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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
Study period:
From 09 to 13 april 2018
Reliability:
1 (reliable without restriction)

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2018
Report Date:
2018

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
no
Qualifier:
according to
Guideline:
other: OECD guidance document no. 23, GUIDANCE DOCUMENT ON AQUATIC TOXICITY TESTING OF DIFFICULT SUBSTANCES AND MIXTURES, adopted 14. Dec. 2000
Deviations:
not applicable
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent

Sampling and analysis

Analytical monitoring:
yes

Test solutions

Vehicle:
no

Test organisms

Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
Genus: Desmodesmus
Species: subspicatus
SAG Strain Number: 86.81
Taxonomic position: Chlorophyta - Chlorophyceae

The culture of Desmodesmus subspicatus was obtained in January 2016 by MBM Sciencebridge GmbH (Institut für Pflanzenphysiologie of Universität Göttingen). The algae are kept as stock culture on solid agar at 2 - 8 °C. From the stock culture, a permanent culture was prepared. From an aliquot of the permanent culture, the pre-culture was prepared.

Study design

Test type:
static
Water media type:
freshwater
Remarks:
The algal medium corresponds to the OECD TG 201 medium.
Limit test:
no
Total exposure duration:
72 h

Test conditions

Reference substance (positive control):
yes
Remarks:
Potassium dichromate K2Cr2O7 (CAS No. 7778-50-9)

Results and discussion

Effect concentrationsopen allclose all
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
ca. 119.32 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
ca. 94.42 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
ca. 32 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
ca. 97.87 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
cell number
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
ca. 81.89 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
cell number
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
ca. 32 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
cell number

Any other information on results incl. tables

Findings

The cell numbers were determined with an electronic particle counter, the details are given in chapter 16, Annex 2: Detailed Data. The means and standard deviations of the cell numbers of the blank control and the treatments are presented in the following table:

Nominal Concentration in mg/L

Parameter

CellNumber/mL

0 h

24 h

48 h

72 h

Blank control

Mean

2420

11153

56403

318640

Blank control

SD

0

1042

5668

28078

1

Mean

2420

10127

60200

296233

1

SD

0

771

3999

28223

3.2

Mean

2420

9533

40673

213680

3.2

SD

0

1756

10372

30790

10

Mean

2420

11487

60693

328980

10

SD

0

945

3231

2003

32

Mean

2420

11073

67180

349833

32

SD

0

775

9598

21496

100

Mean

2420

8293

27313

134787

100

SD

0

704

3110

15085

SD = Standard Deviation

Light intensity

 

0 h

24 h

48 h

72 h

Lightintensity[Lux]

5000

5000

5000

5000

pH values

Nominal Concentrationin mg/L

0 h

72 h

Blank control

7.6

7.9

1

7.6

8.6

3.2

7.6

8.4

10

7.6

8.2

32

7.7

8.8

100

7.7

8.9

Analytical determination

At the start and at the end of the test, the content of the test item in the test solutions was estimated by determination of the dissolved organic carbon (DOC) content in the test solutions using a carbonanalyser. Therefore IC and TC was measured for one replicate per treatment.

Because of the poor solubility, only in the highest concentration the test item could be detected in small quantities. Since the other treatments are all within the same range as the blank control, however, the statistical evaluation is based on the nominal values.

The details are given in the following tables:

Nominal
Concentration

MeasuredTC
 t = 0 h

MeasuredTC
 t = 72 h

MeasuredIC
 t = 0 h

MeasuredIC
 t = 72 h

mg/L

mg/L

mg/L

mg/L

mg/L

Blank control

7.42

6.59

7.09

5.86

1

7.59

6.24

7.13

5.43

3.2

7.57

6.71

7.23

6.11

10

7.83

6.24

7.25

5.26

32

8.13

5.78

7.17

4.63

100

9.25

8.39

7.09

6.65

LOQ (Limit of quantification) TC = 5.43 mg/L .

LOQ (Limit of quantification) IC = 2.03 mg/L.

Nominal
Concentration

Measured

DOC (TC-IC)
 t = 0 h

Measured DOC (TC-IC)
 t = 72 h

Measured

DOC minus blank control
t = 0 h

Measured

DOC minus blank control

t = 72 h

mg/L

mg/L

mg/L

mg/L

mg/L

Blank control

0.33

0.73

--

--

1

0.46

0.81

0.14

0.08

3.2

0.34

0.60

0.02

-0.14

10

0.58

0.98

0.25

0.25

32

0.96

1.14

0.63

0.41

100

2.17

1.74

1.84

1.01

 

Nominal
Concentration Test Item

Calculated

Concentration

 Test Item
 t = 0 h

Calculated

Concentration

 Test Item
 t = 72 h

% of Nominal concentration
t = 0 h

% of Nominal concentration
t = 72 h

mg/L

mg/L

mg/L

%

%

Blank control

--

--

--

--

1

0.2

0.1

19

11

3.2

0.0

-0.2

1

-6

10

0.4

0.4

4

4

32

0.9

0.6

3

2

100

2.6

1.4

3

1

 

Growth rate, yield

Nominal Concentration in mg/L

Parameter

GrowthRate

(0-72h) [day-1]

Yield (0-72h)
[Cell Concentration/mL]

Blank control

Mean

1.63

316220

SD

0.03

28078

1

Mean

1.60

293813

SD

0.03

28223

3.2

Mean

1.49

211260

SD

0.05

30790

10

Mean

1.64

326560

SD

0.00

2003

32

Mean

1.66

347413

SD

0.02

21496

100

Mean

1.34

132367

SD

0.04

15085

SD = Standard Deviation

 

Inhibition

Nominal concentration in mg/L

% Inhibition

GrowthRate (0-72h)

Yield(0-72h)

Blank control

0

0

1

1.5

7.1

3.2

8.3

33.2

10

-0.7

-3.3

32

-2.0

-9.9

100

17.7

58.1

 

Parameter

Value

95% confidenceinterval

NOEC (GrowthRate) 72 h

32mg/L

--

NOEC (Yield) 72 h

32 mg/L

--

LOEC (GrowthRate) 72 h

100mg/L

--

LOEC (Yield) 72 h

100mg/L

--

72h ErC10

94.42 mg/L

n.d.

72h EyC10

81.89 mg/L

n.d.

72h ErC50

119.32 mg/L

n.d.

72h EyC50

97.87 mg/L

n.d.

n.d. not determinable due to mathematical reasons

Validity

Parameter

Validitycriteria

Observed value

Assessment

Increase factorbiomass

factor 16in72 h

132

Valid

Mean coefficient of variation of daily growth rates

max. 35%

8%

Valid

Coefficient of variation of average growth rate during the whole test period

max. 7%

2%

Valid

 

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
A GLP-study has been performed to assess the toxicity of the test item againstDesmodesmussubspicatusaccording to OECD 201 resp. EU C.3. The study was performed using 5 concentrations ranging from 1 to 100 mg/L nominal concentration. Incubation time was 72 hours. Significant inhibition of algal growth was observed at the highest concentration. The following results for the test item were determined:
NOECr = 32 mg/L
ErC50 = 119.32 mg/L
ErC10 = 94.42 mg/L
NOECb = 32 mg/L
EbC50 = 97.87 mg/L
EbC10 = 81.89 mg/L
Executive summary:

A GLP-study has been performed to assess the toxicity of the test item againstDesmodesmussubspicatusaccording to OECD 201 resp. EU C.3. The study was performed using 5 concentrations ranging from 1 to 100 mg/L nominal concentration. Incubation time was 72 hours. The cell concentration of each replicate was determined by measuring the cell numbers every 24 hours with an electronic particle counter. Growth rate µ and the yield were determined from the cell number at the respective observation times.

Significant inhibition of algal growth was observed at the highest concentration.

At the start and at the end of the test, the content of the test item in the test solutions was estimated by determination of the dissolved organic carbon (DOC) content in the test solutions using a carbonanalyser. Because of the poor solubility, only in the highest concentration the test item could be detected in small quantities. Since the other treatments are all within the same range as the blank control, however, the statistical evaluation is based on the nominal values.

The slight decrease in the test item concentration at the end of the test may be due to presence of the test organism (adsorption or ingestion onto the algae cells). Since the algae cells have been removed for DOC measurement.

The 72h-EC50 values of potassium dichromate (K2Cr2O7, CAS No. 7778-50-9) were determined in a separate reference test. The values lay within the range of the laboratory (growth rate 0.73 - 1.10 mg/L, yield 0.21 – 0.66 mg/L).

The following results for the test item were determined:

Endpoint

NOEC

LOEC

EC10

EC50

Growth Rate

32 mg/L

100 mg/L

94.42 mg/L

119.32 mg/L

Yield

32 mg/L

100 mg/L

81.89 mg/L

97.87 mg/L