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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:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Acceptable, well-documented publication which meets basic scientific principles

Data source

Reference
Reference Type:
publication
Title:
Accumulation and elimination of Lanthanum by duckweed (Lemna minor L.) as influenced by organism growth and Lanthanum sorption to glass
Author:
Weltje, L. et al.
Year:
2002
Bibliographic source:
Environmental Toxicology and Chemistry 21(7): 1483-1489

Materials and methods

Principles of method if other than guideline:
La kinetics were studied in duckweed with different exposure regimes: 1. La uptake from refreshed medium, 2. La uptake from non-refreshed medium, 3. La uptake from non-refreshed medium and elimination in refreshed medium.
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Lanthanum
- Molecular formula (if other than submission substance): La Cl3*7(H2O)
- CAS No.: 10025-84-0
- Analytical purity: 99.999%
- Lanthanum was spiked with the radionuclide 140La (t1/2 = 40.3 h), which emits beta and gamma radiation. (Main E(gamma) are 329, 487,
816, and 1,596 keV).

Sampling and analysis

Analytical monitoring:
yes

Test solutions

Vehicle:
no
Details on test solutions:
Lanthanum was spiked with the radionuclide 140La (t1/2 = 40.3 h), which emits beta and gamma radiation. 140La was prepared by irradiating a quartz vial containing a solution of 0.1 mM LaCl3.7H2O in Milli-Q water at a neutron flux of 1.60 X 10E17/(m2·s) for 24 h in the Hoger Onderwijs Reactor of the institute. The solution was allowed to decay for 3 h to eliminate the short-lived chloride isotope 38Cl (t1/2 = 37.2 min) and was subsequently added to the rest of the medium components to make up a final La concentration of 10 nM.

Test organisms

Test organisms (species):
Lemna minor
Details on test organisms:
no data available

Study design

Test type:
semi-static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
192 h
Remarks on exposure duration:
1. exp.: 192 h; 2. exp.: 167 h, 3. exp.: 169 h

Test conditions

Hardness:
no data
Test temperature:
25 +/- 28°C
pH:
initial pH of 5.05 +/- 0.05
Dissolved oxygen:
no data
Nominal and measured concentrations:
10 nmol/L
Details on test conditions:
Plants were cultured axenically and exposed in a climate chamber at a light intensity of 10,000 lux and a day:night regime of 16:8 h. Relative humidity was approximately 70% and the temperature 25 +/- 28°C. The exposure substrate was a sterilized low-level nutrient medium, adapted from the Swedish Standards Institute (SIS), with an initial pH of 5.05 +/- 0.05.
Plants were exposed in 200 mL medium in glass vessels, which were closed with a glass lid to minimize evaporation but allow limited gas exchange. Plant fresh weight was determined after spin drying at 3,000 rpm for 10 min at room temperature to remove attached and free-space water.

1. Exp: Twenty glass vessels with medium and 10 nM La and 20 glass vessels with La-free medium were inoculated with 12 duckweed fronds (3–5 colonies). Plants in vessels without La served as a control group to compare their growth rate with La-exposed plants and study possible toxicity or growth stimulation of La. At times 48, 96, 144, and 192 h, plants were transferred to vessels with fresh medium (with or without La). At times 0, 4, 8, 24, 45, 55, 72, 94, 124, 168, and 216 h, the pH of the medium was measured, fresh weight was determined, and La concentrations in media and plants and La amounts on lass vessels were measured.
2. Exp.:Twenty-seven glass vessels with medium and 10 nM La were inoculated with 12 duckweed fronds (3–5 colonies). In addition, three vessels with medium but no plants were followed in time to check for possible precipitation and constancy of pH. The first 48 h were thus the same as for experiment 1. At times 0, 1, 3, 5, 24, 48, 92, 120, and 167 h, pH of the media was measured, plant fresh weight was determined, and La concentrations in media and plants and La amounts on glass vessels were measured. All measurements were performed in triplicate.
3. Exp.: Twenty-eight glass vessels with medium and 10 nM La were inoculated with 12 duckweed fronds (3–5 colonies). In addition, three vessels with medium but no plants were followed in time to check for possible precipitation and constancy of pH. The first 48 h were the same as for experiments 1 and 2. To study elimination, plants from 15 vessels were gently lifted off the surface after 48 h of accumulation and transferred, without spin drying, to vessels with La-free medium. This medium was refreshed at times 55, 72, 120, and 144 h to keep the La concentration in medium as low as possible and thus prevent backflow of La to plants. At times 0, 5.5, 12, 24, 48, 55, 72, 96, 144, and 169 h, pH of the media was measured, fresh weight was determined, and La concentrations in media and plants and La amounts on glass vessels were measured. Measurements were performed in duplicate (accumulation) or triplicate (elimination).
Reference substance (positive control):
no

Results and discussion

Effect concentrationsopen allclose all
Duration:
196 h
Dose descriptor:
NOEC
Effect conc.:
>= 0.01 µmol/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: Test substance: Lanthanum trichloride heptahydrate
Duration:
196 h
Dose descriptor:
NOEC
Effect conc.:
>= 3.71 µg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: Test substance: Lanthanum trichloride heptahydrate
Duration:
196 h
Dose descriptor:
NOEC
Effect conc.:
>= 2.45 µg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: Test substance: lanthanum trichloride anhydrous
Details on results:
During the course of the experiments, duckweed growth was purely exponential, indicating that growth limitation under the present conditions is not occurring. The associated maximum concentration of La in L. minor without effects was 12 nmol/g fresh weight.

Any other information on results incl. tables

The authors stated that L. minor takes up La from medium as LaEDTA2 complex and/or as ionic La3+, reaching a BCFdyn of 32,970 L/kg on a dry weight basis. Elimination study revealed a large (60%) slow and small (40%) fast compartment. The large compartment eliminates mainly by means of maintaining a high growth rate. The proposed model incorporating a mass balance rule and exponential growth of the exposed organism agreed well with the experimental data. Neither stimulating nor toxic effects of 10 nM complexed La on duckweed growth in 9 d were observed.

Applicant's summary and conclusion