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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: This study was selected as the key study because the information provided for the hazard endpoint is sufficient for the purpose of classification and labelling and/or risk assessment.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1996
Report Date:
1996

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
Remarks:
Conducted according to guideline in effect at the time of study conduct
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Purity: 99.7%

Sampling and analysis

Analytical monitoring:
yes
Details on sampling:
- Concentrations: Samples were collected from each concentration prior to its transfer to replicate test vessels at 0 hours and with pooled samples from each replicate after 72 hours
- Sampling method: GC equipped with flame ionizatin detector
- Sample storage conditions before analysis: Not reported

Test solutions

Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION: A 1000 mg/L stock solution was formulated by combining test substance and dilution water in a glass jar. The test substance was added below the water surface with a syringe. The jar was filled to capacity to eliminate head space and was tightly capped. The stock solutions were placed on an orbital shaker adjusted to approximately 150 rpm and incubated at approximately 30°C for 24 hours. Solutions were then incubated at 20±1°C for 24 hours without shaking. Dilution water used to formulate test media and for the control was shaken and incubated in the same manner as the stock solutions. Following the 48-hour incubation, the stock solution was carefully removed from the glass jar, and an effort was made to avoid collecting insoluble test substance. The stock solution was used immediately to formulate test media. Water used for all toxicity testing was sterile enriched media. The dilution water contained <10 mg/L particulate matter.

Test organisms

Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Strain: Selenastrum capricornutum
- Age of inoculum (at test initiation): The subsample of algae used to inoculate media at the start of the test came from a 7-day-old culture

ACCLIMATION PERIOD: 14 days

Study design

Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h

Test conditions

Hardness:
Not reported
Test temperature:
23.5°C
pH:
pH ranged from 7.5-10.5
Dissolved oxygen:
Not reported
Nominal and measured concentrations:
Nominal concentrations: 0, 7.8, 16, 32, 63, and 126 mg/L
Measured concentrations (initial): Not Detected, 7.28, 15.0, 26.5, 53.5, and 120 mg/L
Measured concentrations (final): Not detected at all concentrations
Details on test conditions:
TEST SYSTEM
- Test vessel: 250 mL glass Erlenmeyer flasks; because of the volatile nature of the test substance, test vessels were sealed and were not opened during the exposure period.
- Initial cells density: 10000 cells/mL
- Control end cells density: 652000 cells/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: Not reported

OTHER TEST CONDITIONS
- Photoperiod: 24 hour light and 0 hour dark
- Light intensity and quality: approximately 110 µEin/m2sec
- Test vessels were closed tightly with screw caps and randomly arranged on a rotary shaker adjusted to 100 rpm in an incubator during the test

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: Visually by means of direct microscopic examination with a hemocytometer at 0 and 72 hours

TEST CONCENTRATIONS
- Range finding study data: A rangefinding test was conducted at 0 and 130 mg/L with test vessels loosley covered. At the conclusion of the test, the number of cells/mL at 130 mg/L was 73% of the control vessels. A second rangefinding test was conducted at 0, 60, 130, and 160 mg/L with test vessels loosley covered. At the conclusion of the test, the average number of cells/mL in the test vessels for each concentration was >100% of the control vessels. A third rangefinding test was conducted at 0, 1.0, 10, and 110 mg/L with test vessels closed tightly with screw caps. At the conclusion of the test, the number of cells/mL were: 93% (1.0 mg/L), 90% (10 mg/L), and 56% (110 mg/L) of the control vessels.

Results and discussion

Effect concentrationsopen allclose all
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 120 mg/L
Nominal / measured:
meas. (initial)
Basis for effect:
other: growth rate and biomass
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
120 mg/L
Nominal / measured:
meas. (initial)
Basis for effect:
other: growth rate and biomass
Details on results:
- Exponential growth in the control (for algal test): yes
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: Insoluble material was not observed in any test vessel during the test.
- Other: The algal population grew well, resulting in an average of 652,000 cells/mL in the control after 72 hours. No effects (size differences, unusual cell shapes, colors, flocculations, adherence of cells to test containers, or aggregation of cells) were noted during the test.
Reported statistics and error estimates:
The average specific growth rate was calculated as the natural log of the number of cells/mL at 72 hours, minus the natural log of the number of cells/mL at 0 hours, divided by 72. Results of the toxicity test were interpreted by standard statistical techniques, when possible. The effective concentrations (EC10, EC50, and EC90) values could not be calculated because growth at all concentrations of test substance was equal to at least 90% of the control growth at 72 hours. The no observed effect concentration (NOEC) was determined using a one-way analysis of variance (ANOVA) and Bonferroni’s test. It was calculated using both the number of cells/mL and the average specific growth rate in each test vessel at the end of the test.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
The study and the conclusions which are drawn from it fulfil the quality criteria (validity, reliability, repeatability).

72-hour EC50 >120 mg/L
72-hour NOEC = 120 mg/L
Executive summary:

The acute toxicity test to algae was performed under static conditions with 5 nominal concentrations (7.8, 16, 23, 63, and 126 mg/L) of test substance and a dilution water control at 24±1°C. The test substance was formulated into a supersaturated stock solution (1000 mg/L) in dilution water, mixed in a sealed container for 24 hours at 30°C, and allowed to equilibrate to test temperature for 24 hours. Water was carefully removed from the mixing vessel to avoid insoluble material and used immediately to initiate the toxicity test. Initial measured concentrations were ND, 7.28, 15.0, 26.5, 53.5, and 120 mg/L. Because of the volatile nature of the test substance, the test was performed in sealed 250 mL test vessels that contained 100 mL of test solution. Vessels were not opened during the exposure period.  Exposure of algae to the test substance for 72-hours resulted in and EC50 >120 mg/L, using either the number of cells/mL or the average specific growth rate. The highest tested concentration (120 mg/L) is the approximate limit of solubility of the test substance in algal media. The 72-hour NOEC is 120 mg/L when calculated using the number of cells/mL or the average specific growth rate.