Trichloro(hexadecyl)silane

Toxicity to terrestrial plants

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to terrestrial plants: long-term

Type of information:

experimental study

Adequacy of study:

key study

Study period:

27 Aug - 17 Sep 2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 208 (Terrestrial Plants, Growth Test)

Version / remarks:

2006

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Staatliches Gewerbeaufsichtsamt Hildesheim, Germany

Analytical monitoring:

no

Vehicle:

no

Species:

Allium cepa

Plant group:

Monocotyledonae (monocots)

Details on test organisms:

- Common name: Onion
- Plant family: Amaryllideaceae
- Variety: Exhibition
- Lot: 1300968
- Source of seed: Hild Samen GmbH, Marbach, Germany
- Prior seed treatment/sterilization: untreated seed
- Seed storage: stored dark at the test facility at room temperature (22 ± 10 °C) and protected from moisture until use

Species:

Avena sativa

Plant group:

Monocotyledonae (monocots)

Details on test organisms:

- Common name: Oats
- Plant family: Poaceae
- Variety: KWS Contender
- Lot: F17-BRA-CON-3
- Source of seed: KWS Lochow GmbH, Bergen, Germany
- Prior seed treatment/sterilization: untreated seed
- Seed storage: stored dark at the test facility at room temperature (22 ± 10 °C) and protected from moisture until use

Species:

Beta vulgaris

Plant group:

Dicotyledonae (dicots)

Details on test organisms:

- Common name: Sugar beet
- Plant family: Amaranthaceae
- Variety: Fiorella KWS
- Source of seed: KWS Saat SE, Einbeck, Germany
- Prior seed treatment/sterilization: untreated seed
- Seed storage: stored dark at the test facility at room temperature (22 ± 10 °C) and protected from moisture until use

Species:

Brassica napus

Plant group:

Dicotyledonae (dicots)

Details on test organisms:

- Common name: Rape
- Plant family: Brassicaceae
- Variety: Sherlock
- Source of seed: KWS Saat SE, Einbeck, Germany
- Prior seed treatment/sterilization: untreated seed
- Seed storage: stored dark at the test facility at room temperature (22 ± 10 °C) and protected from moisture until use

Species:

Lactuca sativa

Plant group:

Dicotyledonae (dicots)

Details on test organisms:

- Common name: Lettuce
- Plant family: Asteraceae
- Variety: Larissa
- Lot: 16193.011
- Prior seed treatment/sterilization: untreated seed
- Seed storage: stored dark at the test facility at room temperature (22 ± 10 °C) and protected from moisture until use

Species:

Glycine max (G. soja)

Plant group:

Dicotyledonae (dicots)

Details on test organisms:

- Common name: Soybean
- Plant family: Fabaceae
- Variety: Obelix
- Lot: DSP-96-8-1-18295-5
- Prior seed treatment/sterilization: untreated seed
- Seed storage: stored dark at the test facility at room temperature (22 ± 10 °C) and protected from moisture until use

Test type:

seedling emergence and seedling growth test

Study type:

laboratory study

Substrate type:

natural soil

Limit test:

no

Total exposure duration:

21 d

Remarks:

The test for onion was prolonged until day 28.

Test temperature:

17.5 - 24.5°C

pH:

4.86 ± 0.08

Moisture:

35.8 - 92.5% relative humidity

Details on test conditions:

TEST SYSTEM
- Testing facility: climatic chamber
- Test container: non-porous plastic containers (standard flower pots), diameter: ca. 12 cm
- Amount of soil: 7.6 kg
- Method of seeding: seeding holes made with a seedling pistil, one seed was given into each hole and covered with soil
- No. of seeds per container: 5
- No. of replicates per treatment group: 8
- No. of replicates per control: 8

SOURCE AND PROPERTIES OF SUBSTRATE (if soil): 2:1 mixture of natural soil LUFA 2.2 (batch number: Sp2.22419, loamy sand (DIN classification)) and quartz sand (12a)
- Geographic location: LUFA: Landwirtschaftliche Untersuchungs- und Forschungsanstalt Speyer, Germany; Dörentrup Quarz GmbH Co. KG,Duingen, Germany
- Soil texture (if natural soil)
- % sand: 93.4% (0.063-2 mm)
- % silt: 3.0% (0.002-0.063 mm)
- % clay: 3.7% (< 0.002 mm)
- Grain size: ≤2 mm
- Maximum water holding capacity: 33.2 g/100 g soil dw


NUTRIENT MEDIUM (if used)
- Description: HAKAPHOS® SOFT SPEZIAL 16+8+22(+3)

GROWTH CONDITIONS
- Photoperiod: 16/8 h light/dark
- Light source: tubes (special light source for plants)
- Light intensity and quality: 4713 ± 453, light at the blue and red ends of the spectrum, Grünes Landhaus, Hildesheim, Germany (0.5 ‰ solution for watering)
- Relative humidity: 35.8 - 92.5%
- Watering regime and schedules: daily bottom watering
- Water source/type: fertilized tap water
- Interval of applications: control and test item treatments were applied once at the start of the exposure
- Method of application: test item amounts were weighed out on quartz sand for each test item concentration, blended thoroughly and added to the soil with an appropriate amount of demineralized water; after mixing, treated soil transfer to test containers

EFFECT PARAMETERS MEASURED: number of emerged seedlings, number of dead plants and visual phytotoxic effects (day 7, 14 and 21, onion additionally on day 28), shoot heights and the fresh weights of the shoots (test end)

Nominal and measured concentrations:

Nominal concentrations: 0 (control), 62.5, 125, 250, 500, 1000 mg/kg dw

Reference substance (positive control):

no

Species:

other: Lactuca sativa, Avena sativa

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

250 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: shoot fresh weight

Species:

other: Avena sativa, Beta vulgaris, Brassica napus, Lactuca sativa and Glycine max (G. soja)

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: shoot height, number of emerged seedlings and survival

Species:

other: Beta vulgaris, Brassica napus and Glycine max (G. soja)

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: shoot fresh weight

Species:

Lactuca sativa

Duration:

21 d

Dose descriptor:

EC50

Effect conc.:

961 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: shoot fresh weight

Remarks on result:

other: 95% confidence limits: 583 - > 1000 mg/kg soil dw

Species:

Allium cepa

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: shoot height, number of emerged seedlings and survival, shoot fresh weight

Reported statistics and error estimates:

One Way Analysis of Variance (ANOVA) and Dunnett’s test for the determination of statistically significant differences compared to control replicates. Normality test (Shapiro-Wilk) and an Equal Variance test (Brown-Forsythe) were done first. P-values for both, Normality and Equal Variance test, are 0.05. The α-value for ANOVA (acceptable probability of incorrectly concluding that there is a difference) is α = 0.05. ECx- values were calculated by sigmoidal dose response regression using GraphPadPrism. Four parameters were used for dose-response fitting. Calculation of the confidence intervals for EC-values was carried out using standard procedures provided by GraphPadPrism.

Table 1. Validity criteria defined by OECD guideline 208.

Criterion	Outcome	Criterion fulfilled
Seedling emergence in the controls is at least 70%.	Control emergence (% of seeds) and survival (% of emerged plants): A. cepa: 100% and 100% A. sativa: 83% and 100% B. vulgaris: 93% and 100% B. napus: 98% and 100% L. sativa: 90% and 100% G. max: 96% and 100%	Yes
No visible phytotoxic effects (e.g. chlorosis, necrosis, wilting, deformatons) in control seedlings and the plants of every particular species exhibit normal variation in growth and morphology.	The seedlings exhibited no visible phytotoxic effects and the plants exhibited only normal variation on growth and morphology.	Yes
The environmental conditions for a particular species are identical and the growing media contain the same amount of soil matrix, support media or substrate from the same source.	Environmental conditions and growth media were identical for each plant species.	Yes

Table 2:Oats: Inhibition [%] of Shoot Height, Shoot Fresh Weight, Rate of Emergence and Survival of Plants

Test concentration [mg/kg DW]	Shoot height 1)   [cm]	Inhibition     [%]	Shoot fresh weight [mg]	Inhibition     [%]	Rate of emer- gence 1) [%]	Inhibition     [%]	Survival of  plants 1) [%]	Inhibition     [%]
Control	41.2	-	1293	-	832)	-	100	-
62.5	40.8	1	1206	7	98	-18	100	0
125	39.7	4	1146	11	95	-14	100	0
250	40.9	1	1213	6	93	-12	100	0
500	39.8	3	1125*	13	95	-14	100	0
1000	39.6	4	1023*	21	95	-14	100	0

 

Negative values = Promoted growth                                 

 * = Statistically significant inhibition

1) Normality test failed        

2)= Rate of emergence is inside the natural  margin of deviation, based on experience and the general validity criteria of the guideline

Table 3: Onion: Inhibition [%] of Shoot Height, Shoot Fresh Weight, Rate of Emergence and Survival of Plants

Test concentration [mg/kg DW]	Shoot height 1)   [cm]	Inhibition     [%]	Shoot fresh weight [mg]	Inhibition     [%]	Rate of emer- gence 2) [%]	Inhibition     [%]	Survival of plants1)[%]	Inhibition     [%]
Control	16.7	-	216	-	100	-	100	-
62.5	16.8	-1	222	-3	98	2	100	0
125	18.1	-8	232	-7	85	15	98	3
250	16.4	2	207	4	83**	17	100	0
500	17.0	-2	226	-5	95	5	100	0
1000	17.6	-5	231	-7	100	0	100	0

Table 4: Sugar Beet: Inhibition [%] of Shoot Height, Shoot Fresh Weight, Rate of Emergence and Survival of Plants

Test concentration [mg/kg DW]	Shoot height1)   [cm]	Inhibition     [%]	Shoot fresh weight [mg]	Inhibition     [%]	Rate of emer- gence 2) [%]	Inhibition     [%]	Survival of  plants1) [%]	Inhibition     [%]
Control	7.6	-	465	-	93	-	100	-
62.5	8.1	-7	519	-12	93	0	100	0
125	8.1	-7	520	-12	98	-5	100	0
250	8.1	-7	521	-12	100	-8	100	0
500	8.4	-11	519	-12	100	-8	100	0
1000	7.9	-4	486	-5	100	-8	98	3

 Negative values = Promoted growth

** = statistically significant inhibition, but not test item related (as inhibition does not increase with the concentration); the result is not considered to set endpoints

1) Normality test failed

2) Normality test and equal variance test failed

Table 5: Rape: Inhibition [%] of Shoot Height, Shoot Fresh Weight, Rate of Emergence and Survival of Plants

Test concentration [mg/kg DW]	Shoot height 1)   [cm]	Inhibition     [%]	Shoot fresh weight [mg]	Inhibition     [%]	Rate of emer- gence 1) [%]	Inhibition     [%]	Survival of  plants 1) [%]	Inhibition     [%]
Control	13.0	-	1139	-	98	-	100	-
62.5	14.4#	-11	1140	0	90	8	100	0
125	13.9#	-7	1056	7	98	0	100	0
250	13.8	-6	1033	9	98	0	100	0
500	14.4#	-11	1087	5	93	5	100	0
1000	12.9	1	920	19	90	8	100	0

 

Table 6: Lettuce: Inhibition [%] of Shoot Height, Shoot Fresh Weight, Rate of Emergence and Survival of Plants

Test concentration [mg/kg DW]	Shoot height 1)   [cm]	Inhibition     [%]	Shoot fresh weight [mg]	Inhibition     [%]	Rate of emer- gence 1) [%]	Inhibition     [%]	Survival of  plants 1) [%]	Inhibition     [%]
Control	5.6	-	486	-	90	-	100	-
62.5	4.9**	13	324**	33	90	0	100	0
125	5.9	-5	500	-3	88	2	100	0
250	5.6	0	438	10	88	2	100	0
500	4.9	13	333*	31	93	-3	100	0
1000	4.4*	21	239*	51	78	13	100	0

 

Negative values = Promoted growth 

# = Statistically significant promoted growth

* = Statistically significant inhibition

** = statistically significant inhibition, but not test item related (as inhibition does not increase with the concentration); the result is not considered to set  endpoints

1) Normality test failed

Table 6:Soybean: Inhibition [%] of Shoot Height, Shoot Fresh Weight, Rate of Emergence and Survival of Plants

Test concentration [mg/kg DW]	Shoot height 1)   [cm]	Inhibition     [%]	Shoot fresh weight [mg]	Inhibition     [%]	Rate of emer- gence1)[%]	Inhibition     [%]	Survival of  plants 1) [%]	Inhibition     [%]
Control	21.6	-	2673	-	96	-	100	-
62.5	23.0	-6	2577	4	100	-4	100	0
125	22.5	-4	2660	0	100	-4	100	0
250	23.0	-6	2691	-1	92	4	100	0
500	22.0	-2	2555	4	96	0	100	0
1000	21.4	1	2495	7	96	0	100	0

 Negative values = Promoted growth

1) Normality testfailed

Validity criteria fulfilled:

yes

Remarks:

For further details please refer to “Any other information on results incl. tables".

Executive summary:

The phytotoxicity of the test substance to six terrestrial plant species was determined according to OECD 208 (2006) in seedling emergence and seedling growth tests over a period of 21 days. The test for onion was prolonged until day 28 since 50 % emergence of the control seedlings was reached after 14 days.

For shoot height, number of emerged seedlings and survival of plants statistically no significant differences were observed for all tested plant species. For these species the NOEC is 1000 mg/kg dw. For shoot fresh weight statistically significant differences were determined for the plant species oats and lettuce. For these species the NOEC is 250 mg/kg dw. For the plant species onion, sugar beet, rape and soybean the NOEC is 1000 mg/kg dw and the LOEC is ≥ 1000 mg/kg dw.

Reference 2

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 attached justification for grouping of substances in IUCLID Section 13.

Reason / purpose for cross-reference:

read-across source

Species:

other: Lactuca sativa, Avena sativa

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

250 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: shoot fresh weight

Species:

other: Avena sativa, Beta vulgaris, Brassica napus, Lactuca sativa and Glycine max (G. soja)

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: shoot height, number of emerged seedlings and survival

Species:

other: Beta vulgaris, Brassica napus and Glycine max (G. soja)

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: shoot fresh weight

Species:

Lactuca sativa

Duration:

21 d

Dose descriptor:

EC50

Effect conc.:

961 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: shoot fresh weight

Remarks on result:

other: 95% confidence limits: 583 - > 1000 mg/kg soil dw

Species:

Allium cepa

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: shoot height, number of emerged seedlings and survival, shoot fresh weight

Description of key information

NOEC (21 days) = 250 mg/kg soil dw (OECD 208, Lactuca sativa, Avena sativa, RA to CAS No. 16415-12-6)

Key value for chemical safety assessment

Long-term EC10, LC10 or NOEC for terrestrial plants:

250 mg/kg soil dw

Additional information

Measured data on the toxicity towards terrestrial organisms was not available for trichloro(hexadecyl)silane (CAS No. 5894-60-0), therefore data was read-across from the structural analogue substance trimethoxy(hexadecyl)silane (CAS No. 16415-12-6) for the assessment of acute and chronic toxicity towards terrestrial plants. Both substances hydrolyse in the aquatic environment and under moist conditions, but with very different hydrolysis rates (DT50 = << 2 min at room temperature and pH 7 (target); DT50 > 14 d at pH 7 (source)). However, both form the same silanol hydrolysis product hexadecylsilanetriol. The second hydrolysis product of the target substance is hydrochloric acid, while the second hydrolysis product of the source compound is methanol. Hydrochloric acid and methanol are both well described substances in the public domain literature and both are not expected to contribute to the overall environmental toxicity of target and source substances (OECD SIDS, 2002; OECD SIDS 2004). Therefore, hydrochloric acid and methanol can be disregarded in the environmental hazard assessment. Further information can be found in an attached read-across justification in Section 13 of IUCLID.

One study is available testing the toxicity of trimethoxy(hexadecyl)silane (CAS No. 16415-12-6) to six terrestrial plant species according to OECD guideline 208 and under GLP conditions.

The seedling emergence and seedling growth test was performed over a period of 21 days. The test for onion was prolonged until day 28 since 50 % emergence of the control seedlings was reached after 14 days.Test systems comprised two monocotyledons (oats, Poaceae; onion, Amaryllideaceae), and four dicotyledons (sugar beet, Amaranthaceae; rape, Brassicaceae; lettuce, Asteraceae; soybean, Fabaceae) and was conducted with test concentrations of 62.5, 125, 250, 500 and 1000 mg/kg soil dw.

For shoot height, number of emerged seedlings, and survival of plants no statistically significant differences were observed for all tested plant species. For these species the NOEC is 1000 mg/kg dw. For shoot fresh weight statistically significant differences were determined for the plant species oats and lettuce. For these species the NOEC is 250 mg/kg dw. For the plant species onion, sugar beet, rape and soybean the NOEC is 1000 mg/kg dw and the LOEC is ≥ 1000 mg/kg dw.