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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:
2013-02-05 to 2013-02-08
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study, GLP.
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Version / remarks:
(2006)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
The limit concentration and the control were analytically verified via HPLC-DAD after 0 hours (test start) and 72 hours (test end). Samples at test start were taken from additional replicates without algae. After 72 hours samples were taken directly from pooled test replicates.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
The stock solution (100 mg/L test item was weighed out) was freshly prepared with dilution water and dispersed by agitation.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Common name: Green alga
- Strain: Desmodesmus subspicatus CHODAT SAG 86.81
- Source (laboratory, culture collection): Sammlung von Algenkulturen (SAG), Pflanzenphysiologisches Institut der Universität Göttingen, Nikolausberger Weg 18, 37073 Göttingen, Germany
- Age of inoculum (at test initiation): four day old preculture
- Method of cultivation: Fresh stocks were prepared every month on Z-Agar. Light intensity: 35 – 70 µE/m²/s for 24 h per day

ACCLIMATION
- Acclimation period: no data
- Culturing media and conditions (same as test or not): Nutrient medium Z according to LÜTTGE et al. (1994)
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Test temperature:
21.0 - 22.5°C
pH:
initial: control 8.24; test item 8.17
final: control 8.35; test item 8.19
Nominal and measured concentrations:
nominal: 0, 100 mg/L (measured concentrations were within 98% of nominal at the end of the test)
Details on test conditions:
TEST SYSTEM
- Test vessel: sterile Erlenmeyer flasks, volume: 250 mL, sealed with cotton wool plugs, 100 mL test volume
- Aeration: agitation, test containers were placed on a rotary shaker and oscillated at approximately 70 rpm
- Initial cells density: 4332 cells/mL
- Control end cells density: 697650 cells/mL (mean)
- No. of vessels per concentration (replicates): 6
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: according to OECD guideline 201

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: no
- Photoperiod: 24 h light
- Light intensity and quality: 60 – 120 µE/m²/s (measured 69.4 µE/m²/s, CV 6.16%)

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
Cell density was measured daily via Chlorophyll-a-fluorescence, excitation at 436 nm, emission at 685 nm. Dilution water was used as background signal

TEST CONCENTRATIONS
- Range finding study
- Test concentrations: 10, 100 mg/L
- Results used to determine the conditions for the definitive study: growth rate inhibition 0% at 10 mg/L and 2% at 100 mg/L
Reference substance (positive control):
yes
Remarks:
Potassium dichromate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
biomass
Details on results:
- microscopic evaluation of the cells at start and end of the incubation period revealed no morphological and microbiological (e.g. contamination with bacteria) abnormalities
Results with reference substance (positive control):
- Results with reference substance valid? yes
- ErC50: 0.631 mg/L, 95% CL 0.583 - 0.687; valid range: 0.682 ± 0.452 mg/L
- EyC50: 0.256 mg/L, 95% CL 0.247 - 0.265; valid range: 0.314 ± 0.144 mg/L
Reported statistics and error estimates:
EC10- and EC50-values of the growth rate and yield inhibition after 72 hours were calculated by sigmoidal dose-response regression. Calculation of the confidence intervals EC10- and EC50-values were carried out using standard procedures.

Mean cell densities [cells/mL] during the final test:

Geometric mean measured test item concentration[mg/L]

Exposure time [h]

0

24

48

72

100

4332

19755

114898

655114

Control

4332

21752

139584

697650

  

Growth rate, yield during the final test: 

Geometric mean measured test item concentration [mg/L]

Growth rate [/d]

Rate-related inhibition [%]

Yield [cells/mL]

Inhibition of yield [%]

100

1.67 (-)

1.15

650782 (-)

 6.14

control

1.69

693318

 

Statistically significant differences of growth rates and yield compared to control values are marked (+), not significant differences are marked (-).

 

 

The study meets the validity criteria of the guideline:

- The cell growth increased 161-fold after 72 hours in the control (required: at least 16-fold).

- The mean coefficients of variation for section-by-section specific growth rates (days 0-1, 1-2 and 2-3) in the control cultures was 13.9% (required: < 35%).

- Coefficient of variation of average specific growth rates during the whole test period in replicate control cultures was 2.42 % (required: < 7 %).

Validity criteria fulfilled:
yes
Conclusions:
In this study THFMA caused no inhibition on growth of the freshwater green alga Desmodesmus subspicatus after 72 hours exposure. The nominal NOEC for inhibition of specific growth rate and yield after 72 hours was 100 mg/L. The 72 h ErC10 and ErC50 were > 100 mg/L.
Executive summary:

In a 72 hour acute toxicity study, the cultures of Desmodesmus subspicatus CHODAT SAG 86.81 were exposed to THFMA at concentrations of nominal 0 (control) and 100 mg/L under static conditions in accordance with the OECD guideline 201 (adopted 23 March 2006). 

The test item caused no inhibition of growth. The NOEC-values for inhibition of growth rate and yield after 72 hours was 100 mg/L (based on the nominal concentration of the test item). The 72 h EC10 and EC50 values of growth rate and yield were all > 100 mg/L (nominal).

Microscopic evaluation of the cells at start and end of the incubation period revealed no morphological abnormalities.

 

Results Synopsis

 

Test Organism: Desmodesmus subspicatus CHODAT SAG 86.81

Test Type: Static

 

72 hr ErC50: > 100 mg/L              

72 hr EyC50: > 100 mg/L

72 hr ErC10: > 100 mg/L

72 hr EyC10: >100 mg/L 

72 hr NOEC(growth rate): 100 mg/L              

72 hr NOEC(yield): 100 mg/L              

 

Endpoint(s) Effected:  growth rate, yield

NOTE: Any of data in this dataset are disseminated by the European Union on a right-to-know basis and this is not a publication in the same sense as a book or an article in a journal. The right of ownership in any part of this information is reserved by the data owner(s). The use of this information for any other, e.g. commercial purpose is strictly reserved to the data owners and those persons or legal entities having paid the respective access fee for the intended purpose.

Description of key information

72 h ECr10 > 100 mg/L / 72 h ErC50 > 100 mg/L; OECD guideline 201; GLP

Key value for chemical safety assessment

EC50 for freshwater algae:
100 mg/L
EC10 or NOEC for freshwater algae:
100 mg/L

Additional information

One short-term study in freshwater algae is available for THFMA, which is considered reliable without restriction (Klimisch score 1).

In a 72 hour acute toxicity study, the cultures of Desmodesmus subspicatus CHODAT SAG 86.81 were exposed to THFMA at concentrations of nominal 0 (control) and 100 mg/L under static conditions in accordance with the OECD guideline 201 (adopted 23 March 2006). 

Microscopic evaluation of the cells at start and end of the incubation period revealed no morphological abnormalities. The test item caused no inhibition of growth. The NOEC-values for inhibition of growth rate and yield after 72 hours was 100 mg/L; the 72 h EC10 and EC50 values of growth rate and yield were all > 100 mg/L (based on the nominal concentration of the test item).