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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:
23. - 30. June 2014
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: According to OECD guideline under GLP
Cross-referenceopen allclose all
Reason / purpose:
reference to same study
Reason / purpose:
reference to other study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2014

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
Principles of method if other than guideline:
Not relevant
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: particulate/powder
Remarks:
migrated information: powder
Details on test material:
- Name of test material (as cited in study report): Imidazotriazinon
- Analytical purity: 99%
- Lot/batch No.: BXR6KDD
- Expiration date of the lot/batch: 05-Jul-2016
- Stability under test conditions: At least 3 days
- Storage condition of test material: Room temperature

Sampling and analysis

Analytical monitoring:
yes

Test solutions

Vehicle:
no

Test organisms

Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Study design

Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h

Results and discussion

Effect concentrations
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
11.35 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 8.8 - 16.2 mg/L

Any other information on results incl. tables

Table¿1¿1: Inhibition of the growth rate [%] of Desmodesmus subspicatus after 72  hours exposure to Imidazotriazinon

Dilution

Concentration

Inhibition [%]

of Imidazotriazinon

of Imidazotriazinon (mg/L) *

of

in the test vessels

in the test vessels

Growth rate

0

0.0 (control)

0.0

1:100

0.093

-1.0

1:50

0.186

0.5

1:25

0.372

0.1

1:10

0.93

2.1

1:5

1.86

21.4

1:1.25

7.44

39.2

* Calculated from TOC values

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
Imidazotriazinon had a concentration-depended inhibitory effect on the growth of Desmodesmus subspicatus. The ErC50 (growth rate) was 11.354 mg/L [95 % confidence limits: 8.838-16.176] on the basis of measured concentrations. The NOEC was 0.93 mg/L, the LOEC was 1.86 mg/L.
Executive summary:

The purpose of this study was to determine the effects of the test compound Imidazotriazinon on the growth of the green algae Desmodesmus subspicatus. The study was conducted in agreement with the test guideline OECD no. 201.

The test substance Imidazotriazinon was incubated in an aqueous solution including nutrients with an algae population of Desmodesmus subspicatus for a test duration of approximately 72  hours in an incubator shaker apparatus.

The nutrient solution was made up of mainly ammonium, phosphates and some trace elements.

For the preparation of the test solutions a suspension with a nominal loading of 100 mg/L Imidazotriazinon was suspended in demineralized water, sonicated for approximately 30 min and constantly stirred for approximately 24 hours. This suspension was filtered through a glass-fiber filter. The filtered solution was used for the preparation of the test solutions. The highest concentration was a 1:1.25 dilution obtained by adding nutrient solution and inoculum, the further concentrations were obtained by dilutions of 1:5, 1:10, 1:25, 1:50 and 1:100 with demineralized water, nutrient solution and inoculum. Additionally, a control solution was prepared with demineralized water without test material.

The organic carbon concentration of the ultrasonified and filtered stock solution was analyzed with a TOC analyzer. The final concentrations in the test vessels were calculated based on the dilution factor. The algae were exposed to each concentration in triplicate. Six vessels were prepared for the control. The algae were incubated under standardized conditions (continuous light, controlled temperature) in an incubator shaker apparatus. As a parameter for the growth of the algae population, the algae cells were measured with a coulter counter. The growth rate was calculated on the basis of the cell counts.

The calculated growth rate of each concentration was compared to those of the controls, and the inhibition was calculated.

Imidazotriazinon had a concentration-depended inhibitory effect on the growth of Desmodesmus subspicatus. The ErC50(growth rate) was 11.354 mg/L [95 % confidence limits: 8.838-16.176] on the basis of measured concentrations. The NOEC was 0.93 mg/L, the LOEC was 1.86 mg/L.