Registration Dossier

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:
23. Sep. 2009- 05.May. 2009
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2009
Report date:
2009

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 221 (Lemna sp. Growth Inhibition Test)
Version / remarks:
OECD Guidelines for the Testing of Chemicals, No. 221: “Lemna sp. Growth Inhibition Test”, adopted March 23, 2006.
GLP compliance:
yes (incl. QA statement)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Type:
Constituent
Test material form:
liquid

Sampling and analysis

Analytical monitoring:
not specified
Details on sampling:
Dosage and Concentrations
The following nominal concentrations of test item were tested: 0.10, 0.32, 1.0, 3.2, 10, 32, and 100 mg/L. Additionally, a control (test water without addition of the test item) was tested in parallel.
The test medium of the highest nominal concentration of 100 mg/L was prepared by mixing 100 mg of the test item into 1000 mL of test water using intense stirring (15 minutes at room temperature). The test medium was diluted with test water to prepare the test media of the test item concentrations stated above. The test media were prepared just before the start of the test and at the test medium renewals on Day 3 and Day 5.
The selection of the test concentrations was based on the results of a range-finding test (non- GLP).

See more information in the study report attach

Test solutions

Vehicle:
not specified
Details on test solutions:
See in section 3.3.1 Experimental Conditions on the study report attach

Test organisms

Test organisms (species):
Lemna gibba
Details on test organisms:
TEST ORGANISM
- Common name: Lemna gibba
- Strain: Lemna gibba G3 (family Lemnaceae, Macrophyta).
- Source (laboratory, culture collection): Bayer CropScience AG, 40789 Monheim, Germany in 2007.
- Age of inoculum (at test initiation) and Method of cultivation: The plants were axenically cultivated in the laboratories of Harlan Laboratories Ltd. for more than four weeks prior to the test under standardized conditions in the same nutrient medium as used in the test.

ACCLIMATION
The pre-culture was maintained under the conditions of the test (nutrient medium, light
conditions and temperature) for seven days prior to the start of the test. The test was started with plants from an exponentially growing culture. Only young, rapidly growing colonies without visible lesions were used.

Study design

Test type:
not specified
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
7 d

Test conditions

Hardness:
3.0 mmol/L (= 300 mg/L as CaCO3)
Test temperature:
See in table 10 on the study report
pH:
See in table 9 on the study report
Dissolved oxygen:
Not specify
Salinity:
See the table on section 3.3.1 Experimental Conditions on the study report attach
Conductivity:
Not specify
Nominal and measured concentrations:
The following nominal concentrations of test item were tested: 0.10, 0.32, 1.0, 3.2, 10, 32, and 100 mg/L. Additionally, a control (test water without addition of the test item) was tested in parallel.
Details on test conditions:
See in the study report attach
Reference substance (positive control):
yes

Results and discussion

Effect concentrationsopen allclose all
Key result
Duration:
7 d
Dose descriptor:
NOEC
Effect conc.:
0.1 mg/L
Nominal / measured:
nominal
Conc. based on:
other: Frond Number
Basis for effect:
growth rate
Duration:
7 d
Dose descriptor:
LOEC
Effect conc.:
0.32 mg/L
Nominal / measured:
nominal
Conc. based on:
other: Frond Number
Basis for effect:
growth rate
Key result
Duration:
7 d
Dose descriptor:
NOEC
Remarks:
NOEC=EC10
Effect conc.:
0.02 mg/L
Nominal / measured:
nominal
Conc. based on:
other: Frond Numbers
Basis for effect:
yield
Duration:
7 d
Dose descriptor:
LOEC
Effect conc.:
0.1 mg/L
Nominal / measured:
nominal
Conc. based on:
other: Frond Number
Basis for effect:
yield
Duration:
7 d
Dose descriptor:
NOEC
Effect conc.:
0.32 mg/L
Nominal / measured:
nominal
Conc. based on:
other: Dry weight of the Plant
Basis for effect:
growth rate
Duration:
7 d
Dose descriptor:
LOEC
Effect conc.:
1 mg/L
Nominal / measured:
nominal
Conc. based on:
other: Dry weight of the Plant
Basis for effect:
growth rate
Duration:
7 d
Dose descriptor:
NOEC
Remarks:
NOEC=EC10
Effect conc.:
0.046 mg/L
Nominal / measured:
nominal
Conc. based on:
other: Dry weight of the Plant
Basis for effect:
yield
Duration:
7 d
Dose descriptor:
LOEC
Effect conc.:
0.1 mg/L
Nominal / measured:
nominal
Conc. based on:
other: Dry weight of the Plant
Basis for effect:
yield
Key result
Duration:
7 d
Dose descriptor:
EC50
Effect conc.:
1.6 mg/L
Nominal / measured:
nominal
Conc. based on:
other: Frond Number
Basis for effect:
yield
Details on results:
See the details on results in the study report
Results with reference substance (positive control):
RESULTS AND DISCUSSION
The influence of the test item on the growth of Lemna gibba is shown in Table 1-Table 6 and Figure 1-Figure 5. The section-by-section growth rates (calculated on the basis of frond numbers) are given in Table 7.
On Day 3, no abnormalities in growth and appearance of the test plants were recorded in the control and the test concentrations of 0.10 to 10 mg/L. At the next concentrations of 32 and 100 mg/L, the roots of the plants were shorter compared to the control based on visual assessment and the plants lost their roots.
On Day 5 and 7, no abnormalities in growth and appearance of the test plants were recorded in the control and the test concentrations of 0.10 and 0.32 mg/L At the concentrations of 1.0 to 100 mg/L, the roots of the plants were shorter compared to the control, the newly formed fronds were stunted and chlorosis was determined.
After the exposure period of 7 days, the test item had a statistically significant inhibitory effect on the growth of Lemna gibba (growth rate based on frond number and dry weight) at the concentration of 0.32 and 1.0 mg/L and at all higher test concentrations, respectively (Table 3-Table 6). Yield based on frond number and dry weight was already significantly inhibited at the concentration of 0.10 mg/L and at all higher test concentrations (Table 3-Table 6) according to statistics.
The concentration of 0.020 mg/L was determined to be the 7-day NOEC based on the EC10 calculated by Probit analysis. The 7-day LOEC was determined to be 0.10 mg/L since the growth of the plants was statistically significantly lower than in the control after the exposure period of 7 days.
The biological results can be summarized as follows (based on nominal concentrations of the test item): See in the table present on page 18 of the study report.
The doubling time (Td) of frond number in the control was calculated to be 2.0 days (Td = ln 2 / μ). According to the test guideline, the validity criterion for the study (Td < 2.5 days corresponding to an average growth rate of 0.275 day-1) was fulfilled, indicating that the Lemna growth was satisfactory under the test conditions.
No remarkable observations were made concerning the appearance of the test media. All test media were clear throughout the test medium renewal periods (Table 8).
At the start of the test medium renewal periods, the pH of the test media and the control ranged from 7.5 to 8.4 (Table 9). At the end of the renewal periods, pH values between 8.3 and 9.1 were measured. The increase of the pH during the renewal periods was caused by the CO2 consumption of the plants due to their growth. The water temperature was 22 °C during the test period (Table 10).

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
The substance do not classified EC50=1.6 < 1mg/L
Executive summary:

The influence of the test item on the growth of the freshwater aquatic plant Lemna gibba (duckweed) was investigated in a 7-day semi-static test, based on the OECD Guideline No 221 “Lemna sp. Growth Inhibition Test” (2006).

The following nominal concentrations of the test item were tested: 0.10, 0.32, 1.0, 3.2, 10, 32, and 100 mg/L. Additionally, a control was tested in parallel.

The biological results based on nominal concentrations of the test item were as follows:

See the table on page 10 of the study report.