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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:
10 July 2017 - ****
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
Following a preliminary range-finding test, Pseudokirchneriella subcapitata was exposed to Water Accommodated Fractions (WAFs) containing the test material over a range of nominal loading rates 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.
Samples of the algal populations were removed daily and cell concentrations determined for each control and treatment group, using a Coulter® Multisizer Particle Counter.
Vehicle:
no
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
Strain CCAP 278/4.
Liquid cultures of Pseudokirchneriella subcapitata were obtained from the Culture Collection of Algae and Protozoa (CCAP), SAMS Research Services Ltd, Scottish Marine Institute, Oban, Argyll, Scotland.

The master cultures were maintained in the laboratory under constant aeration and illumination at 21 ± 2°C.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
24 ± 1 ºC
pH:
The pH value of the control cultures was observed to increase from pH 7.4 at 0 hours to pH 8.5 at 72 hours.
Nominal and measured concentrations:
Nominal loading rates of 6.25, 12.5, 25, 50 and 100 mg/L
Analysis of the 100 mg/L loading rate WAF test preparations at 0 and 72 hours showed that measured concentrations of less than the Limit of Quantification (LOQ) of the analytical method, determined to be 0.012 mg/L.
Details on test conditions:
As in the range-finding tests, 250 mL glass conical flasks were used. Six flasks each containing 100 mL of test preparation were used for the control and three flasks each containing 100 mL were used for each treatment group.
Reference substance (positive control):
yes
Remarks:
potassium dichromate
Key result
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks:
yield and biomass
Key result
Duration:
72 h
Dose descriptor:
LOELR
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks:
yield and biomass
Details on results:
Chemical Analysis of Test Loading Rates
Chemical analysis of the test preparations at 0 and 72 hours (see Annex 5) showed measured test concentrations of less than the limit of quantification (LOQ) of the analytical method employed, which was determined to be 0.012 mg/L, were obtained. This does not indicate that no test item was in solution, just that any the measured dissolved test item was present at a concentration of less than the LOQ.
Any dissolved test item may have been comprised of one or several components of the test item. Given that toxicity cannot be attributed to a single component or mixture of components but to the test item as a whole, the results were based on nominal loading rates only.
Measured concentrations were observed in the range-finding test. Given that concentrations of less than the LOQ were observed in the definitive test and also in the Acute Toxicity to Daphnia Magna test performed on this test item (Envigo Study Number CH46FV), it was considered that the measured concentrations in the range finding test were due to undissolved particles of test item in the media. It was also considered that the presence of these undissolved particles contributed to the toxicity observed in the range-finding test. During the definitive test, microscopic observations did not show any undissolved particles of test item in the media.

Growth Data
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.

Inhibition of Growth Rates
ErL10 (0 - 72 h): >100 mg/L loading rate WAF
ErL20 (0 - 72 h): >100 mg/L loading rate WAF
ErL50 (0 - 72 h): >100 mg/L loading rate WAF
There were no statistically significant differences (P>=0.05), between the control and any of the loading rate WAF test groups and the "No Observed Effect Loading Rate" (NOEL) based on growth rate was therefore 100 mg/L loading rate WAF.

Inhibition of Yield
EyL10 (0 - 72 h): >100 mg/L loading rate WAF
EyL20 (0 - 72 h): >100 mg/L loading rate WAF
EyL50 (0 - 72 h): >100 mg/L loading rate WAF
There were no statistically significant differences (P>=0.05), between the control and any of the loading rate WAF test groups and the "No Observed Effect Loading Rate" (NOEL) based on yield was therefore 100 mg/L loading rate WAF.
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:
There were no statistically significant differences (P>=0.05), between the control and any of the loading rate WAF test groups and the "No Observed Effect Loading Rate" (NOEL) based on growth rate was therefore 100 mg/L loading rate WAF.
Validity criteria fulfilled:
yes
Conclusions:
The effect of the test material on the growth of Pseudokirchneriella subcapitata was investigated and the 72-hour EL50 values based on growth rate, yield and biomass were determined to be greater than 100 mg/L loading rate WAF. The No Observed Effect Loading Rate was 100 mg/L loading rate WAF.
Executive summary:

Analysis of the 100 mg/L loading rate WAF test preparations at 0 and 72 hours showed that measured concentrations of less than the Limit of Quantification (LOQ) of the analytical method, determined to be 0.012 mg/L, were obtained,. This does not indicate that no test item was in solution, just that the measured dissolved test item was present at a concentration of less than the LOQ.

Any dissolved test material may have been comprised of one or several components of the test item. Given that the toxicity cannot be attributed to a single component or a mixture of components but to the test item as a whole, the results were based on nominal loading rates only.

Exposure ofPseudokirchneriella subcapitatato the test material resulted in EL50values of greater than 100 mg/L loading rate WAF. The No Observed Effect Loading Rate was 100 mg/L loading rate WAF.

Description of key information

The effect of the test material on the growth of Pseudokirchneriella subcapitata was investigated and the 72-hour EL50 values based on growth rate, yield and biomass were determined to be greater than 100 mg/L loading rate WAF.  The No Observed Effect Loading Rate was 100 mg/L loading rate WAF.

Key value for chemical safety assessment

Additional information