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Toxicity to terrestrial plants

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Reference
Endpoint:
toxicity to terrestrial plants: short-term
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 208 (Terrestrial Plants Test: Seedling Emergence and Seedling Growth Test)
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
no
Vehicle:
no
Details on preparation and application of test substrate:
- Method of mixing into soil (if used): The test item was weighed separately for each concentration using an analytical balance. As the test item was lumpy the test item was pressed through a sieve onto fine quartz and this mixture was pressed through the sieve again. Afterwards pure fine quartz was pressed through the sieve. This procedure was done for each concentration. Afterwards the test item was mixed with the fine quartz sand by a blender for around 10 minutes and then applied with this mixture to the soil. The test item treated fine quartz sand was mixed with the soil by using a laboratory mixer for around 10 minutes. The amount of quartz sand depended on the water content of the used charge of soil and was the same in all test item treatment groups (1st application: 62.5 g quartz sand per kg soil; 2nd application: 63.1 g quartz sand per kg soil). For the control the same amount of untreated quartz sand as in the test item treated groups was added to the soil. The application was done with a rotary mixer. The soil for one treatment was treated in one to two batches and then split into the replicates
Species:
Brassica napus
Plant group:
Dicotyledonae (dicots)
Details on test organisms:
- Common name: Oilseed Rape
- Plant family: Brassicaceae
- Prior seed treatment/sterilization: untreated seeds
Species:
Glycine max (G. soja)
Plant group:
Dicotyledonae (dicots)
Details on test organisms:
- Common name: Soybean
- Plant family: Fabaceae
- Prior seed treatment/sterilization: untreated seeds
Species:
Avena sativa
Plant group:
Monocotyledonae (monocots)
Details on test organisms:
- Common name: Oat
- Plant family: Poaceae
- Prior seed treatment/sterilization: untreated seeds
Test type:
other: Seedling Emergence and Seedling Growth Test
Study type:
laboratory study
Substrate type:
artificial soil
Limit test:
no
Total exposure duration:
14 d
Remarks:
after 50 % seedling emerge in the control.
Test temperature:
1st exposure period: Mean: 21.3 °C (Min: 15.3 °C; Max: 25.3 °C)
2nd exposure period: Mean: 21.4 °C (Min: 15.5 °C; Max: 26.6 °C)
Moisture:
Humidity:
1st exposure period: Mean: 71 % (Min: 44 %; Max: 100 %)
2nd exposure period: Mean: 78 % (Min: 54 %; Max: 100 %)
Details on test conditions:
TEST SYSTEM
- Test environment: The test was performed in a growth chamber under controlled conditions.
- Test container (type, material, size): Commercial plastic flower pots were used (∅ 12 cm or ∅ 14 cm)
- Method of seeding: Only untreated seeds were used. The seeds were introduced manually into the soil. After sowing the pots were placed on saucers and watered.
- No. of seeds per container: 5
- No. of replicates per treatment group: 6
- No. of replicates per control: 6

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
The soil was steam sterilized, delivered and analysed by the LUFA Speyer, Germany. Following parameters were analysed (the certificate of analysis was added to the raw data):
Soil Type: LUFA 2.3 (USDA: sandy loam)
Particle Size: all particles ≤ 0.2 cm
Corg: 0.94 ± 0.10%
pH: 6.8 ± 0.2
No pesticide treatments were performed in the year of sampling and for at least the two previous years.
According to Nelson and Sommers (1996) the value of the Corg can be converted into total organic matter content (TOM) with a conversion factor of 1.724. This corresponds to a percentage of TOM of 1.62%. Since the TOM deviates from the TOM of the standard soil (3.4%), a conversion of the EC50 values is performed by multiplication of the effect concentrations with factor 2.1.

NUTRIENT MEDIUM (if used)
- Fertilizer: After development of the first true leaves, Flory® 9 “Hydro” (Planta-Düngemittel GmbH) at 2 g/L and Terraflor®-AZ (Terraflor GmbH) at 0.2 g/L were added to the water one to three times a week, depending on the development of the plants.

GROWTH CONDITIONS
- Photoperiod: 16 h light : 8 h dark
- Light intensity and quality:
1st exposure period: Mean: 13600 Lux (Min: 9600 Lux; Max: 18710 Lux)
2nd exposure period: Mean: 13326 Lux (Min: 8440 Lux; Max: 18600 Lux)
- Day/night temperatures:
- Relative humidity (%):
- Wind velocity:
- Air exchange rate:
- Watering regime and schedules:
- Water source/type:
- Volume applied:
- Interval of applications:
- Method of application:
- Any pest control method/fertilization (if used):

ACCLIMATION PERIOD:

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
Fresh Weight:
The fresh weight of the above ground part of all survived plants of a pot (each pot is considered as a replicate) was determined 14 days after 50% seedling emergence in the control. If all plants of a pot were dead the value for this replicate was assessed as “0”.
Dry Weight:
The dry weight of the above ground part of all survived plants of a pot (each pot is considered as a replicate) was determined after determination of the fresh weight and after drying of the plants. Plants were dried at a temperature of 80 °C for at least 48 h.
Plant Height:
The height of the above ground part of all plants of a pot (each pot is considered as a replicate) was determined 14 days after 50% seedling emergence in the control. The height of dead plants was measured if possible.
Germination:
Germination was checked every working day until 50% of the control plants had emerged. Further checks were done weekly.
Mortality:
The number of living and dead plants was recorded 14 days after 50% seedling emergence in the control. A plant was considered dead if no living tissue could be found on the leaves or shoots. All other plants were considered living.
Phytotoxicity:
Visual phytotoxicity (e.g. chlorosis, necrosis, abnormal growth) was recorded weekly according to EPPO Standard PP 1/135 (3) after 50% seedling emergence in the control.
Growth Stages:
Growth stages at day 14 after 50% seedling emergence in the control were reported according to BBCH-Monograph - Growth stages.

VEHICLE CONTROL PERFORMED: no

TEST CONCENTRATIONS
Two applications were performed because the concentration range in the first application did insufficiently cover the effect concentrations
Nominal and measured concentrations:
1st Application:
Brassica napus, Glycine max and Avena sativa were tested with 62.5, 125, 250, 500 and 1000 mg test item/kg soil dry weight.
2nd Application:
Glycine max and Avena sativa were tested with 4.12, 12.3, 37.0, 111, 333 and 1000 mg test item/kg soil dry weight. Brassica napus was tested with 0.457, 1.37, 4.12, 12.3, 37.0, 111, 333 and 1000 mg test item/kg soil dry weight.
Reference substance (positive control):
no
Species:
Brassica napus
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
12.3 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Summary of Effect Concentrations (based on Dry Weight)
Species:
Brassica napus
Duration:
14 d
Dose descriptor:
LOEC
Effect conc.:
37 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Summary of Effect Concentrations (based on Dry Weight)
Species:
Brassica napus
Duration:
14 d
Dose descriptor:
EC50
Effect conc.:
222 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Summary of Effect Concentrations (based on Dry Weight)
Species:
Glycine max (G. soja)
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
4.12 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Summary of Effect Concentrations (based on Dry Weight)
Species:
Glycine max (G. soja)
Duration:
14 d
Dose descriptor:
LOEC
Effect conc.:
12.3 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Summary of Effect Concentrations (based on Dry Weight)
Species:
Glycine max (G. soja)
Duration:
14 d
Dose descriptor:
EC50
Effect conc.:
2 587 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Summary of Effect Concentrations (based on Dry Weight)
Remarks on result:
other: EC50 value is extrapolated.
Species:
Avena sativa
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
37 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Summary of Effect Concentrations (based on Dry Weight)
Species:
Avena sativa
Duration:
14 d
Dose descriptor:
LOEC
Effect conc.:
111 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Summary of Effect Concentrations (based on Dry Weight)
Species:
Avena sativa
Duration:
14 d
Dose descriptor:
EC50
Basis for effect:
other: Summary of Effect Concentrations (based on Dry Weight)
Remarks on result:
other: not determined due to mathematical reasons
Species:
Brassica napus
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
37 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Summary of Effect Concentrations (based on Height)
Species:
Brassica napus
Duration:
14 d
Dose descriptor:
LOEC
Effect conc.:
111 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Summary of Effect Concentrations (based on Height)
Species:
Brassica napus
Duration:
14 d
Dose descriptor:
EC50
Effect conc.:
1 772 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Summary of Effect Concentrations (based on Height)
Remarks on result:
other: EC50 value is extrapolated.
Species:
Glycine max (G. soja)
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Summary of Effect Concentrations (based on Height)
Species:
Glycine max (G. soja)
Duration:
14 d
Dose descriptor:
LOEC
Effect conc.:
> 1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Summary of Effect Concentrations (based on Height)
Species:
Glycine max (G. soja)
Duration:
14 d
Dose descriptor:
EC50
Basis for effect:
other: Summary of Effect Concentrations (based on Height)
Remarks on result:
other: not determined due to mathematical reasons
Species:
Avena sativa
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
37 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Summary of Effect Concentrations (based on Height),
Species:
Avena sativa
Duration:
14 d
Dose descriptor:
LOEC
Effect conc.:
111 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Summary of Effect Concentrations (based on Height),
Species:
Avena sativa
Duration:
14 d
Dose descriptor:
EC50
Basis for effect:
other: Summary of Effect Concentrations (based on Height),
Remarks on result:
other: not determined due to mathematical reasons
Details on results:
In the 1st application the lowest tested concentration was 62.5 mg/kg and thus many of the relevant effect concentrations were below the tested concentration range. In consequence the evaluation was performed only based on the 2nd application. Generally the results in the higher concentration range tested in both applications where comparable for the 1st and 2nd application.
The germination rate was not statistically significantly reduced for any species tested.
No mortality was observed for any species tested.
Main phytotoxic effects observed were growth reduction (all species), chlorosis (all species) and necrosis (Brassica napus and Glycine max).
Because of the low organic matter content of the tested soil (1.62%), a conversion to values in standard soil with an organic matter content of 3.4% would result in values with a factor of 2.1 higher than the values provided above:
The normalized values for the most sensitive species in terms of weight was an EC50 value for fresh weight of 800 mg/kg soil dry weight and an EC50 value for dry weight of 466 mg test item/kg soil dry weight for Brassica napus. The normalized EC50 values for Glycine max were 2409 mg/kg soil dry weight for fresh weight and 5433 mg test item/kg soil dry weight for dry weight. The normalized EC25 values for Avena sativa were 630 mg/kg soil dry weight for the fresh weight and 670 mg test item/kg soil dry weight for the dry weight.
Validity criteria fulfilled:
yes
Conclusions:
The most sensitive species in terms of weight was Brassica napus with an EC50 value for fresh weight of 381 mg/kg soil dry weight and an EC50 value for dry weight of 222 mg test item/kg soil dry weight. The EC50 values for Glycine max were 1147 mg/kg soil dry weight for fresh weight and 2587 mg test item/kg soil dry weight for dry weight. The EC25 values for Avena sativa were 300 mg/kg soil dry weight for the fresh weight and 319 mg test item/kg soil dry weight for the dry weight.

Description of key information

The study provided was conducted to recognised testing guidelines and with GLP certification.

Key value for chemical safety assessment

Short-term EC50 or LC50 for terrestrial plants:
222 mg/kg soil dw

Additional information

The toxicity of the test item to terrestrial plants was tested in a Seedling Emergence and Seedling Growth Test according to OECD 208 using Oilseed Rape, Soybean and Oat (IBACON 2013). The most sensitive species in terms of weight was Brassica napus (Oilseed Rape) with an EC50 value for fresh weight of 381 mg/kg soil dry weight and an EC50 value for dry weight of 222 mg test item/kg soil dry weight. The EC50 values for Glycine max (Soybean) were 1147 mg/kg soil dry weight for fresh weight and 2587 mg test item/kg soil dry weight for dry weight. The EC25 values for Avena sativa (Oat) were 300 mg/kg soil dry weight for the fresh weight and 319 mg test item/kg soil dry weight for the dry weight.

The germination rate was not statistically significantly reduced for any species tested.

No mortality was observed for any species tested.

Main phytotoxic effects observed were growth reduction (all species), chlorosis (all species) and necrosis (Brassica napus and Glycine max).

Because of the low organic matter content of the tested soil (1.62%), a conversion to values in standard soil with an organic matter content of 3.4% would result in values with a factor of 2.1 higher than the values provided above: The normalized values for the most sensitive species in terms of weight was an EC50 value for fresh weight of 800 mg/kg soil dry weight and an EC50 value for dry weight of 466 mg test item/kg soil dry weight for Brassica napus. The normalized EC50 values for Glycine max were 2409 mg/kg soil dry weight for fresh weight and 5433 mg test item/kg soil dry weight for dry weight. The normalized EC25 values for Avena sativa were 630 mg/kg soil dry weight for the fresh weight and 670 mg test item/kg soil dry weight for the dry weight.

Information concerning long-term effects on the toxicity to terrestrial plants is not available for the test substance. The test substance is not supposed to be directly applied to soil and an indirect exposure is unlikely since the log Koc is below 3 and the substance has no cationic properties. Both parameters indicate a low adsorption potential of the test substance. Therefore, binding to sewage sludge is unlikely and as a consequence a transfer to the soil compartment is not expected.

Additionally, an environmental exposure assessment was performed in order to determine possible risks of the test compound to the environment. According to the results of the exposure assessment, all the relevant uses of the test substance are considered to be safe with a Risk Characterization Ratio below 1. Hence, further tests on long-term effects to terrestrial plants are not provided.