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Ecotoxicological information

Toxicity to aquatic plants other than algae

Administrative data

Endpoint:
toxicity to aquatic plants other than algae
Type of information:
experimental study
Adequacy of study:
key study
Study period:
08/10/2001 - 16/01/2002
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP, Guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2002
Report date:
2002

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
EPA OPPTS 850.4400 (Aquatic Plant Toxicity Test using Lemna spp. Tiers I & II))
Deviations:
no
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 221 (Lemna sp. Growth Inhibition Test)
Deviations:
no
GLP compliance:
yes

Test material

Constituent 1
Chemical structure
Reference substance name:
1-methyl-2-nitro-3-(tetrahydrofuran-3-ylmethyl)guanidine
EC Number:
605-399-0
Cas Number:
165252-70-0
Molecular formula:
C7H14N4O3
IUPAC Name:
1-methyl-2-nitro-3-(tetrahydrofuran-3-ylmethyl)guanidine
Test material form:
other: solid
Details on test material:
Purity 99.2%
Batch No. 2100910

Sampling and analysis

Analytical monitoring:
yes
Details on sampling:
Duplicate samples of the fresh prepared test solutions were taken on days 0 and 4.
Duplicate samples of the old test solutions were taken on days 2 and 7.
All samples were stored at about -20°C.

Test solutions

Vehicle:
no

Test organisms

Test organisms (species):
Lemna gibba
Details on test organisms:
Species/strain: Lemna gibba G3
Source: Bayer AG, Crop Protection Institute for Environmental Biology, D-40789 Monheim, Germany
Age: more than two weeks

Study design

Test type:
semi-static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
7 d
Post exposure observation period:
3 days

Test conditions

Hardness:
not determined
Test temperature:
24 °C
pH:
7.4 – 7.6 at start of test medium renewals
8.6 – 9.2 at the end of test medium renewals
Dissolved oxygen:
Not reported
Salinity:
Not applicable
Nominal and measured concentrations:
See table below
Details on test conditions:
The Lemna colonies in each test vessel were inspected for changes in frond and colony number and appearance (discoloration, sinking root length or other abnormalities) on days 2, 4 and 7. The number of living and dead fronds and the number of colonies were counted. Fronds visibly projecting over the edge of the mother frond were counted as separate fronds.

Additionally, the dry weight of a sample of fronds identical to that used to inoculate the test vessels was determined at the start of the test. At test termination, the dry weight of all colonies per vessel was determined. The colonies were dried at approx. 60°C to constant weight. Inhibition of Lemna growth was determined from:

• mean frond numbers
• the average specific growth rates
• the area under the growth curves (AUC)
• the final biomass determined on the basis of dry weight (DW)
Reference substance (positive control):
no

Results and discussion

Effect concentrations
Duration:
7 d
Dose descriptor:
EC50
Effect conc.:
> 110 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: mean frond numbers, average specific growth rate, area under growth curves, final biomass determined on the basis of dry weight
Details on results:
Dinotefuran concentration in the freshly prepared test medium of the highest test concentration of nominal 110 mg/L was 106% of the nominal value at the start of the first and last test medium renewal. At the end of the first and last test medium renewal, 92% and 99% of the nominal value were found after 48 and 72 hours, respectively. Test item mean concentration (calculated as the average over all measurements in the test medium) was 101% of the nominal value.
The growth of Lemna gibba was not inhibited up to and including the highest test concentration of 110 mg/L. The mean frond and colony number, the average specific growth rates (r), and the AUC after the test period of 7 days were not statistically significantly reduced compared to the control values at any concentration (results of Dunnett-tests, one-sided, α = 0.05). The dry weight of the plants after the test period of 7 days was statistically not significantly lower compared to the control at any concentration. The plants showed no mortality or other abnormalities at any concentration or in the control.
Dinotefuran did not inhibit the growth of Lemna gibba during the exposure period of 7 days up to and including 110 mg/L. As a result, this concentration was determined as the 7-day NOEC (highest concentration tested without toxic effects after a test period of 7 days). This value could be higher, but concentrations greater than 110 mg/L were not tested.

After the 7 days test duration, the 7-day LOEC (lowest concentration tested with toxic effects) and the EC-values (EC5, EC10, EC50, and EC90) for the growth parameters could not be quantified due to the absence of a toxic effect of Dinotefuran up to and including the highest test concentration of 110 mg/L.

The doubling time (Td = In 2 / r) of Lemna growth in the control was determined to be 1.9 days. This shows that the growth of Lemna gibba was sufficiently high.

The pH values in the freshly prepared test media ranged from 7.4 to 7.6 at the start of the test medium renewal periods. Measured pH values were between 8.6 to 9.2 at the end of the test medium renewal periods. This increase of the pH during the test was caused by the CO2-consumption of the plants due to their rapid growth. All test media were clear solutions and remained clear throughout the test medium renewal periods.

See Tables 1 to 4.
Results with reference substance (positive control):
Not applicable
Reported statistics and error estimates:
Frond number, growth rate (r), AUC, and dry weight were determined or calculated for each test vessel, followed by calculation of the arithmetic mean frond number, mean growth rate, mean area, and mean dry weight, respectively, per test concentration and control. For the growth of Lemna after the 7-day exposure period, the 7-day NOEC (highest concentration without toxic effects) and the LOEC (lowest concentration with toxic effects) were determined by testing the growth parameters (mean frond numbers, average specific growth rate (r), the AUC, and the mean dry weight of the plants) at the test concentrations on statistically significant differences to the control values by multiple Dunnett-tests. The EC values (EC5, EC10, EC50, and EC90) for the growth parameters could not be calculated since no toxic effect of the test item on the growth of the plants was determined up to and including the highest test concentration.

Any other information on results incl. tables

Table 1: Influence of the test item on Lemna gibba growth: growth rates (r) and percentage inhibition of r

Nominal test item concentration [mg/L]

Growth rate r (1/day) and % inhibition of r

0 – 48 h

0 – 96 h

0 – 168 h

r

%

r

%

r

%

Control

0.35

0

0.36

0

0.36

0

11

0.32

8.0

0.34

4.3

0.34

4.8

20

0.35

0.2

0.37

-2.0

0.35

2.3

35

0.31

12.2

0.33

9.4

0.34

6.9

62

0.31

12.9

0.34

6.5

0.34

4.7

110

0.32

8.0

0.35

3.9

0.35

3.2

Growth rates (r) were not significantly lower than the corresponding control value at any test item concentration (Dunett-test, one-sided smaller, α = 0.05)

 

Table 2: Influence of the test item on Lemna gibba growth: areas under growth curves (AUC) and percentage inhibition of AUC

Nominal test item concentration [mg/L]

Areas under the growth curve (AUC) and percentage inhibition

0 – 48 h

0 – 96 h

0 – 168 h

AUC

%

AUC

%

AUC

%

Control

296

0

1520

0

7952

0

11

264

10.8

1384

8.9

7060

11.2

20

296

0

1560

-2.6

7716

3.0

35

248

16.2

1272

16.3

6564

17.5

62

248

16.2

1320

13.2

6960

12.5

110

264

10.8

1392

8.4

7284

8.4

AUC was not significantly lower than the corresponding control value at any test item concentration (Dunett-test, one-sided smaller, α = 0.05)

 

Table 3: Final biomass on the basis of dry weight (mg per test vessel) of Lemna colonies after 7 days

Vessel No.

Nominal test item concentration [mg/L]

Control

11

20

35

62

110

1

20.1

14.9

19.9

14.1

17.1

16.2

2

14.0

16.2

14.3

18.3

17.6

17.6

3

21.3

12.9

19.7

16.3

19.6

19.4

Mean*

18.5

14.7

18.0

16.2

18.1

17.7

SD

3.9

1.7

3.2

2.1

1.3

1.6

% inhibition#compared to control

-

21.5

2.9

12.9

2.3

4.3

Mean: arithmetic mean

SD: standard deviation

* all mean values not significantly lower than in control (Dunett-test, one sided, smaller, α = 0.05)

# % inhibition based on the increase in biomass (mean final dry weight minus starting dry weight).

Dry weight of three colonies with in total 12 fronds at test start: 0.86 mg

Table 4:         Total number of fronds and colonies per test vessel at the counting dates

Nominal test item concentration
(mg/L)

Vessel No.

Frond number (#F) and colony number (#C) per test vessel

Inhibition of mean frond number*

0 h (Day 0)

48 h (Day 2)

96 h (Day 4)

168 h (Day 7)

#F

#C

#F

#C

#F

#C

#F

#C

Control

1

2

3

12

12

12

3

3

3

24

25

24

6

6

6

52

51

49

12

12

12

167

126

163

34

32

33

 

Mean

SD

12.0

0.0

3.0

0.0

24.3

0.6

6.0

0.0

50.7

1.5

12.0

0.0

152.0

22.6

33.0

1.0

-

11

1

2

3

12

12

12

3

3

3

24

23

22

6

6

5

49

50

44

12

12

12

126

150

126

30

35

29

 

Mean

SD

12.0

0.0

3.0

0.0

23.0

1.0

5.7

0.6

47.7

3.2

12.0

0.0

134.0

13.9

31.3

3.2

12.9%

20

1

2

3

12

12

12

3

3

3

23

24

26

6

6

7

47

53

57

12

12

12

142

128

158

34

28

34

 

Mean

SD

12.0

0.0

3.0

0.0

24.3

1.5

6.3

0.6

52.3

5.0

12.0

0.0

142.7

15.0

32.0

3.5

6.7%

35

1

2

3

12

12

12

3

3

3

23

21

23

6

6

6

48

43

42

12

11

10

130

130

120

31

28

28

 

Mean

SD

12.0

0.0

3.0

0.0

22.3

1.2

6.0

0.0

44.3

3.2

11.0

1.0

126.7

5.8

29.0

1.7

18.1%

62

1

2

3

12

12

12

3

3

3

19

24

24

6

6

5

40

51

48

10

12

11

120

133

150

28

33

35

 

Mean

SD

12.0

0.0

3.0

0.0

22.3

2.9

5.7

0.6

46.3

5.7

11.0

1.0

134.3

15.0

32.0

3.6

12.6%

110

1

2

3

12

12

12

3

3

3

22

24

23

6

6

6

45

46

53

11

12

12

125

140

154

29

28

35

 

Mean

SD

12.0

0.0

3.0

0.0

23.0

1.0

6.0

0.0

48.0

4.4

11.7

0.6

139.7

14.5

30.7

3.8

8.8%

Mean: arithmetic mean

SD: standard deviation

* % inhibition of mean frond number compared to the control at the test end (after 168 hours)

Mean frond and colony numbers at the test end (after 168 hours) were not significantly lower than the control values at any test item concentration (according to Dunnett-tests, one-sided smaller, α = 0.05).

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
Dinotefuran did not inhibit the growth of Lemna gibba during the exposure period of 7 days up to and including 110 mg/L. This concentration was determined as the 7-day NOEC (highest concentration tested without toxic effects after a test period of 7 days). Due to the absence of a toxic effect of dinotefuran up to and including the highest test concentration of 110 mg/L, the 7-day LOEC (lowest concentration tested with toxic effects) and the EC10 and EC50 values after the 7-day test period could not be quantified for the different growth parameters, nonetheless, these parameters were clearly higher than 110 mg/L.

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