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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:
Feb 25 - Feb 28, 2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP guideline study with analytical monitoring
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Version / remarks:
2011
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
Ministerium für Arbeit, Integration und Soziales des Landes Nordrhein-Westfalen, Düsseldorf, 07 Feb 2011
Analytical monitoring:
yes
Details on sampling:
The concentration of the test item was analysed in all test solutions sampled at the beginning of the exposure period prior to the addition of the algae and in samples of the algae cultures taken from replicates pooled per test concentration at the end of the exposure period.
Duplicate samples of 750 µL were taken from the pooled replicates, given in 2 mL glas vials and analysed immediately. The retain samples has been stored at -20 °C.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: The highest test concentration (100 mg pure substance/L) was prepared by solving 136.43 mg of the test item (purity 73.3 %) in 1000 mL growth medium and stirring for 2 hours at room temperature. To obtain the other required test concentrations the highest test concentration was serially diluted with growth medium.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Common name: green algae
- Source (laboratory, culture collection): SAG, Culture Collection of Algae at Pflanzenphysiologisches Institut of the University at Göttingen, Albrecht von Haller Institut, Untere Klarspüle 2, 37073 Göttingen, Germany
- Method of cultivation: The stock cultures are maintained fulfilling the criteria of the OECD guideline (OECD No. 201).
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
23.0 °C
pH:
7.9 - 9.4
Nominal and measured concentrations:
Nominal test concentrations: control, 0.95, 3.05, 9.77, 31.25, 100 mg/L
Mean measured test concentrations (study initiation): < LOQ, 0.9, 2.79, 9.01, 30.3, 100 mg/L
Mean measured test concentrations (study end): Recovery rates: 84.7 - 100%

Limit of Quantification (LOQ): 0.1 µg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: conical flasks with air-permeable silicone-sponge caps
- Material, size, fill volume: glass, 250 ml, 100 ml
- Initial cells density: 10 000 cells/ml
- Control end cells density: 329.1E+4 cells/ml
- No. of vessels per concentration (replicates): 8
- No. of vessels per control (replicates): 4

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: sterilised synthetic OECD medium prepared with purified water

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Photoperiod: continuously illuminated
- Light intensity and quality: 7310 - 7602 lux

EFFECT PARAMETERS MEASURED:
- Determination of cell concentrations: cell concentrations using an electronic particle counter recorded after 24, 48 and 72

TEST CONCENTRATIONS
- Range finding study: yes
- Test concentrations: 0.75, 3.0, 18 mg/L
- Results used to determine the conditions for the definitive study: growth rate inhibition at 18 mg/L after 72h: 4.4%
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
31.25 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: yield
Results with reference substance (positive control):
ErC50 (72 h) = 2.42 mg/L

Table 1: Validity criteria for OECD 201.

Criterion from the guideline

Outcome

Validity criterion fulfilled

The biomass in the control cultures should have increased exponentially by a factor of at least 16 within the 72-hour test period.

329

yes

The mean coefficient of variation for section-by-section specific growth rates (days 0-1, 1-2 and 2-3, for 72-hour tests) in the control cultures must not exceed 35%

12.4%

yes

The coefficient of variation of average specific growth rates during the whole test period in replicate control cultures must not exceed 7% in tests with Pseudokirchneriella subcapitata and Desmodesmus subspicatus. For other less frequently tested species, the value should not exceed 10%.

2.6%

yes

 

Validity criteria fulfilled:
yes
Remarks:
Please see Table 1 at "Any other information on results incl. tables"

Description of key information

ErC50 (72 h) > 100 mg a.i./L (nominal) and NOErC (72 h) = 31.25 mg a.i./L (nominal) for Pseudokirchneriella subcapitata.

Key value for chemical safety assessment

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

Additional information

The toxicity of the substance to aquatic algae was tested in a GLP guideline study conducted according to OECD 201. Green algae of the species Pseudokirchneriella subcapitata were exposed to nominal test substance concentrations of 0.95, 3.05, 9.77, 31.25, 100 mg/L. The substance concentrations in freshly prepared and from test solutions at the end of the exposure period analytically verified by liquid chromatography (LC) and tandem mass spectrometry detection (LC-MS/MS). The mean measured test concentrations after 72 h were values were within the range of ± 20 %, the nominal concentrations (i.e. <LOQ, 0.81, 2.65, 8.51, 29.4, and 96.7 mg/L). Sterilised synthetic OECD medium prepared with purified water was used as test medium.
Algal cell concentrations were determined after 24, 48 and 72 h in samples taken directly from the test vessels. A slight concentration-dependent inhibition of growth rate and yield was observed. The determined NOErC (72 h) was 31.25 mg/L based on nominal concentrations. The ErC50 (72 h) was >100 mg/L (nominal).