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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
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Guideline study performed in compliance with GLP, available as unpublished report, no restrictions, fully adequate for assessment.
Qualifier:
according to guideline
Guideline:
OECD Guideline 208 (Terrestrial Plants Test: Seedling Emergence and Seedling Growth Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
- Substance: TBzTD
- Aggregate state at room temperature: solid
- Colour: off-white
- Solubility: in water 0.001 to 0.01 mg/L (at 20.5°C)
- Stability: is considered stable under the test conditions
- Storage: in original container, at room temperature (+10°C to +30°C), in the dark
- Lot No. 80600108
- Purity: 97.7% according to certificate of analysis
- Date of analysis: June 19, 2008
- Expiry date: June 01, 2010
Analytical monitoring:
no
Vehicle:
no
Details on preparation and application of test substrate:
On the basis of the results of the non-GLP range finding test, the following concentrations were tested:

- 4050 mg test item/kg soil dry weight
- 1350 mg test item/kg soil dry weight
- 450 mg test item/kg soil dry weight
- 150 mg test itemlkg soil dry weight
- 50 mg test itemlkg soil dry weight

Control: untreated control (the same amount of untreated quartz sand as in the test item treated groups will be added to the soil)

The specified amounts of test item were mixed with fine quartz sand (572.3 g (1st application) and 806.4g (2nd application)) by using a laboratory mixer for around 10 minutes. The test item treated fine quartz sand was mixed with the soil (14.2 kg (1st application) and 18.0 kg (2nd application)) by using a laboratory mixer for around 10 minutes. The soil for one treatment of the 15t application was treated in two batches and soil for one treatment of the 2nd application was treated in one batch. Then the soil was split into the replicates.
Species:
Brassica napus
Plant group:
Dicotyledonae (dicots)
Details on test organisms:
- Family: Brassicaceae
- Common name: Oilseed Rape
- Source: Syngenta Seeds
Species:
other: Vicia faba
Plant group:
Dicotyledonae (dicots)
Details on test organisms:
- Family: Fabaceae
- Common name: Bean
- Source: Saaten-Union GmbH
Species:
Helianthus annuus
Plant group:
Dicotyledonae (dicots)
Details on test organisms:
- Family: Compositeae
- Common name: Sunflower
- Source: SOC-France
Species:
Cucumis sativus
Plant group:
Dicotyledonae (dicots)
Details on test organisms:
- Family: Curcurbitaceae
- Common name: Cucumber
- Source: Nunhems
Species:
Avena sativa
Plant group:
Monocotyledonae (monocots)
Details on test organisms:
- Family: Poaceae
- Common name: Oat
- Source: Nordsaat Saatzucht-gesellschaft mbH
Species:
Allium cepa
Plant group:
Monocotyledonae (monocots)
Details on test organisms:
- Family: Liliaceae
- Common name: Onion
- Source: Hild
Test type:
other: seedling emergence and seedling growth test
Study type:
laboratory study
Substrate type:
other: LUFA 2.3 (USDA: sandy loam)
Limit test:
no
Total exposure duration:
21 d
Remarks:
14 and 21 days after 50% seedling emergence in the control depending on the growht of the seedlings
Test temperature:
For Helianthus annuus, Cucumis sativus, Avena sativa and Allium cepa:
Day (max. 27°C, min 23°C), Night (max 22°C, min 18°C), Humidity (max 81%, min 49%), Light intensity (Mean 7510 Lux)

For Brassica napus and Vicia faba:
Day (max 27°C, min 23°C), Night (max 22°C, min 18°C), Humidity (max 81%, min 49%), Light intensity (mean 8070 Lux)
Moisture:
A spot check on soil moisture was carried out daily. Bottom watering (through saucers) was done where necessary. Water was given in order to assure optimal water supply of the plants.
Details on test conditions:
- Number of pots and plants: 6 pots containing 5 seeds were tested for each treatment group. Each pot presented one replicate. 30 seeds per species and treatment group were tested.
- Light regime: 16h light: 8h dark
- Fertilizer: After development of the first true leaves, Flory 9 "Hydro" (Planta) at 1 g/L and Fetrilon 13 % (Compo) at 0.023 g/L were added to the water one to three times a week, depending on the development of the plants.
Nominal and measured concentrations:
On the basis of the results of the non-GLP range finding test, the following concentrations were tested:

- 4050 mg test item/kg soil dry weight
- 1350 mg test item/kg soil dry weight
- 450 mg test item/kg soil dry weight
- 150 mg test itemlkg soil dry weight
- 50 mg test itemlkg soil dry weight
Species:
Brassica napus
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
4 050 mg/kg soil dw
Nominal / measured:
nominal
Basis for effect:
other: all evaluated effects
Species:
Brassica napus
Duration:
14 d
Dose descriptor:
LOEC
Effect conc.:
> 4 050 mg/kg soil dw
Nominal / measured:
nominal
Basis for effect:
other: all evaluated effects
Species:
other: Vicia faba
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
4 050 mg/kg soil dw
Nominal / measured:
nominal
Basis for effect:
other: all evaluated effects
Species:
other: Vicia faba
Duration:
14 d
Dose descriptor:
LOEC
Effect conc.:
> 4 050 mg/kg soil dw
Nominal / measured:
nominal
Basis for effect:
other: all evaluated effects
Species:
Helianthus annuus
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
4 050 mg/kg soil dw
Nominal / measured:
nominal
Basis for effect:
other: all evaluated effects
Species:
Helianthus annuus
Duration:
14 d
Dose descriptor:
LOEC
Effect conc.:
> 4 050 mg/kg soil dw
Nominal / measured:
nominal
Basis for effect:
other: all evaluated effects
Species:
Cucumis sativus
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
4 050 mg/kg soil dw
Nominal / measured:
nominal
Basis for effect:
other: all evaluated effects
Species:
Cucumis sativus
Duration:
14 d
Dose descriptor:
LOEC
Effect conc.:
> 4 050 mg/kg soil dw
Nominal / measured:
nominal
Basis for effect:
other: all evaluated effects
Species:
Avena sativa
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
1 350 mg/kg soil dw
Nominal / measured:
nominal
Basis for effect:
other: fresh weight
Remarks on result:
other: all other evaluated effects had a NOEC of 4050 mg/kg
Species:
Avena sativa
Duration:
14 d
Dose descriptor:
LOEC
Effect conc.:
4 050 mg/kg soil dw
Nominal / measured:
nominal
Basis for effect:
other: fresh weight
Remarks on result:
other: all other evaluated effects had a NOEC of 4050 mg/kg
Species:
Allium cepa
Duration:
21 d
Dose descriptor:
NOEC
Effect conc.:
4 050 mg/kg soil dw
Nominal / measured:
nominal
Basis for effect:
other: all evaluated effects
Species:
Allium cepa
Duration:
21 d
Dose descriptor:
LOEC
Effect conc.:
> 4 050 mg/kg soil dw
Nominal / measured:
nominal
Basis for effect:
other: all evaluated effects
Details on results:
Brassica napus:
- Fresh weight (14 days): not reduced at any test concentration, plant development was not delayed
- Germination: germination rate between 96.7% and 100% (control = 90%) (no significant diff with control)
- Mortality (14 days): no stat sign mortality occurred
- Phytotoxicity (14 days): slight phytotoxic effects were chlorosis, growth reduction and discoloration scattered in single pots at several concentrations

Vicia faba :
- Fresh weight (14 days): not reduced at any test concentration, plant development was not clearly delayed compared to controls
- Germination: germination rate between 86.7 and 96.7% (control 83.3%) (no sign diff with control)
- Mortality (14 days): no stat sign mortality occurred
- Phytotoxicity (14 days): only slight growth retardation scattered in single pots at several concentrations

Helianthus annuus:
- Fresh weight (14 days): not reduced at any test concentration, plant development was not delayed compared to controls
- Germination: germination rate between 70% an d86.7% (controls 80%) (no sign diff with control)
- Mortality (14 days): no stat sign mortality occurred
- Phytotoxicity (14 days): Slight phytotoxic effects were chlorosis (in one pot at 450 mg test item/kg), growth reduction (in one pot at 50, 450 and 4050 mg test item/kg) and abnormal stems (in one pot at 4050 mg test item/kg).

Cucumis sativus:
- Fresh weight (14 days): The fresh weight was reduced at all tested concentrations (2.9% to 11.4) except the concentration of 150 test item/kg, where an increased fresh weight was observed (3.4%). The reduction was statistically significant at 450 mg test item/kg (11.4%). This effect is considered to be not test item related as at 1350 and 4050 mg test item/kg the fresh weight reduction was statistically not significant. The plant development was not delayed compared to controls.
- Germination: germination rate 100% (controls 100%)(no sign diff with controls)
- Mortality (14 days): no stat sign mortality occurred
- Phytotoxicity (14 days): no phytotoxic effects

Avena sativa:
- Fresh weight (14 days): The fresh weight was reduced at all the tested concentrations (9.3 to 21.3%). This reduction was statistically significant at 450 and 4050 mg test item/kg (21.3%). The effect at 450 mg test item/kg is considered to be not test item related as at 1350 mg test item/kg the fresh weight reduction was statistically not significant. The statistical significance at 4050 mg test item/kg must not necessarily be a treatment related effect since there was no clear dose relation over the concentrations. However, due to the lack of a higher concentration, 4050 mg test item/kg is considered to be the lowest observed effect concentration (LOEC). The plant development was not delayed compared to controls.
- Germination: germination rate ranged from 83.3% to 90% (control 90%)(no sign diff with controls)
- Mortality (14 days): no stat sign mortality occurred
- Phytotoxicity (14 days): The only phytotoxic effects were necrosis in one pot at the concentration of 4050 mg test item/kg (25%; 20% due to one dead seedling) and slight necrosis and growth reduction (3%) in one pot at the concentration of 50.0 mg test item/kg.

Allium cepa:
- Fresh weight (21 days): not stat sign reduced at any tested concentration
- Germination: germination rate between 86.7% and 90% (control 70%)(no sign diff with control)
- Mortality (14 days): no stat sign mortality occurred
- Phytotoxicity (14 days): Phytotoxic effects were necrosis and growth reduction at the test concentration of 150 mg/kg (23%; 20% due to one dead seedling), necrosis at the test concentrations of 450 mg/kg (40%; 40% due to two dead seedlings) and 1350 mg/kg (25%; 25% due to one dead seedling) and slight chlorosis, growth reduction and abnormal leaves scattered at all concentrations tested.
Reported statistics and error estimates:
Fresh weight data were tested for normal distribution and homogeneity of variance using the Kolmogoroff-Smimov-Test (α = 0.05) and the Cochran-Test (α = 0.05). Because the data were normally distributed and homogeneous the Dunnett Test (multiple comparison, one-sided smaller, α = 0.05) was used for comparing treatment groups and control.

For the mortality and germination data Fisher's Exact-Test was used (two-sided, α = 0.05).

The computer programs used to perform the statistical analyses were ToxRat Professional, Version 2.09, ToxRat® Solutions GmbH, © 2001­ 2005.

The NOEC and LOEC was calculated if possible
Validity criteria fulfilled:
yes
Conclusions:
TBzTD was tested for effects on seedling emergence and seedling growth of 6 species out of 6 different plant families.

The most sensitive species in terms of fresh weight was Avena sativa with a NOEC of 1350 mg TBzTD/kg soil dry weight and a LOEC of 4050 mg TBzTD/kg soil dry weight. All other tested plant species showed a NOEC based on fresh weight of 4050 mg TBzTD/kg soil dry weight.

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

Mortality was observed for Allium cepa at 150, 450 and 1350 mg TBzTD/kg (3.7% to 7.7%) and for Avena sativa at 4050 mg TBzTD/kg (4.0%). None of the mortality counts turned out to be statistically significant. For Brassica napus, ViciaJaba, Helianthus annuus and Cucumis sativus no mortality was observed.

Phytotoxic effects observed were slight chlorosis (Brassicca napus, Helianthus annuus and Allium cepa), necrosis (Avena sativa and Allium cepa) and slight growth reduction (Brassicca napus, Vicia Jaba, Helianthus annuus, Avena sativa and Allium cepa). Additionally Brassica napus seedlings showed discoloration of leaves in three pots, Helianthus annuus seedlings showed abnormal growth of the stems in one pot and some pots of Allium cepa showed abnormal growth of the leaves.

Description of key information

The seedling emergence and early growth of higher plants under the influence of tetrakis(phenylmethyl)thioperoxydi(carbothioamide) (TBzTD) has been tested according to a method OECD 208 (Terrestrial Plant Test: Seedling Emergence and Seedling Growth Test) with six species belonging to six different families. A NOEC of 1350 mg TBzTD/kg and a LOEC of 4050 mg TBzTD/kg soil dry weight has been established for the most sensitive species. All other tested plant species showed a NOEC based on fresh weight of 4050 mg TBzTD/kg soil dry weight.

Key value for chemical safety assessment

Short-term EC50 or LC50 for terrestrial plants:
4 050 mg/kg soil dw

Additional information

TBzTD was tested for effects on seedling emergence and seedling growth of 6 species out of 6 different plant families. The most sensitive species in terms of fresh weight was Avena sativa with a NOEC of 1350 mg TBzTD/kg soil dry weight and a LOEC of 4050 mg TBzTD/kg soil dry weight. All other tested plant species showed a NOEC based on fresh weight of 4050 mg TBzTD/kg soil dry weight. The germination rate was not statistically significantly reduced for all species tested. Mortality was observed for Allium cepa at 150, 450 and 1350 mg TBzTD/kg (3.7% to 7.7%) and for Avena sativa at 4050 mg TBzTD/kg (4.0%). None of the mortality counts turned out to be statistically significant. For Brassica napus, ViciaJaba, Helianthus annuus and Cucumis sativus no mortality was observed. Phytotoxic effects observed were slight chlorosis (Brassicca napus, Helianthus annuus and Allium cepa), necrosis (Avena sativa and Allium cepa) and slight growth reduction (Brassicca napus, Vicia Jaba, Helianthus annuus, Avena sativa and Allium cepa). Additionally Brassica napus seedlings showed discoloration of leaves in three pots, Helianthus annuus seedlings showed abnormal growth of the stems in one pot and some pots of Allium cepa showed abnormal growth of the leaves.

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