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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
Study period:
11 September 2013 - 16 November 2015
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
- Concentrations: 0.0162, 0.0519, 0.166, 0.531, and 1.70 mg/L.
- Sample storage conditions before analysis: Samples were analysed immediately after sampling. At each sampling occasion a second sample was refrigerated in case further analysis was required.
Vehicle:
yes
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Controls: Control and solvent control solutions were evaluated concurrently with the test solutions.
- Chemical name of vehicle: Tetrahydrofuran (THF)
- Concentration of vehicle in test medium: 0.01% (v/v) (0.1 mL in 1 L aqueous media)
- Evidence of undissolved material: N/A. At the start of the test the test media were colourless.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Strain: CCAP 278/4
- Age of inoculum (at test initiation): Secondary liquid cultures were incubated for four days to provide an inoculum in the log phase of growth, characterised by a cell density of 9.60 x 10^5 cells/mL.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
23.4 - 24.5°C
pH:
7.04 - 9.21
Nominal and measured concentrations:
Nominal: 0.0162, 0.0519, 0.166, 0.531, and 1.70 mg/L
Measured (0 hours): nd, 0.0507, 0.110, 0.363, 0.721 mg/L
Measured (72 hours): nd, nd, 0.0683, 0.229, 0.864 mg/L
nd = None detected (less than the limit of detection of 0.05 mg/L)
Details on test conditions:
TEST SYSTEM
- Type: closed
- Material, size, headspace, fill volume: 65 mL glass vials, completely filled to leave no headspace, sealed with teflon lids and metal caps
- Initial cells density: 1 x 10^4 cells/mL
- Control end cells density: 392811 (solvent control, mean of six replicates)
- No. of vessels per concentration: 3
- No. of vessels per control: 6
- No. of vessels per vehicle control: 6

GROWTH MEDIUM
- Standard medium used: yes

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: Not adjusted after the start of the test.
- Photoperiod: 72 hours continuous illumination
- Light intensity and quality: nominally 4440 to 8880 lux

EFFECT PARAMETERS MEASURED:
- Determination of cell concentrations: Particle counter, samples taken at 24, 48, and 72 hours.


TEST CONCENTRATIONS
- Spacing factor for test concentrations: c.a. 3.2
- Range finding study
- Test concentrations: 0.019, 0.19, 1.9 mg/L
- Results used to determine the conditions for the definitive study: Yes. Note that the highest concentration used was approaching the limit of solubility of the test material.
Reference substance (positive control):
no
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
0.59 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL = 0.540, 0.640 mg/L)
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
0.13 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL = 0.100, 0.160 mg/L)
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
0.21 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
biomass
Remarks on result:
other: 95% CL = 0.160, 0.270 mg/L)
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
0.05 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
biomass
Remarks on result:
other: 95% CL = 0.0.0300, 0.100 mg/L)
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
0.087 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Remarks on result:
other: Value calculated using the estimated concentration at 72 hours, which was less than the limit of quantitation. Effect level was the same for both growth rate and yield (biomass)
Key result
Duration:
72 h
Dose descriptor:
LOEC
Effect conc.:
0.288 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Remarks on result:
other: Effect level for both growth rate and yield (biomass)
Details on results:
- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test):
On Day 1, a few abnormal cells were present in all groups but this was considered to be insignificant as very few cells were affected.
On Day 2, swollen and distorted cells were observed in the control and at a concentration of 0.0162 mg/L (ca. 10 - 15 %), in the solvent control (ca. 25%) and at nominal concentrations of 0.0519 to 1.7 mg/L (ca. 30%).
On Day 3, swollen and distorted cells were observed in the control and at nominal concentrations of 0.0162 and 0.0519 mg/L (ca. 10 - 15 %), in the solvent control (ca. 25-30%) and at nominal concentrations of 0.166 to 1.7 mg/L (ca. 50%). The presence of abnormal cells in the control groups did not have an impact on growth rate, so these observations were not considered to have affected the validity of the test.

- Any stimulation of growth found in any treatment: Growth was stimulated in the dilution medium control and at the lowest test level when compared to the solvent control; although this was identified at being statistically significant (p<0.05), it was not considered to be of biological relevance as the extent of the stimulation was less than 20%.
Validity criteria fulfilled:
yes
Conclusions:
The effect of TCD on the growth of the unicellular green alga Pseudokirchneriella subcapitata has been assessed over a 72 hour period.
After 72 hours of exposure to TCD, the ErC50 (growth rate) and EyC50 (yield) were 0.590 and 0.210 mg/L respectively, based on measured and estimated concentrations.
The “no observed effect concentration” (NOEC) for growth rate and yield was 0.0867 mg/L based on estimated concentrations, and the “low observed effect concentration” (LOEC) for growth rate and yield was 0.288 mg/L based on measured concentrations.

Description of key information

Key value for chemical safety assessment

EC50 for freshwater algae:
0.59 mg/L
EC10 or NOEC for freshwater algae:
0.087 mg/L

Additional information