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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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effects on growth of green algae
Type of information:
experimental study
Adequacy of study:
key study
Study period:
13 - 18 Jul, 1990
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
according to guideline
EPA OPP 122-2 (Algal Toxicity, Tiers I and II)
Version / remarks:
version: 1982
The initial cell density was 3 000 cells/mL.
GLP compliance:
Analytical monitoring:
Details on sampling:
At test initiation, samples were removed from the 500-mL volumetric flasks of the test solutions and the controls and frozen for analysis. In addition, six quality control (QC) samples were prepared and used to judge the precision andquality control maintained during the analytical process.
At test termination, test solutions from each treatment level were composited and three QC samples were prepared.
Details on test solutions:
A 0.5145-g portion of test item was weighed into a sterile beaker, rinsed into a 50 mL volumetric flask with acetone and diluted to 50 mL with acetone to create a primary stock solution of 10 mg/mL. A 0.05 mLvolume of this stock was transferred to a 500 mL volumetric flask and diluted to volume with sterile MBL medium to create the highest nominal test concentration of 1 mg/L. Serial dilutions of the 10mg/mL primary stock in acetone created 6 more secondary stock solutions containing 5, 2.5, 1.3, 0.63, 0.31 and 0.16 mg/mL. Equal volumes (0.05 mL) of secondary stock solution were transferred to 500 mL volumetric flasks and diluted to volume with sterile MBL medium to create nominal test concentrations of 0.5, 0.25, 0.13, 0.063, 0.031 and 0.016 mg a.i./L. A 500 mL solution was also prepared containing algal growth medium only and designated the control. A solvent control solution was prepared containing 0.05 mLof acetone diluted to 500 mLwith algal growth medium and was equivalent to the concentration of solvent present in all test solutions.
Test organisms (species):
Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)
Details on test organisms:
4-day old inoculum from the laboratory culture.
Test type:
Water media type:
other: Marine Laboratory Medium
Limit test:
Total exposure duration:
120 h
Not specified
Test temperature:
22 - 26 °C
7.4 - 10.1
Dissolved oxygen:
Not specified
Not applicable
220 - 310 µmhos/cm
Nominal and measured concentrations:
Nominal concentrations: 0.016, 0.031, 0.063, 0.13, 0.25, 0.5 and 1.0 mg a.i./L
Mean measured concentrations: 0.016, 0.018, 0.041, 0.088, 0.18, 0.26 and 0.53 mg a.i./L
Details on test conditions:
The flasks were impartially placed on an Orbit Shaker. The shaking rate of each shaker was set at 100 rpm. Lighting was provided continuously at an intensity of 4,000-5,000 lux at the solution surface. All glassware used in this study was silanized.
Stock cultures were grown In 125 mLglass flasks containing 50mL of medium. The flasks were covered with stainless steel caps which permitted gas exchange.
The initial cell density was 3 000 cells/mL in each of the three replicate per treatement and controls.
At each 24-hour interval cell counts were conducted on each replicate vessel using a hemacytometer and microscope. One sample was taken from each flask for counting.
Key result
120 h
Dose descriptor:
Effect conc.:
0.22 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
act. ingr.
Basis for effect:
growth rate
Key result
120 h
Dose descriptor:
Effect conc.:
0.009 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
act. ingr.
Basis for effect:
growth rate

Please refer to "overall remark/ attached background material" field for result tables.

Validity criteria fulfilled:
not specified
The present guideline study was conducted in compliance with GLP. Under the test conditions used, the EC10 and EC50 120h for P. subcapitata were 0.0087 mg a.i./L and 0.22 mg a.i./L, respectively. The NOEC was defined as 0.016 mg a.i./L.

Description of key information

From key study, the 120-h ErC50 and ErC10 for aquatic algae exposed to the present test material were 0.22 mg a.i./L and 0.0087 mg a.i./L in freshwater.

Key value for chemical safety assessment

EC50 for freshwater algae:
0.22 mg/L
EC10 or NOEC for freshwater algae:
0.009 mg/L

Additional information

In the key study (1990), the toxicity of test substance to aquatic algae was investigated in a 120-hours static test with Pseudokirchneriella subcapitata according to US EPA OPP 122-2 guideline. An initial cell density of 3.0 x 103cells/mL was achieved in each of the replicates per test concentration. Algae were exposed to mean measured test item concentrations of 0.016, 0.018, 0.041, 0.088, 0.18, 0.26 and 0.53 mg a.i./L, alongside with a control containing only test medium and solvent control. Based on the mean measured concentration 120-h ErC50 was 0.22 mg a.i./L and EC10 (120 h) was determined to be 0.0087 mg a.i./L.

Additionally, four studies on N. pelliculosa, S. costatum, A. flos-aquae and D. subspicatus were conducted with the substance. These studies are only mentioned in the endpoint summary because they were deviated from the current guideline for some parts.The 120-h EC50 for N. pelliculosa, S. costatum, A. flos-aquae were 0.043 mg a.i./L; 0.13 mg a.i./L and > 0.63 mg a.i./L, respectively. The 96 -h EC50 for D. subspicatus  was 5.3 mg/L. The 120 -h EC10 for N. pelliculosa was 0.0085 mg a.i./L, the 120 -h NOEC for S. costatum, A. flos-aquae were 0.033 mg a.i./L and ≥ 0.63 mg a.i./L, respectively. The 96 -h NOEC for D. subspicatus was 0.32 mg a.i./L.