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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:
28 June to 04 August 2018
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)
Version / remarks:
2011
GLP compliance:
yes
Specific details on test material used for the study:
Appearance: Clear colourless liquid
Batch: 170918339
Purity: 97.2%
Solubility in water: very low
Analytical monitoring:
yes
Details on sampling:
- Concentrations: 0.1, 1, 100 mg/L
- Sampling method: 6.0 mL of sample were collected from the approximate centre of the test vessels at t=0 h, t=24h, and t=48 h
- Sample storage conditions before analysis: Samples were stored in a freezer (≤-15°C) until analysis at the analytical laboratory of the Test Facility.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: 3-d period of magnetic stirring to ensure maximum dissolution of the test item (100 mg/L) in medium. The obtained mixture was allowed to settle for 3 hours. Then, the aqueous Saturated Solution (SS) was collected via siphoning and used as the highest test concentration. Lower test concentrations were prepared by subsequent dilutions of the SS in test medium. All test solutions were clear and colorless at the end of the preparation procedure.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Common name: freshwater green algae
- Strain: NIVA CHL 1
- Source (laboratory, culture collection): In-house laboratory culture
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Hardness:
24 mg CaCO3/L
Test temperature:
23°C
pH:
8.1 ± 0.2
Nominal and measured concentrations:
Nominal concentrations: 1.0, 10, 100 mg/L

Measured concentrations of highest test concentration: At the start of the test, the measured concentrations were 0.032 and 0.026 mg/L in the samples taken from test solutions with and without algae, respectively. In the samples with algae, the measured concentration at the end of the test was 0.028 mg/L, while the concentration measured after 24 hours of exposure was at the level of the observed carry-over within the analytical system. In the samples without algae, 0.012 and 0.015 mg/L were measured after 24 and 72 hours of exposure.
Details on test conditions:
TEST SYSTEM
- Test vessel: 100 mL, all-glass with aluminium caps, perforated for ventilation
- Material, size, headspace, fill volume: 50 mL of test solution
- Initial cells density: 1 x 104 cells/mL
- No. of vessels per concentration (replicates): 6 replicates for the highest concentration; 3 replicates per intermediate test concentration, 1 extra replicate of each test group for sampling purposes after 24 hours of exposure
- No. of vessels per control (replicates): 6 replicates

GROWTH MEDIUM
- Standard medium used: Yes (M2 test medium)

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Milli-RO water

OTHER TEST CONDITIONS
- Light intensity and quality: Continuously using TLD-lamps with a light intensity within the range of 95 to 99 µE.m-2.s-1

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Cell densities were recorded at 24-hour intervals in the control and the limit concentration. Intermediate concentrations were measured only at the end of the exposure period.
- Determination of cell concentrations: At the beginning of the test, cells were counted using a microscope and a counting chamber. Thereafter, cell densities were determined by spectrophotometric measurement of samples at 680 nm using a spectrophotometer with immersion probe (path length = 10 mm).
Reference substance (positive control):
yes
Remarks:
potassium dichromate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 0.01 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 0.01 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
NOELR
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: loading rate
Duration:
72 h
Dose descriptor:
NOELR
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Remarks on result:
other: loading rate
Duration:
72 h
Dose descriptor:
EL10
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: loading rate
Duration:
72 h
Dose descriptor:
EL10
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Remarks on result:
other: loading rate
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: loading rate
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Remarks on result:
other: loading rate
Results with reference substance (positive control):
- Results with reference substance valid? Yes

It should be noted that small concentrations were detected in the control samples, which were at the level of the observed carry-over within the analytical system at the start of the test and after 24 hours of exposure. At the end of the test, the determined concentration in the control was higher. The source of this could not be determined with certainty. Considering the algal growth in the control group and that this was observed only at the end of the test, it was considered likely to be the result of a contamination during sampling or sample preparation.

Validity criteria fulfilled:
yes
Conclusions:
Under the conditions of the present study with Raphidocelis subcapitata (formerly known as Pseudokirchneriella subcapitata), no inhibition of growth rate or inhibition of yield was recorded at any of the concentrations of 1,1’-(1,1,3-trimethylpropane-1,3-diyl)bis(cyclohexane) tested.

The 72h-EC50 for growth rate inhibition was beyond the range tested, i.e. exceeded a TWA concentration of 0.0098 mg/L being considered to represent the maximum solubility of the test item in test medium at a loading rate of 100 mg/L.
The 72h-EC50 for yield inhibition was beyond the range tested, i.e. exceeded a TWA concentration of 0.0098 mg/L being considered to represent the maximum solubility of the test item in test medium at a loading rate of 100 mg/L.
The 72h-NOEC for growth rate inhibition was 0.0098 mg/L. The 72h-NOEL for growth rate inhibition was 100 mg/L.
The 72h-NOEC for yield inhibition was 0.0098 mg/L. The 72h-NOEL for yield inhibition was 100 mg/L.

Description of key information

Under the conditions of the present study with Raphidocelis subcapitata (formerly known asPseudokirchneriella subcapitata), no inhibition of growth rate or inhibition of yield was recorded at any of the concentrations of 1,1’-(1,1,3-trimethylpropane-1,3-diyl)bis(cyclohexane) tested.

The 72h-EC50 for growth rate inhibition (ErC50) was beyond the range tested, i.e. exceeded a TWA concentration of 0.0098 mg/L being considered to represent the maximum solubility of the test item in test medium at a loading rate of 100 mg/L.

The 72h-EC50 for yield inhibition (EyC50) was beyond the range tested, i.e. exceeded a TWA concentration of 0.0098 mg/L being considered to represent the maximum solubility of the test item in test medium at a loading rate of 100 mg/L.

The 72h-NOEC for growth rate inhibition was 0.0098 mg/L. The 72h-NOEL for growth rate inhibition was 100 mg/L.

The 72h-NOEC for yield inhibition was 0.0098 mg/L. The 72h-NOEL for yield inhibition was 100 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
100 mg/L
EC10 or NOEC for freshwater algae:
100 mg/L

Additional information