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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:
12.03.2018 - 22.03.2018
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
Remarks:
For the determination of the growth curve not the cell amount was used, but the fluorescence. In a pre-test the correlation of cell amount and fluorescence was confirmed.
GLP compliance:
no
Analytical monitoring:
no
Details on sampling:
A stock solution was prepared with the test item. Different dilutions with ultrapure water were prepared thereof.
50 mL-test preparations contained 40 ml of the related dilution as well as 5 ml algal medium and 5 ml algal culture (consisting of algal medium and Desmodesmus subspicatus CHODAT). The tests were performed in duplicate over a 72 h period of time.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
20 – 22 °C
pH:
8.3 - 9.5
Nominal and measured concentrations:
0,1 mg/l, 0,5 mg/l, 1,25 mg/l, 2,5 mg/l, 5,0 mg/l, 10 mg/l, 20 mg/l
Details on test conditions:
In pre-tests it was found out that a direct correlation of growth rate and measurable fluorescence exists. Hence, the measurement of the fluorescence of all samples was performed using a fluorescence measuring device (Kontron) after 0, 24, 48 and 72 h.
Reference substance (positive control):
yes
Remarks:
K2Cr2O7
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
2.3 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: fluorescence

Table 2a: Fluorescence of all test samples with methylhydroquinone and control (=0 mg/l) in 72 h, test series 1

concentration [mg/l]

Fluorescence

0 h

24 h

48 h

72 h

I

II

mean

I

II

mean

I

II

mean

I

II

mean

0,00

6,6

6,1

6,35

10,9

10,5

10,7

12,7

12,7

12,7

16,8

16,7

16,75

0,10

6,6

6,3

6,45

9,5

7,7

8,6

10,4

10,3

10,4

13,8

13,8

13,80

0,50

6,6

7,7

7,15

9,1

9,1

9,1

10,7

9,7

10,2

14,0

14,0

14,00

10,00

6,7

7,2

6,95

7,8

7,6

7,7

7,7

8,8

8,3

10,6

10,4

10,50

20,00

7,5

7,4

7,45

6,5

6,4

6,5

7,7

7,0

7,4

8,5

8,7

8,60

 

Table. 2b: Fluorescence of all test samples with methylhydroquinone and control (=0 mg/l) in 72 h, test series 2 

concentration [mg/l]

Fluorecence

0 h

24 h

48 h

72 h

I

II

mean

I

II

 mean

I

II

 mean

I

II

mean

0,00

9,5

8,8

9,15

11,6

10,5

11,05

13,7

14,3

14

16,5

16,5

16,5

1,25

9,9

10

9,95

10,2

10,4

10,30

11,8

10,5

11,2

12,9

13,1

13,0

2,50

10,9

9,5

10,20

10,1

9,5

9,80

10,7

11,6

11,2

12,6

11,9

12,3

5,00

10,3

9,8

10,05

8,8

7,8

8,30

8,8

9,7

9,3

10,0

11,1

10,6

Table 3: Growth rate of Desmodesmus subspicatus CHODAT at different concentrations of test item methylhydroquinone in relation to the respective control (= 100%)

concentration [mg/l]

growth rate over 72 h

Desmodesmus subspicatus in %

0,10

71,73

0,50

69,49

1,25

54,03

2,50

48,94

5,00

45,01

10,00

33,77

20,00

32,39

Validity criteria fulfilled:
not specified
Conclusions:
The toxicity of methylhydroquinone to algae was investigated in a study acc. to OECD Guideline 201 (Alga, Growth Inhibition Test). The 72 h EC50 was determined to be 2.3 mg/L (based on recalculated initial concentrations).
Executive summary:

The toxicity of methylhydroquinone to algae was investigated in a study acc. to OECD Guideline 201 (Alga, Growth Inhibition Test). The effect concentration for growth rate is: EC50 (72 h) = 2,3 mg/L.

Description of key information

The toxicity of methylhydroquinone to algae was investigated in a study acc. to OECD Guideline 201 (Alga, Growth Inhibition Test). The effect concentration for growth rate is: EC50 (72 h) = 2,3 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
2.3 mg/L

Additional information