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Toxicity to aquatic plants other than algae

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Endpoint:
toxicity to aquatic plants other than algae
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From 25 March 2015 to 24 April 2015
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 221 (Lemna sp. Growth Inhibition Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
Samples were taken from the control and each test group from the bulk test preparation on Day 0 and from the pooled replicates on Day 7. All samples were stored frozen prior to analysis. Duplicate samples were taken at each occasion and stored frozen for further analysis if necessary.
Only samples at the No Observe Effect Concentration (NOEC) were analyzed.
Vehicle:
no
Details on test solutions:
Range-finding Test
A nominal amount of test item (100 mg) was dissolved in culture medium and the volume adjusted to 1 liter to give a 100 mg/L test concentration from which a series of dilutions was made to give further test concentrations of 10, 1.0 and 0.1.0 mg/L.
Each of the prepared concentrations was inverted several times to ensure adequate mixing and homogeneity.


Definitive Test
A nominal amount of test item (200 mg) was dissolved in culture medium and the volume adjusted to 2 liters to give a 100 mg/L test concentration from which a series of dilutions was made to give further test concentrations of 32, 10, 3.2 and 1.0 mg/L.
Each of the prepared concentrations were inverted several times to ensure adequate mixing and homogeneity.
Test organisms (species):
Lemna minor
Details on test organisms:
The test was carried out using Lemna minor. A culture of Lemna minor was obtained from Canadian Phycological Culture Centre, University of Waterloo, Ontario, Canada. Cultures were maintained in the laboratory by the periodic replenishment of culture medium. The culture was maintained in the laboratory at a temperature of 24 ± 1ºC under continuous illumination (intensity approximately 7000 lux) for at least 7 days prior to the start of the test.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
7 d
Post exposure observation period:
None
Hardness:
No data
Test temperature:
The temperature and light intensity in the incubator were recorded daily.
pH:
The pH of each control and test flask was recorded on Day 0 and Day 7.
Dissolved oxygen:
No data
Salinity:
No data
Nominal and measured concentrations:
Range-finding Test: Nominal test concentrations of 0.10, 1.0, 10 and 100 mg/L
Definitive Test: Nominal test concentrations of 1.0, 3.2, 10, 32 and 100 mg/L
Details on test conditions:
Culture Medium
The culture medium used for both the range-finding and definitive tests was the same as that used to maintain the stock culture.

Procedure
Range-finding Test
The test concentrations to be used in the definitive test were determined by a preliminary range-finding test. The range-finding test was conducted by exposing Lemna minor to a series of nominal test concentrations of 0.10, 1.0, 10 and 100 mg/L for a period of 7 days.

The test was conducted in glass conical flasks (500 mL). Two replicate flasks were prepared for each control and test concentration. The test item was dissolved directly in culture medium.

A nominal amount of test item (100 mg) was dissolved in culture medium and the volume adjusted to 1 liter to give a 100 mg/L test concentration from which a series of dilutions was made to give further test concentrations of 10, 1.0 and 0.1.0 mg/L.

Each of the prepared concentrations was inverted several times to ensure adequate mixing and homogeneity.

The control group was maintained under identical conditions but not exposed to the test item.

At the start of the range-finding test the number of fronds present in each test and control culture was recorded along with observations on frond size, appearance, root length and number of colonies present. The flasks were then incubated at 24 ± 2 ºC under continuous illumination (intensity approximately 7000 lux) on a black, non-reflective surface for 7 days.
On Days 2 and 5 the test solutions were renewed, and observations on the test organisms were recorded on days 2, 5 and 7.

In order to determine the stability of the test item under test conditions a sample of each test concentration was taken for chemical analysis on Day 0 (fresh media) and Day 5 (old media). An additional sample of each test concentration was prepared on Day 0 and incubated alongside the test until Day 7 in order to determine stability over the entire test duration. All Day 0 and Day 5 samples were stored frozen prior to analysis.


Definitive Test
Based on the results of the range-finding test the following test concentrations were assigned to the definitive test: 1.0, 3.2, 10, 32 and 100 mg/L.


Experimental Preparation
A nominal amount of test item (200 mg) was dissolved in culture medium and the volume adjusted to 2 liters to give a 100 mg/L test concentration from which a series of dilutions was made to give further test concentrations of 32, 10, 3.2 and 1.0 mg/L.

Each of the prepared concentrations were inverted several times to ensure adequate mixing and homogeneity.

The concentration and stability of the test item in the test preparations were verified by chemical analysis on Day 0 and Day 7.


Exposure Conditions
As in the range-finding test glass conical flasks were used. Three flasks each containing 250 mL of solution were prepared for the control and each treatment group.

The control group was maintained under identical conditions but not exposed to the test item.

Each control and test flask was inoculated with 3 colonies of Lemna minor (total 9 fronds). The flasks were then incubated at 24 ± 2 ºC under constant illumination (intensity approximately 7000 lux) on a black, non-reflective surface for 7 days.

A static testing regime was employed.

Evaluations
Test Organism Observations
The number of fronds present in each test and control culture was recorded on days 0, 3, 5 and 7 along with observations on frond size, appearance, root length and number of colonies present.

In addition the dry weight of the fronds in each control and treatment group was determined on day 7. At the start of the test six replicate samples of fronds identical to those used to inoculate the test vessels were taken and the dry weight determined. At the end of the test dry weight of colonies from each control and test vessel was determined by blotting the colonies dry and drying at 60 °C to constant weight.

Data Analysis
Doubling Time
The doubling time (Td) of frond number, and hence performance of the test against the validation criterion of doubling time, was calculated for the control vessels using the following formula:

Td = ln 2/µ

Where:
µ = the average specific growth rate for the control vessels.


Response Variables
In order that the test results are acceptable to regulatory authorities worldwide, the effects on the growth of Lemna were evaluated using both response variables (a) and (b) described below:

a) Average specific growth rate: this response variable was calculated on the basis of changes in the logarithms of frond numbers, and in addition, on the basis of changes in the logarithms of dry weight over time (expressed per day) in the controls and each treatment group.

b) Yield: this response variable was calculated on the basis of changes in frond number, and in addition, on the basis of changes in dry weight in the controls and in each treatment group until the end of the test.

It should be noted that toxicity values calculated using these two response variables are not comparable and the difference must be recognized when using the results of the test. ECx values based upon average specific growth rate (ErCx) will be higher than results based upon yield (EyCx) under the test conditions of this Guideline, due to the underlying mathematics of the respective approaches. This is not to be interpreted as a difference in sensitivity between the response variables: simply the values are different mathematically. The concept of average specific growth rate is based upon the general exponential growth pattern of Lemna in non-limited cultures. Toxicity is estimated on the basis of the effects on the growth rate without being dependent on the absolute level of the specific growth rate of the control, slope of the concentration-response curve or on test duration. Results based upon yield are dependent upon all these variables.

Average Specific Growth Rate
The average specific growth rate for a specific period was calculated as the logarithmic increase in the growth variables -frond numbers and dry weight - using the formula below for each replicate of the control and treatment groups:

µi-j = (1n(Nj) – 1n(Ni)) / t

Where:
µi-j = average specific growth rate from time i to j
Ni = number of fronds or dry weight in the test or control vessel at time i
Nj = number of fronds or dry weight in the test or control vessel at time j
t = time period from i to j

For each control and treatment group the mean value for growth rate along with the standard deviation was calculated.

Percentage inhibition of growth rate (Ir) was calculated as follows:

%Ir = ((µc - µt) / µc) x 100

Where:
% Ir = percentage inhibition of average specific growth rate
µc = mean value of µ for the control
µt = mean value of µ for the treatment group


Yield
Effects on yield were determined on the basis of frond numbers and dry weight present in each test vessel at the start and end of the test. For dry weight, the starting biomass was determined on the basis of a sample of fronds taken from the same batch used to inoculate the test vessels. For each test concentration and control, the mean value for yield along with variance estimates was calculated.

Percentage inhibition in yield (I ) was calculated for each treatment group as follows:


%Iy = ((bc – bt) / bc) x 100

Where:
% Iy = percentage reduction in yield
bc = final biomass minus starting biomass for the control group
bt = final biomass minus starting biomass for the treatment group

Determination of ECx Values
Percentage inhibition (arithmetic axis) was plotted against test concentration (logarithmic axis) and a line fitted by computerized interpolation using the Xlfit software package (IDBS). ECx values were then determined from the equation for the fitted line.

It was not possible to calculate 95% confidence limits for the EC50 values as the data generated did not fit the models available for the calculation of confidence limits.
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Duration:
7 d
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
7 d
Dose descriptor:
NOEC
Effect conc.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:

Range-finding Test
The results showed no significant effect on growth at the test concentration of 0.10 and 1.0 mg/L. However, growth was observed to be reduced at 10 and 100 mg/L.

Based on this information test concentrations of 1.0, 3.2, 10, 32 and 100 mg/L were selected for the definitive test.

Chemical analysis of the test preparations on Days 0, 5 and 7 showed measured test concentrations to be near nominal with the exception of the 1.0 mg/L test sample on Day 5 where a measured concentration of 67% of nominal was obtained. This value was considered to be erroneous given that a measured concentration of 90% of nominal was obtained for this test sample on Day 7. Overall these results indicated that the test item was stable under test conditions.


Definitive Test
Growth Data Based on Frond Number
Accordingly the following results based on inhibition of average specific growth rate and yield were determined from the frond number data:


Average Specific Growth Rate
ErC10 (frond number) = >100 mg/L
ErC20 (frond number) = >100 mg/L
ErC50 (frond number) = >100 mg/L

Where:

ErCx = the test concentration that reduced average specific growth rate by x%.
Statistical analysis of the average specific growth rate data was carried out for the control and all test concentrations using one way analysis of variance incorporating Bartlett's test for homogeneity of variance (Sokal and Rohlf 1981) and Dunnett's multiple comparison procedure for comparing several treatments with a control (Dunnett 1955). There were no statistically significant differences between the control, 1.0, 3.2, 10, 32 and 100 mg/L test concentrations (P≥0.05) and therefore the "No Observed Effect Concentration" (NOEC) in terms of inhibition of average specific growth rates calculated from frond numbers was 100 mg/L.


Yield
EyC10 (frond number) = 30 mg/L
EyC20 (frond number) = >100 mg/L
EyC50 (frond number) = >100 mg/L

Where:

EyCx = the test concentration that reduced yield by x%.

Statistical analysis of the yield data was carried out for the control and all test concentrations using one way analysis of variance incorporating Bartlett's test for homogeneity of variance (Sokal and Rohlf 1981) and Dunnett's multiple comparison procedure for comparing several treatments with a control (Dunnett 1955). There were no statistically significant differences between the control, 1.0, 3.2, 10, 32 and 100 mg/L test concentrations (P≥0.05) and therefore the "No Observed Effect Concentration" (NOEC) in terms of inhibition of yield calculated from frond numbers was 100 mg/L.

Growth Data Based on Dry Weight
Accordingly the following results based on inhibition of average specific growth rate and yield were determined from the dry weight data:


Average Specific Growth Rate
ErC10 (dry weight) = >100 mg/L
ErC20 (dry weight) = >100 mg/L
ErC50 (dry weight) = >100 mg/L

Where:

ErCx = the test concentration that reduced average specific growth rate by x%.

Statistical analysis of the average specific growth rate data was carried out for the control and all test concentrations using one way analysis of variance incorporating Bartlett's test for homogeneity of variance (Sokal and Rohlf, 1981) and Dunnett's multiple comparison procedure for comparing several treatments with a control (Dunnett, 1955). There were no statistically significant differences between the control 1.0, 3.2, 10, 32 and 100 mg/L test concentrations (P≥0.05) and therefore the "No Observed Effect Concentration" (NOEC) in terms of inhibition of average specific growth rate calculated from dry weight was 100 mg/L.

Yield
EyC10 (dry weight) = 44 mg/L
EyC20 (dry weight) = >100 mg/L
EyC50 (dry weight) = >100 mg/L

Where:

EyCx = the test concentration that reduced yield by x%.

Statistical analysis of the yield data was carried out for the control and all test concentrations using one way analysis of variance incorporating Bartlett's test for homogeneity of variance (Sokal and Rohlf 1981) and Dunnett's multiple comparison procedure for comparing several treatments with a control (Dunnett 1955). There were no statistically significant differences between the control, 1.0, 3.2, 10, 32 and 100 mg/L test concentrations (P≥0.05) and therefore the "No Observed Effect Concentration" (NOEC) in terms of inhibition of yield calculated from dry weight was 100 mg/L.
Results with reference substance (positive control):
A positive control (Harlan Study Number 41403075) used 3,5-dichlorophenol as the reference item at concentrations of 0.625, 1.25, 2.5, 5.0 and 10 mg/L.

Exposure conditions and data evaluation for the positive control were similar to those in the definitive test.

Exposure of Lemna minor to the reference item gave the following results:

The average specific growth rate (frond number) EC50 was 3.4 mg/L with 95 % confidence limits of 3.1 - 3.6 mg/L). The NOEC was 2.5 mg/L and the LOEC was 5.0 mg/L.
The average specific growth rate (dry weight) EC50 was 3.4 mg/L with 95 % confidence limits of 3.2 - 3.7 mg/L). The NOEC was 1.25 mg/L and the LOEC was 2.5 mg/L.
The yield (frond number) EC50 was 2.6 mg/L with 95 % confidence limits of 2.4 - 2.9 mg/L). The NOEC was 2.5 mg/L and the LOEC was 5.0 mg/L.
The yield (dry weight) EC50 was 2.7 mg/L with 95 % confidence limits of 2.5 - 2.9 mg/L). The NOEC was 1.25 mg/L and the LOEC was 2.5 mg/L.

The results from the positive control with 3,5-dichlorophenol were within the normal ranges for this reference item.
Reported statistics and error estimates:
One way analysis of variance incorporating Bartlett's test for homogeneity of variance (Sokal and Rohlf, 1981), and Dunnett's multiple comparison procedure for comparing several treatments with a control (Dunnett, 1955), were carried out on the average specific growth rate and yield data at 7 days for the control and all test concentrations to determine any statistically significant differences between the test and control groups. All statistical analyses were performed using the SAS computer software package (SAS, 1999-2001).

DefinitiveTest

Verification of Test Concentrations

Analysis of the 100 mg/L test preparations on Day 0 (fresh media) and Day 7 (old media) showed measured test concentrations to range from 98 % to 107 % of nominal and so the results are based on nominal concentrations only.

 

 

Validation Criteria

The following data show that the doubling time of the control cultures was 1.75 days in line with the OECD Guideline that states the doubling time should be less than 2.5 days:

 

Mean frond number in control cultures at day 0: 9

Mean frond number in control cultures at day 7: 102

Water Quality Criteria

Temperature was maintained at 24 ± 2 ºC throughout the test.

Frond Numbers and Percentage Inhibition of Growth from the Range-finding Test

Nominal Concentration

(mg/L)

Number of Fronds

Average Specific Growth Rate

Yield

Day 0

Day 2

Day 5

Day 7

(0 – 7 Day)

% Inhibition

(0 – 7 Day)

% Inhibition

Control

R1

9

12

36

68

0.289

-

59

-

R2

9

15

43

81

0.314

72

Mean

9

14

40

75

0.302

66

0.10

R1

9

13

35

79

0.310

[1]

70

[2]

R2

9

12

37

72

0.297

63

Mean

9

13

36

76

0.304

67

1.0

R1

9

13

35

68

0.289

2

59

5

R2

9

12

40

76

0.305

67

Mean

9

13

38

72

0.297

63

10

R1

9

12

33

62

0.276

9

53

21

R2

9

12

30

60

0.271

51

Mean

9

12

32

61

0.274

52

100

R1

9

12

27

50

0.245

19

41

38

R2

9

12

29

49

0.242

40

Mean

9

12

28

50

0.244

41

R1– R2= Replicates 1 and 2

Frond Numbers from the Definitive Test

Nominal Concentration (mg/L)

Number of Fronds

Day 0

Day 3

Day 5

Day 7

Control

R1

9

23

49

105

R2

9

24

56

111

R3

9

21

41

90

Mean

9

23

49

102

1.0

R1

9

21

41

87

R2

9

24

53

104

R3

9

22

44

100

Mean

9

22

46

97

3.2

R1

9

24

45

86

R2

9

22

42

90

R3

9

21

43

99

Mean

9

22

43

92

10

R1

9

22

48

100

R2

9

21

45

96

R3

9

23

51

116

Mean

9

22

48

104

32

R1

9

21

40

82

R2

9

24

53

107

R3

9

24

52

89

Mean

9

23

48

93

100

R1

9

23

35

66

R2

9

22

50

93

R3

9

26

51

99

Mean

9

24

45

86

R1– R3= Replicates 1 to 3

Inhibition of Average Specific Growth Rate and Yield Based on Frond Numbers

Nominal Concentration
(mg/L)

Average Specific Growth Rate

Yield

(0 – 7 Day)

% Inhibition

(0 – 7 Day)

% Inhibition

Control

Mean

0.346

-

93

-

SD

0.016

11

1.0

Mean

0.339

2

88

5

SD

0.014

9

3.2

Mean

0.331

4

83

11

SD

0.011

7

10

Mean

0.349

[1]

95

[2]

SD

0.014

11

32

Mean

0.332

4

84

10

SD

0.020

13

100

Mean

0.321

7

77

17

SD

0.031

18

SD– Standard Deviation

[Increase in growth compared to controls]

Dry Weights from the Definitive Test

Nominal Concentration

(mg/L)

Dry Weight (mg)

Day 0*

Day 7

Control

R1

 

11.0

R2

 

10.1

R3

 

8.9

Mean

0.6

10.0

1.0

R1

 

9.2

R2

 

9.4

R3

 

9.2

Mean

0.6

9.3

3.2

R1

 

9.9

R2

 

8.2

R3

 

9.3

Mean

0.6

9.1

10

R1

 

11.1

R2

 

9.4

R3

 

12.4

Mean

0.6

11.0

32

R1

 

8.7

R2

 

10.7

R3

 

8.6

Mean

0.6

9.3

100

R1

 

6.4

R2

 

8.6

R3

 

9.0

Mean

0.6

8.0

*Mean value determined from 6 replicate weighings

R1– R3= Replicates 1 to 3

Inhibition of Average Specific Growth Rate and Yield Based on Dry Weight

Nominal Concentration
(mg /l)

Average Specific Growth Rate

Yield

(0 – 7 Day)

% Inhibition

(0 – 7 Day)

% Inhibition

Control

Mean

0.401

-

9.4

-

SD

0.016

1.1

1.0

Mean

0.391

2

8.7

7

SD

0.002

0.1

3.2

Mean

0.389

3

8.5

10

SD

0.013

0.9

10

Mean

0.414

[3]

10.4

[11]

SD

0.020

1.5

32

Mean

0.391

2

8.7

7

SD

0.018

1.2

100

Mean

0.368

8

7.4

21

SD

0.027

1.4

SD– Standard Deviation

pH Values in the Definitive Test

Nominal Concentration

(mg/L)

Time (Days)

0

7

Control

R1

6.8

8.0

R2

6.7

8.0

R3

6.7

8.0

1.0

R1

6.7

7.9

R2

6.7

7.9

R3

6.7

7.9

3.2

R1

6.7

7.9

R2

6.7

7.9

R3

6.7

7.9

10

R1

6.7

7.8

R2

6.7

7.8

R3

6.7

7.8

32

R1

6.7

7.7

R2

6.7

7.7

R3

6.8

7.6

100

R1

6.8

7.6

R2

6.8

7.5

R3

6.8

7.5

R1– R3= Replicates 1 to 3

Validity criteria fulfilled:
yes
Conclusions:
The effect of the test item on the growth of Lemna minor has been investigated over a 7-Day period and gave the following results.
The average specific growth rate (frond number) EC50 was >100 mg/L.
The average specific growth rate (dry weight) EC50 was >100 mg/L.
The yield (frond number) EC50 was >100 mg/L.
The yield (dry weight) EC50 was >100 mg/L.
The NOEC was 100 mg/L.
Executive summary:

Introduction

A study was performed to assess the effect of the test item on the growth of the freshwater plant Lemna minor. The method followed that described in the OECD Guideline “Lemna Growth Inhibition Test (March 2006)”.

 

 

Methods…….

Following a preliminary range-finding test, Lemna minor was exposed to an aqueous solution of the test item at concentrations of 1.0, 3.2, 10, 32 and 100 mg/L (three replicate flasks per concentration) for a period of 7 days, under constant illumination at a temperature of 24 ± 2°C. 

 

The number of fronds in each control and treatment group was recorded on days 0, 3, 5 and 7 along with observations on plant development.

 

 

Results…….

Chemical analysis of the 100 mg/L test preparations on Day 0 (fresh media) and Day 7 (old media) showed measured test concentrations to range from 98% to 107% of nominal and so the results are based on nominal test concentrations only.

 

Exposure of Lemna minor to the test item based on nominal concentrations gave the following results:

Response Variable

Measurement Variable

EC50(mg/L)

No Observed Effect Concentration (NOEC) (mg/L)

Average Specific Growth Rate

Frond Number

>100

100

Dry Weight

>100

100

Yield

Frond Number

>100

100

Dry Weight

>100

100

Endpoint:
toxicity to aquatic plants other than algae
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
This read-across is based on the hypothesis that the source and the target substance have very similar physicochemical and (eco)toxicological properties because their chemical structures are nearly identical. An analogue approach has thus been employed. The target substance is the meta-isomer of the dye Reactive Blue 049, where the sulphonate group is bound at the meta-position of the aminobenzene moiety. The source chemical is the reaction mass of both the meta-isomer and the para-isomer of Reactive Blue 049.
The presence of sulphonate groups make both dyes highly water soluble and therefore less critical for human health and environmental issues. Based on their chemical similarity, similar properties are expected in both humans and the environment.

2. SOURCE AND TARGET CHEMICAL(S)
Source: Reactive Blue 49 meta/para (CAS# 72214-18-7 / EC# 276-481-8)
Target: Reactive Blue 49 meta (CAS# 72927-99-2 / EC# 277-040-2)

3. ANALOGUE APPROACH JUSTIFICATION
see attachment under 4.2 Melting point / freezing point
Reason / purpose:
read-across source
Key result
Duration:
7 d
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
7 d
Dose descriptor:
NOEC
Effect conc.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Conclusions:
The effect of the source substance on the growth of Lemna minor has been investigated over a 7-Day period and gave the following results.
The average specific growth rate (frond number) EC50 was >100 mg/L.
The average specific growth rate (dry weight) EC50 was >100 mg/L.
The yield (frond number) EC50 was >100 mg/L.
The yield (dry weight) EC50 was >100 mg/L.
The NOEC was 100 mg/L.
The structurally related target substance will show similar results when tested in Lemna.
Executive summary:

A study was performed to assess the effect of the test item Reactive Blue 49 on the growth of the freshwater plant Lemna minor. The method followed that described in the OECD Guideline “Lemna Growth Inhibition Test (March 2006)”.

…….

Following a preliminary range-finding test,Lemna minorwas exposed to an aqueous solution of the test item at concentrations of 1.0, 3.2, 10, 32 and 100 mg/L (three replicate flasks per concentration) for a period of 7 days, under constant illumination at a temperature of 24 ± 2°C. 

The number of fronds in each control and treatment group was recorded on days 0, 3, 5 and 7 along with observations on plant development.

 

Chemical analysis of the 100 mg/L test preparations on Day 0 (fresh media) and Day 7 (old media) showed measured test concentrations to range from 98% to 107% of nominal and so the results are based on nominal test concentrations only.

 

Exposure ofLemna minorto the test item based on nominal concentrations gave the following results:

Response Variable

Measurement Variable

EC50(mg/L)

No Observed Effect Concentration (NOEC) (mg/L)

Average Specific Growth Rate

Frond Number

>100

100

Dry Weight

>100

100

Yield

Frond Number

>100

100

Dry Weight

>100

100

Description of key information

The average specific growth rate (frond number) EC50 was > 100 mg/L. 
The average specific growth rate (dry weight) EC50 was > 100 mg/L.
The yield (frond number) EC50 was > 100 mg/L.
The yield (dry weight) EC50 was > 100 mg/L.
The NOEC was 100 mg/L.

Key value for chemical safety assessment

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

Additional information

A GLP compliant OECD guideline 221 study was performed to determine the effects of the structural analogue material. The exponentially growing culture of Lemna gibba (Duckweed) with an observation period of ‘7’ days. The effect of read-across test item on the growth of the Lemna gibba culture compared with control was determined and the concentration that inhibited growth rate by 50 % (ErC50) and the concentration that inhibited yield by 50% (EyC50) each of which in turn based upon frond number and frond dry weight were calculated.

The effect of the read-across test item on the growth of Lemna minor has been investigated over a 7-Day period and the following results were observed:

The average specific growth rate (frond number) EC50 was >100 mg/L.

The average specific growth rate (dry weight) EC50 was >100 mg/L.

The yield (frond number) EC50 was >100 mg/L.

The yield (dry weight) EC50 was >100 mg/L.

The NOEC was 100 mg/L.

For the structurally related target substance, similar results are anticipated.