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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:
April 26-30, 1993
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Guideline study without GLP or analytical confirmation
Justification for type of information:
Please see Category Approach
Reason / purpose:
read-across source
Qualifier:
according to
Guideline:
EPA OTS 797.1050 (Algal Toxicity, Tiers I and II)
Deviations:
no
GLP compliance:
no
Analytical monitoring:
no
Vehicle:
no
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
Strain 1648, class Chlorophyceae originally obtained from Carolina Biological Supply Company; source is SLI culture
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
96 h
Test temperature:
24-25 degrees Celcius
pH:
7.5 at initiation. 9.6-10 at 96 hours
Nominal and measured concentrations:
0, 16, 31, 63, 130, 250, 500, 1000 mg/L active ingredient (nominal)
Details on test conditions:
TEST SYSTEM- Test vessel: - Type (delete if not applicable): closed - Material, size, headspace, fill volume: 125-mL Erlenmeyer flasks with 50 mL of test solution - Aeration: shaking table set at 100+/-10 rpm- Type of flow-through (e.g. peristaltic or proportional diluter): - Renewal rate of test solution (frequency/flow rate):- Initial cells density: 67 x 10+4 cells/mL (inoculated with 0.75 mL)- Control end cells density: - No. of organisms per vessel:- No. of vessels per concentration (replicates): 3- No. of vessels per control (replicates): 3- No. of vessels per vehicle control (replicates):GROWTH MEDIUM- Standard medium used: yes (AAP medium)- Detailed composition if non-standard medium was used:TEST MEDIUM / WATER PARAMETERS- Source/preparation of dilution water:- Total organic carbon:- Particulate matter:- Metals:- Pesticides:- Chlorine:- Alkalinity:- Ca/mg ratio:- Conductivity:- Culture medium different from test medium:- Intervals of water quality measurement: OTHER TEST CONDITIONS- Sterile test conditions: yes- Adjustment of pH:- Photoperiod: 24 hr light- Light intensity and quality: 350-425 footcandles and 3800-4600 lux. Duro-Test, Inc. Vita-Life fluorescent lights- Salinity (for marine algae):EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : - Determination of cell concentrations: [counting chamber - hemacytometer (Neubaure improved)- Chlorophyll measurement:- Other: TEST CONCENTRATIONS- Spacing factor for test concentrations: 2X- Justification for using less concentrations than requested by guideline: - Range finding study - Test concentrations: 0.010 to 1000 mg/L - Results used to determine the conditions for the definitive study: controls 104 and exposed ranged from 100 to 44 x10+4 cells/mL
Reference substance (positive control):
no
Key result
Duration:
96 h
Dose descriptor:
EC50
Effect conc.:
>= 230 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
cell number
Duration:
96 h
Dose descriptor:
NOEC
Effect conc.:
31 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
cell number
Details on results:
At test termination, cell fragments and bloated cells were observed in the 500 and 1000 mg A.I./L treatment levels while thin cells were observed in the 63, 130 and 250 mg A.I./L treatment levels. Normal algal cells were observed in the 16 and 31 mgA.I./L treatment levels and in the controls. The control cultures averaged 102 x 10+4 cells/mL at termination. Cell densities at 16, 31, 63, 130, 250, 500 and 1000 mg A.I./L averaged 96, 97, 76, 69, 59, 29 and 11 x 10+4 cells/mL at termination. Statistical analysis (William's test) demonstrated a significant reduction in cell density in the 63 mgA.I./L and higher treatment levels. The 96-hour no observed effect concentration for cell density was determined to be 31 mg A.I./L. The 96-hur EC10 and EC90 values were calculated to be 41 and 1300 mg A.I./L, respectively. No test concentration completely inhibited algal growth. A subsample of the composite of three replicates of the highest test concentration was diluted with fresh AAP medium for the determination of growth recovery. After six days in fresh medium the 1.6 x 10+4 cells/mL became 127 x 10+4 cells/mL. Therefore, it is concluded that the test substance has an algistatic rather than algicidal effect at 1000 mg A.I./L.
Reported statistics and error estimates:
The 95% confidence limits of the 96-hr EC50 are 47 to 1200 mg A.I./L.
Validity criteria fulfilled:
yes
Conclusions:
The test substance has an algistatic rather than algicidal effect at 1000 mg A.I./L.; the EC50 is 230 mg A.I./L

Description of key information

The key study reported a 96-hour EC50 of >= 230 mg/L active substance based on Selenastrum capricornutum (new name: Pseudokirchnerella subcapitata) cell density (with a 95% CL of 47 to 1200 mg/L). 

Key value for chemical safety assessment

EC50 for freshwater algae:
230 mg/L
EC10 or NOEC for freshwater algae:
31 mg/L

Additional information

The key study is a reliable 1993 USEPA Guideline study (EPA OTS 797.1500 - Algal Toxicity). The freshwater Selenastrum sp. was exposed to a range of nominal concentrations of the test substance, sodium xylenesulphonate that reported a 96 -hour EC50 of >= 230 mg/L active substance based on cell density (with a 95% CL of 47 to 1200 mg/L). There was an apparent dose response and the 96-hour NOEC was 31 mg/L. The test substance was observed to be algistatic but not algicidal at the highest concentration tested (1000 mg/L active substance).

Two supporting studies were available. A 1994 EPA Guideline study (EPA OTS 797.1500) with the test substance calcium xylenesulphonate was conducted under GLP requirements and with analytical confirmation reported a 96 -hour EC50 of 758 mg/L active substance (with a 95% confidence limit of 592-924 mg/L) and a NOEC of 240 mg/L based on growth rate of Selenastrum sp. A 1995 EU Guideline study (EU C.3 Algal Inhibition Test) of sodium toluenesulphonate conducted under GLP requirements and with analytical confirmation reported a 72 -hour EbC50 of 150 mg/L active substance based on cell density and a 72 -hour ErC50 of 310 mg/L based on specific growth rate of Scenedesmus sp. The 72 -hour NOEC is 40 mg/L active substance based on biomass.