Trichloro(hexadecyl)silane

Toxicity to soil macroorganisms except arthropods

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to soil macroorganisms except arthropods: long-term

Type of information:

experimental study

Adequacy of study:

key study

Study period:

04 Jul - 31 Aug 2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 222 (Earthworm Reproduction Test (Eisenia fetida/Eisenia andrei))

Version / remarks:

2016

Deviations:

yes

Remarks:

Food was provided on day 0 instead of day 1 due to good experience with this procedure. The room temperature increased to maximum 23 °C for about 8 hours on day 55. These deviations are considered to have no impact on quality and integrity of the study.

GLP compliance:

yes (incl. QA statement)

Remarks:

Staatliches Gewerbeaufsichtsamt Hildesheim, Germany

Analytical monitoring:

no

Vehicle:

yes

Details on preparation and application of test substrate:

- Method of mixing into soil: respective test item amount was weighed out for each test item concentration, solved in Acetone and mixed with quartz sand (10 g per replicate). After complete evaporation of the solvent, the spiked quartz sand was added to the artificial soil.
- Controls: artificial soil moistened with demineralised water without test or reference item
- Chemical name of vehicle: acetone
- Concentration of vehicle in test medium: 2.5 mL per replicate
- Evaporation of vehicle before use: yes

Test organisms (species):

Eisenia fetida

Animal group:

annelids

Details on test organisms:

TEST ORGANISM
- Common name: earthworm
- Source: breeding stock culture maintained at the test facility
- Age at test initiation: 2-12 (age did not deviate by more than 1 month)
- Weight at test initiation: 0.46 - 0.47 g (wet mass)

ACCLIMATION
- Acclimation period: 2 days prior to test start

Study type:

laboratory study

Substrate type:

artificial soil

Limit test:

no

Total exposure duration:

8 wk

Test temperature:

18 - 23°C

pH:

6.11 - 6.44

Moisture:

19.4 - 24.4%

Details on test conditions:

TEST SYSTEM
- Test container (material, size): round 2 L plastic boxes (diameter: 15 cm, bottom surface: 177 cm2, height: 14 cm) with transparent and perforated lids
- Amount of soil or substrate: 600 g dw (5 cm height)
- No. of organisms per container (treatment): 10
- No. of replicates per treatment group: 4
- No. of replicates per control: 8
- No. of replicates per vehicle control: 8

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Composition (if artificial substrate): 5 % peat (air-dried and finely ground), 20 % kaolin (kaolinite content > 30 %), 74 % air-dried quartz sand (sand with > 50 % particle size of 0.05 - 0.2 mm), 0.20 % calcium carbonate (CaCO3)

OTHER TEST CONDITIONS
- Photoperiod: 16:8 h light:dark
- Light intensity: 612 ± 77.2 lux

EFFECT PARAMETERS MEASURED: body weight of the adult earthworms (day 0, 28), adult earthworm mortality (day 28), the number of unhatched cocoons and number of offspring (juveniles) hatched from the cocoons (day 56)

VEHICLE CONTROL PERFORMED: yes

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2
- Range finding study
- Test concentrations: 0, 1, 10, 100, 1000 mg/kg dw
- Results used to determine the conditions for the definitive study: No mortality observed at any test concentration after 14 days.

Nominal and measured concentrations:

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

Reference substance (positive control):

yes

Remarks:

Carbendazim (0.5, 1, 2, 4 mg/kg dw)

Duration:

56 d

Dose descriptor:

NOEC

Effect conc.:

500 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Remarks:

biomass

Details on results:

- Mortality at end of exposure period: No significant effects observed in the controls and all test item concentrations on day 28
- Total mass of adults at beginning of test: 0.46 - 0.47 g (wet mass)
- Changes in body weight of live adults at end of exposure period: at the test item concentration 1000 mg/k dw the earthworm biomass was statistically significantly reduced
- No. of offspring produced: at the test item concentration 1000 mg/k dw earthworm reproduction was statistically significantly reduced
- Behavioural abnormalities: No significant effects observed in the controls and all test item concentrations on day 28

Results with reference substance (positive control):

- Results with reference substance valid? yes
- Relevant effect levels: NOEC: 0.5 mg/kg dw, LOEC 1 mg/kg dw

Reported statistics and error estimates:

- Adult Mortality: Qualitative Trend Analysis by Contrasts (Monotonicity of Concentration/Response), Chi2 2x2 Table Test with Bonferroni Correction
- Reproduction and Biomass: Shapiro-Wilk’s Test on Normal Distribution, Levene’s Test on Variance Homogeneity (with Residuals), Trend Analysis by Contrasts (Monotonicity of Concentration/Response), William’s Multiple Sequential t-test Procedure
- The α-value (acceptable probability of incorrectly concluding that there is a difference) was α = 0.05. For the endpoint of reproduction, the arithmetic mean and the variance (coefficient of variation) per treatment and controls were calculated.

Table 1: Validity criteria for OECD 222.

Criterion from the guideline to be satisfied in the controls	Outcome	Validity criterion fulfilled
Each replicate (containing 10 adults) to have produced ≥ 30 juveniles by the end of the test.	≥ 30	yes
The coefficient of variation of reproduction is ≤ 30%.	< 30 %	yes
Adult mortality over the initial 4 weeks of the test is ≤ 10%.	≤10 %	yes

Table 2: Body weight changes

Application rate [mgtest item/kg SDW]	Replicate	Mean body weights per replicate		Mean body weight change of earthworms
		Test start	28 days	Per replicate		Mean ± SD		Sig.
		[g]	[g]	[g]	[%]	[g]	[%]
Control	1	0.46	0.51	0.05	10.9	0.06 ± 0.02	11.8 ± 4.13	–
	2	0.47	0.55	0.08	17.0
	3	0.46	0.49	0.03	6.5
	4	0.47	0.53	0.06	12.8
	5	0.46	0.51	0.05	10.9
	6	0.47	0.53	0.06	12.8
	7	0.46	0.54	0.08	17.4
	8	0.47	0.50	0.03	6.4
Solvent Control	1	0.46	0.50	0.04	8.7	0.05 ± 0.02	10.8 ± 3.26	–
	2	0.47	0.52	0.05	10.6
	3	0.46	0.50	0.04	8.7
	4	0.47	0.50	0.03	6.4
	5	0.46	0.52	0.06	13.0
	6	0.47	0.54	0.07	14.9
	7	0.46	0.53	0.07	15.2
	8	0.47	0.51	0.04	8.5
Pooled Control						0.05 ± 0.02	11.3 ± 3.64	-
62.5	1	0.46	0.51	0.05	10.9	0.06 ± 0.01	11.8 ± 2.65	No
	2	0.47	0.54	0.07	14.9
	3	0.46	0.50	0.04	8.7
	4	0.47	0.53	0.06	12.8
125	1	0.46	0.54	0.08	17.4	0.07 ± 0.01	15.1 ± 3.21	No
	2	0.47	0.54	0.07	14.9
	3	0.46	0.54	0.08	17.4
	4	0.47	0.52	0.05	10.6
250	1	0.46	0.52	0.06	13.0	0.07 ± 0.03	15.5 ± 5.75	No
	2	0.47	0.56	0.09	19.1
	3	0.46	0.50	0.04	8.7
	4	0.47	0.57	0.10	21.3
500	1	0.46	0.48	0.02	4.3	0.06 ± 0.03	12.3 ± 5.35	No
	2	0.47	0.54	0.07	14.9
	3	0.46	0.53	0.07	15.2
	4	0.47	0.54	0.07	14.9
1000	1	0.46	0.48	0.02	4.3	0.03 ± 0.02	6.93 ± 3.15	Yes
	2	0.47	0.52	0.05	10.6
	3	0.46	0.48	0.02	4.3
	4	0.47	0.51	0.04	8.5

Table 3: Reproduction Rate (Number of Juveniles after 8 Weeks)

Application rate [mg test item/kg soil dry weight]	Replicate	Number of juveniles	Mean±SD	CV              [%]	[%] of pooled control	Sig.
Control	1	94	117 ± 16.9	14.5	94.4	-
	2	137
	3	115
	4	127
	5	102
	6	141
	7	106
	8	110
Solvent Control	1	188	131 ± 28.5	21.8	106	-
	2	111
	3	158
	4	102
	5	135
	6	122
	7	118
	8	117
Pooled Control			124 ± 23.9	19.3	-	-
62.5	1	127	108 ± 34.3	31.8	87.1	No
	2	70
	3	145
	4	89
125	1	100	119 ± 25.4	21.4	96.0	No
	2	115
	3	105
	4	156
250	1	126	135 ± 22.8	16.9	109	No
	2	114
	3	167
	4	132
500	1	110	121 ± 25.2	20.8	97.6	No
	2	122
	3	155
	4	96
1000	1	73	80 ± 19.3	24.1	64.5	Yes
	2	68
	3	71
	4	109

Table 4: NOEC, LOEC and EC-values

Endpoint	[mg test item/kg SDW]
LOECmortality	> 1000
LOECbiomass	1000
LOECreproduction	1000
NOECmortality	1000
NOECbiomass	500
NOECreproduction	500
EC-valuesmortality, biomass (95 % Confidence Interval)	EC10, 20, 50: > 1000 (n.d.)
EC-valuesreproduction (95 % Confidence Interval)	EC10: 820 (753– 964) EC20: 907 (831 to n.d.) EC50: > 1000 (973 to n.d.)

n.d. = not determined

Validity criteria fulfilled:

yes

Remarks:

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

Executive summary:

Effects of test substance concentrations between 62.5 and 1000 mg/ kg dw on mortality, biomass and the reproductive potential of the earthworm species Eisenia fetida (Annelida, Lumbricidae) were determined according to OECD 222 (2016). All validity criteria recommended by the test guidelines were fulfilled. The NOEC for mortality was determined to be 1000 mg/kg dw. The derived NOEC for biomass and reproduction was 500 mg/kg dw.

Reference 2

Endpoint:

toxicity to soil macroorganisms except arthropods: short-term

Type of information:

experimental study

Adequacy of study:

key study

Study period:

06 - 21 Aug 2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP - Guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 207 (Earthworm, Acute Toxicity Tests)

Version / remarks:

1984

GLP compliance:

yes (incl. QA statement)

Remarks:

Staatliches Gewerbeaufsichtsamt Hildesheim, Germany

Analytical monitoring:

no

Vehicle:

yes

Details on preparation and application of test substrate:

- Method of mixing into soil (if used): respective test item amounts were weighed out for each test item concentration, dissolved in acetone (2.5 mL per replicate) and mixed thoroughly with quartz sand (10 g per replicate). After evaporation of the solvent, spiked quartz sand was added to the artificial soil (2485 g). Humidity of the soil to a moisture of 54 % of the WHC max was adjusted by demineralised water (321 g). Then test medium was mixed thoroughly to ensure a homogenous distribution, and about 555 g SDW were filled into each test vessel.
- Other: soil moisture content and the max water holding capacity were determined prior to experimental starting

Test organisms (species):

Eisenia fetida

Animal group:

annelids

Details on test organisms:

TEST ORGANISM
- Common name: earthworm
- Source: own breeding, kept in covered plastic vessels containing potting compost
- Age at test initiation (mean and range, SD): adult earthworms
- Weight at test initiation (mean and range, SD): 0. 46 ± 0.06 to 0.47 ± 0.07 g/worm
- Feeding during breeding: litter of dried stinging nettle leaves and porridge oats. The amount of food is portioned due to the feeding rate and due to the density of the earthworm population in the vessels.
- Pretreatment: earthworms were washed in demineralised water, dabbed dry on a paper towel, weighed individually and placed onto the surface of the test medium

ACCLIMATION
- Acclimation period: 2 d
- Acclimation conditions (same as test or not): in artificial soil

Study type:

laboratory study

Substrate type:

artificial soil

Limit test:

no

Total exposure duration:

14 d

Test temperature:

18.5 - 22 °C

pH:

5.39 - 5.94

Moisture:

24.1 - 27.4%

Details on test conditions:

TEST SYSTEM
- Test container (material, size): glass dishes, 1.5 L volume (during the test they were covered with perforated plastic film to prevent the test medium from drying)
- Amount of soil or substrate: 555 g SDW/vessel
- No. of organisms per container (treatment): 10
- No. of replicates per treatment group: 4
- No. of replicates per control: 4
- No. of replicates per solvent control: 4 (artifical soil with addition of quartz sand spiked with acetone and moistened with demineralised water without test item)

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
-Peat, air-dried and finely ground: 10 %
- Kaolin, kaolinite content > 30 %: 20 %
- Air-dried quartz sand (sand with > 50 % particles size of 0.05 to 0.2 mm): 69%
- Calcium carbonate (CaCO3) to achieve a pH of 6.0 ± 0.5: 0.40 %
- Maximum water holding capacity (in % dry weigth): 52.3 g/100 g SDW

OTHER TEST CONDITIONS
- Photoperiod: 24 h
- Light intensity: 445 ± 30 Lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): pH-value and moisture content were analysed in all vessels, the control and solvent control using mixed samples of all replicates, at the start and end of the test. Live weight of earthworms was determined individually on the day of application (day 0) and on day 14. The mean weight change was assessed at day 14 after application. Mortality, behaviour and morphological changes of the earthworms were recorded 7 and 14 d after application.

VEHICLE CONTROL PERFORMED: yes

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2
- Range finding study: yes
- Test concentrations: control, solvent control, 1, 10, 100 and 1000 mg/L
- Results used to determine the conditions for the definitive study: no mortalities were observed up to the highest test concentration. 4 concentrations were chosen based on these results for the definitive test.

Nominal and measured concentrations:

0 (control), 62.5, 125, 250, 500 and 1000 mg product/kg SDW (nominal)

Reference substance (positive control):

yes

Remarks:

2-Chloroacetamide

Duration:

14 d

Dose descriptor:

LC50

Effect conc.:

> 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

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:

mortality

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:

mortality

Results with reference substance (positive control):

- Results with reference substance valid? yes
- Relevant effect levels: LC50 28.2 mg/kg SDW

Reported statistics and error estimates:

The NOEC/LOEC was determined by calculation of statistical significance of mortality and biomass. Dunnett's Multiple t-Test. Procedure was carried out for the determination of statistically significant differences compared to the control. When running the test, a Normality Test and an Equal Variance Test were done first. The a-value (acceptable probability of incorrectly concluding that there is a difference) is a = 0.05.

No LCx-values were determined, since there were no effects after 14 days of exposure.

No significant pathological symptoms and no changes in the earthworm behaviour were observed in the control as well as in the test item concentrations after 7 and 14 d of exposure.

During the test the biomass loss (inhibition) of the earthworms was below 20% in the control.

Validity criteria fulfilled:

yes

Conclusions:

A 14-d NOEC value of >= 1000 mg/kg SDW and a NOEL of >1000 mg/kg SDW have been determined for the effects of the test substance on mortality of Eisenia fetida, based on nominal concentrations of the test substance.

Reference 3

Endpoint:

toxicity to soil macroorganisms except arthropods: 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

Reason / purpose for cross-reference:

read-across source

Duration:

14 d

Dose descriptor:

LC50

Effect conc.:

> 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other:

Remarks:

Result from OECD 207 study

Duration:

56 d

Dose descriptor:

NOEC

Effect conc.:

500 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Remarks:

biomass

Remarks on result:

other:

Remarks:

Result from OECD 222 study

Description of key information

NOEC (56 d) = 500 mg/kg soil dw (OECD 222, Eisenia fetida, RA to CAS No. 16415-12-6)

LC50 (14 d) > 1000 mg/kg soil dw (OECD 207, Eisenia fetida, RA to CAS No. 16415-12-6)

Key value for chemical safety assessment

Long-term EC10, LC10 or NOEC for soil macroorganisms:

500 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 soil macroorganisms excpet arthropods. 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.

Two studies are available, in which the short-term and long-term toxicity of the source substance trimethoxy(hexadecyl)silane (CAS No. 16415-12-6) to soil macroorganisms was assessed according to OECD guidelines 207 and 222, respectively, and under GLP conditions.

The acute study was conducted under static conditions for 14 days with test item concentrations of 62.5, 125, 250, 500 and 1000 mg/kg soil dw mixed into artificial soil. 40 test organisms with an individual weight of 0.33 to 0.6 g were divided into 4 replicate groups, each containing 10 test organisms. No mortality, pathological symptoms or changes in earthworm behavior was observed in any control or test item concentrations after 14 days exposure. The NOEC was determined to be 1000 mg/kg soil dw.

In the long-term study, a 56 d test with artificial soil according to OECD 222 was performed with the earthworm Eisenia fetia and five test item application rates of 62.5, 125, 250, 500 and 1000 mg/kg soil dw. Each application rate was mixed into artificial soil containing 5 % peat. A control and a solvent control including untreated artificial soil was tested under the same conditions as the test item treatments. 80 test organisms were inserted into 8 control and 8 solvent control replicates, each. 40 test organisms were divided into 4 replicates for each test item treatment (10 earthworms per replicate). They had an individual body weight between 0.40 and 0.53 g at test start. After 56 days of exposure in soil, neither evident earthworm mortalities (< 10%) nor evident pathological symptoms or changes in the behavior of adult earthworms were observed in the controls and all test item concentrations. At the test item concentration 1000 mg/kg soil dw, the earthworm biomass and earthworm reproduction was statistically significantly reduced after 56 days. Therefore, the NOEC for biomass and reproduction was determined to be 500 mg/kg soil dw.