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Toxicity to aquatic algae and cyanobacteria

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Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: read-across from a guideline study
Justification for type of information:
The read-across justification is presented in the Endpoint summary Aquatic toxicity, because for fish, Daphnia, and algae the same source substance is used, and the reasoning is included in one document. The accompanying files are also attached there.
Reason / purpose:
read-across source
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
0.69 mg/L
Basis for effect:
growth rate
Remarks on result:
other: read-across from Terpinolene
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
0.27 mg/L
Basis for effect:
growth rate
Remarks on result:
other: read-across from Terpinolene
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2013
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
The pH varied more than 1.5 units in control and test flask except at the highest test concentration
Justification for type of information:
This information is used for read-across to the Terpene hydrocarbon alcohols.
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
yes
Remarks:
The pH varied more than 1.5 units in control and test flask except at the highest test concentration
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Principles of method if other than guideline:
not applicable
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
PHYSICO-CHEMICAL PROPERTIES
Vapour pressure: 101 Pa et 20°C, 133 Pa at 25°C
Water solubility (under test conditions): not specified but non GLP pre-experiments were carried out to determine an appropriate method for preparing test solution
Analytical monitoring:
yes
Details on sampling:
- Concentrations: samples for analysis were taken from the control and all test concentrations.
- Sampling method: samples were taken at the start (t = 0 h) and every day thereafter until the end of the test.
- Storage: samples were analysed directly after sampling.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
Method: preparation was performed in closed conditions and minimum headspace to avoid loss of test substance through volatilisation from water. A water volume of 1 L was placed in vessel. An excess of substance (4 g) was added to the surface of water. The stock solution was prepared by slow-stirring and maintaining the vortex in the centre extending maximally ca. 10% of vessel depth. After 24 ± 2 hours of gentle stirring, the saturated aqueous phase was taken out of the drain port. The first 100 mL were discarded and samples were taken from the following stock solution and chemically analyzed.

Evidence of undissolved material: no (the test sample formed a clear colourless solution)

Controls: test water without test substance but treated in the same way as the test substance solutions.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
Common name: Algae
Strain: Pseudokirchneriella, CCAP 278/4
Origin: Museum National d’Histoire Naturelle - 12, rue Buffon, Case N°19 - 75005 PARIS, bred in the laboratory under standardised conditions according to the test guidelines
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Post exposure observation period:
no
Hardness:
150 mg/L as NaHCO3
Test temperature:
23 +/- 2°C
pH:
7.98-8.10 (control and test vessels, start) 8.26-10.04 (control and test vessels, end)
Dissolved oxygen:
not reported
Salinity:
not applicable
Nominal and measured concentrations:
Nominal concentrations: 0.005-0.02-0.05-0.14-0.41-1.22 mg/L
Measured concentrations: 0.003-0.014-0.034-0.095-0.390-0.920 mg/L
Details on test conditions:
TEST SYSTEM
Test vessel: closed glass flask (100 mL)
Aeration: yes
Shaking: during incubation, the algal cells were kept in suspension by continuous shaking.
Initial cells density: 5000 cells/mL
Control end cells density: 70.6 x 10^4 cells/mL
No. of vessels per concentration (replicates): 3
No. of vessels per control (replicates): 6
Additional replicate of each test concentration without algae: 1 (to assess potential loss through bioaccumulation or adsorption on algae cells)

GROWTH MEDIUM
Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
Source/preparation of dilution water: original medium of OECD Guideline 201, prepared using sterilised water
Culture medium: original medium of OECD TG 201
Intervals of water quality measurement: temperature was measured continuously in the growth chamber, over the study period and pH was recorded at the beginning and at the end of the test in one vessel per concentration and the control.

OTHER TEST CONDITIONS
Sterile test conditions: yes
Photoperiod: continuous illumination
Light intensity and quality: 4400-8880 Lux

EFFECT PARAMETERS MEASURED
Determination of cell concentrations: cell numbers were counted daily by microscope using a counting chamber.

TEST CONCENTRATIONS
Spacing factor for test concentrations: less than 4

Range finding study
Test concentrations: 0.6-1.0-2.0 mg/L
Reference substance (positive control):
yes
Remarks:
Potassium dichromate
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
0.692 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL: 0.604-0.811
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
0.273 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL: 0.204-0.331
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
0.302 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: Yield
Remarks on result:
other: 95%CL 0.180-0.494
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
0.054 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
other: Yield
Remarks on result:
other: 95% CL 0.010-0.107
Details on results:
- Exponential growth in the control (for algal test): yes (cell density: 141-fold increase within 72 hours)
- Observation of abnormalities (for algal test): no
Results with reference substance (positive control):
- Results with reference substance valid
- EC50: 0.96 mg/L (growth rate)
Reported statistics and error estimates:
The software ToxRat® Professional was used for the determination of the effective concentrations. The EC50 value was determined by Probit analysis using linear max. likelihood regression.
Validity criteria fulfilled:
yes
Conclusions:
The 72-h ErC50 and the 72-h ErC10 values for freshwater algae (P. subcapitata) are 0.692 mg/L and 0.273 mg/L, respectively, based on measured concentrations.
Executive summary:

For algae, a toxicity study was performed according to OECD TG 201 and in compliance with GLP criteria. Following a preliminary range-finding test, cultures of freshwater algae (P. subcapitata) were exposed to Terpinolene at nominal concentrations of 0.005, 0.02, 0.05, 0.14, 0.41 and 1.22 mg/L (three replicate flasks per test concentration and six replicates for control) for 72 h, under constant illumination and shaking at a temperature of 21-25°C. Measurements of biomass, growth inhibition and yield were done by determination of cell densities at 24, 48 and 72 h using a counting chamber. The results obtained with positive control (potassium chromate) were in accordance with guideline requirements. The concentrations of the test item (with and without algae) were measured at the start of the study and at the 72-h incubation period. The concentrations were not satisfactorily maintained within ± 20% of the initial concentrations, thus the results were based on the geometric mean of measured exposure concentrations in the abiotic test.

The 72h-EC10 and 72h-EC50 values, based on growth rate, were 0.273 and 0.692 mg/L respectively, calculated as geometric mean of measured concentration.

Description of key information

The toxicity to aquatic algae and cyanobacteria is assessed based on read-across from the close structural analogue Terpinolene to Terpene hydrocarbon alcohols.

Terpinolene's algae toxicity

For Terpinolene, an algae study was performed according to OECD TG 201 and in compliance with GLP criteria. Following a preliminary range-finding test, cultures of freshwater algae (P. subcapitata) were exposed to Terpinolene at nominal concentrations of 0.005, 0.02, 0.05, 0.14, 0.41 and 1.22 mg/L (three replicate flasks per test concentration and six replicates for control) for 72 h, under constant illumination and shaking at a temperature of 21-25°C. Measurements of biomass, growth inhibition and yield were done by determination of cell densities at 24, 48 and 72 h using a counting chamber. The results obtained with positive control (potassium chromate) were in accordance with guideline requirements. The concentrations of the test item (with and without algae) were measured at the start of the study and at the 72-h incubation period. The concentrations were not satisfactorily maintained within ± 20% of the initial concentrations, thus the results were based on the geometric mean of measured exposure concentrations in the abiotic test. The 72h-EC50 and 72h-EC10 values, based on growth rate, were 0.692 and 0.273 mg/L respectively, calculated as geometric mean of measured concentration.

Key value for chemical safety assessment

EC50 for freshwater algae:
0.692 mg/L
EC10 or NOEC for freshwater algae:
0.273 mg/L

Additional information