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Ecotoxicological information

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:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
test procedure in accordance with national standard methods with acceptable restrictions
Qualifier:
according to
Guideline:
other: modified provisional algal assay procedure (PAAP)
GLP compliance:
no
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Basic ASM Medium, sterile distilled water, and test chemical were dispensed into 600 mL Erlenmeyer flasks
- Controls: Yes
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Common name: Green algae
- Strain: Selenastrum capricornutum, number 1648
- Source: Slant agar cultures obtained from the Indiana University culture collection
- Age of inoculum (at test initiation): Seven day-old stock cultures were used for each inoculation. A portion of the stock culture was analyzed for chlorophyll "a", dry weight, and absorbance at 750 nm immediately prior to use in the algal assay.
- Method of cultivation: New stock cultures were prepared at weekly intervals by inoculating approximately 500 mL of fresh Basic ASM Medium with 10 mL of algal suspension.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
7 d
Test temperature:
20 °C ± 1 °C
pH:
7.0
Nominal and measured concentrations:
Control, 0.4, 4.0 and 40 mg/L
Details on test conditions:
TEST SYSTEM
Test vessel:
- Type: open
- Material, size, headspace, fill volume: 600 mL Erlenmeyer flasks, 10 mL of algal suspension and brought up to a final volume of 500 mL with basic ASM medium
- Aeration: Diffused aeration from a compressed air supply, after three-stage filtration, which included final passage through sterile cotton, no stirring or shaking.
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3

GROWTH MEDIUM
- Standard medium used: Yes (ASM medium but not standard for algae toxicity testing according to OECD 201)

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Basic ASM Medium; Stock solutions of the test item used in formulating the final medium were prepared from reagent grade chemicals, dissolved in distilled water, and sterilized by passage through a 0.45 µm Millipore filter. All glassware utilized in the algal assays were successively washed with several portions each of 6N HCl, 70% isopropanol, and Millipore filtered distilled water.

OTHER TEST CONDITIONS
- Sterile test conditions: Yes
- Adjustment of pH: Yes, 7.0
- Photoperiod: Continuous overhead illumination
- Light intensity and quality: Two 40 watt Sylvania soft-white fluorescent tubes, suspended 18 inches from the flasks (corresponding to approximate light intensity of 500 foot-candles)

EFFECT PARAMETERS MEASURED:
- Determination of cell concentrations: Measurement of absorbance at 750 nm.
- Other: Algal assays were conducted over a period of seven days. At the end of each experiment, additional samples were taken for analysis of dry weight and chlorophyll "a".

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 10
Range finding study: No range-finding test was performed
Reference substance (positive control):
no
Duration:
7 d
Dose descriptor:
NOEC
Effect conc.:
0.4 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Yield
Duration:
7 d
Dose descriptor:
EC50
Effect conc.:
> 0.4 - < 4 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Yield

Table 1: Biological Results based on 7 -day Cell yield and Growth Rate constant

Conc

7-day cell yield

Growth rate

Effect

[mg/L]

% Difference from Control

95% confidence Interval (Controls)

% Difference from Control

95% confidence Interval (Controls)

 

0.4

+0.5

±52.7

78.0

±40.5

N

4.0

-69.9

±52.7

50.3*

±40.5

I

40.0

-92.1

±52.7

12.1*

±40.5

I

I: Inhibition; N = No effect

* due to imprecise at this adsorption range these values are not reliable

Description of key information

EC50 (7 d) between 0.4 and 4.0 mg/L (yield, Selenastrum capricornutum, modification of the provisional algal assay procedure (PAAP))

Key value for chemical safety assessment

Additional information

One experimental study is available investigating the toxicity of the test item to aquatic algae (National Association of Photographic Manufacturers, 1977). The study was performed without analytical monitoring of the test item concentration exposing the freshwater species Selenastrum capricornutum to the test item concentration of 0.4, 4.0 and 40 mg/L under static conditions for 7 days. Inhibition effects were observed at 4.0 and 40 mg/L of 69.9 and 92.1%, respectively (at 0.4 mg/L no effect was observed). Since the EC50 value was not defined only a range can be given (0.4 to 4 mg/L). The lower  concentration of 0.4 mg/L were used for PNEC derivation as the worst case.