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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
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
yes (incl. certificate)
Remarks:
The Department of Health of the Government of the United Kingdom
Analytical monitoring:
yes
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: A stock solution was prepared by adding 550 mg test substance to 11 L culture medium. The substance was dispersed by stirring (1500 rpm) for 24 hours. The mixture was then filtered (0.2 μm Gelman Acrocap filter). To 1 L of the stock solution (100% v/v saturated solution) 7.6 mL of algal suspension were added.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Strain: CCAP 278/4
- Source: Culture Collection of Algae and Protozoa (CCAP), SAMS Research Services Ltd, Scottish Marine Institute, Oban, Argyll, Scotland


ACCLIMATION
- Culturing media and conditions: same as in test
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Test temperature:
24 ± 1 ºC
pH:
7.9 - 8.1
Nominal and measured concentrations:
Nominal substance concentration: 100% v/v saturated solution
Details on test conditions:
TEST SYSTEM
- Test vessel: conical flasks
- Material, size, fill volume: glass, 250 mL nominal, 100 mL fill volume
- Initial cells density: 5000 cells/mL
- No. of vessels per concentration (replicates): 6
- No. of vessels per control (replicates): 6

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The culture medium was prepared using reverse osmosis purified deionized water* and the pH adjusted to 7.5 ± 0.1 with 0.1N NaOH or HCl.
- Intervals of water quality measurement: at test start and test termination

OTHER TEST CONDITIONS
- Photoperiod: continuous illumination
- Light intensity and quality: approx. 7000 lux, warm white lighting (380 – 730 nm)


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: cell density after 0, 25, 49 and 72 hours (Coulter® Multisizer Particle Counter)


TEST CONCENTRATIONS
- Range finding study
- Test concentrations: 1.0, 10 and 100% v/v
- Results used to determine the conditions for the definitive study: no effects observed at any of the tested concentrations
Reference substance (positive control):
yes
Remarks:
potassium dichromate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
100 other: % v/v saturated solution
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 other: % v/v saturated solution
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:
- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test): none
Results with reference substance (positive control):
ErC50 (72 h): 1.1 mg/L; NOEC (72 h): 0.50 mg/L
Reported statistics and error estimates:
Growth rate and yield data were analysed using a Student’s t-test incorporating Bartlett's test for homogeneity of variance (Sokal and Rohlf, 1981; SAS, 1999 - 2001).

The test substance concentration was analysed for verification of test concentrations at 0 and 72 hours by HPLC-MS-MS (Perkin Elmer, API 3000; triple stage quadrupole mass spectrometer). The test concentration at 0 hours was below the limit of quantitation (LOQ= 0.014 mg/L). At 72 hours a test concentration of 0.015 mg/L was measured.

Description of key information

No toxicity up to the limit of water solubility.

Key value for chemical safety assessment

Additional information

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 with the OECD Guidelines for Testing of Chemicals (2006) No 201, "Freshwater Alga and Cyanobacteria, Growth Inhibition Test" referenced as Method C.3 of Commission Regulation (EC) No 761/2009.

The test substance is highly insoluble in water and pre-study solubility work conducted indicated that it was not possible to obtain a testable solution of the test item using traditional methods of preparation e.g. ultrasonication and high-shear mixing. A pre-study media preparation trial indicated that the use of a saturated solution method of preparation was most appropriate for this test item.

Exposure of Pseudokirchneriella subcapitata to the test item gave EC50 values of greater than 100% v/v saturated solution. The No Observed Effect Concentration was 100% v/v saturated solution.

Analysis of the 100% v/v saturated solution test preparation at 0 hours showed a measured test concentration of less than the limit of quantitation (LOQ) of the analytical method employed, which was determined to be 0.014 mg/L was obtained. Analysis of the test preparation at 72 hours showed a measured test concentration of 0.015 mg/L was obtained. This study showed that there were no toxic effects at saturation.