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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:
guideline study with acceptable restrictions
Qualifier:
according to
Guideline:
other: U.S.T.C. procedure PRO/ALGAE 224-7 outlined with reference to the test method in CFR 40, Part 797.1050 "Algal Acute Toxicity Tests"
Deviations:
no
Principles of method if other than guideline:
Not relevant
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
- Concentrations: 32, 63, 125, 250 and 500 mg/l
- Sampling method: Two sets of the test concentrations (without inoculum), along with a blank media control, were analyzed for initial SOC. One set was incubated under the test conditions and the other was refrigerated at 4 °C. The SOC was then analyzed again at "96 hours".
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION:
- Method: Both marine and freshwater media are prepared with distilled water in non-metallic containers and reconstituted with known nutrients, salts and trace elements. Stock culture maintenance media is sterilized before use. Test media is generally sterilized by filtration (<0.45 micron), although some media may be autoclaved. Sufficient media may be prepared in advance and stored refrigerated. Certain nutrients and enrichments, kept separate and sterile, may be added just before use if the formulation requires.
- Controls: Yes
Test organisms (species):
other: Selenastrum capricornutum
Details on test organisms:
TEST ORGANISM
- Common name: Selenastrum capricornutum
- Source (laboratory, culture collection): USTC Stock Culture, origin EPA, Cincinnati, Ohio
- Age of inoculum: 4 - 5 days
- Method of cultivation: For routine propagation, algal cultures are incubated at 20 ±2 °C under 400 + 50 ft. candles, using a 16 hour-light.: 8 hour-dark photoperiod. The cultures are manually shaken periodically. Stocks are subcultured on a regular basis, at 1 to 4. week intervals.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
96 h
Post exposure observation period:
Not relevant
Hardness:
50 mg/l CaCO3
Test temperature:
24 ±2 °C
pH:
7.1 - 7.4
Dissolved oxygen:
No data
Salinity:
Not relevant
Nominal and measured concentrations:
Nominal: 32, 63, 125, 250 and 500 mg/l (17, 33, 65, 130, 260 TOC)
Measured (t = 0h): 18, 40, 45, 123 and 240 TOC (106, 121, 69, 95 and 92% of nominal)
Measured (t = 96h, preserved at 4 °C): 3, 23, 42, 89 and 245 TOC (17, 58, 93, 72 and 102% of nominal)
Measured (t = 96h, light, 24 °C): 1, 5, 37, 87 and 242 TOC (6, 13, 82, 71 and 101% of nominal)
Details on test conditions:
TEST SYSTEM
- Test vessel: Erlenmeyer flask
- Type: closed
- Material, size, headspace, fill volume: borosilicate glass, 125 ml
- Aeration: Aeration by mixing test solutions to saturation prior to test, no aerration during test
- Initial cells density: 10,000 cells/ml
- Control end cells density:
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3

GROWTH MEDIUM
- Standard medium used: yes, OECD/EPA formulations, low metals

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: distilled water
- Alkalinity: 30 mg/l CaCO3
- Conductivity: 130 umhos
- Culture medium different from test medium: yes
- Intervals of water quality measurement: temperature daily, pH at start and end of experiment

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: yes
- Photoperiod: 16h light, 8h dark
- Light intensity and quality: fluorescent, 400 to 450 ft candles

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: hemocytometer

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2
Reference substance (positive control):
no
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
62.9 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95%CL: 54.2 - 71.8 mg/l, initial measured concentrations in line with nominal concentrations
Duration:
96 h
Dose descriptor:
EC50
Effect conc.:
87.6 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95%CL: 54.5 - 137.4 mg/l, initial measured concentrations in line with nominal concentrations
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
18.5 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: Initial measured concentrations in line with nominal concentrations
Duration:
96 h
Dose descriptor:
EC10
Effect conc.:
39.9 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: Initial measured concentrations in line with nominal concentrations
Details on results:
- Exponential growth in the control (for algal test): yes
Results with reference substance (positive control):
Not relevant
Reported statistics and error estimates:
Probit analysis by EPA computer program.

For detailed results, see attached file "Results.doc".

Validity criteria fulfilled:
yes
Remarks:
>16x increase in controls, growth rates meet validity criteria
Conclusions:
The acute toxicity (72h-EC50) of Diacid 1550 potassium salt towards Selenastrum capricornutum is 87.6 mg/L.
Executive summary:

The acute toxicity of Diacid 1550 potassium salt towards Selenastrum capricornutum was investigated according to U.S.T.C. procedure PRO/ALGAE 224-7 outlined with reference to the test method in CFR 40, Part 797.1050 "Algal Acute Toxicity Tests" under GLP. Algal cells were exposed to nominal concentrations of 32, 63, 125, 250 and 500 mg/L and were observed for 96 hours. Based on the nominal concentrations the 72h-EC10, 96h-EC10, 72h-EC50 and 96h-EC50 were found to be 18.5, 39.9, 62.9 and 87.6 mg/L respectively.

Description of key information

 The acute toxicity (96h-EC50) of Diacid 1550 potassium salt towards Selenastrum capricornutum is 87.6 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
87.6 mg/L
EC10 or NOEC for freshwater algae:
39.9 mg/L

Additional information

The acute toxicity of Diacid 1550 potassium salt towards Selenastrum capricornutum was investigated according to U.S.T.C. procedure PRO/ALGAE 224-7 outlined with reference to the test method in CFR 40, Part 797.1050 "Algal Acute Toxicity Tests" under GLP. Algal cells were exposed to nominal concentrations of 32, 63, 125, 250 and 500 mg/L and were observed for 96 hours. Based on the nominal concentrations the 72h-EC10, 96h-EC10, 72h-EC50 and 96h-EC50 were found to be 18.5, 39.9, 62.9 and 87.6 mg/L respectively.