diuron (ISO); 3-(3,4-dichlorophenyl)-1,1-dimethylurea

Toxicity to aquatic plants other than algae

Link to relevant study record(s)

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).

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).