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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:
From July 22, 2016 to November 18, 2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)
GLP compliance:
yes
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
- Source (laboratory, culture collection): National Chiayi University Freshwater Bioresource Center
- Acclimation period: 2-4 days
Water media type:
freshwater
Total exposure duration:
72 h
Test temperature:
21-24 °C
Nominal and measured concentrations:
0.34, 0.58, 0.98, 1.67 and 2.84 mg/L.
Details on test conditions:
- Test vessel: 125 mL glass flask
- Test volume: 60 mL
- Type of cover: sealed with silicone plugs
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3
- Light intensity and quality: 4440-8880 lux
Duration:
72 h
Dose descriptor:
EC50
Remarks:
ErC50
Effect conc.:
2.81 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Remarks:
EyC50
Effect conc.:
0.76 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass

Table 1. The algal biomass for the definitive test

Group

(mg/L)

Mean of algal biomass (×104cells/mL) ± standard deviation

Day 0

Day 1

Day 2

Day 3

Control group

0.00

1.00 ± 0.00

4.41 ± 0.21

15.61 ± 2.25

52.86 ± 2.82

Test group

2.84

1.00 ± 0.00

2.74 ± 0.13

5.15 ± 0.21

7.08 ± 0.12

1.67

1.00 ± 0.00

2.93 ± 0.16

8.67 ± 0.81

19.90 ± 3.92

0.98

1.00 ± 0.00

3.00 ± 0.97

8.12 ± 1.81

17.21 ± 7.65

0.58

1.00 ± 0.00

4.32 ± 0.29

12.25 ± 2.38

34.72 ± 4.05

0.34

1.00±0.00

4.32 ± 0.15

14.42 ± 1.53

40.70 ± 3.05

Table 2. Theaverage specific growth ratefor the definitive test

Group

(mg/L)

Mean of average specific growth rate (d-1) ± standard deviation

(Coefficient of variation [%])

Day 0-1

Day 1-2

Day 2-3

Day 0-3

Control group

0.00

1.48 ± 0.05

(3.17)

1.26 ± 0.10

(7.88)

1.23 ± 0.10

(7.96)

1.32 ± 0.02

(1.33)

Test group

2.84

1.01 ± 0.05

(4.78)

0.63 ± 0.04

(6.89)

0.32 ± 0.03

(10.51)

0.65 ± 0.01*

(0.83)

1.67

1.07 ± 0.05

(5.06)

1.08 ± 0.12

(10.85)

0.82 ± 0.11

(13.96)

0.99 ± 0.07*

(7.06)

0.98

1.07 ± 0.31

(29.24)

1.01 ± 0.15

(14.64)

0.71 ± 0.21

(29.41)

0.93 ± 0.14*

(14.79)

0.58

1.46 ± 0.07

(4.67)

1.03 ± 0.14

(13.20)

1.05 ± 0.22

(20.50)

1.18 ± 0.04

(3.31)

0.34

1.46 ± 0.03

(2.36)

1.20 ± 0.13

(10.81)

1.06 ± 0.22

(20.89)

1.23 ± 0.03

(2.03)

Table 3.The percent inhibition in average specific growth rate and percent inhibition of yield for the definitive test

Group

(mg/L)

Logarithm of concentration

(mg/L)

Percent inhibition in average specific growth rate (%)

Percent inhibition of yield (%)

2.84

0.45

50.27

88.06

51.09

88.51

50.66

88.28

1.67

0.22

31.03

72.19

21.32

58.21

22.51

60.24

0.98

-0.01

36.84

78.31

17.84

51.75

34.63

76.15

0.58

-0.24

13.72

42.84

7.82

27.24

10.51

34.82

0.34

-0.47

3.28

12.53

7.94

27.61

5.26

19.28

Table 4. ECX and 95% confidence interval for the definitive test

Parameter

ErC10a

ErC20

ErC50

EyC10b

EyC20

EyC50

ECX(mg/L)

0.54

0.78

2.81

< 0.34

< 0.34

0.76

95% confidence interval-lower

< 0.34

0.62

2.29

< 0.34

< 0.34

0.65

95% confidence interval-upper

0.64

1.06

> 2.84

< 0.34

0.38

1.06

a ErCxwas calculated by percent inhibition in average specific growth rate.

b EyCxwas calculated by percent inhibition of yield.

 

Table 5. The pH value for the definitive test

Group

(mg/L)

Mean of pH value ± standard deviation

Day 0

Day 3

Control group

0.00

7.70 ± 0.05

7.84 ± 0.07

Test group

2.84

7.65 ± 0.05

7.71 ± 0.04

1.67

7.55 ± 0.03

7.83 ±0.06

0.98

7.67 ± 0.13

7.74 ± 0.04

0.58

7.63 ± 0.22

7.62 ± 0.09

0.34

7.76 ± 0.09

7.60 ± 0.10

Validity criteria fulfilled:
yes
Conclusions:
According to OECD 201 test method, the ErC50 and the EyC50 of Everdirect SH12 was 2.81 mg/L and 0.76 mg/L respectively.
Executive summary:

This test using the procedures outlined in the SuperLab Study Plan for M62-151100086001EN which is based on the SOP for the OECD 201 (SOPE-504) and OECD 201 (OECD, 2011). The results of this OECD 201 test for Everdirect SH12 show that test validity criteria was met. In the alga growth inhibition test (definitive test), the test article concentrations applied were 0.34, 0.58, 0.98, 1.67 and 2.84 mg/L. Under the test conditions, the ErC50 and the EyC50 of Everdirect SH12 was 2.81 mg/L and 0.76 mg/L respectively.

Description of key information

Respectively, the ErC50 and the EyC50 of Everdirect SH12 was 2.81 mg/L and 0.76 mg/L for Pseudokirchneriella subcapitata (OECD TG201).

Key value for chemical safety assessment

EC50 for freshwater algae:
2.81 mg/L

Additional information

The biomass in the control group have increased exponentially by a factor of at least 16 within the 72-hour test period. The specific growth rate in the control group was more than 0.92 d-1. The mean coefficient of variation for specific growth rates (Day 0-1, Day 1-2, Day 2-3, and Day 0-3) in the control group were not exceed 35%. The coefficient of variation of average specific growth rates during the whole test period in replicate control groups were not exceed 7%. The variation in the pH values in the beginning and end of the tests was less than 1.5 units. Under the test conditions, the ErC50 and the EyC50 of Everdirect SH12 was 2.81 mg/L and 0.76 mg/L respectively.