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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Administrative data

Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2009
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP - Guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2009

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Version / remarks:
(2006)
GLP compliance:
yes (incl. QA statement)

Test material

Constituent 1
Chemical structure
Reference substance name:
Benzothiazole
EC Number:
202-396-2
EC Name:
Benzothiazole
Cas Number:
95-16-9
Molecular formula:
C7H5NS
IUPAC Name:
1,3-benzothiazole
Details on test material:
- Name of test material (as cited in study report): Benzothiazol
- Analytical purity: 97 %

Sampling and analysis

Analytical monitoring:
yes
Details on sampling:
Sampling schedule
- Control : at 0 and 72 hours
- Test concentrations : at 0 and 72 hours

Test solutions

Vehicle:
no

Test organisms

Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Strain: No. 86.81 SAG
- Source (laboratory, culture collection): Institute of Plant Physiology at the University of Göttingen (Germany), "The Collection of Algal Cultures"
- Method of cultivation: exponentially-growing stock cultures; 23 +/- 2°C; nutrient medium according to BRINGMANN & KÜHN (1977)
- initial cell density: ca 5000 cells/ml

ACCLIMATION
- Acclimation period: 3 days prior to test
- Culturing media: same as in test
- Culturing conditions: 23 ± 2 °C

Study design

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

Test conditions

Test temperature:
21 - 25 °C (± 2 °C)
pH:
7.3 - 8.0
Nominal and measured concentrations:
- nominal concentrations: 6.3, 12.5, 25, 50 and 100 mg/l
- measured concentrations: 5.1, 10.4, 21.0, 41.7 and 85.8 mg/l
- 5 test concentrations
- 1 control
Details on test conditions:
TEST SYSTEM
- Test vessel:
- Material, size, headspace, fill volume: 300 mL Erlenmeyer flasks with cotton stoppers
- Initial cells density: ca. 5000 cells/ml
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3


GROWTH MEDIUM
- Standard medium used: yes => OECD TG 201 medium


TEST MEDIUM / WATER PARAMETERS
- Culture medium different from test medium: yes (culture medium: according to Bringmann and Kuehn, 1977; test medium: according to OECD 201)


OTHER TEST CONDITIONS
- Photoperiod:continuous uniform illumination
- Light quality: 400 - 700 nm
- Light intensity: 60 - 120 µE. x m-2 x s-1 (equivalent to 4000 - 8000 lx)


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: microcell counter (Sysmex F300, Digitana)

Results and discussion

Effect concentrationsopen allclose all
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
48.7 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL: 45.4 - 52.3
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
21.9 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: 95% CL: 18.5 - 24.9
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
5.1 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
growth rate
Reported statistics and error estimates:
All calculations were carried out using the statistics programme ToxRatPro Version 2.10 (released 19.02.2009).

Any other information on results incl. tables

The results are expressed in terms of measured initial concentrations.

Effective concentrations ranged from 80.2-85.8% of nominal values at 0 hours, and from 71.3-84.8% of nominal values at 72 hours, respectively. As the concentration of the test substance fell below 80% results must be based on measured values.

Based on initial concentrations values ranged from 88.8-98.8% after 72 hours of exposure, which indicates that the test substance in general remained stabile over the exposure period.

In such cases results must be based on the measured initial test substance concentration.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Executive summary:

Lanxess, 2009:

In a GLP study according to OECD TG 201 the adverse effect of Benzothiazol on the yield and on the growth rate of the freshwater algal species Desmodesmus subspicatus was assessed. Exponentially growing algal cells were exposed to a range of nominally concentrations of 6.3, 12.5, 25, 50 and 100 mg/L. After an exposure period of 72 hours an EC50 of 48.7 mg/l, an EC10 of 21.9 mg/l and a NOEC of 5.1 mg/l was found based on the growth rate. These results are expressed in terms of measured initial concentrations.