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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:
supporting study
Study period:
1998-03-03 to 1998-03-06
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study without detailed documentation
Qualifier:
according to guideline
Guideline:
EU Method C.3 (Algal Inhibition test)
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
- Concentrations: 6.2, 12.5, 25, 50, 100 mg/L
- Sampling method: No data
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Dilution of stock solution in test medium
- Controls: Inoculum in nutrient medium and water for dilution
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Common name: Scenedcsmus subspicatus CHODAT
- Source (laboratory, culture collection): Institute of Plant Physiology, University of Goettingen
- Inoculum: Algal suspension taken from an exponentially growing pre-culture which serves to adjust an initial cell density of 10 000 cells per milliliter
- Method of cultivation: in a light chamber at 23 ± 2 degrees C and with a quantum flux which equals 120 µE/m²/s
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Post exposure observation period:
None
Test temperature:
23°C
pH:
7.0-10.4
Dissolved oxygen:
N/A
Salinity:
N/A
Nominal and measured concentrations:
Nominal concentrations: 6.2, 12.5, 25, 50, and 100 mg/L
Measured concentrations: 8.2, 11.0, 19.2, 38.3, and 76.7 mg/L (at 0 h); 11.0, 13.7, 21.9, 41.1, and 76.7 mg/L (at 72 h)
Details on test conditions:
TEST SYSTEM
- Initial cells density: 10 000 cells per milliliter

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: deionized water
- 100 ml of test medium

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: counting - Microcellcounter Sysmex F-300 Digitana (SOP 2030-0001902-96 D)

TEST CONCENTRATIONS
- Test concentrations: 6.2,12.5, 25, 50, 100 mg/L
- Results used to determine the conditions for the definitive study: biomass, growth rate, cell density, TOC determination
TEST SYSTEM
- Test vessel: Erlenmeyer flasks (300 ml) with stoppers
- Material, size, headspace, fill volume: 100 mL test medium
- Aeration: No
- Initial cell density: 10,000 per mL
- Control end cells density: 674,000
- No. of vessels per concentration (replicates): No data
- No. of vessels per control (replicates): No data

GROWTH MEDIUM
- Standard medium used: No data
- Detailed composition if non-standard medium was used: No data

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Deionised water
- Total organic carbon: No data
- Particulate matter: No data
- Metals: No data
- Pesticides: No data
- Chlorine: No data
- Alkalinity: See pH measurements
- Ca/Mg ratio: No data
- Conductivity: No data
- Culture medium different from test medium: No data
- Intervals of water quality measurement: No data

OTHER TEST CONDITIONS
- Sterile test conditions: No data
- Adjustment of pH: No data
- Photoperiod: Continuous
- Light intensity and quality: 120 µE/m²/s
- Salinity (for marine algae): N.a.

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

TEST CONCENTRATIONS
- Spacing factor for test concentrations: Factor 2
- Range finding study: No
Reference substance (positive control):
not specified
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
12.2 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
cell number
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
ca. 20.3 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
cell number
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
ca. 13.2 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
ca. 29.7 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
> 20.3 - < 39.2 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 39.2 - < 75.6 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): No data
- Any stimulation of growth found in any treatment: No
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: No data
- Effect concentrations exceeding solubility of substance in test medium: No
Reported statistics and error estimates:
EC50 and EC10 estimated using binary regression (probit).
NOEC and LOEC determined using Dunnett's test.
Validity criteria fulfilled:
yes
Conclusions:
The NOEC and LOEC for Reactive Navy FC63805 on Scenedesmus subspicatus (CHODAT) is 12.2 mg/L and 20.3 mg/L, respectively. The EC10 and EC50 (biomass) over 72 hours are 13.2 and 29.7 mg/L, respectively. The EC10 and EC50 (growth rate) are 13.2 and 20.3-39.2 mg/L, respectively.
Executive summary:

In a 72 hour growth inhibition study, cultures of Scenedesmus subspicatus (CHODAT) were exposed to Reactive Navy FC63805 at concentrations of 6.2, 12.5, 25, 50, and 100 mg/L in accordance with EU method C.3.  The NOEC and LOEC values based on cell density were 12.2 and 20.3 mg/L, respectively. The EC10 and EC50 values based on biomass were 13.2 and 29.7 mg/L, respectively. The EC10 and EC50 values based on growth rate were 20.3–39.2 and 39.2–75.6 mg/L, respectively.

This toxicity study is classified as acceptable and satisfies the guideline requirements for an algal inhibition test. However, due to reporting deficiencies and inaccurate presentation of effect values derivation of distinct key values for chemical assessment (i.e. EC10, EC50, or NOEC for chemical action) is not possible.

 

Results Synopsis

Test organism: Scenedesmus subspicatus (CHODAT)

72 hr NOEC based on cell density: 12.2 mg/L

72 hr LOEC  based on cell density: 20.3 mg/L

72 hr EC10 based on biomass: 13.2 mg/L

72 hr EC50 based on biomass: 29.7 mg/L

72 hr EC10 based on growth rate: 20.3–39.2 mg/L

72 hr EC50 based on growth rate: 39.2–75.6 mg/L

Description of key information

Two studies on algal growth inhibition by Reactive Navy FC63805 were conducted according to EU method C.3. The test design of one study was modified in order to allow discrimination of effects caused by chemical action (toxicity) vs physical effects (light attenuation). There are indications of slight chemical toxicity of Reactive Navy FC63805 to algae, but the presentation of the data does not allow derivation of an EC10, EC50, or NOEC for chemical effects. Therefore, all effects are related to chemical exposure and substance toxicity to represent the worst-case in the chemical safety report.

Key value for chemical safety assessment

EC50 for freshwater algae:
27 mg/L
EC10 or NOEC for freshwater algae:
8.1 mg/L

Additional information

In a 72 hour growth inhibition study cultures of Scenedesmus subspicatus (CHODAT) were exposed to Reactive Navy FC63805 at nominal concentrations of 0, 12.5, 2.5, 50, 100 mg/L in accordance with EU method C.3.  The test design was modified to allow discrimination between chemical action (toxicity) and physical effects (light attenuation by the coloured test substance). The EC10 and EC50 values based on biomass in the algicidal test (direct exposure) were < 9.5 and 9.5–20.3 mg/L, respectively. The EC10 and EC50 values based on growth rate in the algicidal test (direct exposure) were 8.1 and 27 mg/L, respectively. The EC10 and EC50 values based on biomass in the algistatic test (light attenuation) were < 9.5 and 9.5–20.3 mg/L, respectively. The EC10 and EC50 values based on growth rate in the algistatic test (light attenuation) were 9.5–20.3 and 20.3–37.8 mg/L, respectively. Due to reporting deficiencies and inaccurate presentation of effect values, derivation of key values for chemical assessment (i.e. EC10, EC50, or NOEC for chemical action) are directly referred to chemical exposure and substance toxicity to represent the worst-case scenario. The supporting study without modification for light absorption effects confirms the results (72 -h ErC10 >20.3 and <39.2 mg/L; 72 -h ErC50 >39 and <76 mg/L)