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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:
28.03.2019 - 24.06.2019
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
yes
Vehicle:
yes
Remarks:
water
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
A saturated solution with a nominal loading of 100 mg test item/L was prepared once 24 ± 1 hour prior to the start of the exposure. An appropriate amount of the test item was weighed out. The test
item was applied onto a glass slide. The glass slide with the test item was inserted into a brown glass bottle with an appropriate amount of dilution water (see Table 2). The saturated solution was
stirred for 24 ± 1 hours (1100 rpm, room temperature) with a magnetic stirrer. After a separation phase of 1 hour the saturated solution was removed by siphoning from the middle of the flask.
Undissolved particles were removed by membrane filtration (membrane filter 0.45 μm, RC, Macherey-Nagel). The filter was saturated in order to avoid adsorption during the filtration. The first
25 ml of the filtrate were discarded. The filtration was interrupted for 15 minutes to allow adsorption and saturation of the filter material with dissolved test item. Thereafter, the filtration was
continued. The next 25 ml were discarded. The following test item solution was used in the test. During filtration, the filter was always kept covered. The saturated solution was checked via laser beam
(Tyndall effect) for undissolved test item. The Tyndall effect was slightly positive.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
Test organism: Pseudokirchneriella subcapitata HINDÁK CCAP 278/4 (axenic)
Origin:
Sammlung von Algenkulturen (SAG), Pflanzenphysiologisches Institut der Universität Göttingen, Göttingen, Germany
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Hardness:
32 mg CaCO3/L
Test temperature:
21.0-23.0 °C
pH:
7.92 - 9.48
Nominal and measured concentrations:
The geometric mean measured test item concentrations were calculated to: 5.42 - 17.9 - 56.6 - 176 - 406 μg/L
nominal: 6.25, 12.5, 25.0, 50.0, 100.0 mg/L
Details on test conditions:
The study was performed as a static test in open vessels under culture conditions. The flasks contained 100 mL either reconstituted water or test medium (test item group).
The duration of exposure was 72 hours. The algal biomass in each flask was determined daily during the exposure period via Chlorophyll a-fluorescence.
Microscopic evaluation of the cells at the start and at the end of the incubation period was carried out.
Reference substance (positive control):
yes
Remarks:
potassium dichromate
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
81.4 µg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: SD: 70.6 - 108 µg/L
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
48.5 µg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: SD: 39.5 - 55.3 µg/L
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
5.42 µg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Results with reference substance (positive control):
The toxicity of potassium dichromate (SIGMA ALDRICH, batch number MKBV0900V, purity 99.0%, GAS RN 7778-50-9) to the unicellular freshwater green alga Pseudokirchnerief/a subcapitata was determined over a period of 72 hours from 2019-03-05 to 2019-03-08. The reference item toxicity is in the valid range following test facility SOPs.
ErC50 = 0.752 mg/L, EyC50 = 0.405 mg/L
Reported statistics and error estimates:
The EC50-values for inhibition of growth rate (ErC50) and yield (EyC50) after 72 hours were 81.4 (70.6 - 108) μg/L and 37.1 (27.2 – 49.6) μg/L, respectively.

1) Cell Densities


Geometric mean measured test item concentration

Replicate

Cell density [cells/mL]

[µg/L]

No.

0 hours

24 hours

48 hours

72 hours

406

1

5416

5922

3965

2989

2

5416

5010

4686

2960

3

5416

7704

5241

2663

Mean

5416

6212

4631

2871

176

1

5416

7950

5143

2775

2

5416

6750

5810

3892

3

5416

10574

8218

8130

Mean

5416

8425

6390

4932

  56.6

1

5416

14427

73953

408228

2

5416

17620

136487

969509

3

5416

16259

133118

839338

Mean

5416

16102

114519

739025

  17.9

1

5416

24379

199859

1306861

2

5416

12319

186666

1148262

3

5416

20193

195020

1483764

Mean

5416

18964

193848

1312962

    5.42

1

5416

21605

231121

1727213

2

5416

24688

263649

1899930

3

5416

22038

226662

1876855

Mean

5416

22777

240477

1834666

Control

1

5416

25217

232133

2093043

2

5416

23540

242580

1970029

3

5416

23953

272771

1941113

4

5416

25540

274612

1876904

5

5416

21544

212535

1664805

6

5416

20081

194143

1491943

Mean

5416

23313

238129

1839640



2) Evaluation after 72 hours
Statistically significant differences of growth rates and yield compared to control values are marked (+), not significant differences are marked (-).

Geometric mean measured test item concentration

Replicate

Growth rate

Inhibition of growth rate

Yield

Inhibition of yield

[µg/L]

No.

[d-1]

[%]

[cells/mL]

[%]

406

1

 

-0.198

100

 

-2427

100

2

 

-0.201

100

 

-2456

100

3

 

-0.237

100

 

-2753

100

Mean

(+)

-0.212

100

(+)

-2545

100

176

1

 

-0.223

100

 

-2641

100

2

 

-0.110

100

 

-1524

100

3

 

0.135

93

 

2714

100

Mean

(+)

-0.066

98

(+)

-484

100

  56.6

1

 

1.44

26

 

402812

78

2

 

1.73

11

 

964093

47

3

 

1.68

13

 

833922

55

Mean

(+)

1.62

17

(+)

733609

60

  17.9

1

 

1.83

6

 

1301445

29

2

 

1.79

8

 

1142846

38

3

 

1.87

4

 

1478348

19

Mean

(+)

1.83

6

(+)

1307546

29

    5.42

1

 

1.92

1

 

1721797

6

2

 

1.95

-1

 

1894514

-3

3

 

1.95

0

 

1871439

-2

Mean

(-)

1.94

0

(-)

1829250

0

Control

1

 

1.99

 

 

2087627

 

2

 

1.97

 

 

1964613

 

3

 

1.96

 

 

1935697

 

4

 

1.95

 

 

1871488

 

5

 

1.91

 

 

1659389

 

6

 

1.87

 

 

1486527

 

Mean

 

1.94

 

 

1834224

 


3) Section-by-Section and Average Specific Growth Rates of the Control Group (0 - 72 hours)

 

Replicate No.

Specific growth rate [d-1]

Mean

(0 - 72 hours)

SD

±

CV
[%]

Mean CV [%]

section-by-section

0 - 24 hours

24 - 48 hours

48 - 72 hours

Control

1

1.54

2.22

2.20

1.99

0.388

19.5

23.2

2

1.47

2.33

2.09

1.97

0.446

22.7

3

1.49

2.43

1.96

1.96

0.473

24.1

4

1.55

2.38

1.92

1.95

0.413

21.2

5

1.38

2.29

2.06

1.91

0.472

24.7

6

1.31

2.27

2.04

1.87

0.500

26.7

 

 

 

Mean

1.94

 

 

 

 

 

SD ±

0.04

 

 

 

 

CV [%]

2.15

 


4) Environmental Conditions

Geometric mean measured test item concentration

pH-values

[µg/L]

Start; 0 hours

End; 72 hours

406

8.10

7.92

176

8.01

8.07

  56.6

8.02

8.55

  17.9

8.01

9.39

    5.42

8.04

9.48

Control

8.11

9.47

Room temperature [°C]:

min.: 21.0

max.: 23.0

mean value: 22.0

 

Light intensity
[lux]

n = 24

mean value: 5499

range of the measured values: 4751 to 6050 equalling -13.6 to 10.0%

CV [%]: 6.01



5) Measured Concentration of the test material in the Definitive Test with Algae

Sampling date

Fresh Media,
0 hours

Old Media,
72 hours

 

Dilution level of the saturated Solution [%]

Test item

 

Meas. conc.

[µg/L]

Meas. conc.

[µg/L]

%

Geometric mean measured concentration

[µg/L]

100

485

341

70

406

50.0

253

122

48

176

25.0

132

24.3

18

  56.6

12.5

60.6

5.30

9

  17.9

6.25

27.9

1.05

4

    5.42

Control

< LOQ

< LOQ

 



Validity criteria fulfilled:
yes
Conclusions:
The 72-h EC50 for growth rate was determined to be 81.4 µg/L and the 72-h EC10 value was determined to be 48.5 µg/L based on growth rate.
Executive summary:

The information for this endpoint study record was obtained from an experimental study. The OECD GLP criteria were met and the methods applied are fully compliant with OECD TG 201.

The study was conducted under static conditions with an initial cell density of 5416 cells/mL.

A saturated solution with a nominal loading of 100 mg test item/L was prepared once at room temperature 24 ± 1 hour prior to the start of the exposure. An appropriate amount of the test item was weighed out. The test item was applied onto a glass slide. The glass slide with the test item was inserted into a glass bottle with an appropriate amount of dilution water (see Table 2). The saturated solution was stirred for 24 ± 1 hour (1100 rpm, room temperature) with a magnetic stirrer. After a separation phase of 1 hour (at room temperature), the saturated solution was removed by siphoning (from the approximate middle of the glass flask) and used in the test. The saturated solution was checked via laser beam (Tyndall effect) for undissolved test item. The Tyndall effect was slightly positive.

Five test item concentrations were tested in a geometrical series with a dilution factor of 2: 6.25 - 12.5 - 25.0 - 50.0 - 100% of the saturated solution, corresponding to the geometric mean measured test item concentration of 5.42 – 17.9 – 56.6 – 176 – 406 µg/L. Three replicates were tested for each test item concentration and six replicates for the control. The environmental conditions were within the acceptable limits

.

The 72-h EC50 for growth rate was determined to be 81.4  µg/L and the 72-h EC10 value was determined to be 48.5 µg/L based on growth rate.

Description of key information

OECD 201: EC50 (72 h, Growth Rate) = 81.4 µg/L, EC10 (72 h, growth rate) = 48.5 µg/L

Key value for chemical safety assessment

EC50 for freshwater algae:
81.4 µg/L
EC10 or NOEC for freshwater algae:
48.5 µg/L

Additional information