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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:
From 2001-05-10 to 2002-02-18
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
This study was performed according to OECD Guideline 208 with GLP statement. Three species (tomato, oat and soybean) were tested. However, necrosis in solvent controls and a poor dose-effect relationship for shoot weights were observed for two species: tomato and oat. Therefore, the results with these two species must be taken into account with caution.
Qualifier:
according to guideline
Guideline:
OECD Guideline 208 (Terrestrial Plants Test: Seedling Emergence and Seedling Growth Test)
Deviations:
no
Principles of method if other than guideline:
not applicable.
GLP compliance:
yes
Analytical monitoring:
no
Details on sampling:
- Concentrations: 12, 37, 110, 330, and 1000 mg/kg
- Sampling method: Oats pots were observed on days 4, 11, 18, and 25 (test termination), soybean pots were observed on days 5, 12, 19, and 26 (test termination), while tomato pots were observed on days 7, 14, 21, and 28 (test termination) to determine percent emergence, mortality and the morphological abnormalities of the emerged shoots. Observations of the morphological abnormalities were reported as the percentage of plants exhibiting the abnormality. At test termination, the shoot portions of each plant were severed at the substrate surface and individually placed in labeled, prepared aluminium tins. Plants were dried in radiant heat ovens at approximately 70°C for a minimum of three days before determining dry weights.
Vehicle:
yes
Details on preparation and application of test substrate:
- Method of application to soil surface: Priori to planting, 100 mL of test solution was added to the surface of each pot. Each pot also received approximately 100 mL of nutrient solution via subirrigation.
- Controls: idem to test conditions, but they received only water solution.
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): acetone
- Concentration of vehicle in test medium (stock solution and final test solution): 1%
- Evaporation of vehicle before use: no data
Species:
Avena sativa
Plant group:
Monocotyledonae (monocots)
Details on test organisms:
- Common name: oat
- Plant family: Poaceae
- Variety: Jerry
- Source of seed: Gartner Seed Farm, Mandan, North Dakota
- Prior seed treatment/sterilization: none
- Historical germination of seed (germination of seed lot tested): no data
- Seed storage: at 4°C in the dark until test initiation.
Species:
Glycine max (G. soja)
Plant group:
Dicotyledonae (dicots)
Details on test organisms:
- Common name: soybean
- Plant family: Fabaceae
- Variety: Edible early Hakucho
- Source of seed: Park seed compagny, Greenwood, South Carolina
- Prior seed treatment/sterilization: none
- Historical germination of seed (germination of seed lot tested): no data
- Seed storage: at 4°C in the dark until test initiation.
Species:
Lycopersicon esculentum
Plant group:
Dicotyledonae (dicots)
Details on test organisms:
- Common name: tomato
- Plant family: Solanaceae
- Variety: Celebrity
- Source of seed: Park seed compagny, Greenwood, South Carolina
- Prior seed treatment/sterilization: none
- Historical germination of seed (germination of seed lot tested): no data
- Seed storage: at 4°C in the dark until test initiation.
Test type:
seedling emergence toxicity test
Study type:
laboratory study
Substrate type:
natural soil
Limit test:
no
Total exposure duration:
28 d
Remarks:
none
Post exposure observation period:
no data
Test temperature:
15-35°C
pH:
no data
Moisture:
no data
Details on test conditions:
TEST SYSTEM
- Testing facility: Springborn Lab.
- Test container (type, material, size): polypropylene pots, 13 cm diameter on top, and 9 cm diameter on bottom. 13 cm tall.
- Amount of soil: 1.2 Kg of support medium

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Geographic location: Fairhaven, Massachussets
- Pesticide use history at the collection site: no data
- Collection procedures: no data
- Sampling depth (cm): no data
- Organic carbon (%): 1.3

NUTRIENT MEDIUM (if used)
- Description: nutrient solution according to US FDA, 1987

GROWTH CONDITIONS
- Photoperiod: 16:8
- Light source: footcandles
- Light intensity and quality: 8600 lux. Sodium vapor lights and natural light
- Day/night temperatures: 15-35°C

VEHICLE CONTROL PERFORMED: yes

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3
Nominal and measured concentrations:
- nominal concentrations: 12, 37, 110, 330, and 1000 mg/Kg for the three species.
- No measured concentrations.
Reference substance (positive control):
no
Species:
Avena sativa
Duration:
25 d
Dose descriptor:
EC25
Effect conc.:
200 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: shoot weight
Key result
Species:
Avena sativa
Duration:
25 d
Dose descriptor:
EC50
Effect conc.:
> 1 100 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: shoot weight, and seedling emergence
Key result
Species:
Avena sativa
Duration:
25 d
Dose descriptor:
other: Highest concentration without observed effect
Effect conc.:
117 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: shoot weight
Species:
Glycine max (G. soja)
Duration:
26 d
Dose descriptor:
EC25
Effect conc.:
> 1 100 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: shoot weight, and seedling emergence
Key result
Species:
Glycine max (G. soja)
Duration:
26 d
Dose descriptor:
EC50
Effect conc.:
> 1 100 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: shoot weight, and seedling emergence
Species:
Glycine max (G. soja)
Duration:
26 d
Dose descriptor:
other: Highest concentration without observed effect
Effect conc.:
1 100 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: shoot weight, and seedling emergence
Species:
Lycopersicon esculentum
Duration:
28 d
Dose descriptor:
EC25
Effect conc.:
> 1 100 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: shoot weight, and seedling emergence
Key result
Species:
Lycopersicon esculentum
Duration:
28 d
Dose descriptor:
EC50
Effect conc.:
> 1 100 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: shoot weight, and seedling emergence
Species:
Lycopersicon esculentum
Duration:
28 d
Dose descriptor:
other: Highest concentration without observed effect
Effect conc.:
1 100 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: shoot weight, and seedling emergence
Details on results:
no data
Results with reference substance (positive control):
not applicable
Reported statistics and error estimates:
no data

All the data for the three species are presented in attached file.

Validity criteria fulfilled:
no
Remarks:
Necrosis in solvent controls and a poor dose-effect relationship for shoot weights were observed for tomato and oat.
Conclusions:
The 25d-EC50 to oat, the 26d-EC50 to soybean and the 28d-EC50 to tomato, based on percent emergence and shoot weight, were determined to be greater than the highest concentration tested: 1000 mg/Kg, corresponding to 1100 mg/Kg based on the whole product (maximum rate tested). The highest concentration without observed effect were determined to be 117 mg/Kg for shoot weight of oat (as whole product) and 1100 mg/Kg for percent emergence and shoot weight of soybean an tomato (as whole product). Necrosis in solvent controls for oat and tomato and a poor dose-effect relationship for shoot weights were observed. Therefore, the results with these two species must be taken into account with caution.
Executive summary:

Effects of the test substance have been assessed on seedling emergence and seedling growth test following OECD 208 part A, under GLP.

 

Three different species have been used for this experiment: oat (Avena sativa), soybean (Glycine max) and tomato (Lycopersicon esculentum); and different nominal treatment rates: 12, 37, 110, 330, and 1000 mg/Kg during 25 to 28 days.

 

The 25d-EC50 to oat, the 26d-EC50 to soybean and the 28d-EC50 to tomato, based on percent emergence and shoot weight, were determined to be greater than the highest concentration tested: 1000 mg/Kg, corresponding to 1100 mg/Kg based on the whole product (maximum rate tested).

The highest concentration without observed effect were determined to be 117 mg/Kg for shoot weight of oat (as whole product) and 1100 mg/Kg for percent emergence and shoot weight of soybean an tomato (as whole product). The results, based on the whole product, are presented below.

Table 6.3.3/1: summary of results

Species

EC25(mg/Kg)

EC50(mg/Kg)

Highest concentration without observed effect (mg/Kg)

Oat

200 (sw)

> 1100 (e, sw)

117 (sw)

Soybean

> 1100 (e, sw)

> 1100 (e, sw)

1100 (e, sw)

Tomato

> 1100 (e, sw)

> 1100 (e, sw)

1100 (e, sw)

Notes: values presented as greater than were empirically estimated to be greater than the highest concentration tested.

 e = percent emergence, sw = shoot weight.

Necrosis in solvent controls and a poor dose-effect relationship for shoot weights were observed for oat and tomato. Therefore, the results with these two species must be taken into account with caution.

Description of key information

OECD Guideline 208, GLP, key study, validity 2:

Soybean: 26d-EC50 > 1100 mg/Kg dw; 26d-NOEC = 1100 mg/kg dw.

Oat: 25d-EC50 > 1100 mg/kg dw; 25d-NOEC = 117 mg/kg. Necrosis in solvent controls and a poor dose-effect relationship for shoot weights were observed. Therefore, the results must be taken into account with caution.

Tomato: 28d-EC50 > 1100 mg/kg dw; 28d-NOEC = 1100 mg/kg dw. Necrosis in solvent controls and a poor dose-effect relationship for shoot weights were observed. Therefore, the results must be taken into account with caution.

Even if the plant study available is considered as an acute test (based on number of tested species), the NOEC value obtained for oat (117 mg/kg) is the lowest compared to the long-term toxicity data on soil microorganisms. Therefore, this NOEC value is used for risk assessment.

Key value for chemical safety assessment

Short-term EC50 or LC50 for terrestrial plants:
1 100 mg/kg soil dw
Long-term EC10, LC10 or NOEC for terrestrial plants:
117 mg/kg soil dw

Additional information

One study is available, to assess the effects of the registered substance on seedling emergence and seedling growth. This study was conducted according to OECD 208 part A, under GLP.

Three different species have been used for this experiment: oat (Avena sativa), soybean (Glycine max) and tomato (Lycopersicon esculentum); and different nominal treatment rates: 12, 37, 110, 330, and 1000 mg/Kg during 25 to 28 days.

The 25d-EC50 to oat, the 26d-EC50 to soybean and the 28d-EC50 to tomato, based on percent emergence and shoot weight, were determined to be greater than the highest concentration tested: 1000 mg/Kg, corresponding to 1100 mg/Kg based on the whole product (maximum rate tested).

The highest concentration without observed effect (NOEC) were determined to be 117 mg/Kg for shoot weight of oat (as whole product) and 1100 mg/Kg for percent emergence and shoot weight of soybean an tomato (as whole product).

Necrosis in solvent controls and a poor dose-effect relationship for shoot weights were observed for oat and tomato. Therefore, the results with these two species must be taken into account with caution.

Even if the plant study available is considered as an acute test (based on number of tested species), the NOEC value obtained for oat (117 mg/kg) is the lowest compared to the long-term toxicity data on soil microorganisms. Therefore, this NOEC value is used for risk assessment.