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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:
15 Nov - 18 Nov 2005
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
yes
Remarks:
according to the Japanese GLP Standard
Analytical monitoring:
yes
Details on sampling:
- Concentrations: 0, 100 mg/L
- Sampling method: test solution for analysis was separately prepared for analysis at the initiation of the test. After exposure, same volume of test solution was sampled directly from each test vessel and cetrifuged (3000 rpm, 10 min) to get rid of alga.
- Sample storage conditions before analysis: analysis was conducted immediately after sampling, no storage
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: test item is immiscible with water and therefore a WAF was prepared by adding the test item in dilution water. After 30 minutes sonication, test water was stirred (750 rpm) for 24 hours at 23± 2 °C. Test water was filtered with No. 2 filter paper.
- Controls: dilution water
- Evidence of undissolved material (e.g. precipitate, surface film, etc): test water was colorless after preparation
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Common name: green algae
- Strain: ATCC22662
- Source: American Type Culture Collection
- Method of cultivation: on rotary shaker

ACCLIMATION
- Acclimation period: 5 days (11/11/2005 - 15/11/2005)
- Culturing media and conditions (same as test or not): same as test
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Test temperature:
22.0 - 22.7 (23 ± 2 °C)
pH:
7.7 - 9.9
Nominal and measured concentrations:
nominal concentration: 100 mg/L
measured concentration: 0.053 (at the initiation), 0.00619 (after exposure) mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: 300 mL Erlenmeyer flask with an air-permeable stopper
- Type: open
- Material, fill volume: glass, 100 mL
- Aeration: no
- Initial cells density: 1000 cells/mL
- Control end cells density: 2883100 ± 120600
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: not stated
- Intervals of water quality measurement: Determination and observation: pH (0 and 72 hour), temperature (0, 24, 48. 72 h) and apperance of test solutions (after preparation) were determined.

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: not adjusted
- Photoperiod: continuously
- Light intensity and quality: 4000 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: counting chamber; electronic particle counter; after 0, 24, 48 and 72 h.

TEST CONCENTRATIONS
- Range finding study
- Test concentrations: control, 10.0, 50.0, 100 mg/L
- Results used to determine the conditions for the definitive study: growth inhibition rate: 10.0 mg/L: -8%, 50.0 mg/L: -11%, 100 mg/L: -40%
Reference substance (positive control):
yes
Remarks:
potassium dichromate (reagent grade)
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
WAF
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
> 39.8 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Remarks:
refers to N N'-ethylene-bis-octadecanamide
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
WAF
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
> 39.8 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Remarks:
refers to N N'-ethylene-bis-octadecanamide
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 0.006 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
> 0.006 mg/L
Nominal / measured:
meas. (not specified)
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): not observed
- Unusual cell shape: not observed
- Flocculation: not observed
- Adherence to test vessels: not observed
- Aggregation of algal cells: not observed
Results with reference substance (positive control):
- Results with reference substance valid? Yes
- EbC50: 0.430 ± 0.0698 mg/L (n=17)
- Other: this test is performed every 6 months.
Reported statistics and error estimates:
The EC50 values and associated 95% confidence limits could not be determined statistically because the test was conducted at one concentration level. The NOEC were determined by Student's t-testm subsequent to F test for homogeneity of variances. Statistical analyses were performed using Yukms Statlight #3 software (Yukms Corp., Tokyo) and all tests of significant were at α=0.05.

Table 1. Measured Concentration of the Test Substance in Test Cultures

Loading Rate (*1)

(mg/L)

Measured Concentration (mg/L)

(Percent of 0hr)

0 Hour

72 Hour

Control

<0.002

<0.00002

100

0.053

0.00619

(12)

(*1): The ratio of test substance to water (in mg/L) used in the preparation of the WAF.

Table 2. Cell Densities of Pseudokirchneriella subcapitata during the 72 -Hour Exposure

Loading Rate

[Measured Conc. at 0 hr]

(mg/L)

Cell Densities (cells/mL)

 

0 Hour

24 Hour

48 Hour

72 Hour

Control

Average

10000

82800

756900

2883100

SD

0

11900

123400

120600

100

[0.053]

Average

1000

83000

778900

3413100

SD

0

16300

138300

70200

Table 3: 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.

>16

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%

<35%

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%.

<7%

yes

Validity criteria fulfilled:
yes
Remarks:
Please refer to table 3 in section "Any other information on results incl. tables"

Description of key information

The substance is not toxic to aquatic algae.

Key value for chemical safety assessment

Additional information

The toxicity of the substance to the freshwater algae Pseudokircheneriella subcapitata was investigated in a limit test following the OECD Guideline 201. A water accommodated fraction (WAF) with a nominal loading rate of 100 mg/L was prepared. The test concentration was verified by LC/MS. Effects on growth rate of Pseudokircheneriella subcapitata were not observed up to the highest attainable concentration. Therefore, an EC50 (72 h) > 0.053 mg/L (measured) and a NOEC (72 h) ≥ 0.053 mg/L (measured) was determined.

Based on the available study results, the substance is not considered toxic to aquatic algae.