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Toxicity to aquatic plants other than algae

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Reference
Endpoint:
toxicity to aquatic plants other than algae
Type of information:
experimental study
Adequacy of study:
other information
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP Guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 221 (Lemna sp. Growth Inhibition Test)
Version / remarks:
reported as draft guideline Lemna growth inhibition test, June 1984
Deviations:
yes
Remarks:
modifications of the test medium to reach sufficient doubling time during the test duration of 7 days, the deviation did not influence the results of the study negatively
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
yes
Vehicle:
yes
Details on test solutions:
The stock solution was prepared by weighing 100 mg Diuron in 10 ml N,N-Dimethylformamide. The stock solution was mixed with a magnetic stirrerTest concentrations were made by adding appropriate aliquots to yield nominal test concentration
A solvent control of 0.073 mg/L of N,N-Dimethylformamide was included in this study
Test organisms (species):
Lemna gibba
Details on test organisms:
TEST ORGANISM
- Common name: Duckweed
- Source (laboratory, culture collection): laboratory culture
- Age of inoculum (at test initiation): less than 10 day old
Test type:
static
Water media type:
freshwater
Total exposure duration:
7 d
Test temperature:
24 ± 2 °C
pH:
5.5 - 6.1
Nominal and measured concentrations:
Nominal conc: 0, 2.97, 8.9, 26.7, 80.1, 240, 721 µg/L
Measured conc: 0, 3.40, 10.7, 29.8, 91.1, 271, 814 µg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: glass dishes
- Material, size, headspace, fill volume: diameter 10cm, height 6cm, total volume 400 ml.
- No. of organisms per vessel: 12
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3
- No. of vessels per vehicle control (replicates): 3

TEST MEDIUM / WATER PARAMETERS
See Table 1.

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: yes
- Photoperiod: Continuous
- Light intensity and quality: 7852 lux
Duration:
7 d
Dose descriptor:
NOEC
Effect conc.:
3.4 µg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
7 d
Dose descriptor:
LOEC
Effect conc.:
10.7 µg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
7 d
Dose descriptor:
EC50
Effect conc.:
18.3 µg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
growth rate
Reported statistics and error estimates:
Growth data, expressed as average growth rate of total frond area were used to conduct t-tests to determine if controls could be pooled, chi-square tests to determine normality and Bartlett’s test for homogeneity of variance. Data not fitting a normal distribution were analysed by the non-parametric Kruskal-Wallis test and Dunns multiple Comparison test to determine any significant difference. Growth data were analysed using Bonferonni’s t-test. Conclusions of statistical significance based on 95% confidence limits. The EC50 value was determined by either moving average, binomial probability of probit analysis

Table 2. Frond counts and growth rate

 

Initial measured concentration (µg/L)

Day 0

Day 2

Day 5

Day 7

Growth rate [µ]

(0     7)

 

Control

A

B

C

Mean

SD

12

12

12

12

0

24

22

24

23

1

66

67

65

66

1

105

106

119

110

8

0.310

0.311

0.328

0.316

0.010

 

Pooled controls:

0.322

Solvent control

A

B

C

Mean

SD

12

12

12

12

0

23

27

23

24

2

64

77

62

68

8

106

135

115

119

15

0.311

0.346

0.323

0.327

0.018

 

3.40

A

B

C

Mean

SD

12

12

12

12

0

23

22

24

23

1

52

55

53

53

2

96

92

92

93

2

0.297

0.291

0.291

0.293

0.004

 

10.7

A

B

C

Mean

SD

12

12

12

12

0

22

23

22

22

1

42

46

45

44

2

66

73

70

70

4

0.244

0.258

0.252

0.251

0.007

 

29.8

A

B

C

Mean

SD

12

12

12

12

0

18

21

14

18

4

25

26

23

25

2

34 S

34 S

24 S

31

6

0.149

0.149

0.099

0.132

0.029

 

91.1

A

B

C

Mean

SD

12

12

12

12

0

13

14

13

13

1

15

14

13

14

1

13

15

13

14

1

0.011

0.032

0.011

0.018

0.012

 

271

A

B

C

Mean

SD

12

12

12

12

0

13 X

12

13 X

13

1

13 X

12

13 X

13

1

12 X, CL

12 XX, CL

13 X, CL

12

1

0.000

0.000

0.011

0.004

0.007

 

814

A

B

C

Mean

SD

12

12

12

12

0

12 X

14 X

12 X

13

1

12 X

12 X

14 X

13

1

12 X, CL

14 X, CL

12 X, CL

13

1

0.000

0.022

0.000

0.007

0.013

 

Executive summary:

A short-term toxicity test is available for Diuron, in accordance with the prevailing OECD guidelines (OECD 221) and GLP. Based on measured concentrations the 7 d EC50(growth) was calculated to be 18.3 µg/L with the LOEC and NOEC values of 10.7 µg/L and 3.4 µg/L, respectively. Therefore the test substance (Diuron) can be considered as acutely toxic to Lemna gibba (duckweed).

Description of key information

Diuron is toxic to Lemna gibba (duckweed).

Key value for chemical safety assessment

Additional information

The (7 d) EC50 (growth) and NOEC values forLemna gibba(duckweed) were 18.3 µg/L and 3.4 µg/L respectively following exposure to Diuron according to a OECD 221 test (Dorgerloh, 1999).