measured by HPLC analysis at the beginning and after 24, 48 h and 72 h of exposure. These analyses revealed that the concentration was stable over the 72-h test period (95% of the initially measured concentration) and was within 80-120% of the nominal concentration. Therefore, the effective concentrations ErCx/EyCx were assessed based on the nominal concentration.

With respect to the endpoint growth rate, no significant effects were observed at 100 mg/l nominal concentration, as compared to the blank controls.

With respect to the endpoint yield (algal biomass), no significant effects were observed at 100 mg/l nominal concentration, as compared to the blank controls.

Therefore, the 72h ErC50 and EyC50 values of Adenosine (CAS no. 58-61-7) on the green alga Desmodesmus subspicatus were estimated to be >100 mg/l nominal concentration.

The NOErC and NOEyC values were both 100 mg/l nominal concentration.

All validity criteria were fulfilled.