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Ecotoxicological information

Toxicity to terrestrial plants

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Endpoint:
toxicity to terrestrial plants: long-term
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
Please refer to the analogue justification provided in Section 13.
Reason / purpose for cross-reference:
read-across source
GLP compliance:
yes
Reference substance (positive control):
no
Species:
Brassica oleracea var. capitata
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
>= 5 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: Seedling emergence, percent survival, shoot dry weight, morphological abnormalities and plant condition.
Species:
Zea mays
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
>= 5 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: Seedling emergence, percent survival, shoot dry weight, morphological abnormalities and plant condition.
Species:
Cucumis sativus
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
>= 5 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: Seedling emergence, percent survival, shoot dry weight, morphological abnormalities and plant condition.
Species:
Avena sativa
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
>= 5 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: Seedling emergence, percent survival, shoot dry weight, morphological abnormalities and plant condition.
Species:
Allium cepa
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
>= 5 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: Seedling emergence, percent survival, shoot dry weight, morphological abnormalities and plant condition.
Species:
Lolium perenne
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
>= 5 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: Seedling emergence, percent survival, shoot dry weight, morphological abnormalities and plant condition.
Species:
Raphanus sativus
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
>= 5 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: Seedling emergence, percent survival, shoot dry weight, morphological abnormalities and plant condition.
Species:
Glycine max (G. soja)
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
>= 5 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: Seedling emergence, percent survival, shoot dry weight, morphological abnormalities and plant condition.
Species:
Helianthus annuus
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
>= 5 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: Seedling emergence, percent survival, shoot dry weight, morphological abnormalities and plant condition.
Species:
Lycopersicon esculentum
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
>= 5 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: Seedling emergence, percent survival, shoot dry weight, morphological abnormalities and plant condition.
Details on results:
NOEC values for all 10 species can be reported in terms of the mean measured concentration: NOEC >= 2.8 mg a.i./kg soil dry weight

SEED GERMINATION
- Percent seed germination: see table 2 for the number of non-emerged seeds per concentration for each species
- Root length: not measured
- Root discolouration/malformation: not measured
- Other effects:
- Results with reference substance valid? No reference substance used.

SEEDLING EMERGENCE
- Percent seedling emergence: see table 2 for the number of non-emerged seeds per concentration for each species. See table 4 for percentage emergence of seedlings per concentration for each species.
- Percent survival: all species displayed 100% survival, see table 5 for the mean percentage survival of seedlings per concentration for each species.
- Plant height: not measured
- Dry weight: see table 6 for mean seedling weight per concentration for each species.
- Abnormal seed development or appearance: see table 3 for morphological abnormalities per concentration for each species.


INJURY RATING SYSTEM: plants were recorded as: healthy (H), necrotic (N), chlorotic (C), leaf blotching (LB), dead plant (DP), non-emerged (NE), not applicable (NA) or other. See table 3 for details of morphological abnormalities per concentration for each species. .
Reported statistics and error estimates:
The No-Observed-Effect Concentration (NOEC), the highest test concentration, which demonstrated no statistically adverse effect (p <0.05) when compared to the control data, as well as the lowest concentration which caused a significant adverse effect, the Lowest-Observed-Effect Concentration (LOEC), were determined for percent emergence, survival, and shoot dry weight. Data were first checked for normality and for homogeneity of variance using the appropriate qualifying tests. All statistical determinations were made at the 95% level of certainty, except in the case of the tests for normality of variance and homoscedasticity, where the 99% level of certainty was applied.
Emergence and survival were analysed using a Fisher's Exact Test, Weight was analysed using an Equal Variance t-Test when data was normally distributed and had equal variance, unequal variance t-Test for normally distributed data with unequal variance, and a Wilcoxon Rank-Sum Two-Sample test was used when data was not normally distributed with either equal or unequal variance.

Table 1. Measured and nominal concentrations of dimethylsilanediol at test initiation and termination

Nominal concentration (mg a.i./kg soil dwt)

Measured concentration at test initiation

(mg a.i./kg soil dwt)

Initiation percent of nominal (%)

Measured concentration at test termination

(mg a.i./kg soil dwt)

Test termination percent of nominal (%)

Mean (SD)

Overall mean percentage of nominal

 Control  <LOQ  N/A  <LOQ  N/A  N/A  N/A
 5.0  4.3  85  1.2  24  2.8 (2.2)  55
 5.0  4.4  87        
 5.0  4.4  87        
 Mean  4.3  87  1.2  24    

Table 2. Number of non-emerged seeds per test concentration (N=40)

Species

Nominal concentration (mg a.i./kg soil dwt)

Control

0.050

0.50

5.0

Brassica oleracea var. capitata

2

0

0

2

Zea mays

1

0

1

2

Cucumis sativus

1

0

0

0

Avena sativa

1

1

0

2

Allium cepa

3

0

2

4

Lolium perenne

5

3

1

3

Raphanus sativus

3

0

1

1

Glycine max

7

3

1

6

Helianthus annuus

2

2

1

5

Lycopersicon esculentum

0

0

1

3

Table 3. Morphological observations of emerged plants

Species

Nominal concentration (mg a.i./kg soil dwt)

Control

0.050

0.50

5.0

Brassica oleracea var. capitata

38 H

16 H

16 H

38 H

Zea mays

39 H

16 H

15 H

38 H

Cucumis sativus

39 H

16 H

16 H

40 H

Avena sativa

39 H

15 H

40 H

38 H

Allium cepa

37 H

16 H

13 H

36 H

Lolium perenne

35 H

13 H

15 H

37 H

Raphanus sativus

37 H

16 H

15 H

37 H

Glycine max

38 H, 1 DP, 1 N

13 H

15 H

34 H

Helianthus annuus

38 H

14 H

39 H

35 H

Lycopersicon esculentum

40 H

16 H

15 H

37 H

H = healthy, DP = dead plant, N = necrotic

Table 4. Mean percentage emergence of seedlings (as mean (SD))

Species

Nominal concentration (mg a.i./kg soil dwt)

Control

0.050

0.50

5.0

Brassica oleracea var. capitata

95 (11)

100 (0)

100 (0)

95 (11)

Zea mays

98 (8)

100 (0)

94 (13)

95 (11)

Cucumis sativus

98 (8)

100 (0)

100 (0)

100 (0)

Avena sativa

98 (6)

94 (9)

100 (0)

95 (7)

Allium cepa

93 (11)

100 (0)

88 (18)

90 (10)

Lolium perenne

88 (9)

81 (27)

94 (9)

93 (11)

Raphanus sativus

93 (12)

100 (0)

94 (13)

98 (8)

Glycine max

83 (17)

81 (24)

94 (13)

85 (13)

Helianthus annuus

95 (11)

88 (14)

94 (13)

88 (18)

Lycopersicon esculentum

100 (0)

100 (0)

94 (13)

93 (17)

Table 5. Mean percentage survival of seedlings (as mean (SD))

Species

Nominal concentration (mg a.i./kg soil dwt)

Control

0.050

0.50

5.0

Brassica oleracea var. capitata

100 (0)

100 (0)

100 (0)

100 (0)

Zea mays

100 (0)

100 (0)

100 (0)

100 (0)

Cucumis sativus

100 (0)

100 (0)

100 (0)

100 (0)

Avena sativa

100 (0)

100 (0)

100 (0)

100 (0)

Allium cepa

100 (0)

100 (0)

100 (0)

100 (0)

Lolium perenne

100 (0)

100 (0)

100 (0)

100 (0)

Raphanus sativus

100 (0)

100 (0)

100 (0)

100 (0)

Glycine max

98 (8)

100 (0)

100 (0)

100 (0)

Helianthus annuus

100 (0)

100 (0)

100 (0)

100 (0)

Lycopersicon esculentum

100 (0)

100 (0)

100 (0)

100 (0)

Table 6. Mean seedling weight (g) (as mean (SD))

Species

Nominal concentration (mg a.i./kg soil dwt)

Control

0.050

0.50

5.0

Brassica oleracea var. capitata

0.1261 (0.0159)

0.1469 (0.0175)

0.1627 (0.0078)

0.1482 (0.0249)

Zea mays

0.4285 (0.0587)

0.4558 (0.0486)

0.4925 (0.0694)

0.5129 (0.0823)

Cucumis sativus

0.2534 (0.0180)

0.3106 (0.0324)

0.2905 (0.0218)

0.3120 (0.0193)

Avena sativa

0.728 (0.0078)

0.0701 (0.0156)

0.0900 (0.0137)

0.0886 (0.0147)

Allium cepa

0.0155 (0.0021)

0.0151 (0.0013)

0.0189 (0.0029)

0.0216 (0.0035)

Lolium perenne

0.0099 (0.0015)

0.0106 (0.0006)

0.0127 (0.0001)

0.0122 (0.0031)

Raphanus sativus

0.1209 (0.0143)

0.1303 (0.0106)

0.1382 (0.0230)

0.1280 (0.0146)

Glycine max

0.4052 (0.0812)

0.4320 (0.0305)

0.4136 (0.0435)

0.4106 (0.0812)

Helianthus annuus

0.1845 (0.0237)

0.2141 (0.0321)

0.2150 (0.0375)

0.2160 (0.0331)

Lycopersicon esculentum

0.1195 (0.0198)

0.1316 (0.0405)

0.1371 (0.0254)

0.1497 (0.0432)

Table 7. Percentage inhibition of emergence, survival and shoot dry weight in the highest test concentration (5.0 mg a.i./kg dw, as nominal) compared to the control

Species

Percentage inhibition of the highest test concentration compared to the control

Percent emergence

Percent survival

Shoot dry weight

Brassica oleracea var. capitata

0

0

-17

Zea mays

3

0

-20

Cucumis sativus

-3

0

-23

Avena sativa

3

0

-22

Allium cepa

3

0

-39

Lolium perenne

-6

0

-24

Raphanus sativus

-5

0

6

Glycine max

-3

-3

-1

Helianthus annuus

8

0

-17

Lycopersicon esculentum

8

0

-25

Validity criteria fulfilled:
yes
Remarks:
Control seedling emergence and survival were >=81% and >=98% respectively, for all species tested. Control environmental conditions were the same as the treatment. The same abnormalities were not observed in the control as in the treatment groups.
Conclusions:
14-day NOEC values of ≥5 mg a.i./kg soil dry weight in terms of nominal concentration and ≥2.8 mg a.i./kg soil dry weight in terms of mean measured concentration were determined for ten plant species after exposure to dimethylsilanediol in a seedling emergence test. The species tested were Brassica oleracea var. capitata, Zea mays, Cucumis sativus, Avena sativa, Allium cepa, Lolium perenne, Raphanus sativus, Glycine max, Helianthus annuus and Lycopersicon esculentum. No statistically significant adverse effects at the highest nominal concentration tested of 5 mg a.i./kg soil dry weight were observed.
Endpoint:
toxicity to terrestrial plants: long-term
Type of information:
experimental study
Adequacy of study:
key study
Study period:
6 April 2021 - 30 November 2021
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 208 (Terrestrial Plants, Growth Test)
Deviations:
no
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
- Concentrations: control and 5.0 mg a.i./kg
- Sampling method: Samples were collected from the soil prepared at test initiation (day of dosing) and from each replicate of the control and treated soil at test termination (day 14 for the last species remaining in the exposure), and analyzed for test substance concentrations. At test initiation, soil was collected from the bulk soil prepared before division into replicate vessels (pots). At test termination, soil was collected as composite samples of each replicate (pot) for the limit treatment and control, from every species still remaining in the exposure.
- Sample storage conditions before analysis: not reported. Analyses were generally processed and analyzed on the same day. When samples are analyzed at a later date, data quality and integrity are ensured by the preparation of QC samples which serve as an indication of stability during storage.
Vehicle:
no
Details on preparation and application of test substrate:
- Method of application to filter paper (if used):
- Method of mixing into soil (if used): The appropriate amount of stock solution (20 mL of stock per 1.0 kg dry weight of soil) was volumetrically dispensed to the support medium (soil), which was then mixed using an industrial cement mixer for 15 minutes. After preparation, approximately 1.0 kg of support medium for each concentration was added to the corresponding replicate pots.
- Controls: An equivalent amount of deionized water (20 mL per 1.0 kg dry weight of soil) without test substance was added to the control support medium, which was also mixed in an industrial cement mixer for 15 minutes.
Species:
Brassica oleracea var. capitata
Plant group:
Dicotyledonae (dicots)
Details on test organisms:
- Common name: Cabbage
- Plant family: Brassicaceae
- Variety: Stonehead hybrid
- Source of seed: Park Seed Company, Hodges, South Carolina
- Prior seed treatment/sterilization: no prior treatment reported
- Historical germination of seed (germination of seed lot tested): not reported
- Seed storage: upon receipt, seeds were stored refrigerated in the dark until use.
Species:
Zea mays
Plant group:
Monocotyledonae (monocots)
Details on test organisms:
- Common name: Corn
- Plant family: Poaceae
- Variety: Field
- Source of seed: Carolina Biological Supply Company, Burlington, North Carolina
- Prior seed treatment/sterilization: no prior treatment reported
- Historical germination of seed (germination of seed lot tested): not reported
- Seed storage: upon receipt, seeds were stored refrigerated in the dark until use.
Species:
Cucumis sativus
Plant group:
Dicotyledonae (dicots)
Details on test organisms:
- Common name: Cucumber
- Plant family: Cucurbitaceae
- Variety: Marketmore 76
- Source of seed: Johnny's Selected Seeds, Winslow, Maine
- Prior seed treatment/sterilization: no prior treatment reported
- Historical germination of seed (germination of seed lot tested): not reported
- Seed storage: upon receipt, seeds were stored refrigerated in the dark until use.
Species:
Avena sativa
Plant group:
Monocotyledonae (monocots)
Details on test organisms:
- Common name: Oat
- Plant family: Poaceae
- Variety: Otana
- Source of seed: Granite Seed Company, Lehi, Utah
- Prior seed treatment/sterilization: no prior treatment reported
- Historical germination of seed (germination of seed lot tested): not reported
- Seed storage: upon receipt, seeds were stored refrigerated in the dark until use.
Species:
Allium cepa
Plant group:
Monocotyledonae (monocots)
Details on test organisms:
- Common name: Onion
- Plant family: Amaryllidaceae
- Variety: Talon F1 OG
- Source of seed: Johnny's Selected Seeds, Winslow, Maine
- Prior seed treatment/sterilization: no prior treatment reported
- Historical germination of seed (germination of seed lot tested): not reported
- Seed storage: upon receipt, seeds were stored refrigerated in the dark until use.
Species:
Lolium perenne
Plant group:
Monocotyledonae (monocots)
Details on test organisms:
- Common name: perennial ryegrass
- Plant family: Poaceae
- Variety: Linn
- Source of seed: Granite Seed Company, Lehi, Utah
- Prior seed treatment/sterilization: no prior treatment reported
- Historical germination of seed (germination of seed lot tested): not reported
- Seed storage: upon receipt, seeds were stored refrigerated in the dark until use.
Species:
Raphanus sativus
Plant group:
Dicotyledonae (dicots)
Details on test organisms:
- Common name: radish
- Plant family: Brassicaceae
- Variety: Rover F1
- Source of seed: Johnny's Selected Seeds, Winslow, Maine
- Prior seed treatment/sterilization: no prior treatment reported
- Historical germination of seed (germination of seed lot tested): not reported
- Seed storage: upon receipt, seeds were stored refrigerated in the dark until use.
Species:
Glycine max (G. soja)
Plant group:
Dicotyledonae (dicots)
Details on test organisms:
- Common name: Soybean
- Plant family: Fabaceae
- Variety: N7003CN
- Source of seed: North Carolina Foundation Seed Producers, Inc., Zebulon, North Carolina
- Prior seed treatment/sterilization: no prior treatment reported
- Historical germination of seed (germination of seed lot tested): not reported
- Seed storage: upon receipt, seeds were stored refrigerated in the dark until use.
Species:
Helianthus annuus
Plant group:
Dicotyledonae (dicots)
Details on test organisms:
- Common name: Sunflower
- Plant family: Asteraceae
- Variety: Sunny Smile F1
- Source of seed: Johnny's Selected Seeds, Winslow, Maine
- Prior seed treatment/sterilization: no prior treatment reported
- Historical germination of seed (germination of seed lot tested): not reported
- Seed storage: upon receipt, seeds were stored refrigerated in the dark until use.
Species:
Lycopersicon esculentum
Plant group:
Dicotyledonae (dicots)
Details on test organisms:
- Common name: tomato
- Plant family: Solanaceae
- Variety: Celebrity F1
- Source of seed: Johnny's Selected Seeds, Winslow, Maine
- Prior seed treatment/sterilization: no prior treatment reported
- Historical germination of seed (germination of seed lot tested): not reported
- Seed storage: upon receipt, seeds were stored refrigerated in the dark until use.
Test type:
seedling emergence toxicity test
Study type:
laboratory study
Substrate type:
natural soil
Limit test:
yes
Total exposure duration:
14 d
Test temperature:
Day (16-hour light cycle): Mean temperature 28ºC (SD 2.1); Range 19-45 ºC
Night (8-hour dark cycle): Mean temperature 21ºC (SD 1.2); Range 19-26 ºC
pH:
5.9
Moisture:
Soil moisture was 3.38%
Details on test conditions:
TEST SYSTEM
- Testing facility: Smithers laboratory greenhouse
- Test container (type, material, size): polypropylene pots, 11 cm tall with a top diameter of 14 cm and a bottom diameter of 11 cm
- Amount of soil: 1.0 kg per container
- Method of seeding: Seeds were impartially selected and planted at a depth of approximately 1 cm below the surface of the soil in each pot, in a circular pattern around the inside perimeter of the pot
- No. of seeds per container: 4 for cabbage, radish, soybean, tomato, corn, cucumber and sunflower. 8 for onion, perennial rye and oat.
- No. of plants (retained after thinning): Not applicable
- No. of replicates per treatment group: Control and 5.0 mg a.i./kg nominal limit concentration: 10 for cabbage, radish, soybean, tomato, corn, cucumber and sunflower; 5 for onion, perennial rye and oat.
0.050 and 0.50 mg a.i./kg nominal non-GLP range finding concentrations: 4 for cabbage, radish, soybean, tomato, corn, cucumber and sunflower. 2 for onion, perennial rye and oat.
- No. of replicates per control: 10 for cabbage, radish, soybean, tomato, corn, cucumber and sunflower. 5 for onion, perennial rye and oat.
0.050 and 0.50 mg a.i./kg nominal non-GLP range finding concentrations: 4 for cabbage, radish, soybean, tomato, corn, cucumber and sunflower; 2 for onion, perennial rye and oat.

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Geographic location: not reported
- Pesticide use history at the collection site: not reported
- Collection procedures: not reported
- Sampling depth (cm): not reported
- Soil texture (if natural soil)
- % sand: 94%
- % silt: 3%
- % clay: 3%
- Soil taxonomic classification: USDA Textural Class: Sand
- Soil classification system: not reported
- Organic carbon (%): 1.2%
- Maximum water holding capacity (in % dry weight): 4.8%
- CEC: 4.1 meq/100g
- Pretreatment of soil: Sand was added to the loam to ensure the organic matter was <3%
- Storage (condition, duration): Not reported

NUTRIENT MEDIUM (if used)
- Description: plants were watered daily with either de-chlorinated Town of Wareham well water or 400 mg/l of Peter’s Professional 20-20-20 solution prepared in de-chlorinated Town of Wareham well water.

GROWTH CONDITIONS
- Photoperiod: 16 hours of light and 8 hours of darkness
- Light source: sodium vapour lights supplemented natural light when necessary
- Light intensity and quality: >= 50 PAR (µmol/m(2)/sec)
- Day/night temperatures: day temperature was 28 degrees C, night temperature was 21 degrees C.
- Relative humidity (%): 42%
- Wind velocity: not reported
- Air exchange rate: not reported
- Watering regime and schedules: daily watering
- Water source/type: dechlorinated well water or nutrient solution (see Nutrient medium above)
- Volume applied: not reported
- Interval of applications: daily watering
- Method of application: sub-irrigation
- Any pest control method/fertilization (if used): none used

ACCLIMATION PERIOD: not reported

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): After application of the material to the support medium, control pots were observed for 50% emergence on a daily basis. Each pot was observed on days 0, 7 and 14 (test termination) after 50% of the control seeds had emerged (per species) to determine percent emergence and percent survival and to record any morphological abnormalities of the emerged shoots. Observations of morphological abnormalities, or phytotoxicity (e.g., chlorosis, necrosis, or leaf blotching) were recorded as the percentage of the plant tissue exhibiting the abnormality. Shoot weight was measured at test termination, by harvesting the above ground portion of the plants. The shoots from each replicate were pooled and placed in appropriately labelled, pre-weighed containers. The shoots were dried for at least 4 days in an oven at approximately 60°C. Once plants were dried, shoot dry weights were measured to the nearest 0.0001 g using an analytical balance. Weight data were not collected for shoots that died during the exposure. Dead shoots were not included in statistical calculations of biological endpoints, with the exception of emergence and survival

- Phytotoxicity rating system (if used): Observations of phytotoxic effects were reported as the percentage of the plant tissue per replicate exhibiting the effect. Percent inhibition for phytotoxicity rating, percent survival and shoot dry weight was calculated relative to the control data according to the following formula: percent inhibition = ((mean control value - mean treatment value)) / mean control value) x 100.

VEHICLE CONTROL PERFORMED: no vehicle used

TEST CONCENTRATIONS
- Spacing factor for test concentrations: limit test
- Range finding study
- Test concentrations: 0.050 and 0.50 mg a.i./kg
- Results used to determine the conditions for the definitive study: The data from the Tier I exposure indicated no significant reduction at a nominal concentration of 5.0 mg a.i./kg (mean measured concentration of 2.8 mg a.i./kg) when compared to the control for all endpoints tested for all test species. Therefore, the Tier I exposure was considered successful.
Nominal and measured concentrations:
Nominal: control, 0.050, 0.50 and 5.0 mg a.i./kg
Measured: control and 2.8 mg a.i./kg (5.0 mg a.i./kg as nominal). 0.050 and 0.50 mg a.i./kg not measured
Reference substance (positive control):
no
Species:
Brassica oleracea var. capitata
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
>= 5 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: Seedling emergence, percent survival, shoot dry weight, morphological abnormalities and plant condition.
Species:
Zea mays
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
>= 5 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: Seedling emergence, percent survival, shoot dry weight, morphological abnormalities and plant condition.
Species:
Cucumis sativus
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
>= 5 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: Seedling emergence, percent survival, shoot dry weight, morphological abnormalities and plant condition.
Species:
Avena sativa
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
>= 5 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: Seedling emergence, percent survival, shoot dry weight, morphological abnormalities and plant condition.
Species:
Allium cepa
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
>= 5 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: Seedling emergence, percent survival, shoot dry weight, morphological abnormalities and plant condition.
Species:
Lolium perenne
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
>= 5 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: Seedling emergence, percent survival, shoot dry weight, morphological abnormalities and plant condition.
Species:
Raphanus sativus
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
>= 5 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: Seedling emergence, percent survival, shoot dry weight, morphological abnormalities and plant condition.
Species:
Glycine max (G. soja)
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
>= 5 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: Seedling emergence, percent survival, shoot dry weight, morphological abnormalities and plant condition.
Species:
Helianthus annuus
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
>= 5 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: Seedling emergence, percent survival, shoot dry weight, morphological abnormalities and plant condition.
Species:
Lycopersicon esculentum
Duration:
14 d
Dose descriptor:
NOEC
Effect conc.:
>= 5 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: Seedling emergence, percent survival, shoot dry weight, morphological abnormalities and plant condition.
Details on results:
NOEC values for all 10 species can be reported in terms of the mean measured concentration: NOEC >= 2.8 mg a.i./kg soil dry weight

SEED GERMINATION
- Percent seed germination: see table 2 for the number of non-emerged seeds per concentration for each species
- Root length: not measured
- Root discolouration/malformation: not measured
- Other effects:
- Results with reference substance valid? No reference substance used.

SEEDLING EMERGENCE
- Percent seedling emergence: see table 2 for the number of non-emerged seeds per concentration for each species. See table 4 for percentage emergence of seedlings per concentration for each species.
- Percent survival: all species displayed 100% survival, see table 5 for the mean percentage survival of seedlings per concentration for each species.
- Plant height: not measured
- Dry weight: see table 6 for mean seedling weight per concentration for each species.
- Abnormal seed development or appearance: see table 3 for morphological abnormalities per concentration for each species.


INJURY RATING SYSTEM: plants were recorded as: healthy (H), necrotic (N), chlorotic (C), leaf blotching (LB), dead plant (DP), non-emerged (NE), not applicable (NA) or other. See table 3 for details of morphological abnormalities per concentration for each species. .
Reported statistics and error estimates:
The No-Observed-Effect Concentration (NOEC), the highest test concentration, which demonstrated no statistically adverse effect (p <0.05) when compared to the control data, as well as the lowest concentration which caused a significant adverse effect, the Lowest-Observed-Effect Concentration (LOEC), were determined for percent emergence, survival, and shoot dry weight. Data were first checked for normality and for homogeneity of variance using the appropriate qualifying tests. All statistical determinations were made at the 95% level of certainty, except in the case of the tests for normality of variance and homoscedasticity, where the 99% level of certainty was applied.
Emergence and survival were analysed using a Fisher's Exact Test, Weight was analysed using an Equal Variance t-Test when data was normally distributed and had equal variance, unequal variance t-Test for normally distributed data with unequal variance, and a Wilcoxon Rank-Sum Two-Sample test was used when data was not normally distributed with either equal or unequal variance.

Table 1. Measured and nominal concentrations of dimethylsilanediol at test initiation and termination

Nominal concentration (mg a.i./kg soil dwt)

Measured concentration at test initiation

(mg a.i./kg soil dwt)

Initiation percent of nominal (%)

Measured concentration at test termination

(mg a.i./kg soil dwt)

Test termination percent of nominal (%)

Mean (SD)

Overall mean percentage of nominal

 Control  <LOQ  N/A  <LOQ  N/A  N/A  N/A
 5.0  4.3  85  1.2  24  2.8 (2.2)  55
 5.0  4.4  87        
 5.0  4.4  87        
 Mean  4.3  87  1.2  24    

Table 2. Number of non-emerged seeds per test concentration (N=40)

Species

Nominal concentration (mg a.i./kg soil dwt)

Control

0.050

0.50

5.0

Brassica oleracea var. capitata

2

0

0

2

Zea mays

1

0

1

2

Cucumis sativus

1

0

0

0

Avena sativa

1

1

0

2

Allium cepa

3

0

2

4

Lolium perenne

5

3

1

3

Raphanus sativus

3

0

1

1

Glycine max

7

3

1

6

Helianthus annuus

2

2

1

5

Lycopersicon esculentum

0

0

1

3

Table 3. Morphological observations of emerged plants

Species

Nominal concentration (mg a.i./kg soil dwt)

Control

0.050

0.50

5.0

Brassica oleracea var. capitata

38 H

16 H

16 H

38 H

Zea mays

39 H

16 H

15 H

38 H

Cucumis sativus

39 H

16 H

16 H

40 H

Avena sativa

39 H

15 H

40 H

38 H

Allium cepa

37 H

16 H

13 H

36 H

Lolium perenne

35 H

13 H

15 H

37 H

Raphanus sativus

37 H

16 H

15 H

37 H

Glycine max

38 H, 1 DP, 1 N

13 H

15 H

34 H

Helianthus annuus

38 H

14 H

39 H

35 H

Lycopersicon esculentum

40 H

16 H

15 H

37 H

H = healthy, DP = dead plant, N = necrotic

Table 4. Mean percentage emergence of seedlings (as mean (SD))

Species

Nominal concentration (mg a.i./kg soil dwt)

Control

0.050

0.50

5.0

Brassica oleracea var. capitata

95 (11)

100 (0)

100 (0)

95 (11)

Zea mays

98 (8)

100 (0)

94 (13)

95 (11)

Cucumis sativus

98 (8)

100 (0)

100 (0)

100 (0)

Avena sativa

98 (6)

94 (9)

100 (0)

95 (7)

Allium cepa

93 (11)

100 (0)

88 (18)

90 (10)

Lolium perenne

88 (9)

81 (27)

94 (9)

93 (11)

Raphanus sativus

93 (12)

100 (0)

94 (13)

98 (8)

Glycine max

83 (17)

81 (24)

94 (13)

85 (13)

Helianthus annuus

95 (11)

88 (14)

94 (13)

88 (18)

Lycopersicon esculentum

100 (0)

100 (0)

94 (13)

93 (17)

Table 5. Mean percentage survival of seedlings (as mean (SD))

Species

Nominal concentration (mg a.i./kg soil dwt)

Control

0.050

0.50

5.0

Brassica oleracea var. capitata

100 (0)

100 (0)

100 (0)

100 (0)

Zea mays

100 (0)

100 (0)

100 (0)

100 (0)

Cucumis sativus

100 (0)

100 (0)

100 (0)

100 (0)

Avena sativa

100 (0)

100 (0)

100 (0)

100 (0)

Allium cepa

100 (0)

100 (0)

100 (0)

100 (0)

Lolium perenne

100 (0)

100 (0)

100 (0)

100 (0)

Raphanus sativus

100 (0)

100 (0)

100 (0)

100 (0)

Glycine max

98 (8)

100 (0)

100 (0)

100 (0)

Helianthus annuus

100 (0)

100 (0)

100 (0)

100 (0)

Lycopersicon esculentum

100 (0)

100 (0)

100 (0)

100 (0)

Table 6. Mean seedling weight (g) (as mean (SD))

Species

Nominal concentration (mg a.i./kg soil dwt)

Control

0.050

0.50

5.0

Brassica oleracea var. capitata

0.1261 (0.0159)

0.1469 (0.0175)

0.1627 (0.0078)

0.1482 (0.0249)

Zea mays

0.4285 (0.0587)

0.4558 (0.0486)

0.4925 (0.0694)

0.5129 (0.0823)

Cucumis sativus

0.2534 (0.0180)

0.3106 (0.0324)

0.2905 (0.0218)

0.3120 (0.0193)

Avena sativa

0.728 (0.0078)

0.0701 (0.0156)

0.0900 (0.0137)

0.0886 (0.0147)

Allium cepa

0.0155 (0.0021)

0.0151 (0.0013)

0.0189 (0.0029)

0.0216 (0.0035)

Lolium perenne

0.0099 (0.0015)

0.0106 (0.0006)

0.0127 (0.0001)

0.0122 (0.0031)

Raphanus sativus

0.1209 (0.0143)

0.1303 (0.0106)

0.1382 (0.0230)

0.1280 (0.0146)

Glycine max

0.4052 (0.0812)

0.4320 (0.0305)

0.4136 (0.0435)

0.4106 (0.0812)

Helianthus annuus

0.1845 (0.0237)

0.2141 (0.0321)

0.2150 (0.0375)

0.2160 (0.0331)

Lycopersicon esculentum

0.1195 (0.0198)

0.1316 (0.0405)

0.1371 (0.0254)

0.1497 (0.0432)

Table 7. Percentage inhibition of emergence, survival and shoot dry weight in the highest test concentration (5.0 mg a.i./kg dw, as nominal) compared to the control

Species

Percentage inhibition of the highest test concentration compared to the control

Percent emergence

Percent survival

Shoot dry weight

Brassica oleracea var. capitata

0

0

-17

Zea mays

3

0

-20

Cucumis sativus

-3

0

-23

Avena sativa

3

0

-22

Allium cepa

3

0

-39

Lolium perenne

-6

0

-24

Raphanus sativus

-5

0

6

Glycine max

-3

-3

-1

Helianthus annuus

8

0

-17

Lycopersicon esculentum

8

0

-25

Validity criteria fulfilled:
yes
Remarks:
Control seedling emergence and survival were >=81% and >=98% respectively, for all species tested. Control environmental conditions were the same as the treatment. The same abnormalities were not observed in the control as in the treatment groups.
Conclusions:
14-day NOEC values of ≥5 mg a.i./kg soil dry weight in terms of nominal concentration and ≥2.8 mg a.i./kg soil dry weight in terms of mean measured concentration were determined for ten plant species after exposure to dimethylsilanediol in a seedling emergence test. The species tested were Brassica oleracea var. capitata, Zea mays, Cucumis sativus, Avena sativa, Allium cepa, Lolium perenne, Raphanus sativus, Glycine max, Helianthus annuus and Lycopersicon esculentum. No statistically significant adverse effects at the highest nominal concentration tested of 5 mg a.i./kg soil dry weight were observed.

Description of key information

NOEC (14 d) of ≥ 2.8 mg a.i./kg soil dw (mean measured, OECD 208, 10 plant species; read across from silanol hydrolysis product DMSD)

Key value for chemical safety assessment

Long-term EC10, LC10 or NOEC for terrestrial plants:
2.8 mg/kg soil dw

Additional information

Dimethoxy(dimethyl)silane (CAS No. 1112-39-6) hydrolyses rapidly in contact with water (DT50 < 0.6 h), to dimethylsilanediol (DMSD, CAS No. 1066-42-8) and methanol (CAS No. 67-56-1). The ECHA guidance R.16 states that “for substances where hydrolytic DT50 is less than 12 h, environmental effects are likely to be attributed to the hydrolysis product rather than to the parent itself” (ECHA, 2016). The ECHA guidance R.16 also suggests that in case the hydrolysis half-life is less than 12 h, the breakdown products, rather than the parent substance, should be evaluated for aquatic toxicity. Methanol is well described in the public domain literature. It has a low environmental hazard profile and is therefore not considered contributory to the overall ecotoxicity of the registered substance (OECD SIDS, 2004). Thus, the ecotoxicity assessment is based on read-across to the silanol hydrolysis product dimethylsilanediol (DMSD, CAS No. 1066-42-8). Details on the read-across can be found in the analogue justification attached in IUCLID Section 13.


 


For the toxicity to terrestrial plants, one experimental laboratory study is available for the silanol hydrolysis product and analogue substance dimethylsilanediol (CAS No. 1066-42-8), which was conducted according to OECD guideline 208 and in compliance with GLP.


In a seedling emergence toxicity test conducted as limit test, 10 plant species were exposed to the limit concentration of 5.0 mg a.i./kg soil dw for 14 d (pH 5.9 and 3.38% moisture). Appropriate amounts of the stock solution (20 mL/kg soil dw) were volumetrically dispensed to the soil and then mixed with an industrial cement mixer for 15 min. 1.0 kg soil was distributed to the test pots and seeds were impartially selected and planted at a depth of approximately 1 cm below the surface.


Analytical monitoring of the control and exposure concentration was performed by LC-MS at test start and test end. The mean measured concentration was 2.8 mg a.i./kg soil dw.


After 28 d, no statistically significant adverse effects at the highest, tested nominal concentration of 5.0 mg a.i./kg soil dw were observed, resulting in a NOEC (14 d) of ≥ 2.8 mg a.i./kg soil dw (mean measured concentration) for the toxicity of dimethylsilanediol (DMSD, CAS No. 1066-42-8) to terrestrial plants.


 


Reference
OECD SIDS, 2004. Methanol - SIDS Initial Assessment Report For SIAM 19, Berlin, Germany: UNEP Publications.