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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:
2017-2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
yes
Remarks:
For details see 'principles of method if other than guideline'
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
yes
Remarks:
For details see 'principles of method if other than guideline'
Principles of method if other than guideline:
Devaitions: At the time of signing the study plan, the only available test item information was the identification Dabco NE1080. Additional test item information was subsequently provided, however, a study plan amendment incorporating this information to the study plan was not issued. The test item information has been included in the report and the omission of this information from the study plan was considered to have no impact on the outcome or integrity of the study
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
Identification: Dabco NE1080
Physical state/Appearance: Clear colorless slightly viscous liquid
Batch: 2153125
Purity: Not provided
Expiry Date: 16 April 2018
Storage Conditions: Room temperature in the dark
Analytical monitoring:
yes
Vehicle:
not specified
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Test temperature:
24 ± 1 °C
pH:
A nominal amount of test item (100 mg) was dissolved in culture medium and the volume adjusted to 1 liter to give a 100 mg/L stock solution. The pH of this stock solution was measured and adjusted to pH 7.5 prior to preparing a series of dilutions to give further stock solutions of 50, 25, 12.5 and 6.25 mg/L.
Nominal and measured concentrations:
Following preliminary range-finding tests and an initial experiment, Pseudokirchneriella subcapitata was exposed to an aqueous solution of the test item at concentrations of 6.25, 12.5, 25, 50 and 100 mg/L (three replicate flasks per concentration) for 72 hours, under constant illumination and shaking at a temperature of 24 ± 1 °C.
Reference substance (positive control):
yes
Remarks:
potassium dichromate
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC20
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:
growth rate
Details on results:
Cell density values were determined at each sampling time and pH values at 0 and 72 hours. Daily specific growth rates for the control cultures and growth rate and yield values for the control and test cultures after 72 hours and percentage inhibition values were measured.

The mean cell densities versus time for the definitive test are also presented.
From the data it is clear that the growth rate (r) and yield (y) of Pseudokirchneriella subcapitata (CCAP 278/4) were not affected by the presence of the test item over the 72-Hour exposure period.


The following results were determined from the data:
6.2.3 Inhibition of growth rate
ErC10 (0 - 72 h) : >100 mg/L
ErC20 (0 - 72 h) : >100 mg/L
ErC50 (0 - 72 h) : >100 mg/L

where ErCx is the test concentration that reduced growth rate by x%
Results with reference substance (positive control):
Exposure of Pseudokirchneriella subcapitata (CCAP 278/4) to the reference item gave the following results:
ErC50 (0 – 72 h) : 1.4 mg/L; 95% confidence limits 1.2 – 1.5 mg/L
EyC50 (0 – 72 h) : 0.60 mg/L; 95% confidence limits 0.52 – 0.69 mg/L
No Observed Effect Concentration (NOEC) based on growth rate: 0.25 mg/L
No Observed Effect Concentration (NOEC) based on yield: 0.25 mg/L
Lowest Observed Effect Concentration (LOEC) based on growth rate: 0.50 mg/L
Lowest Observed Effect Concentration (LOEC) based on yield: 0.50 mg/L

The results from the positive control with potassium dichromate were within the normal ranges for this reference item.
Reported statistics and error estimates:
Statistical analysis of the growth rate data was carried out for the control and all test concentrations using one way analysis of variance incorporating Bartlett's test for homogeneity of variance (Sokal and Rohlf, 1981) and Dunnett's multiple comparison
procedure for comparing several treatments with a control (Dunnett, 1955). There were no statistically significant differences (P≥0.05), between the control, 6.25, 12.5, 25, 50 and 100 mg/L test groups and therefore the "No Observed Effect Concentration" (NOEC) based on growth rate was 100 mg/L.
Validity criteria fulfilled:
yes
Conclusions:
Exposure of Pseudokirchneriella subcapitata to the test item gave EC50 values of greater than 100 mg/L. The No Observed Effect Concentration was 100 mg/L.
Executive summary:

A study was performed to assess the effect of the test item on the growth of the green alga Pseudokirchneriella subcapitata. The method followed was designed to be compatible withthe OECD Guidelines for Testing of Chemicals (2006) No 201, "Freshwater Alga andCyanobacteria, Growth Inhibition Test" referenced as Method C.3 of Commission Regulation(EC) No 761/2009.

Following preliminary range-finding tests and an initial experiment,Pseudokirchneriella subcapitatawas exposed to an aqueous solution of the test item at concentrations of 6.25,12.5, 25, 50 and 100 mg/L (three replicate flasks per concentration) for 72 hours, underconstant illumination and shaking at a temperature of 24 ± 1 °C.Samples of the algal populations were removed daily and cell concentrations determined foreach control and treatment group, using a Coulter®Multisizer Particle Counter.

Analysis of the 100 mg/L test preparations at 0 and 72 hours showed measured testconcentrations to range from 118% to 125% of nominal and so the results are based onnominal test concentrations only.Exposure ofPseudokirchneriella subcapitatato the test item gave EC50values of greater than100 mg/L. The No Observed Effect Concentration was 100 mg/L.



Description of key information

Exposure of Pseudokirchneriella subcapitata to the test item gave EC50 values of greater than 100 mg/L. The No Observed Effect Concentration was 100 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
100 mg/L
EC10 or NOEC for freshwater algae:
100 mg/L

Additional information